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https://ntrs.nasa.gov/search.jsp?R=19780011294 2018-02-12T11:17:10+00:00Z

NASA TECHNICAL NASA TM-73806MEMORANDUM

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(NASA-T!"-73806) DEFINITION AND EFFECT CF '17R-19237CHEMTCAL PROrERTTES CF S T 1PvkCFS TN FPICTION,WERE, AND LU3RICATION (N y SA) 40 P HC A03/MFA01 CSCL 07D 9nclas

G3/25 09451

DEFINITION AND EFFECT OF CHEMICAL PROPERTIES

OF SURFACES IN FRICTION, WEAR, AND LUBRICATION

by Donald H. BuckleyLewis Research CenterCleveland, Ohio 44135

TECHNICAL PAPER to be presented at theInternational Conference on Tribologysponsored by the Office of Na val Research, the Army ResearcOffice, the Advan^:ed Research Projects Agency, and the o,°'^^111?13^97^^

Massachusetts Institute of Technology 1^Ca-nhridge, Massachusetts, June 19-23, 1978

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^^ 06 n- y„ nil C.L^+^L

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DEFINITION AND ITFECT OF CHEMICAL PROPERTIES OF

S'URFACVS iN FRICTION,ION, WFAR, AND ITIARZICATION

by Donald H. Iluckley

National Aeronautics and Space Administration

Lewis Research Center

Cleveland. Ohio 4.11,5

AIIST1t,1CT

Murh t11 tier data rt,latl ► • e 10 the 11rt1}k`rtic`s of surfaces that h:1 ► r

liven used in Ill y }last in analv?,ing. interllretin ► ; and predicting adhesion,

frictio ll and we

*

11 . behav ior folr stIlid surfaces is IlOW susllrt • t. With theC\3 advent tit anal,vtical surface tools, careful and co mplete characterinitiomC of surfaces indicate that wry frequently the outermost layrrs of solidW sill-faces art , nlarked1v ditfert,nt in chemistry than 11.1ti heell previously

thought. These 1:1yers, as will he shown. are rxtrt,mely important inadht`s it'll , friction and wear behavior. Some tit tilt` prollvl'ties to he

discussed ill tilt` 1 1 .1lwr relative to their rode 111 adhesion. friction. \►'1`:11'

anti lubrication will Include: (l) adsorption. both pli\'sical and chemical:

(2) orientation of tilt , solid as well as tilt , lubricant. (S) surface rnrr^;^':(4) surlacr sit grei;atitn: (5) surface versus hulk metallur l;ical effects;

((;) rlectrolltic nature tit the surface: and (7) littndini; mechanisms.

IN i'RODUC ION

i'ht, prolwvtit`s t11 S111'f;1kTs a1'0 r\tl'elllt`i ►' Important In tilt` '? lilt`sit111.

friclioln. wear Alld lubrication of materials. This fact was recornixedby Sir William llardy l over a half a century ago'. It has, ho1wtwer, mil\

revently beell possililt` to delille and iully t'11:1!'al'tel'1: e` tht`st` surfaces.

The advent of silecial surface tools has assisted In the charactrri;.atioln.

`1'Ah t .it rytary 21

I

2

These include: field ion microscopy (FIM), the atom probe, low energygYelectron diffraction (LEED), Auger emission spectroscopy analysis(AES), electron spectroscopy for chemical analysis (ESCA), ellipsometryand scanning electron microscopy (SEM).

Through the yeai s from Hardy to the availability of these tools, con-siderable research has been conducted relative to the physics, chemistry,and metallurgy of solid surfaces, in general, and more specifically asrelated to tribological systems. In light of the current identification ofthe real nature of solid surfaces many of the concepts, mechanisms andtheories previously held may have to be modified or discarded. Thismay be particularly true where bulk properties have been used to predictsurface behavior.

The objective of this paper is to review the importance of surfaceeffects and the need for a careful definition of solid surfaces in friction,wear and lubrication. While in the past the physicist, chemist, andmetallurgist had well defined areas of activity with regard to the behaviorof materials it will become evident that the chemistry of surfaces to

! w'iich this paper is devoted will involve, of necessity, physics and met-allurgy. Some of the prop?rties to be discussed in the paper relative totheir role in adhesion, friction wear and lubrication will include, adsorp-tion, both physical and chemical, orientation of the solid as well as thelubricant, surface energy, surface segregation, surface versus bulkmetallurgical effects, electronic nature of the surface and bonding mech-anisms.

REAL SURFACES

Until approximately ten years ago it was very common to find inclassical teats on surface chemistry a nearly complete absence of thecharacterization of solid surfaces with which gases and liquids wouldinteract. 2 A wealth of literature has been developed through the yearsconcerning adsorption to solid surfaces, particularly chemisorption.Again, very little attention has been paid to the nature of the surface of

FTWT -

ism

s

the solid Involved. Frequent ly M was used to designate the metal

involved where adsorption studies Nvere Conducted With metals.

In the held of trIho loo v because of the i ► 11I)ortanct, of sulr fatces tilt'

I)resenct , of oxides and adsol- hates has li v en recognized. r) Despite this

I't`L'ogltlllL)ll it has been it Common practice to consider solid sulfates,

Uhlch art` usualh metals, as rt':1L'tilig directly \\-tilt the lubricants, ill-

dicawd by way of example lit 6 to 10. Frequently metal

I)OU'dt`I's, Nal'lil'lllatl'I1' Il'l)I1 have been used it s the adsorbing Sul'fat'e

for the lubrtcant 6.7 Metal powders halt,, however, bet'n identified as

being, poor relative to gars adsorption; they are poor with respect to

both surtace Clc':ulluless and characterization. 11 :'he saint' limy he

said wtill regard to liquids.

1; the surface of high purity 11'011 k\':tt'lllllll zone refined) is examined

\%-tilt Augt`r emission SIk`ctroscol)v it is tound t0 contain more than simply

iron as indicated ill 1(a)• I1; Fig. I(at) ill t0 iron, ox ;tell,

carboll, and sulfur are detected on tht` sm - favvs. These elements areStable on tilt' stlr'lace anti r-eSlst ft,( 111MIueS such as heating, to 500 t' L

to at'hteve their removal. The OIIIV method lourld eftectIVe in accom-

I)Ilshing tilt` removal of all tilt , extraneous elements was arl;on tun

lit) itIba rd item .

l i; ,,ii 't` 10l) is all ALI1,'t`I' t`IlliSSi011 Slk`t'tl'lllll f0l' lilt, il'e l ll Sul'fat'e

after argon ion spu ilel, cleaning. Tilt` only element detected is iron.

The sill-late atoms of the iron hou-twer been stralimed by the ion bombard-

ment 11 tit , t lean Iron surtact` is then heated to 5llt lt) C t1) ;1I1111 `al lilt`

stll'tale, tal'1 1011 t1'0lll tilt` bulk diffuses to tilt` surfat,e and contaminates

the surface. A LEER pattern is I)resented In Fig. 22 (a) for this surface

Ill Fit „ . 2 1 ai) flit , flint' l ri-,lltt'st SI)OtS Ill a lTCUIll!"L11a1' itl'l';l}' :il't' dllt,

to the iron (i l l l) crystal surface. The ditlllse and less Intense spots

appearing ill a circular pattern are Lille to the carbon coiitatrllinatIon.

The Au1;t,r spectrum of Fig. a indicates that the surface contaminant is

t ;II'boli.

The re Ill kIval of the carkill b\' al • :;oll ion bo11lbardilit'nt results ill lilt,

LEER pattern of r'ih. 2(1). Tilt` diffraction spo(s art , diffuse and elon-

1 ,aleti A vt,cv modest heating; at 200” C for a very short period of time

.tea► ^^ - - .^.^. t

Y

4

results II. the LEED paltvrn of Fib;. 2(c) for the clean annealed troll

(0 11) surface.

The interaction 111 twee till` simplest of ele't cents %% - till till` flea ► \ Iron

surface beat[lies very involvt,d and must he carefullN' followed to under-

stand tilt , niechanism of interactiutl. This is accomplishcd Nv ► tll tilt, aid

of surfact, analytical tools. It has been very effectively done in the study

of the a henlisorption and chemical reaction of oxygen with iron. 12-1.1

The surfaces of most metals art , not toll different from that observed

for iron and usually thert , alre a I111111he1' of elements [)resent on the sur-

face In addition to those of the metal The rule tit' these elements on the

intcrat11011 ill lubricants with tilt` st ► Ild surface is not full' understood

bllt smile of the'sl' reactions will he d iscutitil'd later 111 reference to gas-

solid surface interacltons.

SURFACE 1^'.NFRGY

If one cleaves a crystalline solid along its cleavage plane, two highly

chemically active surfaces art , generateli. The civavaia , urocess causes

the fracture 111 cohesive bt.nds across tilt , cleavage tnterface and these

fractured bonds lealve tilt' surface in a highly energetic state. The enerkry

of the surface will lx` dependetli on both the ell'rlrental nature of the bonds

brokt,rl and the coordination nalrllber of the at0 ► r1s in tilt' resultault two

surface lavers. As a I'l'111II. tiUl fact' tilt c oy wIll 11e it I11111't1t111 Of tilt`

material I ^' as well as tilt, sllrtare orit,ntatitlll. 16-2 1

Illl'I'e 1s 11:1 llllt`rtll l ll lull p lat tiUI'tal'e l'lll`I't;}' is tillI1V1'talilt 111 tilt`

1 rllloloticat behavior of materials It will tillhience adlic•Ive ponds for

solids In contact anti ht,nce friction and adlit'sive wear. In addition it

will deterillrnc tilt , nature of the interaction of iubt'icaniti a'Ith solids.

The lubricant may either: (l) physic:Illy adsorb; (2) chemisorb; or (;;)

ullticr'l;o detom[ulsilion, as has been observed for sonic hydrocarbons

\0111 a clean metal Surface. Surlace energy has been used ► n the for-)

111ulatton of an adhesive' WOIt' 111COMnis Ill . 23

W11111` ti111'fat't` ellt'i'111' )':111 i ll' 1'el'V Ilt'lilllil Ill understanding till` ad-

ht,sion frictiml, weal . and lubrication behavior of materials. it. present

5

lisrt'ulruess is t`er\' ltnlileti. '1'h(, I ll . tilt- ililt , rrsIrit tit ► 11 tins fuel tilt` ill-

ability to obtain It t uratr rxlx`rinl(,ntal surfut,t` (,n(,rl;y \afar~.

Ali examination tit flit , surfat,t , en(,rg). literature rr% • t.IIs With tits-

Iiariltt `s in l'(,110tAt'd \^alu(,s 101 , : ► n\ tlne n1.Ill`rutl. l;ll l le l lntltratt`s tilt,

111111111IL1111 anti m:lxlttlulll stlrlat,t ( l ilt , 1 \ \'alut,s wil Id, fan tit` ttnlild in tilt`

literaturt` fi l l* s0111t` tit tht` t`lt`lllt,lllal I11(,Ials '1'ht`st` (bill were takenr

(mill a su I11ll lary by WaW t.a. 11,

\\'till( , the broad rallgr of (, p lat`s t11 ► lain(,ti art , of t,tult'ern. tilt , fart(11.11. for (,\:1111111e', Ilit , 1111111i1111i11 lt1 111.1\1111U111 I01 • st1111t` Illt`lMS sllt,ll as

11'011 anti t Ill 't ► 111111111 1.111 within tilt` ralw.t` lotllld 101 , I1111O.Slt`I1 :il't` tit t`\'t`ll

t;r(,:Ilrf Conk erll. It \\'( plat, lit` ttittic Ill I. based u11t 111 1 • rI1t11'ted exjwri-

mew.il data. to identify difterent,ts ill Ihr Surface (,ntl i-g • flit • troll,

t,hrollim111 '.11lti tunl;ste`n.

As has alrtativ been Indicated. tilt` surfat't` energy of solids such asttletals is sc`nsltl\'t to rr\'staIit"'.ra I'll it tlrtriltattoll. Most researt,h(,rs

rtln\'rrsant In Iht` sul l j(,t t tit surt.we rnt`I'I'V reatitl\ • a::r(,e th.lt (tits is tilt,

r:lst, l i lttt,retwes arlst,, however. when atlual rt`sulls are C011111at't`d

The rt , sea l't 11 1't`silIis tit 111 rot` (tit it , l't`I1t tll\'t`st I,;alt1rs who 11.1\'t` lllt`aslired

th(, surlatr tner;:tes fill' \al'1t1us phlies t11 fat'(, i't`nter(,d c'ul/it' nlet:lls

at't, I1l't'stl uted in 1'.1111(, 11 Flit , results :11'(, Ill't,st,nted as Iht, rittici tit (lit,

su[-fat'(, c`n(,rt;irs for till` various plant's over that tt ► r the X111) surCart.

Tilt( result. tit' T.Il l lt` It Indicate That not till\' dot's tilt` value vary

with tllt` 111 \t`^Ilp;:itt r 1 1(11 Illort` ill port:tllll\ 1111` I . ( 1 .11Ive, t 1 1't 1 t`I' t1l lilt`

nit , lals as \1'(`11

11n(, 111 Ilit , nitlst si ►;niC Ica lit re:tstlns I01 , tilt , \\ Itte dtsllartty ill th(,

ski i't:we t`11t`I ov \.1lot's 1't`1 101*1t`d by \'al'lous tll \'t`st1 0.111t 1 1's ltls I t t`t`ll Ill -

attetlll.itt , t't111t 1'( 1 1 t vet, Ilit` i lnllll l'l t wt, ill Illt` mat t , r1.1 Is. till1.1ll 1 ' 1 1 1I1 • t,nll':1-

tloll tit in1l1t1rltlts in tilt bull: tit :1 metal call 111.11-kctily alt(,r (lit` Illt,asurt`d

surface vilvi. . of a nlaterml. Phis is intiiealt'd in tilt tillta tit' Fig. •1 for

sunlit, Ill iron. With an int'reast` in t,t lnt'(,ntI-litit'll tit sulfur, ther(, is all

at't 01111 1 Ilvilig tit`( i east , Ill 1111'lat't` (`11(`1'1;)', F ig. •1.

V\Irenlrlv snl:tlI t'tlnt'rntratlolls tit hulk colitanitn:lnt Ina mel.11 such

-is troll fall have a t`itt`t't ill collt:tl11111.11ull,, it s nl'tat't` Ft ► r

t,x.imple, as li t , It , its 2, 1 1 1 1 111 tit CU1 , 1 1 011 in 11 , 011 \\Ill dittust , to tilt` surtlice,

is

li

svp't'gatt` there and contallllil;lte lt. •i`1 This SVI',I't` ►;at1011 \\• ill ItIIdollhlt'dI\'

itffvl't II It , .1sIIrt'd Slll'tace t`I It , r,t i `s-

niv list` tit IIil;11 Illll'it \' III ;It t`1'l;I IS ;11111 Ilse C;11'VI' LlI l'II;1l'.IC It' I'UM it) II t.t

solid surfacesshuuhi rt'sult in flu` futile(` ut'duitiition of nlratlint;'fuI ',It

face ent`r o), values. Slll'tat't` 1111:11 \11C.l1 ((1111~ ;1l't` l'lll'I't`llll\' bVill"' llst`d

ttll' tilt` nevdt'd surface t'hal;ll'It`I'll.ltlll i ll•()lit' \\• illt'il 11115 I 1 1't l \'t`I1 t'SIk`Cllilly

ust'Cu1 Ill this rr;:ard Is ille I'leld 1oll nlicrost-ope. 11 ' ti ' When used in

C011,11111C110il With tilt' littllll 11roliv. its contribution will he viflianced. It

:;i\es tilt' 1111(1111 IW atttnl N11110llral arran:;t'nit'nt tin a solid surfact` alld

\\'Ith tilt` uttlnl Ilrobl` an amnl by atoill t ht'likik-al analysts.

A1,LOY ('lit•'AIISTItY

In Ilrat• tit'al lubrtt':111t111 s\'stt`Ins tilt` nlcc11anlral ct11l pont'nts ill solid

state contact are most trt`tlut`ntl\ Ilio\'S ralllt'r (11.111 elt'111t'11tal metals.

The colliposition tit thest` :lilt)\' surtaces art` tnlll,lrtallt ill consuit't•ilig

tilt` cht'lilical interactttllls tit Silt h s(hit)s \rlth other soluis, with gases

and With 1111 1 t'it'ailtti. 1':\'t`I1 1\'11(`1'(` t`lt`Illt`lltal lllt`t1ilS itl'E` llst`d, the sill--

faces lit tilt`s(` Illeuds 111.1\' tla\'t' Compositions t`Illll't`t\' dlttt`I't`Ilt tl'tllll tilt`

hull: \\• hull results fr0111 t11lllu11tV sl`LI'VO.111011

The tit'id of tl'lbtlloox colltal11s a 11u111her tit excellt'nt tt`xts. Alan\' of

these books tit' 1101, 110\\'evel', til-ICUSS flit` rt':11 Il,lllll't` tit tilt` Nlll'tltl't` ltl ht'

luhrir:ltt`d (See, ft 1 [' t'xa111111e. Net ' s 23 21: 21) and 311 1. Atllch attention

is :Avell to tilt` cht'nlictr\' tit tut' lul l rit'.1111 hilt ltt(lt' it) the t'lle`ulistr\ tit

tilt, alloy surface to lit' lubricated. In t•air11l`ss to the authors ill these

tt`xls (lit, idl`Iltificatitlll tit lilt'st` sul'fat'es \Pith ~ p i'laf'f` tools Just bee1 toenler"t` at tilt` It111c 111t'st` text. Wt`l't` W11ttt'11 Fllkll-t' tt'xts 1111 tilt' sublt'rt

s11tullti, however. not lit,"Jot't tilt` 111111ortallc ` tit tilt' lut'tal k i t* alloy sur-

f;n't' c11e11ltslry and tilt' inlerat tit/n tit tilt` 111hricant \\• lilt that surface chelll-

isl r\'

With t'letilt'ntal metals. the e`flect ill small cont't'11trattt lls tit In1lluri-

tles sut• I1 as 1111rt-S I1t`1' 1111111( 1 11 Citl- IMll in iron ha\'e been Shown iti affect

surface cht'nlistry. This was discussed earlier in this paper. Sinlital'

efft'cts have lit't'11 oN erved \\• tilt tether lnlllul-ItY clt'mt'nts In a 11u111hel . tit

ill

0

7

different metals. Surface segregation has been noted for oxygen inplatinum, 31 phosphorus in iron, 32 sulfur and carbon in nickel, 33 sulfurin molybdenum, 34 carbon in nickel, 35 and even sodium in lithium. 36The foregoing are only examples, other impurity effects have beenstudied and still other systems, it is certain, will be studied. Witli someof these impurities the metal surface is completely covered by the con-taminant which call from the bulk and even form compounds withthe metal itself at the test surface. These compounds do not exist inthe bu Ik. 34

In lubrication systems, the rubbing; off of surface oxides and adsorb-ates because the solid : urfaces are in c ontact under relative motion is acommon occurrence. Frictional heating of the surface layers call

tho diffusion of impurities to the surface under such conditions.The presence of impurities in metals is therefore important to surfacechemical behavior of the materials in solid state contact. A foreignatom which may simply be all in the bulk can be ar_ alloy con-stituent of the surface or compound with it. 34

When elements are alloyed, the segregation of one element to thesurface can occur and its concentration at the surface can exceed thatin the bulk alloy. Thus, for a given alloy the surface metallurgy candiffer appreciably from the bulk metallurgy. Such surface enrichmenthas been observed with a host of systems. A few examples of such sys-tems include nickel in iron, 37 silver in palladium, 38 gold in copper, 39copper ill , 40 silver in gold, 41 aluminum in copper, 42 fill cop-per, 43 aluminum in iron, 43 and platinum in osmium. 4

The amount of material which call present oil surface of alloysrelative to the bulk concentration of the alloying; element can be appreciableThis is indicated ill data of Table III for aluminum and tin segregatingto the surface of copper and aluminum to the surface of iron. The surfaceconcentration ranges from approximately 3 to 15 times the bulk concen-tration of the al'.,ying element.

One theory relevant to the reason for the segregation of the solute tothe surface of the solvent metal is that involving; lattice strain. It hasbeen postulated that if the solute atom is larger in size than the solvent

i

i

Ai&E

8

atone, it will straits the solvent lattice and therefore there exists the ten

-dt' icy it) squeeze the solute out of tilt' solvent lattice. From tilt` atomic

sLws pi'etiellted Ill Table V1 it appeal's that tilt` exivrill ental results

agret' \\• ills the theory. Still another theory illvolves the concept of sur-

face tilt rp- reduction. The diftit'llltit'S ill USillg st11'l;lCt' VllVrgiVS 11115.

however. already Wen diSCtissed.

Surface st'Rrel;ation of alloti' constituents has a wer\' definite effect

UIVIl tilt' adhesion, friction, \\'car and lubrication of alloy surfaces.

The efft,ct on tilt' adhesion of copper base alloys c;ln he seen In tilt' data

of Fig. 5.

In Fig. 5 a fivefold incrt,ast , ill tilt' adhtsion of copper occurs \\•Ith

flit' addition of as little as one ato ► uiC Ilercc'nt aluminum. Further ln-

C1'e;iSeS ill the :lllllllililllll t'Ullcentration beyond Hilt' percent dO Ilot IWOdut'ei and• further chanl:-e in adhesion behavior. In fact. the adhesion data for

More Allllli1111111 in Fitz. 5 is approximately the same as that obtained for

the coplWl' contaillillg 011t' atomic llt'rcent aitimiilum. The data of Fi g;. 5

\\'ere all obtained With metal and alloy' sill-le cl-vstals ha\'ilig a (111) sur-

t:lce ol'il'll tilt lon in order to vIllllinatt' orientation a:. a pKissible \•ari;lble.

Both LEER and Atioer emission spectroscolly W'el't, used to idt'ntify

the segregation of the aluminum to the copiwi . surface. The surface

struchire resullitlg from this identification is presented in Fig. G. From

an examination of Fig. 6 it can be seen that the outt'I'Most laver of the

solid consists of a l:lycl . of alunlintllll ;Monts. The k1 . 1lSlt\ • of alunlinunl

atoms in this layer will \;lr\' With bulk concentration but tilt , layer is

;ll\\a\'s AL1111lnuns. it is for this reason that no dlllrrence in adhesion

behavior was detected from ant, atonLic IWITC111 to l,ul'e ;llullllnunl.

"file lursenre of sonic alloN. ing elenwnts can. nivii segregation. Ilro-

mote surface chemical activity and thereby adhesion. Such behavior was

;lbsel'\ • t'd tol' 101.11111111.1111 in copper \While with other elements chelllical

surface activit y and adhesion art' reduced. Such a r •t,duetlon t'tft'O is

l ol,`tit'rvvii for 1 it , ill Coppt'r. 43

1 It .11, alloy of till (oat, ato111ic Ix'rcent) Ill colllk l' i• shutter cle;tned.

1 the adht'sloll lx'ha\ • ior of, the alloy is comparable to that for Kure coppt,r

as indicated in the data of Fig. 5. Tll y rvasotl for this is th.lt slnittt,rinl;

- l ='r= ;;

r

9

1

removes the surface segregated tin. Heating, however, to 200 0 C causesthe tin to segregate at the surface and brings about a reduction in adhesion(Fig. 5).

Among ferrous base alloys, both aluminum 43 and silicon 45 have beenfound to segregate to the surface of iron. Aluminum in iron segregatesto the surface and increases adhesion. It also causes, in the clean state,an increase in friction and wear over that observed for iron without alu-mium. 46 Alloy surface chemistry is therefore important to friction andwear as well as adhesion. It should be indicated that, while increased;,urface chemical activity of the aluminum - iron alloy produces an increasein adhesion, friction and wear for dry metal contact, it also results inincreased activity with lubricants which can be beneficial. 46

Silicon allo,7ed with iron behaves in a rather unusual manner. If asilicon - iron alloy is heated, silicon will segregate to the surface. 45When, however, the alloy is cooled to room temperature the silicon re-turns to the bulk. It is a reversible segregation. This is unlike the be-havior of other alloy systems where the segregation is irreversible. If,however, the silicon is allowed to react with oxygen while on the surfacethe formation of silicon oxide prevent s the return of the silicon to theparent lattice from which it came.

In Fig. 7 friction coefficient is plotted as a function of oxygen expo-sure for iron and for an iron 3 1/2 percent silicon alloy. Prior to theadmission of oxygen, the friction coefficient is extremely high for thealloy and the pure iron seizes completely. As the surfaces are exposedto oxygen, the friction for both the alloy and the elemental iron decrease.This decrease occurs, however, much more rapidly for the alloy thanfor the iron. The difference is due to the segregated silicon and its inter-action with oxygen at the surface. The sliding process is capable ofgenerating sufficient frictional heating to cause the silicon to segregateat the alloy surface. Auger analysis confirmed its presence. 45

4

^I

10

GAS-SOLID INTERACTIONS

Specie and Concentration

Almost all surface: im-ohed ill al s ystems, with the ex-ception of thus ,- operated in a good vacuum (e. R. , 10 -10 tore), are ex-posed for interactions with gaseous constituents of the environment.This is true for lubricated as well as unlubricated systems.

Oxygen is probabl y the best "lubricant" available. It will reducet friction coefficients fur clean metals from complete seizure to %values

of less than 1. 0 (See data of Fig. 7). Liquid lubricants will reduce thedry sliding value from less than 1.0 to a % v alue of approximatel y 0. 1.

Extremely small Concentrations of surface films call influence ad-hesion and friction. For example, fractions of a nlonolayer of adsorbedoxv,- n or chlorine oil clean iron, copper or steel surface will reducestatic friction as seen from the data of Fit;. 8. Ill Fit;. 8 static frictionis plo ► ted as the inverse of surface coverage to the point where the sur-face is covered by a nulnolayer. 47 From these data the importance of;;as-solid interactions at the surface of the solid is readil y apparent.

Interaction Mechanisms

There are three basic types of interactions between a gas and solidsurtace: (1) physical adsorpttoll; (2) chcrllisorption; and (3) chemicalreaction. Physical adsorption involves weak lxlnding forces lean der«' gals) and are not specific. Because of the highly energetic state ofclean metal surfaces it is serioush . doubted that such adsor ption occursoi, these surfaces other than with Inert gases. The forces involved arecomparable to those involved In liquiflcatlon. 48

41

C heroical adsorption or chemisorption involves very stron t; chemicalbonds, comparable to those for chemical reaction and further are highlyspecific. They play a very important role ill and friction asindicated ill data of Fit;. 8.

Great care must be taken In using chcmisorptlon data which appearsill the literature. The current use of surface tools in the study of adsorp-

1.

11

tlon has Indicated that car p er I Irlingr are incorrec t 1I1 111.111)• lllh;:111ces.

For examlple, earlier studies have Indicated that gold dot's not chelill:lorll

OM-1.1n1 n. 4 'l Aloft` recent Studies have. ht irrver, with the aid of LFED

r ramd AES analysis, indlt ated that gold tit t dues clivilusorl ► oxN'gen. 'h, ' 1

Ref. 49 indicates that nitrogen does not Ownitsorh to platinuin chile Itef.

52 reports that It dews. The reason for the earlier study not observingadsorption of nitrogen to platlnurll can be found 111 lief. 52. Nitrogen ad-

sorption becomes signitic;lla only :ttter am • carton contamination is re-

111t ► \ • t'd I1'0I11 till' 111.ltllltllll surface b y he:itlii., tit and removing the

CO that forms front the ^;ystenl `t1t11 results itwit ate flit' importance

tit using anal y tical sul'tace tools it) characterize tilt` adsorbing surface.

Orienia r ion of Stolid

Adhesiov and IAction are extivnlely sensitive to sit rtace character

as already Indicated. With various adsorl ► rd gases, friction Is not only

a function of the adsorl ►ed oas but the surface orientation as well. In

Tables IV and V friction coefficients are presented for various Lases

chemliSOl • 11t'd ((I different atomic planes of tungsten (See data for

oxygen and hydrogen sulfide. Table IIII.

An examination of '1'Alle IV indicates tit-it even h y drogen will reduce

the 11'lt'tl011 01 11,111gStl'll rill, tit" til'^ t ► Il all 1111 . 1'1` 11 1MIVS tit tU11r;;Iell With

►► nly the magnitude of the reduttia n vary ing wtih the plane. Ox y gen is

more effective than Su ILII- In I-C&It • Ing tilt , trlctt, ► n of tungsten.

Alolerular SII'Lll'tLII*V

The data of Tahoe V indicates that even the degree of bond unsatura-

tion \%• tilt hvdi-ovalholls ha-, -.ill on friction. The greater tilt' degree

of bond unsaturatlon, the ltnyer the triction coetticlent for .1I:y given

plane. It IS dill It tilt to Interpret these res ults In lt;;ht of adsorption

niechanisnis proposed for the id s-orption of these gases to a tungsten

surface For example. \t • tth the adsorption of eth y lene' whether the ad-

S01 , 11t Wit Is :l tilllg le 01,• IWO sft'p decolllptl+r12

ltlllll process l5 i ll diC1►llle.

i

1'r

Uisagivenlent exists even as toi the net ham!^m for the adsorption of the

sllllltlt` iIVdl'0(:aI'I)0i1 111011allt` tt ► a It ► Ilgslt'll S1114. 'e ^^^► Hopettllll' tuturt,

surface Studies \Aril \rt,ll tharai tort: ed surfaces will resolve this colitlict.

From the data tit Taba V thert , l!;. tit) titu Sidon that what Is present

t ► n the tun:;sten surface varlt`, either 1r cwilp ►sttl- ► n or st ► 'ut rural arrange-

nnnt. otherwise friction differences would not be observed. Tilt. is truenot onl y with tilt` adsorption of tllt` various gases oil :l sm_ll` plant` NO

with dltt'vivnt planes of tungsten as well.

\It1ti1 k it the diffltultIN' ill attc.nlits to stutiv adsurptton of gases. and

lltluuis as well. to solid sur'taieS is tilt' I ► r(intiunit,d t,ltt,t t :111311 t onitt,n-

tratlt ► lls oil bulk lllll)lll'ltlt's tall 11ave on the surlacv. This t6 trut' %fish

Ilie:.' 'g such :.., tungsten and even moot` so with tllt'tal^ liKe iron C mi-

C onlritions of 111 -1C.0 ppill of cal- 1 1011. IlltI'tigell of Nllltlil' 111 bulk 11'011 11'1115

segregatt` to the surface and will have an effect 4 W hen gases are ad-

so rlwd tti weII tharat it , rized Irtin 111*0110MICed triboltlgtcal t , ffvtts art,

st`t'll.

Frictional Vnergy Effects

:fin area to which verb' little attention ha; Lven paid Is the effect of

the interfacial frictional enemies oif twoi surfaces ui rubs ► tnl:; contact ongaset ► ll^ 6o I - litloll St ► illt` sltidlt`S by 1111` I ► t't'seTl ► ai+ ► ht ► 1' illtilt:lle that

tllort' is an vitt'd but It is a Cunt Iloll kit tilt' t 1101111st1•\' of tilt' IdSol•batV

j For exanlplt` it methyl Il ercaptan is adsorix , d t,lito a t Ivan Il't ► I1 stll•t:itt'1 .^ III the presenct' and absence (if •Iltillig. dlttel • eilte• in tilt' quanlltd' of sul-

fur adsorbed are obscrved. These dltterentes are Indicated in the auger

slivctroiscopy data tit Fig. 9.

More sulfur is obser- ed on the itron surface Tn the absen c e tit sliding^i-Ag. 11 ) Frlt lional heatiilg at the intertate call promott' desorption of

the sultul • : tlllz, alid g ear tuuld attt ►unt 101' the lt'sst,r arllt ► unt k it sulfur

o ►hserved with slidin:; These data tiltilt MU that care shOuld i ►t' t.lken in

appl y ing static adst ► I I ► tit ► n results to Uil ►t ► it ►giral systellis.

l; sulfur dioxide is adairbed to a Aran trt ►n surface el l her In the

Pilesl'lltl` (if t ► I • In The absence of slltilnt,. mi difference In acisorption bt-

IN

13

havior is observed. The Auger spectrescopy data of Fig. 10 indicatethe same surface concentration of sulfur and oxygen under both conditions.

The data of Fig. 9 indicate a sensitivity of adsorption to rubbingwith methyl merc• ap±ion while the data of Fig. 10 indicate an absence ofsuch sensitivity. If sliding in Fig. 9 causes desorption of sulfur, thenoxygen bonded to the sulfur must assist in resisting desorption, Fig. 10.This implies stronger bonding of oxygen to iron than exists for sulfur toiron.

The relative stabilities of sulfur and oxygen on an iron surface

can be demoiLstrated with the aid of the data from Fig. 11. The data ofFig. 11 were obtained in experiments in which a well characterized cleaniron surface was first exposed to 10, 000 langmuirs of hydrogen sulfideby the present author. The hydrogen sulfide dissociatively adsorbs onthe iron surface leaving a surface saturated with a sulfide film. If thatsurface is then exposed to oxygen, the oxygen will nearly completelydisplace the sulfur. This phenomena of displacement is evidenced bythe data of Fig. 11.

An oxidized iron surface was exposed to hydrogen sulfide. Sulfurdid not displace the oxygen on the iron surface. Thus, from these re-sults one could infer that iron oxide is more stable than is iron sulfide.It should be indicated that the oxide is t.hermdynamically unstable relativeto the sulfide in hydrogen sulfide when no oxygen is present but the acti-

Ivation energy hum ) must be overcome.

Effect of Mechanical Parameters

Mechanical effects other then simply sliding of the surfaces can havean effect on adsorption and correspondingly on such tribological proper-ties as friction behavior. For example, increasing loads for surfacesin solid state contact as well as increasing sliding velocity between suchsurfaces will increase the generated inter;ac ial energy. It is reasonableco assume that such changes in energy will alter adsorption behavior.

Sliding friction experiments were conducted by the present authorin which an iron surface containing a normal surface oxide was operated

111 .1 \'illy) 011orldt , a t lilt'sphe1' ' at it liresxtlrt , of Ilk 6 tort' 111 a svrit`N

kit eve rlul(,IIts, flit , load \\ • .t1, 111% rca1,rti and both frirlimi fort(, :Intl Atiger

l,t`ah 1111t,111,1t1(,1, for 111101 , 1110 111k , 1111 t i red Tilt l't`.11its t,htaillt`ti itrt` pre -

;lentetl ill 1' 1p; 12•

Ait (,\anluu11 it , it ,11 1•'1 1; 1.' tntilral(,1, 111.11 the colicelliralitm tit k III kII'Ilit'

In tilt` Weal . 1'01111A '1 :kill( , Is a lunt'llklll tit load l'It i `rinr Ctult't,nlratIon

first till'least`s \\'llh load as tilt` tricl Ion coctIicIt`n( tic`: rt`a:'1(,1,. :\I1 tillli -

nitlnl surf:lct , t k l \'rrahr i1, at'ht(,\'rti at whit 11 1n,lnt lilt` 11 , 101011 Ctu`tttrit,nl

11, a1 ,1 1111111111t1111• l lvvollti till-, 1 1 , 1 1,'1 r1111.1%C Ck , \'t`1'arx h\' chlorine tit`

C I't`a g t`S anti (ill y tit`k 1'4 1 .11,t` IN at t 01111 1 a1i1t`ti Iw :1 1't1l'1't`1,1 1011tillh'. tilt' I't1:,1,t`

Ill I I'I1't lt,lt cot'll lt will

Vvey 1ltllc \\'t,ar t,rrur1, 1t ► tilt , 1,urtact's 1 ► r(,1,c111t`t1 Ill VIF, 1 . Theit;

^'ullit,nt1 , • tin tit chlt,rlllc :It flit , surface 1:: il l lt,rr And ^tin1,t,tluc`nll:ill\

r0l • r0tiIt'll tlr t't,l VO.1 i\'t` \\'0:11' 1.14 nt,( 111\'kil\'ed

:\ rt itltiillel'ill l l(, :Itlh , unl tit ti;tl:t 111 Ili(, Itic`1'alurt` tlt,alttl l \1'iill a tlrtll'11-

tIt'll of lul l ricaltile. s ict lc1, (0 solid sul r lak'c1, art, the vc.-mlt tit stat W ex-

1it,surr:; Mort , data tin flit` tl\'n: '.1111 tntc`I'lat'tal ctt(,i tS till ati'.alrl+lltln

:I1'c` ncctit,tl.

I.11 UI1 I SOI.11) IN l'i•'IZACTIONS

Ill IIII + I I, .111, I ll `\: • It,iliti the iltluitl it) stink: Interface alltl Ill(, Chenitc.11

lateraltltln:: that I.Ikt , plate at OW Ilklultl (0 ."Ild 111(rrtat't, Al't` (,\Irc`ntch,

IIllporlunl AS :I t ,,tt .c`tlut`tlt (, k , , 11:;Idt'l - al , lc r es tart it has Ilc`rn r\jIvIldcki

tit Ihr1,t lulcractlow; 11hr ati:: k +rlilloll tit Iltitlltia and the

cltc`t Is tit It\ kiroca:'lnnl t 11.1111 icllrtit. link I1-111:ll ;:t'0u1i.-;, t,lt' . \\:`1't` t`\-

jilt, red haclk :lt file I I MV tit 11.1 rt1\

.\11 area \\'11 t It 11:1 '.: I % cV:l 111`11Ic't It'd In . tilt` f 1'11 , , IM 1.1st 1 1, [lit , effect

tit surlart` IItlulti ., tin tilt , mot hanical 1whavl0l , tit SOIttis i'ht, material.

::t Will 1"l is \(,r\ ianllllar \\ fill Owse click 11, For t,\.lull , lc`, 1,t1111c Sur-

fact , 1 ► Inl:; 1,t'kitl;lrt, ulet-11a111cal ^:tt'(,n 1 ;lhrntnl; tit sul'far(, lavers kit (lit,

lltl \cllllt` t,lht`l lit'odet t` t W t I MWnlu,; tit' Skitlrnlnl l'Ilc•r clt(,t t:+

tlllltil 111:1 ' it role 111 1'': 1wha\ 101 - tit IlICt'llalllt'N1 t't i1t pollt`Ilt" t11 tl'llh,lklt`,ll':11

ti\'sft`111:;

Ii

i;1

40

A

i

1' is•ur y 1.4 11111strates stil'lat'r ellticis In a l\ p al sll't`ss ,All - am !lilt

1':!111. \11111 ce1 , 1a111 Mill'tact' 111111~ ( t, I: . ti\lties) a tiurtact , met hallit All

tili't`Ilt;lht'i11111 ock kirs c alled (lit , i osctw t`tlect liec.luse it was first ob-

.q rr\'rti by 111111 In tilt' strrnl'.lhenlnl; tit ratilunl crystals fly its tixitlr.

In rtilll cast the Iirc'srnt'c 1 Of t ertatn Il(luttis '111 the surface of Solids p rt1-

tiut'r a sk i ttcllml . 0It`%'I Malt,' tit Ihest' Iitlultis .l re lilt) rIcatlls tr, l; ti It , it'

acid!. ^' i't'1111111tiel' tilist'n-titi (tits stlrtat t` stlllt'lllth t i ll 111x11\' stolid`; 111 :!

11111111wi. of ti111t`rt`nt lltlllltt` aria It is thet'ettirr called lilt` NoIllilliticr ettrct.

I•'Itnn Ihr "Irc'ss - StVAIIt citI-ves tit FI t ,. 1:1 It is a ppart''1 1 Ih:tt ^utltlt'r

chellll"tI . \' c.111 lntlut'lict` lilt , 111t't'hallit al lichAVItil' of sollds VIII11` such

as oxides ran slt'rnl;lht'n the 111a1c'rl:ll \0111t` certain lul i rlt'allng 1\ Tit's of

IIIn1` t':I11 mt mast , 1llasllt'ity. Such etlects :Ir y 11111 1011 ant alltl Should

lit'( Iii` ti\'t'l-loo od 111 :II1e1111 1 11111: Ii i ulltiel's(:tlltl 1111 1 1 - walt'ti S\'stt'111.1, These

t 1 11t`t'l:: al'e tit' lllt l ll^t!'.11t'ti In Fw, 1 .1 with ti.lta tl't i 111 11'it'llt i ll :Illti WC.IIl'

t` \1 1t' 1'1111!`111

1'he ti,Ita tit Fig. 1 .1 art` from Irlt'tlt l n anti wt l .tr t'\11t`r1111ents In \011!•11

!lints \\ere rxamlnt'ti till llle surl:lt'r til tilt' lillsal it l t ► f i ll 111:1nr tit a sln^.Iv

Crystal of Attic. "!'lint' surtace sl:llt's tit lilt , TIM' \veer slutilt'ti, :1 cball

surtacr ►;eneralrtl 11\' clea\'al;r 111 Iltluiti illtrt gels, an t 1 \1!11: rt1 surlarr

and :l t le.I\t't1 ill-fact, COW it tilt n9 .1 la\t'r tit :1 pwrt rnt 1101- lt'hlt l ric acid

111 1\'ate l' 1 ht' clt`:1ved t'Ieall -.itrt:lk - r I\ kill lit l it' allalt l :;t l l1 . Ii i Ill!' 11,,vIII.I

^llrlatt' t't t' Ia, the ti\Itil.'t`ti stll'tat't`, -.1 rclw.t lit , 11111! , I1 \ • lilt' Noscov

t'ltt't I Witt Ill y .It iit "It111t 1 11 W0111ti Ix , a 111.1 lilt e - (atIt'll t i t Hit' 1^t'11llhit'I'

effect of 1''Ia;

!'ht' Irtt'lltin ctlrtllt'It'nt a• 11 tunt'ltti11 tit it lati in t^ ig 1 .1 Is I;tt':Itt'r

ti l t' tilt' ! ► \till: t 1 t1 s tiOACt , !hall It Is ti l l' tilt` surtat a 111111'14 alto wit 11 Illt` lit- id

iIIIll I*ht'iie It`s1111`. are as ill it :hl be .1 lit I% , II:ltt'ti 1 11 1 t':ttlst'. 111 it IWI Um' . lllt'

avid laver is a I til l r1calil Cht , 1111"al neat fain•, \\ 1'11 the surtact , le:uls to

(lit , tt i r111a i 1011 tit : [lit t llltlrltle.

lit` \Veit!' ll'at - l. \\ loth~ :ti't' 1 1 1't`st 1 llteti Ill VI !,. 1 . 1 tt i r .111 llll't't' Nt11'1:1t'e

i-I:Itt'S 11it'st' and lilt' 111i!!till 1'eNUlls \\t'i't' t'l i l:tlllt`ti '•. 1 111 t` \'t`:11'ti a}.t i h \'

tilt , 1ireS1 1 111 anthtit' t 1'he greatest anit iunl tit stlr11ACt , tit'ttlrmatioll ot'-

Bill*I't'ti 1\' lIll (ilt` at , id .rojtltloll, 111!` ^lll i ;.I:111t t' \v11lt'ii 1 1 1'1 1t11it ' t's sllrlat e

stiflt'ntnl; lltel l lntirr ctfct'1).

i

I

i1i i

EL

16

Tilt` dean. "as cleaved" costal surface prodl ce(i llltel•Ille(liate

anlolilits of surface deforlllation With tilt` least surface deformation takingplact , ill tit` presence of tilt , surface oxide. Thin, surface clu'll1islry isimportant in the mechanical behavior of t rlbological surfaces.

The mode of deformation as well as tilt , anlourit is affected by the

I presence or absence of surface films. In Fig. 15 the zinc single crystalsurfaces al-v t xamint d after sliding experiments with hexadecativ pre se nt

on tilt , surface. Figure 15 .O is for the surfact , without an oxidt , layerpreformed and Fig. 15(b) is tilt , war track gent`rated in tilt , presence ofan oxide him Without (lit` oxide, def( • rnlation is completely plastic via

slip When the oxide is present deformation twinning- is observed as

shoWn in the pllotonlicrograph of Fig. 15(b). A "ladder" of deformation

iwins is detected in tie wear track of Fig. 15(b) • These twins are com-

pletely absent in Fig. 15(a).

i

SOLID-SOLID INTERFACE

Tilt` sur'fact, t'lu`nlisil' V anti bondln,, across an interface for two solids,

in contact is t'xtl't`lllt`ly important ill undt`i-standin ,_- lilt` adhesion. friction

and weai - behavior of materials. With nivials and alloys. (lit , materials

which have recelved tilt' g1 • cates1 attentloll W1111 respect to chemistry.

V.11 , 101Is propertles have been lound to atfet t Iheir surface chemical ac-

II\'lty. Shell propt`riws include: (I) cr y stal structure; ( 2 ) crystal ori-

entation: (3) st`lld slllllblllly; (4) slll'1:11't` St"'Tt`,;atit l il; (5) surtIct` ellt`1•gy"

and tt;) d bond character.

tilrlll'llll't` :liltt Ol'1l`I1lall01l

`l'It' 111.11111t`1 , Ill WilIt'll Illt`t:llllc atoms bond tO 0110 M10tht`r to (lit , bulk

will tieter(lllmc. the cr\ , stal structure that results interfacial bondin" . of

hexagonal metals l ,eneraliv results in slront, bonding :it tilt` Interface but

ease shear along, basal planes which allows for limited growth In the real

contact area. low adhesive bolidlil, forces (l)ecaust` of CaSV separation^^ tl -alum:: basal plant , $) and low friction..

Crystallographic orientations at metal surfaces are extrvlilt' inn- I

1x11t:1nl ill surface chemistry and in solid to solid interactions. (it`licr-

ally ill any crystal system (e. l;.. C. P. H. , F. C. C, or D.C.C. ) tilt , high

atomic density planes are tilt , low surface clivi-p• planes and corre- 1

i

sl1t 1 101111'. 1y the le;1s; cherllically active. Thus. when { 111 ; plant's art,

hrtnl l ;ht into r'011t.lt • t for fare centered cultic metals the adhesive bonding

is less than Midi two i 1 lt) ; plane,, are Ilrtu l lit into contact. Likvwise.

\\itII It, \apI11.11 metal•, I It' IIdin l : is weaker IIt'( wet , n ; 1)1)1)1 } planes than it

is 1 1 OW( I en { 1t)101 plane., l'his oulentatioll liltluenres hollding effects,

atthesioll, friction.. and atihesi\'e We:111 1 . 51,

The foregoing discussion applies it ) llletals in dean solid state coll-

tavt. When a metal is adsol-bed till a solid surface of the same metal the

s:1111e MW characteristics emst. 1'11 ►1F, for t`\.1111pIt`, tilt` bondini:

t,nen"y too , tun l :stell a0:1t0ills is less on the 111111 plant , than it is for the

1111 ) 111:1111•. 60-61 Ill lief, tit) it is 121 Leal I , .1toill - I for the 1111 1) plclnt,

anti 1:: 1 kcal t; atom -1 for the tit l ) plai1t,. S1m11a1' obser vat it'll s have

l,rr ► 1 lnatit , Ill atihesi011 anti friction studies with tun l ;Sten; — that is. ad-

Ilt,si\'t` IVIldilll; (alld t,0l'1't`sp011ti1111'.Iy frietiolO ar y It • ss t i ll (ilt` 1110 ) thallM

1111 tilt' less dt'llst` .110111ir plaint`s.

Solid Solubility

1'llrtluI 11 the Vc.11s :1 11111111 WI . tit altelllpts have Keen math tt l rt l rre-

latt , the solid sollibilit y of metals (llulk) with atihesloil. friction and wear

Of metal surfaces, t13-t1 t AkiI it , sIoII. f r i v I I o I I aII, IdIi `sI\ v \vva1 . .11'1` 1.11'1"'-

1}' tht, result of sill - fact , propertit's :tlld rt l llsl`tluentl\ surtact` l'ht'lllt`tl'\

rathcr than Hulk cht,lulsti-v shtnll,i lie C011sitirreti Ample e\'idenct, exists

tt 1 t,sta1 1 1ish ' tlltt • rent'es 111 , Nt,t,1 .:urfact , .111d 1 1 1111. 1 1 0111111,; t it, 11 1 1' t`\arllllle,

• tilssinlllar 111elals.

Win. copivi . . . 11111 ;anti .11e voluillt,tel y lnsolkiNt , in hilw.stell. 11`1 1 \ e-

slllte tills I'll It .. ills, I lui l lIIty lht,st' V It' MCIll s Ih l llti VV 1W stl'oni ly to tilt` sllr-

fact , of lun:;stell. With till, them , are I\\tl 11111tiln:; e11et • 1;ies, a \Veakel' tine

comitlral l le to lilt , bindill ! '. t,nt,ro. in dull. tin and .1 second erlt,rgy which

18

is much stronger and occurs in the first monolayer of tin where each tinatone contacts four tungsten atoms. 60 This bond is unusually strong.With gold to tungsten. the bond is intermelallic in nature at the inter-face. 70 Copper alloys with the tungsten surface. 71 j

Adhesion experiments in the field ion niicro:cope have revealedst.i•ong adhesive bonding and transfer of gold to tungsten with surfacecoiiipocuid formation. 72 Adhesion and tran-fer of copper to tungstenhas been observed in sliding friction experiments. 59

IThe foregoing caveat against using bulk properties to predict sur-

face behavior not only applies to metal-nietal contacts but to metalscontacting nunmetals as wall. For example, gold has extremely limitedsolid solubilit y in both silicon and germanium Mess than 10 -5 atomicpercent). fi8 Despite this very Billeted solubility, gold bonds very strong-ly to silicon and germanium in adhesion experiments. ?3

Figure 16 is a photomicrograph of a silicon (111) surface after ad-hesive contact with gold. Heavy transfer of gold to the silicon is ob-served. The amount of transfer is greater than is frequently seen formetals in contact with other metals where complete solid solubilityexists. 59 The gold cohesive bonds were weaker than the gold to siliconinterfacial adhesive hands, thus resulting in I racture in the gold.

Strom interfacial bonding was also observed (Ref. 73) for gold togermanium. Separation of the adhesive junction. however. fractureoccurred in the germanium rather than in the gold. Tit- cohesive bind-ing energies of gold and gernianiuin are nearl y equal. Thus, where theinterfacial binding is stronger than the cohesive binding in the elementsfracture can occur in either. In the studies, of Ref 73, it. take place inthe gei-mamum. The cohesive binding energy of silicon, however, is 1stronger than gold and consequently, fracture occurs in the gold for thisparticular couple.

The foregoing discussion indicates the importance of avoiding theuse of bulk properttes to predict surface behavior. On the basis of thesolid solubility theory, eery little adhesion and transfer should occurfor the particular couples discussed yet the opposite result is observed.Conversely, beryllium is soluble in cobalt yet very little adhesive trans-fer is observed.

1 11

V'l It , nre IIoIidinl^

The importance of surface sel;rel;uti: 1 and surface enet• 1;^• in solid

slate contacts has already ht,en discussed. The role of , d videlice bolid

character of metals tilt himetallic adhesion and friction can lie useful in

iu•t,dicl1111; friction coefficients for Various metals in contact. 7.1 'Phis

concept gives ;ill of llle relative amount of electron rnergry

available at a tree surfarr for bonding based tilt that which is committed

to rt,hesive bondilit; within tilt • uletul itaelt. Rert,ntly. tilt , concept has

keen .111111 led to 1110.11 it, nonnlrtallic hondln', ad it's Ioil. and traction of

metal lu noc-metal couples. 5

SU11NIARY

A critical review of flit, chemtstry of surfaces indicate~ that much

oC tilt , intrrl ► rel:alion of flit , data I;rnrratrd In the pusl nlav not. be suslx^ct

hel • allsl` oC lnatit'tlualt' Characterization of the surfaces. Analytical tools

" are lit,w av;ail.1111t , to assist In tills charavlei• i at ton They have alrt,ady

revt,aled that m aliv Illetal sul'fat'es tit, nt ► t consist tit' nlelallic atolil` but

rather atoms of hulk im u1rltit's which diffuse to the surtart , and ron-

(ammate it. It is nt)a' :1ppurent that flit , wide disparity tit dit , values oft

SUr act , vnergy may lit , a rostllt of these snrlace conl:aminates. TlIvseV

stIrIate tllll -Is al'e 11111 ► t ► rIaII lIt , t'atltit` VV ( I ll tractitIIIs of :a 1110110111\'el' r ;111

ailed adhc:ion :and f1•u'tttnl.

Bulk alloy chemistry can not lit, extended It) the surtace because

t'quIhbriuIll sel;rel .1holl will result in a dlfft,rent surface ailov rherllistry.

'1'ht , adst,rptIon tit lubricating spectes tilt flit , surface of solids is highly

six, cific and not only dependent upon chemistry but orientation as well.

Mechanical surfact , activity influences the adsorption process ill some

llislanres and riot haniral prowl-ties, such as plastic deformation ;ire

lllered by flit , presence of adsol-bates.

SI1*0111: interfacial bt,ndlm, twtween dissimilar materials which:are

insoluble ill hulk orrtlr• s :anti in some 1nsl:anct's tilt , bondln l ; ;anti mate-

rial is (,'Gale ► ' Man st,t,n with those lllalerials whieh

.0.^

20

are completely soluble, one in the other. Such observations argue k

against the use of bulk properties to predict surface behavior.Adhesion, friction, wear and lubr ication are highly dependent upon

surface chemistry and, therefore, surface rather than bulk behaviorshould be used in studying mechanisms which are clearly surface re-lated. Assuming that bulk properties are also surface properties canbe very misleading.

REFERENCES

1. Hardy. W. B. , Collected Papers, The University Press, Cam-bridge, Ent;. , 1936. See papers no. 37(1919), no. 39(1920),no. 40(1920), no. 41(1922), no. 42(1922), no. 43(1923), no.

44(1925), no. 46(1925), no. 50(1926), and no. 57(1928).

2. Adamson, A. W. , Physical Chemistry of Surfaces, 2nd. Edition,Interscience Publishers, New York, 1967.

3. Hayward. D. O. and Trapnell, B. M. W. , Chemisorption, 2nd.Edition, Butterworth, Washington, 1964.

4. Little, L. H. , "Infrared Spectra of Surface Species," Chemisorp-tion and Reactions oil Film. edited by J. R. Anderson,vol. 1, Academic Press, London and New York, 1971, Chapter 6.

p. 489-531.

5. Bowden, F. P. and Tabor, D., The Friction and Lubrication ofSolids. Oxford Press, London, 1950.

6. Forbes, E. S. and Raid, A. J. D., "Liquid Please Adsorption/ 4P

Reactiun Studies of 01-;;11110-Sulfur' Compounds and Their Load-Carrving Mechanism," ASLE Transactions, vol. 16, no. 1,Jan. 1973, pp. 50-60.

7. Barber, R. I., "The Preparation of Some Phosphorus Compoundsand Their Comparison as Load-Carrying Additives by the Four-Ball Machine," ASLE Transactions. vol. 19. no. 4, Oct. 1976,

Ply • 319-328.

+ N

^. Jam_. I

21

8. Cottington, R. L. and Ravner, H. , "Interactions in NeopentylPolyol Ester-Tricresyl Phosphate-Iron System at 500 F," ASLETransactions, vol. 12, no. 4, Oct. 1969, pp. 280-286.

9. Sakura, T. and Sato, K. , "Study of Corrosivity and Correlation• between Chemical Reactivity and Load-Carrying Capacity of Oils

Containing Extreme Pressure Agents," ASLE Transactions,vol. 9, no. 1, Jan. 1966, pp. 77-87.

10. Prutton, C. F., Turnbull, D., and Dloughy, G., "Mechanism ofAction of Organic Chlorine and Sulfur Compounds in Extreme-Pressure Lubrication," Journal of the Institute of Petroleum,London, vol. 32, no. 266, Feb. 1946, pp. 90-118.

11. Hayward, D. O. , "Gas Adsorption," Chemisorption and Reactionson Metallic Films, edited by J. R. Anderson, vol. 1, AcademicPress, London and New York, 1971, Chapter 4, p. 229.

12. Simmons, G. W. and Dwyer, D. J. , "A LEED-AES Study of theInitial Stages of Oxidation of Fe(001)," Surface Science, vol. 48,1975, pp. 373-392.

13. Sewell, P. B. , Mitchell, D. F., and Cohen, M., "Early Stages ofOxidation of Fe(001) Observed By Electron Diffraction and X-rayEmission," Surface Science, vol. 33, 1972, pp. 535 -552.

14. Brucker, C. F. and Rhodin, T. N. , "Oxygen Chemisorption andReaction on a-Fe(100) Using Photoemission and Low-EnergyElectron Diffraction," Surface Science, vol. 57, 197x', pp. 523-539.

15. Wawra, H. H. , "Temperatur-und DruckabhNngegkait der freienOberflachenenergie von festem and flUssigem KC 1 zwischen o o Kand 1400° K," Radex Rundschaw, no. 5, Dec. 1972, pp. 351-364.

16. Tyson, W. R. , "Estimation of Surface Energies from Phonon Fre-quencies for BCC and FCC Metals," Journal of Applied Physics,vol. 47, no. 2, Feb. 1976, pp. 459-465.

j ^ z

• 1

2 2

17. Avet• hach. It. L. , Some 1'hll • sical Aspects of Fracture," fracture.

An Advanced 'Treatise, vol. 1: Alirroscopic and Macroscopic F'ut1-

dantenials, edited by N. Liellowltx, Academic Press, New York,

11168, Chanter 7. pp 4.11-472.

18. hIykura. 11. , "The Vartation of tilt' Surface Tension of Nickel With

Cry stallographic Urtentalion," Ac ta Alet allu^tca. vol. 1.1 , no. 6,

. ] title 1911 1, 111). 570-576-

19. Sundquist. B. E. , "A Direct Determination of the Anisotropy of the

Surface Fier of Solid Liold, Silver. Copper, Nickel, and

Alpha and Gamma Iron." Arta Moallut Ica, vol. 12. no 1,

Jan. 1964, pp. 67 •86.

20. Kumar, R. and Grenl ra, Il. F'.. "tiurlace Enet •p• Anisotropy of

lrltltlltll," Surface Science. vol. 5o , 1 9 75, 1111. 399-40 131.

21. Winterllottom, W. L. and Ciostein. N. A. , "Detet • nlination of the

Anisot ropy of Surface l;ner gy of 'Nletals - I1: I•'XIW I'tlllt`lltal Y-- Plot

of G-old," Acta Metallurgica, v ol. 1 .1, no. 1966. pp. 111 .11-

105 ) .

Rotvrts, R. W. , "Reactions of Saturated 11%drocarbons xvith Clean

Rhodium Films," Annals of New York Academy of Science. vol.

101 . 1963. A rt 3, pp. 766-777.

23. Rabillowict, F.. friction and Wear of Malertals, Johii '%%'ilea • & Sells,

Inc. , Nov York. 1965. -T ^----_-

__--

-1. 1'hrlich, V. , "Atomisttcs of Nletal Surfaces," Sut•face Phenomena

of Metals, Sol'letv fol . Chemical Monograph no. 28. 11.168,

pp. 13-38.

25. IZuch1,-V. D- IL , "Adsorp(ion tit' Fthylene Oxide anti Vinyl Chloride

on as 'roll (1111) Surface and Effect of These Films on Adhesion."

NASA UN 11-5:19'. 1 , 1970.

26. N111ller, A. and Drechsler, M.. "lane 1lessunt , Der Anisotropie

Del . (ll^ert 15t'henener a Voll Iteinenl Wolfram 111it Deal

fildlonen III lkroskoll." Surface Science% . vol Is, 1969. pp. 471-4911.

4JI

^.J

in,

a---4-.

23

27. Brenner. S. S., "The Thermal Rearrangement of Field-EvaporatedIrdium Surfaces," Surface S( ience, vol. 2. 1964, pp. 496-508.

28. Halling. I. , Introduction to Tribolog, Wykeham Publications.London, 1976.

29. Cameron, A. , Princ iples of Lubricanon, Longmans Green and Co.Ltd.. London, 1966.

30. Akhmatov, A. S.. Molecular Plivsics of Boundary Friction. trans-lated from the Russian by N. Kaner. Israel Program for Scien-tific Translaiions. Jerusalem, 1966.

31. Ralph, B.. "Experimen(al Studies of Alloys with Field Io,i Micro-scope," Field Ion Microscopy. edited by J. J. Hren and S.Rant,'mnathan, Phenum Press. 1968. Chapter 10, pl)• 157-170.

32. Shell, C. A. and Riviere, .1. C.. "Quantitative Auger Spectros-copic Analysis of Segregation of Phosphorus in Iron," SurfaceScience. vol. 40. 1973. pp 1.19-156.

33. Sickatus. E. N.. "Sultur aril Carl ►kin 01i the (110) Surface of Nickel,"L` Surface Science, vol. 1:), 19711, pp. 181-1N7.

34. Kunimori. K.. KaNvai, T.. Kondow. T.. Ovishi, T.. and Tamara.K.. "Segiregation of Sulfur on a MOIN • t ►.ienuni Surface Studied byAuger Electron Spectroscopy," Surface Science. % c ol. 46. 1974.

pp. 567-576.

35. Isett. L. C. :-nd Blakely. J. M.. "Binding Enemies of Carbon toNi(100) from EQuilil ► riuril Segregation Studies." Surface Science.Vol. 47, 1 005. pp. 645-649.

36. Powell. G. L.. Clausing. R. E. , and NICL4111-e, G. E., "SodiumSegreganon Unto a Lithium Metal Surtace," Surface Science,vol. 49, 1975. pp. 310-:31-1.

37. Wandelt. K- and Ertl. G . "I-1ectron Spectroscopic Studies of theOxidation of Fe/Ni Alloys," Surface Science. vol. 55, 1976,

pp. 403-4 12

is

n

2.1

313. Wood. 11. J . and \Vise,I1.. "Surface Composition of Pd Au and

Pd-Ag Catal\ s ► s l►} Auger Elect ron 81wet roscopy, "" Surface SO -

ence, vol. 52, 1975, pp. 1511-160.

39. 111cnavid. .1. M. and Fain. S. C.. J r.. "Segregation at Cu-Au Alloy

Surfaces. " Surface Science, vol. 52. 1975, pp. It; 1-173.

•10. Yanl:tshina. T., Watanabe, K.. Y ukuda. Y.. and 1lashil►a. Nt. .

"Observation of Surfaco Composition of Copper-Nickel Alloy by

Au;ar Spectra in tilt, Lower Fnerp- Region (at A1•ollnd 100 CV)."

Surface Science. vol. 50. 1975. lilt. 591-596.

41. Ovvrbury. S. 11. and Somor)ai. G. A., 1e The Surface Composition

of lilt, Silver-Gold System by Au t;t,r Electron Spectroscopy."

Surface Science. 1:176, vol. 55. pp. 209-2211.

42. Ferrante. J. and Buckley. D. N. , "Auger Electron Spectroscopy

Stud}' of Surface Se:;re gation in Ct)pprr-Aluminum Alloy's." NASA

TN U-6095, 1970.

43. Ferrante. J. and Buckley, D. H.. "A lit,viety Of Surface Segregation.

Adhesion and Friction Studies Performed on Copper-Alunllllltlll,

Copper-Tin. and 1i-on- :11u111munl Alloys." ASLE Transactions.

vol. 15, no. 1. J.m. 1 9 72. 1 1 11. I8-214.

44. Rivierv. J. C. , "Auger Spectroscopy of Osmium. and tilt, Sep,ri . ga-

hon of Matinunl to the Osmium Surface." Jour. Less Common

lIvt als, vol. 38. 119 71 4. pp. 193- 21111.

45. Ferrante. .1.. "Auger p lectron Spectroscopy Stud y of Surface Set:-

rt, o"ation In tilt , Binary Alloys Cop1wr -1 Atomic Percent lneilum.

Copper-2 Atomic Percent Tin and lron-C. 55 Atomic Percent

Silicon." NASA `1'N U-6982, 1973.

46. Vucklt,v, D. 111 . "Influence of AI111111n11111 on 1" t • ictioll and WC.11- of

lrm1-Alunitnunl A11ovs Dry and Lullrtcatt,d,"" NASA TN h-6359,

19-11.

25V

47. Wheeler. 1) R. , "Effet t of Adsorl ►ed Chlorine and Oxygen (:i. the

Shear Strength of Iron and Copper . 1 Lai( t tons. " Journal of Applied

Physics. vol 47, no. 3. Afar 1976, pp. 1123-1130

48 Young, D. A1. and Crowell, A. D. , I'livsical Adsorption of Gases.

E;utterwurths, «'ashinglon 1962i

49. H-m-ward, D. O and Trapnell, B. A1. W. , Chemisorption, 2nd.

edition, Dutivi, worths. Wasimigion. 1964.

50. Chesters, Al A - and Sonlortai. G. A The Chemisorpt toil of

Oxygen. Water, and Selectcd lk-drorartwms oil the ;111) and

a Stepped Gold Surfaces. - Surlace S(ience, vol. 52. 1975, pp. 2'.-28.

51 Schrader, A'I. E. , Auger 1:1e( f I , ,) ii S, pet iroscopIc Study of Che III i -

sorplion of Oxy-,cn to 'I1 I Oriented Gold Surfaces," Journal of

Colloid and Interface Science, vol. 59, no 3, May 1977. pp. 456-

4 60 .

52. I3arford, B. D. and live. R. R.. ''Adsorption and Flash Decollipo-

sition of Eth y lene un Tungsten Single-Cr}• stal Faces," Journal of

Vacuum Science and Techno lo , vol. 9, no. 2. 1972, pp. 673-677.

53. Yates. J. T.. and AEadey. T. E., "The Ad`orl ► tu► n of Methane by

Tutiosten X106) and Tungsten (111). ' Journal of Val_uulll SCiellce

and Te(hn ► 11 ► g1 , t• ol 9. nu. 2. 1972. p. 672.

54. Grabkc. H. .1 . 1'auloschke, W. , G. , and Viethaus, H.

"l:qullil ► riunl Surface Segregation of Dissolved Nonmetal Atollls

0II lron(1001 Faces." Surtate Science, vol 63, 1977. pp. .377 -389.

55. Gilman, J. J. , ''l'he Mechanism of Surface Effects in Crystal Plas-

itcitv"' Philosui ►hical liagazine. vol 6 (eighth serics), no. 61.

J:II1. 1961. pp. 159-161.

56. Roscoe, R.. ''The Plastic Dclormati ►► n of Cadmium Single -Crystals, ►Philosophical Magazine. vol. 21, 1936, pp. 399-406.

26

57. Likhtman, V. I. , Rebinder. P. A. , and Karpenko, G. V.. Effect ofSurface-Active Media on the Deformation of Metals, ChemicalPublishing Co., New York (1960).

58. Buckley, D. H.. "Effect of Surface Films on Deformation of Zinc 3Single-Crystal Surface During Slidin T " ASLE Transactions vol. 1415, no. 2, April 1972, pp. 96-102•

59. Buckley, D. H. , "The Influence of Crystal Structure, Orientationand Solubility or the Adlesion and Sliding of Various Metal SingleCrystals in Vacuum 00 -11 Torr)," Adhesion or Cold Welding ofMaterials in Space Environments, ASTM Special Technical Pub-licatiun, no. 431, 1967, pp. 248-259.

60. Ehrlich, G. , and Kirk, C. F., "Binding and Field Desorption ofIndividual Tungsten Atoms." Journal of Chemical Physics. vol.48, no. 4, Feb. 15, 1968, pp. 1465-1480.

l61. Plummer, E. W. and Rhodin, T. N. , "Atomic Binding of Transi-

tion Metals On Clean Single-Crystal Tungsten Surface," Journal{ of Chemical Phvsics, vol. 49, no. 8. Oct. 15, 1968, pp. 3479-{ 3496.

62. Buckley, D. H. , "Influence of Chemtsorbed Films of Various Gases ion Adhesion and Friction of Tungsten." Journal of Applied Physics,vol. 39, no. 9. Aug. 1968, pp. 4224-4233.

63. Keller, D. V., "Adhesion Between Solid Nietals." Wear. vol. 6,1963, pp. 353-365.

64. Sikorski. M. E. , "The Adhesion of Metals and Factors that Influenceit," Wear, vol. 7, 1964, pp. 144-162.

65. Roach. A. E. , Goodzeit, C. L. , and Hunnicutt. R. P.. "ScoringCharacteristics of Thirty-Fight Different Flemental Metals in HighSpeed Sliding Contact with Steel." Transactions of the ASNIF, vol.78. no. 11. Nov. 1956, pp. 1659-1667.

27

66. Ernst, H. and Merchant, M. E. , `'Chip Formation, Friction, andFinish," The Cincinnati Milling Machine Co. , 1940. 1

67. Rabinowicz, E. , "The Dependence of the Adesive Wear Coefficienton the Surface Energy of Adhesion," Wear of Materials -1977 , editedby S. K. Rhee, K. C. Ludema, and W. A. Glasser, American Soci-ety of Mechanical Engineers, Nev; York, 1977, pp. 36-40.

68. Elliott, R. P. , Constitution of Binary Alloys, First Supplement,

McGraw-Hill Book Company, New York, 1965.

69. Nishikawa, O. and Saadat, A. R., "Field Emission and Field IonMicroscope Study of Ga, In and Sn on W: Structure, Work Function,Diffusion and Binding Energy," S urface Science, vol. 60, 1976,pp. 301- 324.

70. Jones, J. P. , "Adsorption of Gold on Tungsten," Surface Phenome -non of Metals , Society of Chemical Industry Monograph, No. 28,London, 1968, pp. 263-290.

71. Taylor, N. J. , "A LEED Study of the Epitoxial Growth of Copper onthe (110) Surface of Tungsten," Surf: c.+ Science, vol. 4, 1966,pp. 161-194.

72. Brainard, W. A. and Buckley, D. H. , "Preliminary Studies by FieldIon Microscopy of Adhesion of Platinum and Gold to Tungsten andIridium," NASA TN D-6492, 1971.

73. Buckley, D. H. and Brainard, W. A. , "Adhesion and Friction of Ironand Gold in Contact with Elemental Semiconductors," NASA TND-8394, 1977.

74. Buckley, D. H. , "The Metal-to-Metal Interface and its Eiiect onAdhesion and Friction," Journal of Colioid and Interface Chemistry,vol. 58, no. 1, Jan. 1977, pp. 36-5^.

Miyoshi, K. and Buckley, D. H. , "Friction and Wear of Single-Crystal and Polycrystalline Manganese-Zinc Ferrite in Contactwith Various Metals," NASA TN (E-9168) (1977).

.R

75

Iti s

TAM A-', t. - VARIATION IN VALUES OF 11VTORTI''D

SURFACE FN1'AWIFS+

It , IIIt'll I'iaL.v t`I It, I'i;^', t`1^ ►;H^('lll^ Temp.

t,lI

lll;t\ 1aill

l^tl 41-115, 11 50 273

No. 2.1 o Wo -273

:V1 .1540 5110 -273

1.' t , 5267 1980 -273

Tl ?730 •13 7:1

C i- W61 1515 -273

W o4 l ll :1370

'11. 11. t1';tlt 1'.t, li.ttit , \ 11 11. , •1(1973)(;02,

I ,

I

TABLE II. - STRUCTURAL DEPENDENCE OF SURFACE ENERGY

ON FACE -CENTRED CU BIC METALS

Plane Sundquist 19 Winterbottom & Mykura18

Gjosteill21

Au, Aj_CLI,Ni Au Ni

(111) 1.00 1.00 1.00

(100) 1. 04 7 1.072 0.95

(311) 1. 119 1. 065 1.00

(110) 1. 15 1. 017 1.01

(210) 1, it; 1.055 1.00

TABLE I1I. - MAXIMUM COVERAGE OF N1INOR CONSTITUENT

ON ALLOY SU 1t F ACFS

Alloy Ratio of surfaL'e Atomic sire from lattice

Coll ee III rat iIII nearest neio-hllor

to hulk diStanre

l'011MIlt 1':c! ioll

Cu -1 a/o Al 6. 5 Cu -2. 556 An st ronl -f. t • . c.

Cu -5 a/o Al .1. 5 :1l -2. 1162 -f. r. c.

Cu -10 a,'o Al 3. 1 Sn -3. 022 -•I'et ra ;"orlal

Cu - l it '0 Sn 15. 0 " 2 Fe-2. 481 -tI. c. e.

Fe-1 0 :1 "o -^l 8.0

Note: Atomic sire -ivvs a rou-11 nleasilre of the amount that the

:1llov atom strains the parcilt lattice.

1

T:1t 1 1,F' IV 1NF•l+l1F'NCV OF V ANIOUS t'111 • 'AIIS01111F'1) t;:1S1•'S ON

FRIC TION t'lll•'F'IACIF'N •1' IVNGSTF'N IN 1'AC1tItA1+

IT-

t • hrmist+rl+t • .1 t'++rflit•1r11t alt trit titan

fzAS For (110) For {^1(1) For (1(10)p1:a11^+ 1tl:attr' plane

\++nt 1, ati 1, ;1 11 .3, 111)

ll j 1, :t:t 1, yY 1, tit,

02 0, 0 5 1,00 1, till

001 1, 1:+ 1, 1h 1, ltl

Itttirr ^:{trrtlltrn, tlt t t 11 .1t+ +tttt,• { p lant• ttt tultt;r:tt • it; It^a+{,

.`Il t;; ^11+ i1n^; \'t'tt4't{\'^ I t l t l t l ,'111 tit`+', lt'nl1 + t't'.111t1't',

?Il tt C ., 1+ressurt+,t

10' t'orr

I

TAI'Z 1 I' V', - INVI VFNCF tit •' 11ONl t SA1'1'R: VION 01' t'lll MISON0,1 t\

(IAA 'S ON I'l%IC Vil1N 1 • l11 •'l • 'F'lt'lV% 1' 0V ITNk;,; V VN IN VACI'VN1•

C lit , III Is, t rt +r+{ 1'ttrttwwill ttt (Hot it'll>; :I's

Vol, 0 1 0 , 1•'.+r 1:` 10) For k 1 00)

1+iant • plant, 1 +l.nit'

F'Iltaltr ;ll.;c'-l`Ily) 1. 111 1. 111

Vth\ Irltr tll.,t • 019

1 11, 11;i tt, H;^ I, : tt

\, t't\ It nt tilt' 11t' 1 ll• .l1 t ► . t+t^ 1, Itt1

{ .;+ 111lit+ r1' { t', • itttt It, t, It t {tlaltt ttl !ul ti^trlt;,` {load , all };, ^ It ilt}; t t' t ,•t { 1+

ttt , 0. 001 om sec ; tt • III I , % , V.1t0IT, :1 1" t'; 1 ttawl+lt'ttt pre 'aski I . c , ltt

Vk+l•1•,

1 a

ta) Before sputter cleaning.

ibi After 3putler cleaning.

NNMT

w

ORIGIN AI: PAGE Ig

OF PWR QUA "T"

Fiqurp t. - Auger spectra for an iron sunac p before and after sputter clpanino.

Hi qh purity iron vacuum tone refined.

1.

t'i

ORIGINAL PAGE IS

OF YOUR QUALITY

1al CARBON CONTAMINANTS. do ARGON BOMBARDED.

tcl CLLAN NURiACE 1110 VI.

Figure 2. - LEED patterns of iron 10111 surface with carbon present and after arson iron bom-bardment.

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500ELECTRON ENERGY, eV

Figure 3. - Auger spectrometer trace of iron10111 surface with carbonpresent on surface.

n

}

0

$

CI

§]

^

n

^ k} 5

Q/

^

^/

k^4^^f

i

^

\R ^..

^\) (gf

^& a_

§%^kf &a

oOa

^ k\ ^' }

^s$ \^/ K am | /

a ngiW,cma

,

^

a a^

^t]n ®t¥r

ee / ƒ s_-

k 2 ^\ ^!§ ^

rm mQ®

c

z

1.

3L

-= i

PAGE IS4.5F- OF POUR QUALITY

4.0

3. 5

rIRON COMPLETE SEIZUREz0 3.0GU_

2.50zz

2.0

t1.5

1.0t IRON

5 PERCENT

S UCON-IRON

010-10 10-8 10-6 10-4 10-2 100 102 104

OXYGEN EXPOSURE, torr-sec

Figure 7. - Coefficient of friction for iron and ^ percent silicon-

iron as function of oxygen exposure. Sliding velocity, 0.001centimeter per second; ambient temperature. 20P C; ambientpressure, 10 10 torr.

Imo__ I I I I I I0 1 2 3 4 5 6

1Ic'

Figure 8. - Static coefficient of friction y s as a func-tion of inverse of adsorbate concentration. p ,

chlorine on copper. q , chlorine on iron. 0oxygen on iron. A , oxygen on stell, 0 , oxygen

on copper (minimum p s )(ref. 471.

40

WJ

NN 30OW r

Z;; O}c. 1nW Q ,VH K1 H

Y mCa°

10WVQ

0 i

IRIOINAU PAGE I5 I

IF POOR QUALI'"

10-1 100 . 10 1102 103 104METHYL AIERCAPTAN ICH 3SHI EXPOSURE, LANGMUI RS

Figure 9. - Auger spectroscopy detection of sullur w wrbed

on a clean iron surface exposed to methyl mercaptan

under static conditions and during sliding friction.Sliding velocity, 30 LentimPters per minute, load,100 grams; ambient temperature, 23 C

NNMrn

0zc U SULFUR l STATIC

O OXYGEN_

;0M SULFUR DURING SLIDING e

Z ♦ OXYGENe

S SULFURW^ e n

41NZ ^W QH

nY >-X 10

° °a

# OXYGEN

va ,. I I I I I

10 -1100 101 102 10i 104SULFUR DIOXIDE EXPOSURE, LANGMUIRS

Figure 10. - Auger spectroscopv detection of sulfur and

oxygen adsorbed on a clean iron surface exposed to

sullur dioxide under static conditions and duringsliding friction. Sliding velocity, 30 centimeters perminute; load, 100 grams; ambient temperature, 23C

oz 1.2L)Uf^

zW

Q

W1.0

1

.a

w ^

.r^ l

1

ORIGINAL P AGF% L5

CMz

50 0j3 poop QU AL1 1"i

Q

40

^ ZDo>

a 30 SULFUR ,(X I PEAK—'coCr

a^ 10

Y 9

LD o/ > /cc ° 10 r OXYGEN / 0

cc^ PEAK -4'Wu= y /

Q0

10 -1 100101 102 103 104 105OXYGEN EXPOSURE, LANGMUIRS

Figure 11. - Auger spectroscopy evidence for the displace-ment of sulfur from an iron surface by oxygen. Initialsulfide film formed by exposure of iron surface to10 000 langmuirs of hydrogen sulfide at 230 C.

N2

QY¢ =..7CL KQ

E5 ^jm 1

2

1.3

0 200 400 600 800 1000

LOAD, 9

Figu re 12. - Coefficient of friction and Auger chloride peak

II

intensity as function of load for vin y l chloride on ironsurface. Ambient pressure, 10 '6 Corr of vinyl chloride;rider specimen, aluminum oxide; sliding velocity,30 centimeters per minute; temperature, 230 C; normaloxides present on iron surface.

MIGINA1. 1'Al;h, lJ'OF' 'P001? 1^t :ll.11'Y

/Mlli SURIM I III 51

i iHl1S(-01 ^

)'Hh1AI

WITH SURFACE A('TIVI

LIQUID (IM18INDIR,^ 11

ELASTIC LIMIT

10-4

STRAIN

Figure 13. - Schematic Illustration of the principal ex-trinsic surface effects tref. 551.

O DRY SLIDING, AS CLEAVED

O OXIDIZED

5 0 5 PERCENT HVDROCHIORIC

ACID IN WATER^ r

.4

/ YE

^ •3

u

O

0

r .,

alo---o---o--^

s0 y0 100 150 100 M 1110 1150

LOAD, g

Figure 14. Width of ssraf track and coefficient of fric-tion produced with ruhl ball sliding on zinc singlecrystal 1011011 surface In [10101 direction. Slidingvelocity, 1.4 millimeters per minute; temperature,23° C; dr1 arum atmosphere•

NNT"

44

I

i

ORIGINAL PAGV -'IF POOR @UALPrb

j

I

*i$l

M

houre 15. • Deformation trac45 developed nn a zinc 100011 1uiface in slidmq ennui wth a ruhv hall under a 2W pram loadand in heiiadwane,

^ y

lNllrl.\ q^ PA('P ISI >t All ? k W AIj fy

riqure 16. - Cots Itan,rerrod to a clean Wi(on 11111 yurfare After aene,we contact, load, 10 ora,

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NASA-Lv-