vaezi 2009 creep life prediction of inconel 738 gt blade

8/6/2019 Vaezi 2009 Creep Life Prediction of Inconel 738 GT Blade

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Joumal of Applied Sk:;]ences 9 ' ( '~ 0); 19S O L , '1955.~2009

. IS S :N : [, 8 :[ ,2 - 5 65 4

© 2 .0 0 9' A s ia n N e tw o rk :for Sc ie n ti fl e I n fo rma ti on

'1M:,ohiimlll~d Vaezi and lMasoud Soleymani'Depar tment 0:[Mechanica l Engineering, Bahol U niversity of T echnology ~P . 0,. B ox 484~ B abol, Iran

2Depa 'r tmen t o f Mechanical E n g ~ : n ; e - e r r n n g : , ; Amirkabir Un~vers~.tyof Technology,

P .!O ;,Box 15875 -- 44 l 3 j T eh ran , I ran

Absb·a,ct,: T he aim of this study is 'life predict ion of TN7.38l .C ga s t ur bi ne b la de via L~S!Qn- Miller p~r~met,er

method and fulfillmeut of some systematic metallngraphic, creep, an d i h a J l l r d n e S$ tests. V,~rdO' IL~s,alculative

methods of l~nUiJ]![IJ]![IJgH fe prediction have boon cons idered and Larson -Miller parameter method is. used , in order

to p re dic t r em a in in g life o f AB ,B ~1 .3 0 ga s tu rb in e b la de , By in ve sti ga ti on o f th e me ta ll og ra ph ie imag e s (t w as

observed tha:~the hardeni ~~ gphase (y') becomes bigger after passieg of a, 'long t ime an d ~]~lderhigh temperature

(78 0°C ) a n d ha s been c on v er te d f ro rn cubic ro almost spherical sterns, It re s ults in a decrease in '~be:u i i ,e : ra"gr fu= -

.'t~h '. " - . " I i ' - " , . , - d A .. . . , . . . ) " Ii '- " . .. . , ; j ! " "]1 ,.,.1 :. ,- . ·'tr '[] I " - • • . . . . ] - - , ' - . - ' -t-:· ,..:I V ,- , I \ - , ]1'·' O i ,- , - ,t,' a f , . ,, ,- ,~ ", _'" ,o ~ e rna rrrx 3J]1.. aeg r a c 3J~ , [O ! [ IJr a oy s meta urgicai proper res ana e_enrua Y generanon 0 0 , conumrous

carbides ]n the grain boun darie s, bign es s an d join in g of y' i p ar ti cle s, g ra in b ou nd ar y r ef in in g a nd . g e n er atio n

of cru-eepvoids, ,1,dlof which, resulted in satisfactorily calculation of remaining life time.

Designing those p ar ts 'w hic h ~1Fework ing at ' [ow

temperature and below creep temperature is usually

p er fo rm ed w ith r es pe ct to y ie ld s tr en gth ~ te n sile s tr en gth

a n d : riI Ju p'~U 'r etr em gtll, v ia appl,y, i,ng pHJper sa fe ty fac tor.

In the se con dltion s, deform adon an d ff,acw~re ]'S mo t

de pen den t on the tim e, S O~,working time for t he se p ar ts ,

h e s n o m ean in g and th e p ar ts will coeti u ue w o rk in g ~nti ]

the s tr es s es a p 'p li, ed thereof a re not exceeding thedesigning stresses, However , about the parts which ar e

'working at high temperatures affiljdhe c re ep phenomenon

occnes therein, de fo rma t io n a J il !l Jd[ ~· aC: lJUu re .f the par ts .

depends on the time, Hence, '[hemaximum wo~]lr]ng time is ,

de fm ed for them ..H ow ever the re are V,UiOU8 d e : f i n i . H O o m ; s ,

about fai lure of ~~ly part , The com pon en ts 'm ost

commonly :r-ejeeted a re the blades, :if ro.:m both the

compressor and the mrbine and the turbine vanes,

The tw o principal causes are damage caused by

in ges te d m aterials an d the hi gh '~,e[1l1p'e]' .~tJ~reperation

(C'iJ~"~er.~005). l\[m]ne blades operate at very high

temperatures, very ![IJ~~rof the edg e of metallurgical alloy

d ev elo pm e nt T his w or kin g condition impl ies , add it iona l lyto be required to FeS ]S :~l ' ilJ ighmechanical Ioadings, tiuat th e

m ate rial is , degraded along ~'he in service life, Three

possible d ama g e mecha n ism s t hr e at en the integrity of the

m rb in e b lad es ; c re ep , multi - a xi al f a ti gu e (as so ci at ed with.

the :in~,et'dJctiol!lJof low cycle fa t igue ill. their longitudinal

dir .eC'~icm , and vibw-a' [ ]omg : i ,nduoed by 'rhe gas :flow in.

the pe rpe ndic ldar on e) 8jffiljd higj1, ten1,pe1f .a t~recolfI''Osio.u

(Silveira et al.~ 2 0(9 ). N ow ad~ .ys,~ devekiopi[]]"ent of

manufacturing technology of th e gars turbines and

demaad for more effectiveness require materials w i : d J J . th e

c~palb iH: [y of supporting higher stresses and temperatures

in longer periods . o f ' time, Nibased superalloys are

one of these materials used . for epplicet ion at b u g : ntemperatures such as ill. the :manu: fac1i1Jur ,i :n ,gf hot gaJs path

rotating mrbine component (M~lr,ahlel'[ et al.; 2006).

Erosion resistance, hot cerrosion resistance and creep

res i s tance in high temperatures (620- '1200°'(: ) aJllfeof th e

characteristics of superallnys. Among the super alloys,nickel-based superalloys which have been strengthen by

the secondary precipitation hardening phase (y~)have

.complex. phy sical metallurgy, The turbine blades ar e

mainly made of CfIJS~ nickel based s,u,peralloys, The IN"?]8

superalloy is one of tile. important nickel based super

allo ys th at h as b ee n developed in '196:8 through ' f i e ] ' 1 owi ~ ~ g

a s e- rie s o f. extensive researches on . the optimization of....emical composition "n ...... . . . . . J I . , : ; ; - - t,i"i; simultaneous improve"", i , [ 1 1 .. ': : . , :t-all '.-;.;. uO],II.],0:11, hi u.lIL~";';f l"':;;'0],'., ! L I I . u ;~~, lLu iu !L I I .Qi 1 , :. i .'0;" ,

th e creep" hot corrosion and o xid atio n r es is ta nc es o f

the alloys used i~1 l and bas ed gas turbin es , T hi s ~ Uoy

has been, designed in two different types: of high carbon

IN 738 C (for casting of t111nparts) 3J![IJ(]low carbon

IN 73 8 L C (:~orcasting ofheavy parts), Tl1(rS alloy ha s high'[1Ll!ptl!Ue-c~'ee]!t rength and excel len t c or ro si on r es is ta nc e

in high temperatures. The nickel based superat loys

s tr en gth i s f funclt iO![ IJof v olum e f ra ct io n, g ra in s s iz es , form

and composition of y i' sediment, w hich . i t i s pos si bl e to

control these factors with respect: to . different degrees,

using heat t re a tmen t, C h ang e ]m th e mechanical properties'b " ' ~ r i - ~ _ " . : i j f - ' j o b , ~ ::1 ] h A : r + i . -carne reSUll i ! .Ql;.J. : 1 I I , r o ' m 't!!Jie " ,n . l! ct ul '' 9. 1 , c ~anges ,~epe[ll~en't

on 'the ' ~ im e , ~ c c o m ] J 'a J n T l . i, e d' w ' u ' ~ hh:~rnpirllgor cb~lg,e ]n th e y'

C O 'F ~ ~ ,p O ' m : d i f n g : A I l! J J tI IO 'F ! ~v1Joha: tnm~d,V~ez~" De~r tment o f 'M e c h a ' U l l~ ' c . a J [E~gi~~~]"hli,g~~ a b o : 1 UUJj~e r s] ty o f T~c~ '[J)Q ]ogy~

P.O. Bo:x,484; B.a' [;.o],~ban TeUFa:x. : +98 (021) 55300292

19'50



J')j, u d S · ' . , 9 ' ( 10') : ' " 9 5 ·I1·f 9 '5 5 " 'i I t' k .n .9T i t p " 'n . i/~.'., ·C.l.. . .•. .. i f .~ J' ![.l-' i:. L:UU; ' - -: " o. I: ir - • • iI I . " ~ ~ , ~ ~ ,. ~ ~

phase perform ance . A fte r pass ing of a 'long tim e the y ~

,gn} 'wSi:under h ig h t empe r at ur e an d c on ve rts f rom cubic

to almost spherical shape, Also under these conditions

some undesired phases such as TCP phase s an d some of

c on tm uo na c a rb id es such a s :Un1j ,n the g r . 1 , ' t i n boundaryare c om pose d. G en eration 0:[ ' ~hege s pe cif .c ation s in tile

structure results i n d ~;g ra daHO on of meta ll u rgical and

m e ch an i c al ]J¥'Ope;rties of th e blade a nd e ve ntu ally its

d e st ru c ti on . .IIp to- I f : IJGJW.~r nany r es ea rc he s p er fo rm ed a bo ut

invest igat ion ()i[ creep an d fa t igue effects on tile

m echan ical prope rtie s o f supe ralloys and lif e pred ic tion

(S "ilveira et al, '}fil'rl9:" Marahleh e r al.. 20(\·~;~Le in st er , 2 0 0: ;'0: "__ ___~. M _~ VU, ~ ____ ~ ~._... -11 vu., _ .:)_'~~ ()

W:i.ls .hire et ( 1 1 . j. .2.008; Vue- et al., 2008;. Debes and

:M iUckaJt2008~ Macl.achlanand and Knowles, 200 ' ]. :;

Baurnshte in ,e t at; 1 9 85 :; Ob ta et al. 1989 ; Y ue ttl' ai.,

'19 9 6 ) . .Wdem]tifi,cilfl '6o~lan d predicti on oU 'th e blade remain ing

life prior to occurrence of the irreparable damages is

significant is su e d ue to. the high production costs.

MAT' E R l I l ' A i I I ' CAND METU'O''1Ii"Ii;;C'. ·' •. L~.: .... ' . ... - !.;.V~

This study was conducted from October, 2006 to

Sep tem he r j 2008. . It was an 'i uternship [pfn].ect an d

spon sored b y Ih lJ,b o [ ' U l f : I J i v e T s i t y (I[ Tecl! i i l l lJo]ogy and

B an de r Im am P etroc he mic al C o . . (B IP C)" It 'w as r ela te d to

th e g as turbine of lI B I PC 'i s p owe r plant

The t es ti u g t m [ " b 'ine b l a d e is the 3rd. st~ge IN'll8 LCb l . : : i i . . . . l l , , : ; ; iC o ma ll b la d e 'iJ ' T I i " h · rJI,»1!....:;,.ii"lI ...... a l a n a l v s i ~ . . . . . .il' ' 1 ' . 1 1 . . . . , '," bl a d £ii,u~.u~ , \i :l i . ittl a;.,..:.;.. . w . . . ~ "';'JI.IIV.I.u.h ..,t:d, ,t:u!.II(:~..J{a,b, u!J: !l.i. !L K:.' " U.~

bas been show n i r a . Table l,

The met allo gr ap hi c p ic tu re s have been take[[]j using

an optical microscope, composed of two parts 'O[ airfoil

.and root o f' tbe blade, The creep tests of tb e three

C Co AI Nb n. I V 1 ' g ZIi'

(%] (%1. [%1. (%) (%) {%) (%)

Si o~ Mil) 'W

(%1. t~ (%) {%]

0,,00· : 1 4 " . 9 2,11 3.. 0,,09 :8 ,0 :5 .,0 0,.8 8 '0.42 0.03 0,03

,MjooL'l :! !i !l i :nlJi~

(:s .IJ.nnl)

f'ig .. l: Location of the s p ec i men s : u pp er a irf oil ~ s ha nk

and root

specimens taken f rom the th ree parts of uppe r airfoil j

m. ]"", I d I e ai 1 ! ' C ' . , , - ~ ' ] " 1 ( " i L r ank) ' ; " r i ' i ' -1 root W ' " ,. ", P-erform- ; : : : . , , , , 1 A' ' I I , . . . ~ ." , l . I . ! · " . . . . . - '~L JJ,,~.II..1 " '\ ~~ , lL. t_IHI.1 . i - ' 1 ! : ,_ IHU1 .!U I . , I . lI...ru. . '. .1:1i3l .'k.,,' , .l Ll . ~ , " , ,' !. .. ,p !U . .. , ;' .IJ ':::IfLll

hardness test on the: three specimens ' [aJk~m from the

aforementioned three parts w as pe rf orm ed, Figme 1 .

" " I I - . "~L.~ ......

locati' ."1]- '

nf· ~ I I - . e -

snecim-;:;,Iii!", "-,....

1 . ] ] . - ' m ' iati " " ' a - 'I ' 1 1 v~~.ll..., ! I ! 'iT

~~I

" IU -! o .F -I I : L ~ ,'u.= ,

U" ~~,lL. . . r.""r~~"" lu~,lLa al Lo lL . . ,=

al. IL-. Jj;".

IM[.ettaUo.gr,a:pllic :iov,es. 'tigations! By invest igat ion 0 : £ th e

met al log rsphi c p i ct ur e s {,o.M) f l 'O I I T h t w o p ar ts o f air fo il a nd

m o t , at the F ig:= .2 ( l j i l f : I J d3.~it e a J l t 1 Lbe s e e n that the h a r d e n i n g

phase or 'i( becomes bigger after p as si ng o JJ ta long t ime

( 6 ] ~OOOh) unde r high t emperature Cf80~C: ) ~MJ]dre sults in

degrade r io n of alloy met al lu rgi cal p rope r ti e s.

y~ grow th depends om di f fusion u lr Ji de r h igh.

tel~lIpe~~atu[,ethat it re sults in j o in i u g y ~p ar ti cl es t og e th e r

a n d i nc re a si ng the p er ce nta ge o f M is matc h 'i(/y . Increase

of Mismatch level results in an increase ~n the straine ne rgy res ulted f rom th e interface a nd a ls o r es ults that tile

y' sediments become unstable ~V~IDJ in a b s e n c e of stress.

The.:(11~ l ! r e · tw o im p o rt a e t carbides, I f : I J C : 1 J m , e l yMC and M:dCf,j.

in . the blade, After passing of time and under high

! F ' i g ..2:. 'O pti Jc ~]m ie ro sc op e ima ge o f th e b l ad e ~'~rfo]'1p~~ij

x 1000

F' ig, 3 :. Op ti ca l m iC ~ : Q , ; , > ' O o : p emage of th ,e b lade ~ : D o t p a rt ,

· x . 1 0 G O



J.. Ji,p,· 'nlo~d··ci; o 'JA). 1 "9 ·50 - ·1055 . 2009.nj ; . o ' " ' _ ~I~ • t ~. ,~- i ;f~~.!'.! ' ~ ~ ,?'~ ~,. ~ ~

Fig..4: Composition of !Continmes· M~]Cu carbides on

grain boundary t .x,JOO

r '~

~,~im,

II

Fig, J: Creep H u e assessmen t '00 ;& 00 . on cavity

classificetion (Neubauer an d 'W'~det 1.983)

temperatures tile M"lJC(1.carbide is made om the grain

boundaries and in lon g tim e a c on rin uou s laye r of carbide

covers the grain boundaries, Figure ·4show's this metter in .

the airfoil of testing blade, Composi ti on of C(ln~]·l!ll!lloms.

carbide ne two rk at the grfIJin boundaries :s~i .gf i ] : f [Cant[

a ff ec ts i n r ed uc in g t he m ec ha ni ca l 8 J m 1 J a t hermo-mechanica l

p ro pe rtie s o f th e b la de , w hic h win ' b e , , c h : U B ~ ~ f i , e d .] g u r i F i c 3 l U ] t I y

by creep and hot tension tests,The :first published attempt to rela te creep-life

consumprion of p la n t c omp on e nts t o c av ita ti on WflJS ~baJt

o f N e ub au er a nd .'Wedel (1983). They characterized cavi ty

e vol ur i o n at four st~.ge,~s show n in F ig. 5 . .

G I ' I O ' ! J l I . ]l ' A : I s ol at ed . c a vi ti e s

G 10, Q" d ..:rnUllp .0::·_ne"]l~,e cavines

G[I!TIJllp! c: Linked cavities (microcracks)G i I " -·IIII]II!ii,D," " ' I f acmcracks

" V~'r ~··IIJ II ~'~l(~ _~J~"~" __ ~ :lJ

. . . r

F 'i g .. '~k Compos it io n o f i so la te d c a'V ] tie s in th e blade aafoil

a re a, x 100

FOE: th e A :region. ! ~bere is . no need for amy safety

B l.' • " dproeeedmg, but :[O~,gro'[up' hie mspecnen penn. s are

defined between '1 to .3 yea rs and for group C th e

replacement of the, parts shall 'be performed within 1 6

months and in group .D the parts shall be prompfly

replaced, Figure 6 S.h.OVlS generation of creep cavities

during service in the testing blade, TIle.cavities g e n e ra t e d .

.at the Pig. 6 .~ show composit ion of group A . Of' isolated

ca v m es ~ - which according to the a fore me nuo ne d

re searchers' idea! there is, no safety and . emerg ency

proceed]ii1l.g:required and the prut still has effective., ]·e ·

re ma in m g ~'Ie.;.

At. m ost of the e ng in e e ri n g p ar ts , i S J . series of reactions

o cc ur 'b etw e en th e alloys end th e env i ronment which

result im generation of some phases 0 0 n . the surface of

alloy, in 3 J w ay that tile alloy DO B ie s] v, s s a t is f a c to ry

applicability, The level ' O f ' COKrOS]o:n . f the h ot p arts in . gas ,

t ;u;!bines lowi th . re spec t to the type of :hue l cnnsumed

thereof, is different, The effect of fuel type on the parts

lifetime, results from th'e distribution 'O f the ,e~],ergy

obtained from fue l ( ! j o t th e c om b us tio n s te p, FO'r in stance

the liq u id fue ls which make more radiating energy,

dependin g om the ir atomizing , c a p : f a b U h i s s . , have the

highest dest ruct ion au pad compare w ith tile g as f ue l .

Also th e suspended panicles and the fuel

compositions ar e other e ff ec ti ve : f~ C lOE :Son the lifetime of

th e part, f ' IDam the a f fec t i ng the parts Hfet i .nflepoims of

',de'w? g ~ s f ue l is bet ter than ~& Iothe r fuels, as ] -~g 'uves thebest e:ner ,gy ' in c om bus tion alM ]d as '[ow sediment effects,

After gas, gasoline b J 8 J S been reported as a . proper fuel,

after w hich are the he a vy fue l and crude oil. The effect of

corrosion om t he ,a]rfoH surface of testing blade ha s been' I L . "'IIiJI" 1snown ] : I '}, . r: i. g. . ,

: IRvest lga t .i~ f i o f 'CR;tf, and bamll0SS '~ts: The .c~'tepest• " iC ',' d L.. f ' I ! . . 'Lresults on. three S o p e c: rU i l ,e n S o specmed tneren ..~ .I! rave ~ j e f : ( n .

shown in Table 2..



J')j, l- d e ., 1 i ' J , 1/'1;) : ' " 9 5 · I1· f t l i 5 5 " 'i I t' k . n . 9- ~PP..tl;f .•Jc.~-;::i l.if~)'.~ J ' _ v - , iy __, LV(! .

Fig.. 7: T1'11eim aC!!'f!. riff' Ci1l1~C']",]ilJ nmducts in the airfnil area.• • : ~ ~ •• ;el ~ v ~.._.t_I i~ . . ~ ~ .. ~~ J ;r'r!L '~~ ~ . . . ~ . J Y ~~~.. .~-~~~"~

x500 .

Table 2~ The 'Clfeepil lg I teM~$oc~~~edwHh th e ~~Ifee~( !i 'i il !S· :S1P~i 'f : ied e m th e

' l b b t d t " : ,

St~·~ss~F'A)

G a r U J g ' e , : I , e l l l g , t h (mnl)

Pri liI"Iiiliii''y d i . Q _ ( i i J '1 ' m )

Soculilcltllr_'f o d i ~ L . (mm)

:~.~mI!!!!I.'JJ e ng t h (mm l )

S e c o l l l d l a : r . y : Iength ( 1 ' 1 1 " 1 1 . 1 : 1 1 )

TeiJ:l:lrperntl! .l~e. rC)

RlJip'~Ure h " I J 1 ~ '(Ill)

l51,OO

: ~ 9 . , O O

J,S~·

1.3543 ,9£

· 4 5 . , 5 5

9g2JJO

] 0 . . , 6 3

151,00

: 1 9 ' . , 0 0

::t~'9

3..3i'

4 , 4 , . , 7 2 -

4 , . 6 , 2 8 .

982JJO

: 1 {U )3

:152,00

: 1 9 ' , 0 0

3 , , 4 8 -

3.324,3,61

4 . 4 . , ; 8 0

9 ' l : f l2 . ,0 0

: 1 . 5 , 1 : &

M i d l d l ~ e i i j : i l . ' . f U l u l

3 55 H V 30 36 2 .HV30

It is evident that by comparing the aforementioned

res ults with. the results of the unused blade weun de rs tan d 'lU iJaJtre ep pro pe rt ie s of Ill.e· used blade is,

def~nitd y decreased and has a ' \{al iety ' of reasons such a s

d ec re as ed vo lu me f rac tion 0:[ p ri ma ry an d. s ec on da ry y~,

increased sizes. of y~particles, , g 1 . ' 3 ] : 1 1 boundaries refming

a nd g ~n~r ,a ti Q t n of . c O : l 1 ti n , 1 L 1 0 U ; 8 . chain s of c a rb ides. The

W f lJ v y grain boundaries by preventing grain boundary

slipping, can improve blade creep properties,

1'1lle.results of hardn .ess test on the three specimens

which obtamed from a J . i i : r J o i t ~ shank. a J i l ! l J d ] ront of the blade

have been shown ]]1 l'Jb]e 3 .

T he [N 7 38 T . J C a ll oy h ar dn e ss ( unu se d blade) is a.bol!]t

400 . ' IV, w b il e c ompa rin g t'h ]s w it h the same speci f ied ] : 1 1

Table 3 h shows that the used blade l,~velof baroness 11~; s .been decreased f f . ' o r 1 . 0 . to, ' ] .5%. , the reason of whichA e p e n d 8 i"'ii i'ii ,~''''I'!I, V I p ' - : : ii . - ~ . , . . . , . ' 1 ~It It" " .r .J :: fI ,D • rifI , , - o r e 'li >0 i:lI, a n d , ; : , , ] ."'" ",'L. i '3 , " . -'u!~~ · !i iU.' lI I,3 ••m [U. ..:;o ';~ .. , j : : ~ i Fue..es stzes merease : U . ~ . i : . . ;t~ ' a J V [U.'..:;iU-

decreased volume fractlon during the service.

'Reuaiming 'nfe ptelicUoo: V a r ious ca lcula tive methods. 'O f

life predktkm i' [ ( ; h l l d . e th e following:

, .a : r,so)l.~,MiUer ''aram.e~ter:: L~Mparam ete r is use ful ~: n

understandi rag and quantifying the time versus

temperature trade-off for vaJili"io'Usmaterials .. Its. us·e

results in a very effective method 1ITh~'ia:~]o~1laliing the

tim e - te rn pe ra fu re (. a~ ld .even r il te -t empe ra t)un~ ) ef fec t s

observed in stress-rupture and creep testing, I.-M

p(I)r,alUleter is specified with respect to th e Eq, '1(La rs on and M] 'Ue :r ~19 .52 ) ::

('I)

where, C . is (I).oefuk:ie~1ltj whose value is dependent 0']1 the

me te ri al c ho se n . .In 'the LaJ~~o]1-·Mile r s tu dy , d ata fo r some

~ O m aterials w ere evaluated: it w as foued tha:~ the

constant C w 'as 'V ery close to 20 for all materi als

(N·a.eem et al.j '1998).

·Manso-o·-Haferd 1 ) 1 : · . .0) '3JraIWettt~::This r ela ti on due to· i t s .

higher flexibility shows ttl)! best conformity 'un

extrapclstieu of rupture data. However, it is no t used

broadly to show the creep damages ..The Maeson- Haferd

·reb.'~]Q;]ls def ined by Bq . .2 (M(I )~ l$o.~ ll~1dHaferd, l '~J53):::

(2)

·where; .T~:and lo g ~ awe c o ns ta nt values resulted. ' f rom th e

te s t data w h ich for most of the n ic ke l based superall oys

strengthen by y' have approx. values of ]00 end .~ j

respect i ve l y ; .

·Monlma:m . .G r . 9 I 1 1 ' t re '~a l t i ion :M o : n k r i l , 1 ( 1 ) ~ l and O~1lt ('1 95 6)

of fered ttl)! followieg ~1f:]a!tiOll ( E q . .3 ) 'between th e '~U1]njmurn

ith lifetireep rate WIt : Cfe.ep. rtenme:

e· 'Xt-" _·C~·r·-""in. -.' !:;II (3)

EX ' I " W ' ! I ' I T i ' e -n 'n.;~ .f'.{,;und 'i!~-~ '[ - ':; ',1ri 'ue- , I I ' : . - " - - • b . '1() ,0' to .,'! !. .. - '] ' , ~"r;U~ ··.u~.U.~•) .1. "." 1 . 1 1 , !. [ -J.' .. ,"~d~- .~.[·om · a i . . 00. .~.'.,.O ..0alUlo [~~

0.95 and the C O j J ) i S , ~ a J ] ' l J [ M r a n g e s from f 1 J ! b O t U , 2 ~!Oabout l5 I'

de pe ndin g ou the m ate rial (1 3,a1 dan j '1992).

]If" b = M~ · i I l - ~ ' ·1 " . 1 1 . . • . D ik - . . .-. •vO ::e.5-... iU~~!It:a.reJahon: . ·olues and Milicka (1916) gave

a better rel ( l ) l t iou between t he ru.p :~ i I, J]~"ei e . ( l ) n d strain ' r a r e

'with respect n o t he 1 \J .1 -G ·quation for the complex alloys,

The Dob es -M ilie k a r el atio n ~ s de fin ed ] by Eq, 4:

(4)

Kou l e q 'u a. ti on s ~K oul et al, ('19:84) ]Jare.~ented.ome new. . ' d : ] I f , ] . • , 1 1 " . - . . " ' d j ' " '~ ' . . - . If , b h . . . . : I I · b " . " J . ' .. . - , I I" ~ ; .. ..m o . e S .[0 ]' ..1 . I I . e p re . . .OCd .On . o [ ! l J ' . . i ll .u eS . • 'V e V a J uanon 0 . 1 1 . U I . e~ ~

existing models, '[bey announced that c r ee p b eha vi or" , , , . 1 1 " sunerallovs 0"" " ·l·-t·.. '1 - 'l~"-. "t f~ ~ ,~ -'- -; - thener ..! !. .. , . .. .. - , 'L., .....u.~. "" .r....,[.~U. I l. ' j' " . . .on H-I.nl.lll!g!lle J slLreng nener :p·.~.la"'.5enas

a maior dif femmoo w ith the bcba vim'S of other



J')j, l- d e ., 1 i ' J , 1/'1;) : ' " 9 5 · I1· f t l i 5 5 . , 1 1 . n . 9- ~ P P .. tl ;f . . Jc.~-;::i l.if~)'.~ J ' _ v - , iy __, L(lV

eugineeri ~lga l l e y s , as a main part O 'f the (1 ) ] ' 10 ' ) ' " ' 1i tet ime i s .

existed at the. tert iary c:ree.p s t ep . Thus, in the models

presen ted] by them, the different pilJlrts of the c~"ee .pCU[1ln;~,

. lud in of' nsi da d·-i ·~·""--·- .-•~ -.•~ -- .•• -. j!-,-"-I-·;-rr·:· .,- '-- ... -- ,J."-"me ..u e s~["dmn0.. p . ~unar y. ~ seeon . ry an t em ..t]ry stages,

creep and also th e times of di f fe ren t creep steps have~ ~.ri'! (Jn.~Iil'! j"o 'lII·.. 't rol i1I,l!' T' l.,i!iI,~"- ,Ii:: "-,r;'~ m "odel 'holiI ( !. . .. . ·i1I,Cin s p e e l ,Ii:: ed b~o]t=.ulwJ0u.,u. ~v', . '' '' '' a i, ,, , .u0[[F l[f ~ ' ! O . I. "v, .- ,.ui:i U'0"",u. Q . 0 ... .h[. - .~.

:E q. 5 (K cm J et ai.~:[984):

(5)

Equa tion 5 is aCCUw,aMover a wide ri ! t lmgeof stresses

(350" , 700 :M: 'a_ )am i rempe ram re s (7 6D ~8 90 °C ) in IN~738:LC.

The method systematically reveals the cr,eep degeneration

ef fec t s 'wUh in cr ea sin g s er vic e U~~'" The relarionship

appea rs '[0 'b e ~ ]jd ep emdem tt of an y cha nges in the

predominant deformation mechanism.

Regarding to th e metallographic picmres (OM) anddispersed creep voids ]] 1 Fig. 6 and also c on s id er in g t he

'voids have not reached the critic ( I ) ] amount. 'we proceed

'with remain ing H'fe predictkm of th e u se d b],ade using

t he L ar so n- M ille r p er am et er caJcvdatloLl meth od, F ir st. of all.", ....1., - 'Id 'L ,;;; - " ti - ",D th -~ - 'di - ~'" thII!. ~:;!I.~,g]ILJ]. . UJL" :me[[1l10I1l.eiJI. 'mal ! . ,aoco:r. I n ,g '~'!.l " . ,if:

aforementioned blade operating documentations, the

blade superficial temperature during service was ,approx.

,?'80°C! the stress applied thereto was 1.:56UP'a and [be

b lad e s er vic e tim e w as a bo nt 6 :[ ~ .oOOh.The : L = M parameter

can b e obtained from the Larson-Miller curve assoc la ted

with ruNi'38 LC alloy. P or th is 31[OY it is e pp ro x, e qu al to

22,,,1.Also it should be mentioned that the C parameter

associated. w ith the e fo re me ntion ed curve is equa l toi ,659;

Thus r , eg~~u ing : to th e L ars on -M ille r p ararn ete r

reletionship, t r : ~ 9 33 2- 5 'h a n d '~ ~~:~9 33 2 -5 -6 ] 000 ~ -.32000 lh

(approx.)

'IIi"n this C't~~,....JI'tI' two methods ( alcul ati ~~ andW.u. IL, .1~ '~l'WIIIL~j ~ I!' -'-'. " . . . .... J j,lv:,· Q, ,t:~."'_"U.!L,t:~IL. '",,'... , .... ;,

experimental) have been implemented for remaining life

prediction of IN 7 3 8 LC gas turbine blade, TIle Larson-

M ille r m etho d u se d as c ale ulari v e m ethod for. predict ion

of remaining ]ife'"Also effects of' c re ep , om the IN t 38 LC

superalloy microstructure havie been considered via.,

implementation of metallogrephic creep and hardness

tests, R e su lts s how ' t l 1 i J f l J t

•' Regarding to th e OM pictures there C a i l l J l be seen

some changes such as cominuous carbides in the

g]',lotinboundaries, b ig ne s s a nd join in g of ~ ( partic le s,

g rain , b ou nd ar y r ef in in g and. generat ion of c~ " eep. . .. o l iI ~,r~ 'It~.:i;;:; ' 1 l' i l, r 'I . , · . . .h ci:"£!I;:;-'- '!IC ~rrn ;a Cligli"'<ii....JloQ;~o~.... rrn "-;'1(;' m '" o ;; , . . . . ·h <:iin',-;."',]" ' -"o tt ¥,[ 1L[r6;:' !'i i¥U'[";" ~~,lJ .. ';j h.lL t.II!~,_l ,t:~.uCl!ILI.u~.lLu I " ,1V1b,. ; c] : ] : . .. . il~

p,roperrJ..es O o f ttbe blade w ithim tbe expec'[atiorll;s of

L f l J r B , o : n ~ · : M i ] l e : [ '

.' By using: th e L ar so n-M ille r m e th od , the use d 3 [fd

s tage b lade ( A BB ,-1 3D type) rem ain in g 'Iir e w as

estimated to b e e qua l to 32~O OOh, which also cQl1rfJrrms

th e afcrernentioaed matter, with respect to th e

manufacturer techn ical documentations. ' R ,egantin~: to due 11L1etallognlp'hic pictures and

hardness test on th e specimens, it may be clsimed

th(l)t the efo rement ioned blade passed through proper

s e rv ic e c o ndi ti on s

t ·Il'

T

WP' ·'C

MHP

·' ' ' I ' : . , ·'Log (t t ) ·~

'Ill

CM ·'M

K ·t ·I" "'

t ·s

~,

E ·,~ "'

e,["- :: :

,[ .,I'_ Ii:]

,

C*

' ~ 1 1 , 1 * ·e, ·

NOME 'N C LA 1 rUR '~ S

Iluptu:re t ime

Oper~tin~:t 'ernperatUl:~'e(K)

L~r$O~1-Mller parameter

M a J J t e r i a 'l constant

M~U1S0~1-.~'fe[fdp~~ull]ete]'

M a J t e r i a 'l constan t

M a J u e r i a J constant

Exponen t

M a t e r i a 'i coastsmCon . ..a...."~"~.· ,,e~jl ':";__~ _ I I L - 'I i~ ~

C o n s ta n t v a l ! , J I. , e

P rim a ry c re e p life

Secondary creep ]i~e

Primary ,creep' strain

Secondary creep strain

Creep 1'3Jre

Secondary creep sIT 1a J]nate

Minimum creep rareConstant value

Constant val u e

C r e e p d uc t ij it y

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