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journa l homepage: www.e lsev ier .com/ locate / jmatprotec

n investigation of the wear behaviour of 0.2% Cual phase steels

. Aboueia,∗, H. Saghafiana, Sh. Kheirandisha, Kh. Ranjbarb

Iran University of Science and Technology, IranShahid Chamran University, Iran

r t i c l e i n f o

rticle history:

eceived 12 September 2006

eceived in revised form

3 January 2007

ccepted 14 September 2007

a b s t r a c t

In order to explore the tribological potential of the dual phase (DP) steel as wear resis-

tant material, the wear characteristics of this steel have been investigated and compared

with those observed in plane carbon normalized (N) steel that has the same composition of

0.2 wt% carbon. Dry sliding wear tests have been carried out using a pin-on-disk wear testing

machine at normal loads of 61.3, 68.5, 75.7 and 82.6 N and at a constant sliding velocity of

1.20 m/s. At these loads, the mechanism of wear is mainly delamination, which has been

confirmed by SEM micrographs of surface, subsurface and wear debris of samples. The wear

eywords:

ual phase steel

elamination wear

icrostructure

rate of the DP steel and N steel have been explained with respect to microstructure and the

wear mechanism.

© 2007 Elsevier B.V. All rights reserved.

A commercial grade of 0.2% C steel with the chemical com-

eat treatment

. Introduction

ual phase (DP) steels consist of hard martensite islandsmbedded in a relatively soft and ductile matrix of ferrite.hey have recently emerged as a potential engineering mate-ial system for automobile and other engineering applicationDavies and Magee, 1979). Low carbon dual phase steels haveound application in making pipe-lines for transportation of

ineral slurry and other wear resistant applications (Tyagit al., 2004). In a recent study they have also been foundo hold good potential for use as farm implements wheretrength and wear resistant become of a great concern (Jhat al., 2003). The tribology of dual phase steels has not yeteen explored extensively, and only a few studies have been

eported (Tyagi et al., 2001, 2004; Jha et al., 2003; Modi, 2007;odi et al., 2003; Basak et al., 1998). Modi (2007) has shown

hat the abrasion resistance of dual phase steel is greatly

∗ Corresponding author at: Department of Metallurgy and Materials Engiehran, Iran.

E-mail address: abouei v@metaleng.iust.ac.ir (V. Abouei).924-0136/$ – see front matter © 2007 Elsevier B.V. All rights reserved.oi:10.1016/j.jmatprotec.2007.09.044

influenced by the microstructure and test conditions. It hasbeen indicated that the wear resistance of dual phase steelsincreases with increasing volume fraction of martensite (Modiet al., 2003; Basak et al., 1998). Tyagi et al. (2001) have foundthat the duplex microstructure of the DP steel offers higherwear resistance than that observed in normalized steel. Thework reported is part of a detailed study on the comparativewear characteristics of plain carbon dual phase (DP) and nor-malized (N) steels, using a standard pin-on-disk wear testingmachine.

2. Experimental procedure

neering, Iran University of Science and Technology, Narmak 16844,

position given in Table 1 was used to fabricate the cylindricalpin samples (30 mm × 6/0 mm Ø). The specimens were heattreated using a vertical tubular furnace. The heat treatments

108 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 3 ( 2 0 0 8 ) 107–112

Table 1 – Composition of steel (wt%)

C 0.21Si 0.26Mn 1.18Cr 0.18Cu 0.20Ni 0.125S 0.032P 0.035

Fig. 1 – Microstructure of steel samples after heat

The wear volume loss for both the DP and the N steels withsliding distance under different loads and a fixed sliding of1.2 m/s is shown in Figs. 2 and 3, respectively. The data has

carried out (Table 2) were normalizing, involved austeni-tization at 950 ◦C for 15 min followed by air cooling, andintercritical annealing, involved heating at 780 ◦C for 6.5 minfollowed by quenching in water at room temperature (Speich,1981). Metallographic structures were analyzed to determinethe structure of both Dual phase and normalized steel. Thesample Brinell hardness was also measured using calibratedstandard hardness-testing machines.

Dry sliding was carried out at a relative humidity of 55–75%at room temperature (25 ◦C) against the counterface of a hard-ened and polished disk made of E52100 steel with HRC 62–65hardness. Pin height losses were automatically measured bya pin-on-disk machine (manual tribometer: type TRM250) atdifferent intervals of distance: Initially, the sample height wasmeasured four times after every 200 m, then three times afterevery 400 m and finally three times after every 800 m. Thusthe total distance of sliding was 4400 m. Samples of DP and Nsteels were tested at loads of 61.3, 68.5, 75.7 and 82.6 N and ata fixed sliding speed of 1.20 m/s. Each test at a given load andsliding velocity was repeated three times with identical newsamples on fresh disk surface, and the data for average vol-ume loss after each interval of time were used for the analysisof wear rate.

The rise in the temperature of the pin samples was mea-sured during wear with a fine chromel–alumel thermocouple(1 mm Ø × 8 mm) brazed on the pin side about 3 mm above thewear contact surface.

The worn surface, subsurface and also wear debris of spec-imens were examined using FLIPS XL30 scanning electronmicroscope (SEM). For examination of subsurfaces, in order toprotect left probable layers on the worn surface, first each pinsurface was coated with Ni, then the pins were cut verticallyin direction of left wear craters.

The X-ray diffraction studies were carried out on the weardebris of both the DP and the N steel samples. However, sincethe quantity was very low, for each steel all the debris wasadded to each other.

Table 2 – Heat treatment, resulting microconstituents and hard

Steel designation Heat treatment

N Austenitization at 950 ◦C for 15 min followedDP Heating at 780 for 6.5 min followed by quench

at room temperature

treatment: (a) dual phase steel (DP) revealing martensite(white) and ferrite (dark) phases and (b) normalized steel(N) depicting pearlite (white) and ferrite (white) phases.

3. Results and discussion

3.1. Characterization of pin samples

The microstructure of both the DP and N steels has darkand white areas when etched with 2% nital, as shown inFig. 1(a) and (b). The DP steel delineates a network of marten-site (white) plus ferrite (dark), and the N steel microstructurehas white areas of pearlite and dark regions of ferrite. TheBrinell hardness of the N and DP steels are 177 and 201 HB,respectively, as shown in Table 2.

3.2. Wear characteristics

nesses of the steel

Microconstituents Hardness (HB)

by air cooling Ferrite + pearlite 177ing in water Ferrite + martensite 201

j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 3 ( 2 0 0 8 ) 107–112 109

Fd

absid

ltat1

ts

Fd

Fig. 4 – Variation of wear rates with load in both DP and N

ig. 2 – Cumulative wear volume with sliding distance atifferent loads in DP steel.

nalyzed on a liner scale using tow separated stages of wearehaviour characterized by tow liner segments. The change inlope has been observed after first four experimental points,n which both lines are in common. Both the lines have beenetermined by the liner least-squares fit.

For both the N and the DP steels (Figs. 2 and 3), the firstinear segment (run-in) is found to be steeper compared tohe second liner segment (steady state). The transition occurst a distance of 800 m. Other researches have observed similarrends in steels (Clayton, 1980; Smith, 1986a,b; Iwabuchi et al.,

988).

Fig. 4 shows the variation of wear rates with load in bothhe first segment (run-in) and the second segment (steadytate) in both the DP and the N steels. It is observed that the

ig. 3 – Cumulative wear volume with sliding distance atifferent loads in N steel.

steel corresponding to the run-in and the steady state ofwear.

wear rates increase linearly with load for both the DP and theN steels. The run-in wear rate in both steel is higher thanthe steady state wear rate and it also increases faster withload.

The wear coefficient, K′, has been determined using Lan-caster equation (Lancaster, 1967):

K′ = V

LS(1)

where V is the cumulative volume loss under a normal load ofL and S is the sliding distance. Fig. 5 shows the variation of thewear coefficient with normal load corresponding to the steadystate of wear for both the N and DP steel. It is observed that

Fig. 5 – Variation of Lancaster coefficient with load in bothDP and N steel corresponding to the steady state of wear.

110 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 3 ( 2 0 0 8 ) 107–112

Fig. 6 – Scanning electron micrographs of subsurfaces of

worn specimens: (a) DP steel at 68.5 N and (b) N steel at68.5 N.

the wear coefficient for both steels has a little increase withincreasing normal load.

Fig. 6(a) and (b) shows the SEM micrographs of the subsur-face of the DP and the N steels. For both the DP and the Nsteels, the continuous cracks are seen around surface. At theloads used in the present investigation, the wear appears to bemanly delamination, as is evident from the subsurface cracks(Suh, 1973). This is further confirmed by an examination ofwear debris, which shows flake-like wear particles, as shownin Fig. 7(a) and (b). These wear particles are also observed onthe worn specimens, being flaked off the surfaces (Fig. 8(a) and(b)).

According to Figs. 6–8, the present mechanism (delamina-tion) involves nucleation of cracks and their propagation to thesurface. The cracks originated within the plastically deformedmaterial beneath the surface, and after growing eventuallyseparated in the form of flake-like wear particles (Suh, 1973).

As observed in Figs. 7 and 8 there are some oxide agglom-erates among wear debris in addition to metallic particles.A higher magnification of this oxide agglomerates has beenshown in Fig. 9. The existence of oxide particles in weardebris has also been confirmed by X-ray diffraction patternsof the wear debris generated during sliding (Fig. 10(a) and (b)).These oxide particles (�-Fe2O3) could be generated from some

entrapped metallic particles between the sliding surfaces. Asthe sliding continues more and more the oxide particles maybe turned to a few large oxide agglomerates. The nature ofoxide observed in the present investigation (�-Fe2O3), could

Fig. 7 – Micrographs showing wear debris of (a) DP steel at68.5 N and (b) N steel at 68.5 N.

be explained on the basis of sliding temperature. Of the threetypes of oxides of iron, �-Fe2O3 has been reported to be alow temperature oxide, which form around temperature lessthan 450 ◦C. Fe3O4 forms between 450 and 600 ◦C, whereasFeO forms at temperature greater than 600 ◦C, as revealed bySullivan et al., on the basis of static oxidation experiments(Sullivan et al., 1980). In the present study the temperaturemeasured at a distance of 3 mm from the sliding surface is100 ◦C. According to the equation given by Ames and Alpas(1995), the flash temperature, i.e. the instantaneous tempera-ture at the contact point during sliding, is found to be 415 ◦C.Thus, not seeing any change in the nature of formed oxidein this investigation may be possibly because of that slidingtemperature does not overweigh the formation temperatureof Fe2O3.

A higher cumulative volume loss, which gives rise to ahigher wear rate in the run-in stage as compared to that in thesteady state, as shown in Figs. 2 and 3, May be explained on thebasis of the initial surface roughness of the wearing material.When two previously unworn surfaces are first brought intocontact, mechanical, Thermal, chemical and microstructuralchanges begin to occur in and adjacent to the contact interface(Blau, 1981). It is well known that the surfaces of the engineer-ing components are rough and have asperities. As the relativemotion of sliding between the two bodies takes place, contact

occurs at these asperities and the surfaces evolves to attainbetter conformity to each other at the end of the run-in stage.The wear in this stage occurs by the removal of high asperities,initial oxide layers, and surface contaminants. Consequently,

j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 3 ( 2 0 0 8 ) 107–112 111

Fig. 8 – Micrographs showing wear surfaces of (a) DP steela6

ts

hTts(bmd

Fa

t normal load of 68.5 N and (b) N steel at normal load of8.5 N.

he material loss and the wear rate are higher in the run-intage of wear.

The wear rate in both run-in and steady state segments isigher for the N steel than for the DP steel, as shown in Fig. 4.he lower wear rate observed in the DP steel in comparison to

he N steel could be due to the lower contact area in the DPteel at a given load resulting from its higher level of hardness

Archard, 1953). The other factor contributing to the observedehaviour of wear rate may be explained on the basis of theechanism of wear in present investigation. According to

elamination mechanism, increasing the hardness decreases

ig. 9 – Scanning electron micrograph of oxidegglomerates among wear debris.

r

Fig. 10 – X-ray pattern of wear debris of (a) DP steel and (b)N steels.

the possibility of subsurface plastic deformation and there-fore, the formation of cracks decreases (Suh, 1973). Thus thehigher wear rate in the N steel with comparatively lower hard-ness may be attributed to the increase of probability of crackformation and propagation during delamination.

The wear coefficient does not change significantly in boththe N and the DP steel, as shown in Fig. 5. The negligible vari-ation of wear coefficient demonstrates the mechanism duringwear does not have any change. Therefore the increase in wearcoefficient with load may be attributed to the increasing wearrate dominating over the increase in the normal load.

4. Conclusions

The present investigation has led to the following conclusions:

1. The wear mechanism in both steels is manly delamina-tion in the range of loads and sliding velocity used in thepresent study, as evident from the wear debris the subsur-face cracks.

2. For a given load, the cumulative wear volumes of DP and Nsteel pins increase with sliding distance under dry sliding.

3. The wear rates in both segments (run-in and steady state)are higher in the N steel than in the DP steel; this maybe attributed to the (1) relatively lower real area of contactand (2) decreasing the probability of cracks formation andpropagation during delamination.

4. The steady state wear coefficient increase linearly with theincreasing normal load but it does not change significantlyfor both the N and the DP steel.

e f e r e n c e s

Ames, W., Alpas, A.T., 1995. Wear mechanisms in hybridcomposites of graphite-20 pct SiC in A356 aluminum alloy.Metall. Mater. Trans. A 26A, 85–98.

Archard, J.F., 1953. Contact and rubbing of flat surfaces. J. Appl.Phys. 24, 981–988.

n g t

plain carbon dual phase steel. Metall. Mater. Trans. A 32,

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Basak, A., Reddy, D.C., Kanth, D.V.K., 1998. Computer modeling ofwear resistance for plain carbon steels. Mater. Sci. Technol.14, 776–782.

Blau, P.J., 1981. Mechanisms for transitional friction and wearbehavior of sliding metals. Wear 72, 55–66.

Clayton, P., 1980. The relations between wear behaviour and basicmaterial properties for pearlitic steels. Wear 60, 75–93.

Davies, R.G., Magee, C.L., 1979. Physical metallurgy of automotivehigh-strength steels. In: Kott, R.A., Morrise, J.W. (Eds.),Structure and Properties of Dual Phase Steels. TMS-AIME,New York, pp. 1–19.

Iwabuchi, A., Hori, K., Kubosawa, H., 1988. The effect of oxideparticles supplied at the interface before sliding on thesevere-mild wear transition. Wear 128, 23–137.

Jha, A.K., Prasad, B.K., Modi, O.P., Das, S., Yegneswaran, A.H., 2003.Correlating microstructural features and mechanicalproperties with abrasion resistance of a high strength lowalloy steel. Wear 254, 20–128.

Lancaster, J.K., 1967. The influence of substrate hardness on the

formation and endurance of molybdenum disulphide films.Wear 10, 103–117.

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Modi, O.P., Prasad, B.K., Jha, A.K., Dasgupta, R., Yegneswaran,A.H., 2003. Low stress wear behavior of 0.2%C steel: influenceof microstructure and test parameters. Tribol. Lett. 15,249–255.

Smith, A.F., 1986a. The friction and sliding wear of unlubricated316 stainless steel in air at room temperature in the loadrange 0.5–90 N. Wear 110, 51–168.

Smith, A.F., 1986b. The unlubricated reciprocating sliding wear ofa martensitic stainless steel in air and CO2 between 20 and300 ◦C. Wear 123, 313–331.

Speich, G.R., 1981. In: Kot, R.A., Bramfitt, B.L. (Eds.), PhysicalMetallurgy of Dual-phase Steels, Fundamentals of Dual-phaseSteels. TMS-AIME, pp. 1–45.

Suh, N.P., 1973. The delamination theory of wear. Wear 25,111–124.

Sullivan, J.L., Quinn, T.F.J., Rowson, D.M., 1980. Developments inthe oxidational theory of mild wear. Tribol. Int. 13, 153–158.

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359–367.Tyagi, R., Nath, S.K., Ray, S., 2004. Development of wear resistant

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