Materials Science and Engineering A 527 (2010) 60916097

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Materials Science and Engineering A

journa l homepage: www.e lsev ier .co

Therm t w

Yucel BirMaterials Instit

a r t i c l

Article history:Received 19 AAccepted 8 Jun

Keywords:Ferrous alloySemisolid procFatigue

deponderfatiguarly 5ent isl streble Cerebstimathe cr

1. Introdu

Hardfacimethods employed to enhance the wear and corrosionoxidationresistance of surfaces [1]. Much effort has been devoted to devel-oping alloys for hard facing applications. A variety of Co-basedalloys are commercially available at present in powder and wireform for hardfacing to extend the service life of industrial compo-nents in wetheir hardndation resisone of theof hardfacinis attributeM23C6 carbresistance bwhile refracvia precipitintermetall

Stellite 6applicationwear and hwork tool stbeen testedunder steeresults. How

Tel.: +90 2E-mail add

over. It ition

Among several advanced deposition techniques employedin cladding wear resistant layers on tool materials, Plasma-Transferred Arc (PTA) process stands out owing to a higherdeposition rate and lower heat input and thus very low dilutionand distortion [16,36]. It has thus been applied extensively in the

0921-5093/$ doi:10.1016/j.ar related applications [210]. Co-based alloys retainess and offer excellent thermal fatigue, wear and oxi-tance at elevated temperatures [1116]. Stellite 6 ismost common wear-resistant alloys for a wide rangeg applications. The wear resistance of Stellite 6 alloyd to the high hardness provided by Cr-rich M7C3 andides [12,17]. Cr also provides oxidation and corrosiony forming an adherent oxide lm at high temperaturestorymetals suchasMoandWcontribute to thestrengthation hardening by forming MC and M6C carbides andic phases such as Co3(Mo,W).

could be the very sought after solution for toolings in steel thixoforming where thermal fatigue, abrasiveigh temperature oxidation render the conventional hoteels entirely inadequate [1822]. Stellite 6 has recentlyamong other materials [21,2335] as monolithic die

l thixoforming conditions and showed encouragingever, cost considerations favor coating hot work tool

62 6773084; fax: +90 262 6412309.ress: yucel.birol@mam.gov.tr.

deposition of coatings for wear and high temperature applications[13,3739]. The present work was undertaken to investigate theperformance of Stellite 6 coating deposited on X32CrMoV33 hotwork tool steel via Plasma Transfer Arc (PTA) process under steelthixoforming conditions.

2. Experimental procedure

Stellite 6 alloy powders fromDeloro Stellite Inc. with an averagediameter of 163mwere deposited on 30mm-thick X32CrMoV33hot work tool steel plates by the PTA overlaying process using aCastolin Eutronic GAP400 P.T.A. unit. The metal powders injectedfrom a powder feeder are melted inside the plasma arc ame andthe melted metal powders thus obtained are deposited on thesubstrate. The chemical compositions of the 3mm-thick coatingthus obtained and the tool steel substrate are listed in Table 1.The coated X32CrMoV33 samples were subsequently austenizedat 1025 C for 30min, quenched in circulating air and nally tem-pered twice at 625 C for 2h yielding a substrate hardness of 45HRC. The clad layer was ground to a nal thickness of 2mm toremove the surface imperfections. Non-destructive testing (NDT)via radiography and eddy current testing was employed to check

see front matter 2010 Elsevier B.V. All rights reserved.msea.2010.06.015al fatigue testing of Stellite 6-coated ho

ol

ute, Marmara Research Center, TUBITAK, Kocaeli, Turkey

e i n f o

pril 2010e 2010

essing

a b s t r a c t

The performance of Stellite 6 coatingArc (PTA) process was investigated uvery favorable impact on the thermaltool steel survivedmuch longer, for neon the coating. Thismarked improvemand its ability to retain its mechanica6 alloy facilitated the formation of staat the surface without spalling and thstresses acting on the coating were eled to thermal fatigue cracking. Onceminor.

ction

ng is one of the most attractive surface engineering

steelscationsconvenm/locate /msea

ork tool steel

sited on X32CrMoV33 hot work tool steel via Plasma Transfersteel thixoforming conditions. The Stellite 6 coating made ae performance of the hotwork tool steel. The coated hotwork000 cycles before the rst thermal fatigue crackwas detectedattributed to thehigher oxidation resistance of Stellite 6 alloyngth at elevated temperatures. The Cr content of the Stelliter-rich oxides which sustained the thermal stresses generatedy retarded crack initiation. The peak compressive and tensileted to be 500MPa and 170MPa, respectively, and eventuallyack initiated, the impact of microstructural features was only

2010 Elsevier B.V. All rights reserved.

employing high temperature alloys for tooling appli-s thus very attractive to use Stellite 6 as hardfacing onal hot work tool steels.

6092 Y. Birol / Materials Science and Engineering A 527 (2010) 60916097

Table 1Chemical composition of the X32CrMoV33 hot work tool steel and the PTA Stellite 6 coating.

Alloy C Si Mn Cr Mo Ni Al Co Cu Nb V W Fe

X32CrMoV3 5

Y. Birol / Materials Science and Engineering A 527 (2010) 60916097 6093

Fig. 4. SEM mwork tool stee

level in thethe dilution

While anized at ovare identiesteel substrin a tempetype structfusion line iapproximatmicroscopeication atdissipated bplanar zonecellular regstantial inteby a columthe fusion lrest of the cmeasured tacross thecin the deponess was mSDAS valuecoatings [37

The rstfrom the liq

a) SEMarse aFig. 5. (of the coicrograph of (a) the interface between the Stellite 6 coating and hotl substrate and (b) of the coating at 500m from the interface.

present work is judged to be acceptable consideringlevels previously reported for the PTA process [41].uniform ne scale solidication structure is recog-

erview magnications (Fig. 2a), several distinct zonesd at still higher resolutions (Figs. 2b and 4a). The toolate, which typically consists of ne carbides dispersedred martensitic matrix, revealed a lamellar, pearlitic-ure in the immediate vicinity of the fusion line. Thes marked by a continuous planar zone, measured to beely 25mthick. This zone appears featureless at opticalresolutions (Fig. 2b). This is taken to imply that solid-the fusion line occurs very rapidly as the heat input isy the underlying substrate almost immediately. Thisis followed by a cellular region. The Fe content in the

ion was found to be as high as 40wt% suggesting sub-rmixing. The cellular region is replaced almost entirelynar dendritic structure at approximately 50m fromine (Fig. 4b). Dendritic features are predominant in theoating. The secondary dendrite arm spacing (SDAS)waso be in the neighbourhood of 7m. The ne structureoatingconrms the rapid solidicationprocess involvedsition process [42,43]. The average as-deposited hard-easured to be 46013HV. Both the hardness and thes are in good agreement with those reported for PTA,44].phase to form in the Stellite 6 coating during coolinguid state is the primary Co-rich dendrites. The remain-

ing liquid emixture ofsequence phard eutectEDS analysiThe majoritally conformparticles inLikewise, Xposed of MM23C6 typeFe, Ni, Si) a(Fig. 6). Theing, instead[47] is belieto dilution ethe stability

Fig. 6. XRDmicrograph of the interdendritic carbides and (b) the EDS analysisnd ne carbides marked in (a).

ventually solidies by a eutectic reaction into a lamellarCo-rich phase and Cr-rich carbides. This solidicationroduces a Co-rich solid solution dendritic matrix withic carbides at interdendritic sites [43,45,46] (Fig. 5). Thes has shown the eutectic carbides to be rich in Cr and Co.y of the coarser carbide particles were found to gener-to the M7C3 stoichiometry while the smaller carbide

side the dendrites are likely to be of the M23C6 variety.RD analysis has shown the coating to be mainly com-

7C3 carbides with an orthorhombic crystal structure,carbides with an f.c.c. crystal structure (M=Co, Cr, W,nd Co-rich matrix phase with an f.c.c. crystal structuref.c.c. structure of the Co-based matrix of the hard fac-of the h.c.p. crystal structure of the monolithic alloyved to be due to the Fe enrichment in the coating dueffect of the deposition process. Fe is known to promoteof the f.c.c. structure of the Co-rich matrix [13].

spectrum of the Stellite 6 coating before the thermal fatigue test.

6094 Y. Birol / Materials Science and Engineering A 527 (2010) 60916097

Fig. 7. (a) Chasample duringthe front and r

Typicalof the coatmaximum alite 6-coate580 C andthe set peaatively smawhich is diheating andacross theas 205 C, 2sets up the

hangcyclin

stanionsther

imatetherlliteen ththe c6 alFig. 8. Cthermal

be subcondit

Thebe estare thethe Stebetwetion ofStellitenge in temperature at the front and rear faces of the Stellite 6-coatedthermal cycling and (b) change in temperature difference betweenear faces.

thermal cycles recorded near the front and rear facesed hot work tool steel are illustrated in Fig. 7a. Thend minimum temperatures at the rear face of the Stel-d hot work tool steel sample were measured to be486 C, respectively, while the front face went throughk temperatures, 750 C and 450 C, every 30 s. This rel-ller amplitude of the thermal cycle at the rear face,splaced to the right due to an apparent delay in bothcooling of the rear face, produces a temperature gap

section of the coated sample which becomes as large5 s into the cycle (Fig. 7b). This temperature intervalrmal stresses at the front face which were shown to

(Fig. 8). Comis warmer tthe coatingtensile streand 170MPthe room tthey couldapplied in alite 6 coatinto be relatiknowntobetemperatur

The respwith a serieits integrityof heat cheings [51]. Sat the focalwhere heatchanges obmal cyclesin Cr-bearinhowever, tovive on thwhat happ

Fig. 9. General view of the front face of Stellite 6-coated hot work tool steele in thermal stresses generated at the front face with time duringg of the Stellite 6-coated hot work tool steel sample.

tial for monolithic Stellite 6 under steel thixoforming[40].mal stresses generated inside the Stellite 6 coating cand from, surface = (T)E(T)(T) [48] where and Emal expansion coefcient and the Youngs modulus of6 coating, respectively and T is the temperature gape front and rear faces of the sample given in Fig. 7b. Dilu-oating with Fe is ignored and the E and values of theloy were used in the estimation of the thermal stressespressive stresses are produced in the coating when ithan the substrate and tensile stresses dominate whencools below the substrate. The peak compressive andsses acting on the coating are estimated to be 500MPaa, respectively. While these stresses are safely belowemperature yield strength of the Stellite 6 alloy [49],be seriously degrading, leading to coating failure whencyclic fashion. Besides, the yield strength of the Stel-g at the thixoforming temperature range is expectedvely lower in spite of the fact that Stellite 6 alloy iscapableof retaining itsmechanical strengthatelevatedes [50].onse to thermal cycling of the Stellite 6 coating is showns ofmacrographs in Fig. 9. The Stellite 6 coating retainedfor several thousand thermal cycles with no evidence

cking or blistering often encountered in thin hard coat-light colouring was noted after 1000 cycles particularlypoint of the ame, i.e. at the centre of the front face,accumulation is maximum. The colour and contrast

served on the coating with increasing number of ther-are best accounted for by the progress of oxidationg alloys [52]. The surface oxidation did not progress,

a point where the oxides scales could no longer sur-

e surface and thus start to spall off. This is exactlyened in the X32CrMoV33 steel samples, the oxides

samples in the course of thermal cycling.

Y. Birol / Materials Science and Engineering A 527 (2010) 60916097 6095

Fig. 10. (a, b) work tool steel sample after 5000 thermal cycles. Front face of the sampleafter (c) metal

of which wcycles [40].

The rstthermal cycthe microsccycling in bcycles earliefacewhereIn fact, sevecoated facestandard m(Fig. 10c). Tthe scale ofis thus judgIt is inferredcrack initiasurface owithey spall ocrack nucle

The crac(Fig. 11a). Pto the axismicrostructthat crackgrowth invcrack was tbides, showintoM23C6This procesume fractiominous thaOxide scale and thermal fatigue cracks at the front face of the Stellite 6-coated hotlographic polishing and (d) chemical etching.ere already too thick after only a thousand thermal

crack was detected on the coating surface after 5000les. Since the samples were checked thoroughly underope every 500 cycles and only visually during thermaletween, the crack might have initiated several hundredr. The crack was located at the very centre of the frontsurface oxides are probably the thickest (Fig. 10a and b).ral cracks of various sizeswere identied once the frontof the thermal fatigue test sample was polished usingetallographic procedures to remove the surface oxideshe crack opening at the surface is relatively larger thanthe dendritic microstructure, i.e. SDAS (Fig. 10d) anded to be a serious threat to the integrity of the coating.from Fig. 10b that oxidation has been instrumental in

tion. Surface scales induce considerable damage at theng to a thermal expansionmismatch, particularlywhenff from the surface. The latter was shown to introduceation sites in hot work tool steels [40].k was found to traverse almost the entire coatingropagation occurred perpendicular to the surface, i.e.of maximum stress, suggesting that the impact ofural featureswas onlyminor. SEMmicrographs suggestpropagation is not interdendritic. Nevertheless, crackolved the fracture of interdendritic carbides when theraversing the dendrite boundaries (Fig. 11b). M7C3 car-n tobepresent in thehigh-Cr Stellite coatings transformcarbideswhen exposed to high temperatures [5,5355].s is promoted under cyclic loading leading to a high vol-n ofM23C6 carbides [56].M23C6 carbides aremore volu-nM7C3 carbides and promote cracking at interdendritic Fig. 11. SEM micrograph showing the crack on vertical section of the sample (a, b).

6096 Y. Birol / Materials Science and Engineering A 527 (2010) 60916097

Fig. 12. Changthe hot work t

sites [57]. Tfractures in

The hardcoated tooltest are shostarting froof the substwas obtainewasmore oness of theincreasing dproducingsteel substrthe interfachard coatinbination ancoating. Whcoatings whof the coatiningly softerincreasinglytensile strethe magnitumore substexpansion m

It is fairperformancbetter withcompares vperformancber of factoindeed very20wt%, oximal cycling[61,62]. Oxiing, stable oenvironmenat the surfacretard crackpartly respoStellite 6-co

4. Conclus

Stellite 6via Plasma

its thermal fatigue performance. The coated hot work tool steelsurvived steel thixoforming conditions much longer, for nearly5000 cycles before the rst thermal fatigue crack was detected onthe coating. This marked improvement is attributed to the higher

ion rnicalllitesustaallingon. Twe

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. Atondfacinrook,ogy, vaghuashanavi Bh(2008. Chia. Yaoashanendrz. 29 (2iu, M.. AntoDavispose MShin,126adu, Dadu, DAoh,. Hou,ugsch000)uens06) 69. Oma5 (20LugscharmetSemi-Telle,695irol, Sirol, Se in hardness across the interface between the Stellite 6 coating andool steel substrate with increasing number of thermal fatigue cycles.

he crack morphology in Fig. 11 suggests that such localdeed occurred and get connected to the growing crack.ness measurements across the section of the Stellite 6-steel samples at various stages of the thermal fatiguewn in Fig. 12. Hardnessmeasurements were performedm the surface of the coating until the hardness levelrate tool steel measured before the thermal fatigue testd. One can see that the hardness of the Stellite 6 coatingr less retained during the thermal fatigue test. The hard-tool steel substrate, on the other hand, decreased withepth from the surface after the rst 500 thermal cyclesa hard coating on a relatively soft substrate. The toolate softened further opening the hardness gap acrosse with increasing number of thermal cycles (Fig. 12). Ag on a relatively soft substrate is not a desirable com-d is known to be a serious risk for the integrity of theile this is not as critical for overlay coatings as for PVDere the substrate support is essential for the integrityg, it could nevertheless present problems. The increas-substrate inevitably responds to thermal stresses bylarger strains. This, in turn, would put an additional

ss component on the coating due to the mismatch inde of the respective plastic strains. This could be much

antial than the thermal strains produced by the thermalismatch.

to conclude from the foregoing that the thermal fatiguee of the Stellite 6-coated hot work tool steel is muchrespect to the uncoated hot work tool steel and alsoery favourably to the monolithic Stellite 6 alloy. Thise of the coated sample can be attributed to a num-

oxidatmechathe Stewhichout spinitiaticoatingand evtiated,

Ackno

F. Aimentsfunded

Refere

[1] K.CHar

[2] P. Cnol

[3] D. R[4] H. K[5] R. R

29[6] K.A[7] M.X[8] H. K[9] R. J

Des[10] R. L[11] K.C[12] J.R.

Pur[13] J.C.

117[14] I. R[15] I. R[16] J.N.[17] Q.Y[18] E. L

2 (2[19] S. M

(20[20] M.Z

A39[21] E.

Chion

[22] R.690

[23] Y. B[24] Y. Brs. The higher oxidation resistance of Stellite 6 alloy, ishelpful [13,16,40,5860].With a Cr content well abovede lms formed on the Stellite 6 coatings during ther-are expected to be Cr-rich (Cr,Co,Fe)2O3 type oxidesdes of this type are well established to be slowly grow-xides and act as a protective layer in highly corrosivets [52]. They can sustain the thermal stresses generatedewithout spalling owing to their plasticity and therebyinitiation [63,64]. The stable hardness of the coating isnsible for the superior thermal fatigue resistance of theated hot work tool steel.

ion

coating deposited on X32CrMoV33 hot work tool steelTransfer Arc process made a very favorable impact on

[25] Y. Birol, I[26] A. Rassili,

AlexandrInternati(S2P), Lim

[27] P. KapranProceedinof Alloys306311

[28] R. Kopp,Z. MituraConferen

[29] P. Kapran[30] Y. Birol, S[31] D.T. Pete

North Am[32] F.L. Riley[33] Y. Birol, I[34] Y. Birol, I[35] Y. Birol, I[36] J.N. Aoh,esistance of Stellite 6 alloy and its ability to retain itsstrength at elevated temperatures. The Cr content of6 alloy facilitated the formation of stable Cr-rich oxidesined the thermal stresses generated at the surfacewith-owing to their plasticity and thereby retarded crack

he peak compressive and tensile stresses acting on there estimated to be 500MPa and 170MPa, respectively,ally led to thermal fatigue cracking. Once the crack ini-mpact of microstructural features was only minor.

gements

ik and O. Cakr are thanked for their help in the exper-KOBATEK for coating tool steel samples. This work wasUBITAK.

y, A.N. Antony, K.J. Bhansali, R.W. Messler, A.E. Miller, M.O. Price,g, vol. 6, ASM, Handbook, 1983, p. 771.H.N. Farmer, ASM HandbookFriction, Lubrication and Wear Tech-ol. 18, rst ed., ASM Metals Park, OH, 1992, pp. 758765., Y.B.C. Wu, Mater. Perform. 36 (1997) 27.i, A. Amadeh, H.M. Ghasemi, Wear 262 (2007) 800806.arath, R. Ramanathan, B. Sundararajan, P. Bala Srinivasan, Mater. Des.) 17251731.ng, Y.C. Chen, J. Mater. Process. Technol. 182 (2007) 297302., J.B.C. Wu, Y. Xie, Mater. Sci. Eng. A 407 (2005) 234244.i, A. Amadeh, M. Farhani, Mater. Sci. Technol. 23 (2007) 165170.ejewski, C. Navas, A. Conde, J.J. de Damborenea, G. Sliwinski, Mater.008) 187192.X. Yao, P.C. Patnaik, X.J. Wu, J. Compos. Mater. 40 (2006) 22032215.ny, JOM 39 (1983) 52.,ASMHandbookProperties. Selections:NonferrousAlloysandSpecial-aterials, vol. 2, ASM International, Material Park, OH, 1990, p. 446.

J.M. Doh, J.K. Yoon, D.K. Lee, J.S. Kim, Surf. Coat. Technol. 166 (2003)..Y. Li, Wear 257 (2004) 11541166..Y. Li, Wear 259 (2005) 453458.Y.R. Jeng, E.L. Chu, L.T. Wu, Wear 225229 (1999) 11141122.J.S. Gao, F. Zhou, Surf. Coat. Technol. 194 (2005) 238243.eider, K. Bobzin, C. Barimani, St. Barwulf, Th. Hornig, Adv. Eng. Mater.3337.termann, K. Uibel, T. Tonnesen, R. Telle, Solid State Phenom. 1161176699.r, E.J. Palmiere, A.A. Howe, H.V. Atkinson, P. Kapranos, Mater. Sci. Eng.05) 5361.eider, Th. Hornig, D. Neuschutz, O. Kyrylov, R. Prange, in: G.L.ta, M. Rosso (Eds.), Proceedings of the 6th International ConferenceSolid Processing of Alloys and Composites, Turin, 2000, pp. 587592.S. Muenstermann, C. Beyer, Solid State Phenom. 116117 (2006).teel Res. Int. 80 (2009) 165171.teel Res. Int. 80 (2009) 588592.ronmak. Steelmak. 36 (2009) 555560.L. Adam,W. Legros,M. Robelet, D. Fischer, A. Cucatto, in: D. Apelian, A.ou, G. Georgiou, J. Jorstad, M. Makhlouf (Eds.), Proceedings of the 8thonal Conference on Semi-Solid Processing of Alloys and Compositesassol, Cyprus, September 21st23rd, 2004.os, D.H. Kirkwood, C.M. Sellars, in: H. Kirkwood, P. Kapranos (Eds.),gs of the Fourth International Conference on Semi-Solid Processingand Composites, The University of Shefeld, Shefeld, UK, 1996, pp..E. Lugscheider, T. Hornig, J. Kallweit, M. Maes, I. Seidl, in: M. Pietrzyk,, J. Kaczmar (Eds.), Proceedings of the Fifth International ESAFORMce on Material Forming, Akapit, Krakow, Poland, 2002, p. 659.os, D.H. Kirkwood, C.M. Sellars, J. Eng. Manuf. 207B (1993) 1.olid State Phenom. 141143 (2008) 289294.rs, E.F. Brush, J.G. Cowie, S.P. Midson, Die Casting Toward the Future,erican Die Casting Association, 2002, pp. 265.

, J. Am. Ceram. Soc. 83 (2000) 245265.ronmak. Steelmak. 36 (2009) 397400.ronmak. Steelmak. 37 (2010) 4146.nt. J. Mater. Form. 3 (2010) 6570.J.C. Chen, Wear 250 (2001) 611620.

Y. Birol / Materials Science and Engineering A 527 (2010) 60916097 6097

[37] A.S.C.M. dOliveira, R. Vilar, G. Feder, Appl. Surf. Sci. 201 (2002)154160.

[38] Y. Ning, P.C. Patnaik, R. Liu, M.X. Yao, X.J. Wu, Mater. Sci. Eng. A 391 (2005)313324.

[39] T. Hejwowski, Vacuum 83 (2009) 166170.[40] Y. Birol, Mater. Sci. Eng. 527 (2010) 19381945.[41] S.C. Agarwal, H. Ocken, Wear 140 (1990) 223233.[42] A. Frenk, N. Henchoz, W. Kurz, Z. Metallkd. 84 (1993) 886892.[43] J.L. de Mol Van Otterloo, J.Th.M. de Hosson, Acta Mater. 45 (1997) 12251236.[44] A.S.C.M. DOliveira, R.S.C. Paredes, R.L.C. Santos, J. Mater. Process. Technol. 171

(2006) 167174.[45] J.R. Davis, Hardfacing, ASM HandbookWelding, Brazing and Soldering, vol. 6,

tenth ed., ASM Metals Park, OH, 1993, pp. 699828.[46] Y Wu, Y. Yuan, Mater. Sci. Eng. A 209 (1996) 231236.[47] Y. Birol, Wear., submitted for publication.[48] G. Dieter, Mechanical Metallurgy, McGraw-Hill, 1986, p. 430.[49] http://www.stellite.co.uk/Portals/0/Stellite%25206%20Final.pdf.[50] S.S. Chang, H.C. Wu, C. Chen, Mater. Manuf. Process. 23 (2008) 708713.

[51] Y. Birol, Surf. Coat. Technol., doi:10.1016/j.surfcoat.2010.06.038.[52] G.C. Wood, Corros. Sci. 2 (1962) 255268.[53] X.L. Wu, G.N. Chen, Acta Metall. Sin. 1998 (1998) 10331038.[54] Q.Y. Hou, J.S. Gao, F. Zhou, Surf. Coat. Technol. 2005 (2005) 238243.[55] W.H. Jiang, H.R. Guan, Z.Q. Hu, Mater. Sci. Eng. A271 (1999) 101108.[56] L. Bourithis, V. Gontzes, G.D. Papadimitriou, J. Mater. Process. Technol. 182

(2007) 608614.[57] M. Vardavoulias, G. Papadimitriou, D. Pantelis, Mater. Sci. Technol. 9 (1993)

711717.[58] R.L. Deuis, J.M. Yellup, C. Subramanian, Compos. Sci. Technol. 58 (1998)

299309.[59] L. Wang, D.Y. Li, Wear 255 (2003) 535544.[60] C. Navas, A. Conde, M. Cadenas, J. de Damborenea, Surf. Eng. 22 (2006) 2634.[61] S. Paldey, S.C. Deevi, Mater. Sci. Eng. A 342 (2003) 5879.[62] S.Y. Lee, S.Y. Lee, Solid State Phenom. 116117 (2006) 8487.[63] K. Bobzin, N. Bagcivan, P. Immich, Solid State Phenom. 141143 (2008)

249254.[64] S.Y. Yoon, J.K. Kim, K.H. Kim, Surf. Coat. Technol. 161 (2002) 237242.

Thermal fatigue testing of Stellite 6-coated hot work tool steelIntroductionExperimental procedureResults and discussionConclusionAcknowledgementsReferences