Cr、V、Ta添加剂对超粗晶和特粗晶硬质合金电化学腐蚀行为的影响
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摘要
以WC–8.4Co、WC–8.4Co–0.4Cr3C2、WC–8.4Co–0.4VC和WC–8.4Co–0.4TaC等4组超粗晶和特粗晶硬质合金为研究对象,采用Tafel曲线和电化学阻抗谱(EIS)研究4组合金在pH=1的H2SO4溶液、pH=7的Na2SO4溶液以及pH=13的NaOH溶液中的电化学腐蚀行为,采用扫描电镜观察合金的腐蚀表面。结果表明,与WC–8.4Co合金相比,在3种不同pH值腐蚀溶液中WC–8.4Co–0.4Cr3C2、WC–8.4Co–0.4VC和WC–8.4Co–0.4TaC合金的耐腐蚀性能均得到改善,Cr3C2改善合金耐腐蚀性能的效果最佳;4组合金在pH=13的NaOH溶液中的耐腐蚀性能均优于其在pH=1的H2SO4溶液中的耐腐蚀性能。合金腐蚀机理为:与溶液接触时,合金中Co粘结相优先腐蚀,产生活性溶解,同时WC发生局域腐蚀。
The electrochemical corrosion behaviors of WC–8.4Co,WC–8.4Co–0.4Cr3C2,WC–8.4Co–0.4VC and WC–8.4Co–0.4TaC extra coarse and super extra coarse cemented carbides were investigated by means of Tafel curves and Nyquist plots.Electrochemical experiments were carried out in H2SO4 solution(pH=1),Na2SO4 solution(pH=7) and NaOH solution(pH=13).Corrosion surface of the alloys were observed by scanning electron microscopy(SEM).The results show that,comparing with WC–8.4Co referential alloy,the corrosion resistances of WC–8.4Co–0.4Cr3C2,WC–8.4Co–0.4VC and WC–8.4Co–0.4TaC alloys in all the three kinds of corrosion solutions are improved.Among the three additives,Cr3C2 demonstrates the strongest ability in the improvement of the corrosion resistance.All the four alloys exhibit better corrosion resistance in NaOH solution(pH=13) than that in H2SO4 solution(pH=1).The corrosion mechanism is as following: while the alloy is in contact with the corrosion solution,a preferential corrosion and active dissolution take place in the Co binder phase and the corrosion reaction also takes place in the local region of WC grains.
The electrochemical corrosion behaviors of WC–8.4Co,WC–8.4Co–0.4Cr3C2,WC–8.4Co–0.4VC and WC–8.4Co–0.4TaC extra coarse and super extra coarse cemented carbides were investigated by means of Tafel curves and Nyquist plots.Electrochemical experiments were carried out in H2SO4 solution(pH=1),Na2SO4 solution(pH=7) and NaOH solution(pH=13).Corrosion surface of the alloys were observed by scanning electron microscopy(SEM).The results show that,comparing with WC–8.4Co referential alloy,the corrosion resistances of WC–8.4Co–0.4Cr3C2,WC–8.4Co–0.4VC and WC–8.4Co–0.4TaC alloys in all the three kinds of corrosion solutions are improved.Among the three additives,Cr3C2 demonstrates the strongest ability in the improvement of the corrosion resistance.All the four alloys exhibit better corrosion resistance in NaOH solution(pH=13) than that in H2SO4 solution(pH=1).The corrosion mechanism is as following: while the alloy is in contact with the corrosion solution,a preferential corrosion and active dissolution take place in the Co binder phase and the corrosion reaction also takes place in the local region of WC grains.
引文
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[2]-KERMAN J,ERICSON T.Cemented carbide body with improved high temperature and thermomechanical properties:USA,6 692 690[P].2004–02–17.
[3]马丽丽.WC–Co硬质合金在水中的腐蚀行为[J].粉末冶金材料科学与工程,2010,15(6):635–639.MA Li–li.Corrosion behavior of cemented carbide in water[J].Materials Science and Engineering of Powder Metallurgy,2010,15(6):635–639.
[4]SUTTHIRUANGWONG S,MORI G.Corrosion properties of Co–based cemented carbides in acidic solutions[J].International Journal of Refractory Metals and Hard Materials,2003,21(3/4):135–145.
[5]KELLNER F J J,LYNCH R,VIRTANEN S.Influence of Ca ions and temperature on the corrosion behavior of WC–Co hardmetals in alkaline solutions[J].International Journal of Refractory Metals and Hard Materials,2010,28(3):370–376.
[6]HUMAN A M,EXNER H E.The relationship between electrochemical behaviour and in–service corrosion of WC based cemented carbides[J].International Journal of Refractory Metals and Hard Materials,1997,15(1/3):65–71.
[7]MORI G,ZITTER H,LACKNER A,et al.Influencing the corrosion resistance of cemented carbides by addition of Cr3C2,TiC and TaC[C]//KNERINGER G,R-DHAMMER P,WILDNER H.Proceedings of the 15th International Plansee Seminar,Reutte,Austria:Plansee Holding AG,2001,2:222–236.
[8]KONADU D S,MERWE J,POTGIETER J H,et al.The corrosion behaviour of WC–VC–Co hardmetals in acidic media[J].Corrosion Science,2010,52(9):3118–3125.
[9]王兴庆,李晓东,郭海亮,等.Al含量对WC–Co硬质合金耐腐蚀性能的影响[J].粉末冶金材料科学与工程,2006,11(4):219–224.WANG Xing–qing,LI Xiao–dong,GUO Hai–liang,et al.Influence of Al content on properties of corrosion resistance of WC–Co cemented carbide[J].Materials Science and Engineering of Powder Metallurgy,2006,11(4):219–224.
[10]陈康华,邹丹,李詠侠.硬质合金钝化与伪钝化行为的研究进展[J].硬质合金,2007,24(3):181–187.CHEN Kang–hua,ZOU Dan,LI Yong–xia.Advance in the study of the passivation pseudopassivation behaviours of cemented carbides[J].Cemented Carbide,2007,24(3):181–187.
[11]SUTTHIRUANGWONG S,MORI G,K-STERS R.Passivity and pseudopassivity of cemented carbides[J].International Journal of Refractory Metals and Hard Materials,2005,23(2):129–136.
[12]史美伦.交流阻抗谱原理及应用[M].北京:国防工业出版社,2001:38–58.SHI Mei–lun.AC impedance spectroscopy principles and applications[M].Beijing:National Defence Industry Press,2001:38–58.
[13]YEO S,KIM D J,PARK J W.Enhanced corrosion resistance of WC–Co with an ion beam mixed silicon carbide coating[J].International Journal of Refractory Metals and Hard Materials,2011,29(5):582-585.
[14]KELLNER F J J,KILLIAN M S,YANG G,et al.TEM and ToF–SIMS studies on the corrosion behavior of vanadium and chromium containing WC–Co hard metals in alkaline solutions[J].International Journal of Refractory Metals and Hard Materials,2011,29(3):376–383.
[15]HOCHSTRASSER S,REISS D,SUTER T,et al.ICP–MS,SKPFM,XPS,and microcapillary investigation of the local corrosion mechanisms of WC–Co hardmetal[J].Journal of The Electrochemical Society,2008,155(8):C415–C426.
[16]HOCHSTRASSER S,MUELLER Y,LATKOCZY C,et al.Analytical characterization of the corrosion mechanisms of WC–Co by electrochemical methods and inductively coupled plasma mass spectroscopy[J].Corrosion Science,2007,49(4):2002-2020.
[17]YAMANAKA Y,TANIUCHI T,SHIRASE F,et al.High–resolution transmission electron microscopy study of WC–Co alloy doped with other metal carbides;VC,Cr3C2,and ZrC[J].Materials Science Forum,2007,558/559:993–996.
[18]KELLNER F J J,HILDEBRAND H,VIRTANEN S.Effect of WC grain size on the corrosion behavior of WC–Co based hardmetals in alkaline solutions[J].International Journal of Refractory Metals and Hard Materials.2009,27(4):806–812.
[19]ZHANG Li,XIE Ming-wei,CHENG Xin,et al.Micro characteristics of binder phase in WC-Co cemented carbides with Cr-V and Cr-V-RE additives[J].International Journal of Refractory Metals and Hard Materials,2013,36(1):211-219.