WC粒度对超音速火焰喷涂WC-10Co-4Cr涂层耐腐蚀性能的影响

摘要

Two kinds of WC-10Co-4Cr coatings on 45# steel substrate were fabricated by High Velocity Oxygen Fuel (HVOF). The cemented carbide feedstock powders containing submicron WC and micron WC particle respectively were produced by the granulating and speedy high temperature sintering process. The microstructures and corrosion-resistance property of the coatings were studied, especially the corrosion processes and corrosion mechanisms were analyzed. The results show that compact microstructure and good coherence in interface of the coatings are obtained. The coating containing submicron WC particle has a relatively low porosity, resulting in the corrosion resistance being superior to the coating containing micron WC particle. Electrochemical corrosion mechanism of the coatings in 3.5%NaCl solution is galvanic corrosion between hard phase WC and binder phase Co. The low Co potential results in the prior corrosion of Co phase. Along with the process of corrosion, the WC particles are shed and the pitting phenomenon occurrs.%采用制粒−高温快速烧结法制备两种分别含亚微米级和微米级WC粒径的WC-10Co-4Cr喷涂粉末，并用超音速火焰喷涂(HVOF)技术在45#钢基体上制备涂层；利用扫描电子显微镜和电化学工作站分别对涂层的显微形貌及耐腐蚀性能进行分析检测，探讨WC粒度对涂层耐腐蚀性能的影响和涂层的电化学腐蚀机理。研究结果表明：两种涂层组织致密，界面结合良好；含亚微米级WC粒径的涂层具有相对较低的孔隙率，使其涂层的耐腐蚀性能优于含微米级WC粒径的涂层。在3.5%NaCl溶液中涂层的硬质相WC和粘结相Co发生电偶腐蚀，且低电位的Co相优先腐蚀，导致WC颗粒脱落，出现凹坑及点蚀现象。