Cr对超音速火焰喷涂WC-Co涂层抗中性盐雾腐蚀性能的影响

研究了超音速火焰喷涂(HVAF)WC-Co和WC-CoCr涂层的抗化学腐蚀性能。采用XPS对超音速火焰喷涂涂层的表面和内部进行了分析,在中性NaCl溶液中对涂层进行了电化学分析。结果表明,WC-Co中的粘结相Co主要呈金属单质,而WC-CoCr涂层中粘结相分别呈单质Co和Cr2O3。电化学极化测试表明,WC-Co涂层处理明显提高了基体的腐蚀电位,而添加Cr后则进一步提高了腐蚀电位。400 h中性盐雾腐蚀结果表明,WC-CoCr涂层的抗化学腐蚀性能优于WC-Co涂层的。腐蚀后的SEM表明,腐蚀介质先腐蚀涂层中的粘结相,当腐蚀介质扩散到基体中则优先腐蚀基体。添加少量的Cr在粘结相中形成了Cr2O3陶瓷钝化相,有利提高HVAF WC-Co涂层的抗腐蚀性能。

Influence of Cr on Corrosion Resistance of HVAF WC-Co Coats to Neutral Salt Spray

Corrosion resistance of high-velocity-airfuel(HVAF) WC-Co and WC-CoCr coats was investigated in this paper.The coats were characterized by XPS and electrochemical analysis.XPS analysis showed that the chemical states of adhesive phase in HVAF WC-Co coat was simple substance Co and in WC-CoCr coat were Co and Cr2O3.Electrochemical polarization showed that the corrosion potential of steel substrate was improved after HVAF WC-Co treatment;while the potential was further improved when adding Cr into WC-Co.Neutral salt spray for 400h displayed that WC-CoCr coat exhibits better corrosion resistance than WC-Co coat.The SEM observation revealed that the adhesive phase is preferentially corroded due to micro-electrochemical corrosion and when the corrosion mediun comes to interface,corrosion of the substrate occurs.For HVAF WC coat,the corrosion were governed by corrosion of adhesive phase,pervasion of corrosion medium and final corrosion of interface between HVAF WC coatings and substrate.Cr exists as Cr2O3 passive phase,which is beneficial to the corrosion resistance of HVAF WC-Co coat.