材料期刊网

采用超音速火焰喷涂(HVOF)方法在碳钢基体上制备了NiCrBSi喷涂层, 对包覆样 品进行900 ℃保温2 h或10 min热处理, 利用电化学阻抗谱(EIS)研究了涂层在3.5%NaCl 水溶液中的腐蚀失效过程和耐蚀性的变化规律. EIS图谱分析表明, 喷态涂层抗介质渗透能力 差, 腐蚀20 h后介质可渗达碳钢基体；900 ℃, 2 h保温热处理涂层腐蚀 15 h后EIS谱发生明 显变化, 产生局部腐蚀；而900 ℃, 10 min处理涂层为均匀腐蚀, EIS谱形可长时间保持稳定. 利用等效电路拟合, 获取了涂层界面反应阻力(腐蚀抗力)随时间变化的关系, 显示高温短 时(10 min)热处理涂层的界面反应阻力高且稳定, 其耐蚀性和抗介质渗透能力远优于喷态 涂层, 但2 h保温热处理涂层的耐蚀性比喷态涂层的差. 利用组织结构分析解释了热处理影响 涂层腐蚀行为的原因.

NiCrBSi alloy powders were sprayed on a low carbon steel substrate using High velocity oxy-fuel (HVOF) spraying technique and then the samples with coating were heat treated in air furnace for 2h or 10min at 900°C. The corrosion failure process and corrosion resistance of coatings in 3.5% NaCl aqueous solution were investigated by using Electrochemical Impedance Spectroscope (EIS). EIS data shows that the as-sprayed coating cannot resist the penetration of corrosive solution and after 20h the steel substrate begins to be corroded. Local corrosion happens in 2h heat-treated coating if contacting coating with brine longer than 15h, while shape of EIS plots can hold stable for a long time and uniform corrosion happens in 10min heat-treated coating. Relationship of corrosion resistance with time for as-sprayed coating and heat-treated coatings in 3.5% NaCl was obtained using equivalent circuits. The corrosion resistance of 10min heat-treated coating and resistance to penetration of aqueous medium are far better than of as-sprayed coating, but the corrosion resistance of heat-treated coatings with long holding time (2h) is inferior to that of as-sprayed coating. The reasons why heat treatment can change the corrosion behavior of sprayed coating were discussed by the aid of analyzing microstructure.