激光熔覆Fe基涂层的耐蚀性能研究

Corrosion Resistance of Laser Cladding Fe-based Coating

采用金相显微镜、扫描电镜、能谱分析仪、X射线衍射仪、硬度测试、电化学腐蚀及盐雾试验机等分析了某立柱激光熔覆Fe基耐腐蚀涂层的组织形貌、元素分布以及耐腐蚀性能。结果表明,涂层组织致密均匀,与基体呈良好的冶金结合;涂层主要由BCC结构的α-Fe与Fe-Cr、Fe-Cr-Ni相组成,其平均硬度(HV_(0.2))为(598.86±15),基体平均硬度(HV_(0.2))为(277.51±18),涂层硬度约为基体硬度的2.2倍,热影响区的平均显微硬度略低,但高于基体材料;电化学测试结果表明,涂层的极化电阻是基体的109倍,极化曲线表明,涂层的腐蚀电位远高于基体的腐蚀电位,涂层的腐蚀电流比基体低两个数量级,远低于基体的腐蚀电流,表明涂层有更好的耐腐蚀性能;盐雾试验表明涂层的耐腐蚀性能达到9级。

The microstructure and element distribution,corrosion resistance of laser cladding Fe-based corrosion-resistant coating on the hydraulic support column were investigated by means of OM,SEM,EDS and XRD,and the corrosion resistance of the coating was analyzed by means of microhardness,electrochemical corrosion and salt spray testing machine.The results reveal that the microstructure of the coating is compact and homogeneous,which has a desirable metallurgical bonding with the substrate.The coating is mainly composed ofα-Fe with BCC structure and(Fe-Cr)as well as(Fe-Cr-Ni)phases.The average hardness of the coating is(598.86±15)HV_(0.2),and that of the substrate is(277.51±18)HV_(0.2),indicating the hardness of the coating is about 2.2 times that of the substrate.The average microhardness of the heat-affected zone is slightly lower,which is still higher than that of the substrate.The electrochemical test results demonstrate that the polarization resistance of the coating is 109 times that of substrate.The polarization curve manifests that the corrosion potential of the coating is much higher than that of the substrate,while the corrosion current of the coating is two orders of magnitude lower than that of the substrate,indicating the better corrosion resistance of the coating.Salt spray test proves that the corrosion resistance of the coating reaches grade 9.