316L不锈钢表面激光熔覆钴基合金组织及锌蚀机理

Microstructue and zinc corrosion mechanism of laser cladding Co-based alloy on 316L stainless steel

采用半导体激光器在316L不锈钢表面制备钴基合金熔覆层,对激光熔覆层的组织形貌、成分、结构及锌蚀机理进行了系统研究.结果表明,选择优化的激光辐照工艺参数,获得的钴基合金熔覆层表面平整、无裂纹、与基材呈良好的冶金结合.钴基合金熔覆层主要由γ-Co,M23C6及耐腐蚀性能优异的Laves相Co3Mo2Si和少量硬质耐磨相Co6W6C组成.在460℃熔融锌中腐蚀试验表明,钴基合金熔覆层的锌蚀机理为选择性腐蚀,熔覆层表层出现一层亮白色腐蚀过渡层,在过渡层内钴基固溶体基体优先发生腐蚀,导致Laves相剥落,从而形成了锌液对钴基合金熔覆层的进一步腐蚀.

Co-based alloy coating was prepared by using semiconductor laser on the surface of 3161.stainless steel.The microstructure.chemical composition,constituent phases and zinc corrosion mechanism of the laser cladding coating has been systematically studied.The results showed that with optimum process parameters of laser irradiation,the crack-free cladding coaling with good metallurgical bond to the substrate and flat surface could be obtained.Co-based alloy cladding coating was mainly composed of γ-Co,M_(23)C_6(M=Cr,Co,Fe) and the laves phases Co_3Mo_2Si of excellent corrosion resistance and hard wear-resistance phase Co_6W_6C.Liquid molten zinc corrosion tests at 460℃ showed that zinc corrosion mechanism of Cobased alloy cladding coating was a selective erosion.Corrosion transition region appeared on cladding surface in the color of bright white.Co-based solid solution matrix is preferably corroded at the transition region,which leads to spalling of laves phases.Therefore,the liquid zinc contributed to corrosion for the Co-based alloy cladding coating.