激光熔覆Fe基非晶合金涂层裂纹分析

Analysis of cracks in laser clad Fe-based amorphous alloy coating

使用激光熔覆技术在304不锈钢基材表面熔覆铁基非晶合金涂层时产生了裂纹,通过对裂纹周围元素、硬度和裂纹易萌生处析出物的定性分析,研究了涂层裂纹成形机理。结果表明,涂层主要有α-Fe、α-Cr、碳化物(M_(7)C_(3)、M_(5)C_(2))、硅化物(CrSi_(2)、FeSi)等物相。裂纹主要由热影响区较大的热应力以及C、Si元素偏析而成的高熔点及高硬度的碳硅化物造成,裂纹带附近组织较为疏松且存在较多的缝隙和孔隙,同时硬质相结合不牢固,使得裂纹带附近硬度相较于同一水平其他无缺陷处的要低。

Cracks occurred when Fe-based amorphous alloy coating was cladding on the surface of 304 stainless steel substrate by using laser cladding technology. The crack forming mechanism was studied by means of qualitative analysis of the elements, hardness and precipitates around the cracks. The results show that the coating mainly contains α-Fe, α-Cr, carbides(M_(7)C_(3),M_(5)C_(2)), silicides(CrSi_(2), FeSi) and other phases. The cracks are mainly caused by the large thermal stress in the heat-affected zone and the high melting point and high hardness carbon silicide formed by the segregation of C and Si elements. The structure near the crack zone is relatively loose and there are more gaps and pores. At the same time, the combination of the hard phase is not strong, so that the hardness near the crack zone is lower than that of other defect-free areas at the same level.