高硬度铁基熔覆层组织、成分及耐蚀性

Microstructure,Composition and Corrosion Resistance of Laser Cladding Fe-Based Coatings with High Hardness

通过在45#钢表面激光熔覆SDFe55合金粉末,制备高硬度(850HV0.2)铁基涂层,采用扫描电镜(SEM)、X射线衍射(XRD)、电子探针(EPMA)以及腐蚀实验设备研究激光熔覆层组织、成分及耐蚀性。结果表明,激光熔覆铁基涂层成型性良好,无裂纹、气孔等缺陷,熔覆层与基体呈冶金结合,由γ(Fe,Ni)和M23C6型碳化物组成。由于大量奥氏体组织、致密细小的枝晶的生成以及碳化物的弥散分布,使激光熔覆层的耐蚀性较45#钢提高。此外,熔覆层晶界处Fe元素含量略低,Cr、Mo元素在晶界处含量略高于晶内,Ni元素在整个熔覆层中均匀分布,合金元素成分分布相对均匀对熔覆层的韧性和耐蚀性起到积极作用。

SDFe55 alloy coating with high hardness （850 HV0.2 ） is prepared on the surface of piston by laser cladding. The structure, composition and corrosion resistance are studied by means of scanning electron microscope （SEM）, X-ray diffraction （XRD）, electron probe micro analysis （EPMA） and corrosion testing. The results show that laser cladding Fe-based coating is uniform without cracks and pores, has metallurgical bonding with the matrix, and is composed by 7（Fe, Ni） and carbides of type M23C6. The corrosion resistance is higher than that of 45~ steel due to combined effects of formation of austenite structure and refined dendrites, as well as disperse distribution of carbides. Moreover, composition distribution in the laser cladding layer is average, and the content of Fe element at the grain boundary is lower, and those of Cr, Mo elements at the boundary are higher than inside grain, while Ni element distributes homogeneously in the whole layer, which is beneficial to the improvement of ductility and corrosion resistance.