对316L不锈钢进行了多层激光熔覆成形试验,采用光学显微镜(OM),扫描电子显微镜(SEM)和电子探针显微分析(EPMA)等手段对其微观组织特征和性能进行了分析测试,揭示了激光熔覆成形316L不锈钢组织形成的规律和机理,获得了无裂纹、无气孔等缺陷的致密熔覆成形组织。熔覆层内部主要由垂直于界面外延生长的柱状树枝晶和平行于扫描方向的转向枝晶组成,枝晶沿着与最大温度梯度最接近的〈100〉方向择优生长。结果表明,熔覆层成分均匀,稀释率小,与基体呈冶金结合,抗拉强度大大超过传统成形方法加工的材料,且具有较好的塑性。

Multi-layer laser cladding experiments of 316L stainless steel are carried out. Microstructural characteristics and properties are analyzed and tested with measurements of optical microscopy (OM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) etc. The microstructural forming regulation and mechanism of laser cladding 316L stainless steel are expounded, compact cladding microstructure free of cracks and porosities is also obtained. The inner cladding microstructure is mainly composed of epitaxial columnar dendrites perpendicular with cladding-substrate interface and tilting dendrite parallel to the direction of scanning speed. The dendrites grow preferentially along the 〈100〉 orientation nearest with the maximum temperature gradient direction. The results show that the composition of the cladding layers is homogeneous, the dilution is insignificant, and the cladding layers present a metallurgical bonding with the substrate. The tensile strength of the cladding layers has greatly surpassed that of the conventionally processed materials and the cladding layers present a better ductility.