通过正交试验研究了激光功率、扫描速度、送粉速度对GH738合金激光沉积修复单道熔高、熔宽、熔深等特征尺寸的影响规律, 优化了工艺参数, 获得无缺陷显微组织; 分析了多道多层沉积试样熔合不良、裂纹等缺陷产生的原因及组织、硬度分布特点。结果表明: 沉积区呈典型的外延生长柱状枝晶, 枝晶间析出少量碳化物; 相对于基体, 热影响区碳化物明显减少, 同时热影响区γ′相尺寸明显增大; 沉积区硬度为350～470 HV0.3, 热影响区硬度为450～480 HV0.3, 均明显低于基体硬度480～510 HV0.3; 且沿沉积高度方向硬度逐渐降低。

The effect of laser power, scanning speed and powder feeding rate on feature sizes of weld height, weld width, weld depth during laser deposition repair single track GH738 alloy were investigated by orthogonal test; the parameters were optimized and defect-free microstructure was obtained; the reason of defects such as ill bonding & cracks in deposition zone and the characters of microstructure & microhardness were analyzed. The results indicate that the microstructure of GH738 deposition zone is made of columnar dendrites which grow epitaxially from the substrate. Few carbides are precipitated in the interdendrite. Compared with the substrate, the carbide in the heat affected zone is obviously reduced;meanwhile the size of γ′ phase in heat affected zone increases obviously. The microhardness of deposi-tion zone(350-470 HV0.3) and heat-affected zone(450-480 HV0.3) is lower than substrate(480-510 HV0.3),and microhardness decrease gradually along the deposition height direction.