针对K640钴基合金粉末进行选区激光熔化(SLM)成形工艺优化实验, 以期获得高致密度K640合金的工艺参数。在固定层厚条件下, 研究了激光功率、扫描速度、扫描间距、扫描线长度对致密度的影响,分析优化参数下成形件的显微组织, 探讨激光线能量密度与成形件粗糙度以及维氏硬度的关系。研究结果表明, 成形件致密度随着激光线能量密度的增加呈先增大后减小趋势, 随着扫描间距和扫描线长度的增加, 致密度不断减小, 最终在激光功率190 W、扫描速度800 mm/s、扫描间距0.08 mm、扫描线长度0.08 mm下获得98.2%高致密度试样; 成形件上表面和侧面粗糙度结果相差较大, 上表面粗糙度随着激光线能量密度的增加而缓慢减小, 而激光线能量密度对侧面粗糙度并无明显影响; 选区激光熔化成形的K640合金平均硬度达到500 HV, 高于传统铸造K640合金硬度。

The process parameters experiment of selective laser melting (SLM)forming K640 cobalt-based alloy was carried out to obtain the optimal process parameters with high relative density. The effects of different parameters including laser power, scan speed, scan spacing and scan vector length on the relative density, surface roughness and hardness were studied under certain layer thickness. The microstructure of the specimens with high density under optimal parameters was then analyzed. Research results show that the relative density increases as the laser energy density increases, but it then decreases as the energy density increases. Besides, the relative density decreases with the increase of the scan spacing and the scan vector length. Ultimately, with the laser power of 190 W, scan speed of 800 mm/s, scan spacing of 0.08 mm, scan vectors length of 0.08 mm, K640 alloy samples fabricated by SLM with 98.2% high relative density are obtained. The surface roughness has great differences between the upper surface and the side surface. With the increase of laser energy density, the upper surface roughness decreases slightly, but the energy density has no obvious effect on the side surface roughness. The average hardness of K640 alloy fabricated by SLM is 500 HV, which is higher than that of the conventional cast K640 alloy.