为了提高选区激光熔化（SLM）成型金属零件的致密度,对激光扫描单道熔池的形成特性进行了研究,探讨了扫描速度、激光功率对熔池宽度的影响,发现熔池附近无粉区宽度与熔池宽度有直接关系,并分析了激光连续扫描粉末情况下的扫描线间搭接缺陷.根据单道熔池的形成特性,提出采用层间错开扫描策略,该扫描策略将零件致密度提高到近100%,使层间与层内的熔池搭接紧密,SLM成型件的拉伸强度、延伸率、显微维式硬度分别达636MPa、15%~20%和250~285.实验结果表明,层间错开扫描策略对SLM直接成型金属零件的致密度与力学性能有明显的改善.

In order to improve the density of metal parts fabricated via selective laser melting（SLM）,the characteristics of the single-track molten pool were investigated,and the influences of scan speed and laser power on the pool width were discussed,with a direct relation between the width of powder-free region around the molten pool and the molten pool width being summarized.Then,the joint defaults of scan lines during continuous scanning were analyzed.Moreover,according to the forming characteristics of the single-track molten pool,a layer stagger strategy of laser scanning was proposed.Experimental results indicate that,by taking the proposed strategy,the density of metal parts increases to about 100%,the molten pools between inner layers and inter-layers are jointed compactly,and the tensile strength,elongation and micro-Vickers hardness of the parts reach 636MPa,15%~20% and 250~285,respectively.It is thus concluded that the proposed layer stagger strategy greatly improves the density and mechanical performance of metal parts fabricated via SLM.