GH4169合金激光选区熔化成形工艺与缺陷特征的相关性

Correlation of forming process and defect characteristics of selective laser melted GH4169 alloy

通过改变激光选区熔化成形工艺,即激光功率和扫描速度,制备多个GH4169试样。采用金相法观察显微组织及其内部缺陷的形貌与分布,采用X射线断层成像获得试样孔隙率,并统计分析缺陷三维特征,研究成形工艺与缺陷特征的相关性。结果表明:当能量输入密度为59.1 J/mm^(3)的优化工艺时成形试样中互相搭接的熔道形貌齐整、随机分布的规则气孔尺寸小于30μm、致密度高达99.9998%。在较窄的工艺窗口下(220~300 W、700~1300 mm/s),试样致密度对扫描速度更为敏感,高扫描速度易形成分布在熔道搭接区内极不规则的未熔合。偏离优化工艺时,缺陷数量增多,部分缺陷尺寸大于30μm,其中高激光功率形成的气孔形状或高扫描速度形成的未熔合形状都与各自的尺寸密切相关,即尺寸越大,形状越不规则,产生的不利影响要远大于规则气孔。

Multiple GH4169 samples were prepared with the regulation of the forming process of selective laser melting(SLM),particularly in laser power and scanning speed.The microstructure including defect morphology and distribution was observed by using metallography.The sample porosity was acquired using X-ray computed tomography(XCT),and the three-dimensional characteristics of defect were also statistically studied.The correlation of forming process and defect characteristics was finally analyzed.The results show that when the optimized energy input density is 59.1 J/mm^(3),the forming samples share common features of overlapping melting trace with a tidy morphology,randomly distributed pores with sizes of less than 30μm and the density is as high as 99.9998%.Within a narrow window of forming process(220-300 W,700-1300 mm/s),the scanning speed takes more responsibility for the sample density,and its high value tends to form extremely irregular lack of fusions(LOFs)that distribute in the overlap of melting trace.As deviating from the optimized process,the number of defects has increased,and some defect sizes are also greater than 30μm.The shapes of pores and LOFs respectively formed by high laser power or high scanning speed are closely related to their own sizes,that is,the larger the size,the more irregular the shape,which produces more detrimental effects than regular pores.