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

Abstract

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/mm3，the forming samples share common features of overlapping melting trace with a tidy morphology，randomly distributed pores with sizes of less than 30 μm 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 30 μm. 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.

Keywords

• selective laser melting
• gh4169 alloy
• forming process
• melting trace
• defect