Free-form manufacturing of pH 15-5 stainless steel via laser powder bed fusion

Abstract

The FYP-URECA research investigates the free-form manufacturing of PH 15-5 stainless steel via laser powder bed fusion. Free-form fabrication requires effective support structures. Therefore, functions, types, and optimization method of support structures were discussed extensively in this report. Furthermore, from literature review, it is found that, there is a lack of research done to investigate the effect of support structure on mechanical properties. The project successfully identified block support as the optimal choice for free-form fabrication. By applying Taguchi analysis, it is discovered that hatch teeth height has no effect on the removability of support structure. Conversely, Hatch teeth top length and hatch teeth base interval affects the removability of support structure. In terms of porosity, operating laser power of 375W and 500mm/s will achieve the lowest amount of porosity. In terms of hardness, no conclusive hardness trend can be identified in PH15-5 stainless steel. Solution heat treatment and ageing process can be used to strengthen the hardness and homogenize hardness distribution. Through microstructural analysis, the increase in hardness is due to the increase in carbide phase fractions after heat treatment. Recommended area for future research includes in situ monitoring to perform free-form manufacturing and heat simulation to optimize support structures.