Effect of processing parameters on the fractions of martensite in 17-4 PH stainless steel fabricated by selective laser melting.

Martensitic phase transformation is an important strengthening mechanism for 17-4 PH stainless steel; this study has investigated the martensite fractions of 17-4 PH stainless steel processed by selective laser melting (SLM) with systematic variation in energy densities through adjustments in laser power, scanning speed, and hatch distance. Interestingly, the fractions of martensite have shown a positive correlation with the energy densities for specific hatch distance. Finite element analysis has suggested that an increase in energy density could promote higher residual stress to induce higher fractions of martensite due to greater thermal contraction during SLM process. Furthermore, this study has shown that a decrease in the hatch distance could induce higher fractions of reverted austenite due to more laser scanning overlaps, leading to a decrease in martensite fractions. Prediction equations based on SLM parameters for martensite fractions in 17-4 PH stainless steel have been established; this work demonstrates that martensite fractions of 17-4 PH stainless steel in as-built state can be designed by SLM process. • 17-4 PH stainless steel has been investigated by different SLM parameters. • Martensite fractions can be controlled by both energy density and hatch distance. • Higher energy density can increase martensite fractions for a given hatch distance. • Finite element analysis successfully correlates with experiments. • An equation to predict martensite fractions has been established. [ABSTRACT FROM AUTHOR]