Effect of laser power on the microstructure and properties of additive manufactured 17-4 PH stainless steel in different fabrication atmosphere

The effect of laser power (400, 600, 800 W) on the microstructure and properties, such as porosity, strength and microhardness, of directed energy deposition 17-4 PH stainless steel in different fabrication atmosphere (atmosphere air and atmosphere Ar) was investigated via the view of thermal process. With the increase of laser power, the porosity of the samples decreased, and the Ar atmosphere further enhanced the effect through a power exponent law. The submicron (similar to 0.5 um) amorphous SiO2 particles and the nanoscale (similar to 35 nm) Cu-rich precipitates dispersed in the matrix strengthened the samples, and the dimensions changed when different atmosphere and heat treatment were employed which in turn influenced the strength and microhardness. The mechanical properties were also affected by content of austenite and the release of oxygen, which were dominated by thermal process and heat treatment.