Entrapped Gas and Process Parameter-Induced Porosity Formation in Additively Manufactured 17-4 PH Stainless Steel

Abstract

Porosity is one of the most significant obstacles to widescale adoption of additive manufacturing since it acts as a stress concentrator that negatively impacts mechanical properties. Suboptimal process parameters and entrapped gas content in powder feedstock are two factors that can induce porosity in additively manufactured parts. This study utilizes laser diffraction, optical and scanning electron microscopy, and micro-x-ray computed tomography to study how four powders with varied entrapped gas concentrations and gas atomization environments create parts with different densities. Process maps of the four 17-4 PH stainless steel powders used in the EOS M 290 laser powder bed fusion machine, were developed. Furthermore, this paper also discusses how process parameters interact with the powder-entrapped gas porosity to influence the in-part porosity and the Charpy toughness of the as-built components.