Effect of Powder Characteristics on Fatigue Performance of Additively Manufactured 17-4 PH Stainless Steel

The characteristics of powder feedstock used during laser powder bed fusion (L-PBF) influence the mechanical performance of the fabricated parts. The flowability, spreadability, and internal porosity of the powder can affect the porosity formation and thus, impact the fatigue performances. Two batches of 17-4 precipitation hardening stainless steel powders supplied by two different vendors were used to fabricate the L-PBF specimens and investigate the effect of powder characteristics on porosity and fatigue behavior. The powder batch with a wider particle size distribution, higher compressibility, higher cohesion between powder particles, and internal porosity resulted in a higher defect content in the fabricated specimens. Higher defect content led to inferior fatigue resistance along with more scatter in the fatigue lives. Fractography revealed the fatigue crack initiation from spherical pores as well as the lack of fusions in both batches.