Microstructure and Non-Metallic Inclusions in 316L Steel Manufactured by HIP from Powder Precursors Surface Modified with Pd/Ru

摘要

Austenitic 316L stainless steel is used in Net Shape and Additive Manufacturing (NSAM) technologies for many different industrial applications. This work reports grain boundary characterization, grain size and non-metallic inclusions in 316L steel manufactured by Hot Isostatic Pressing (HIP) from gas-atomised powder precursors (25 - 45 μm), which were surface modified (surf. mod.) with either Pd or Ru after air melting. The proportions of Σ3 in conjunction with Σ9 coincident site lattice (CSL) boundaries increased in the order of 316L steel powder (11.3% and 1.3%) < HIP'd 316L Ru surf. mod. (34.7% and 1.4%) ≈ HIP'd un-doped sample (37.9% and 1.7%) < HIP'd 316L Pd surf. mod. (51.5% and 2.1%), corresponding to the order of maximum grain size (40, 76, 80 and 104 μm), but not generally to the average grain size (9.8 ± 6.7, 13.8 ± 11.3, 11.0 ± 9.1 and 19.7 ± 14.4 μm, respectively). Pd/Ru surface modification resulted in higher prior powder particle coverage in inclusions.