Investigating the influence of post-deposition heat treatment (PDHT) on the characteristic changes in wire arc additively manufactured 410 martensitic stainless steel thin-wall structure

Abstract

Obtaining the desired material characteristics of an as-deposited martensitic stainless steel (MSS) structure fabricated by wire arc additive manufacturing (WAAM) is challenging due to several factors like inhomogeneity, precipitation, phase transition, etc. This investigation elucidates the impact of post-deposition heat treatment (PDHT) on the microstructural and mechanical properties of the WAAM-processed 410 MSS thin-wall structure and compares it with the as-deposited 410 thin-wall structure. The MSS thin-wall structure consists of retained austenite (γ), delta (δ) ferrite, martensite laths and Cr-rich M23C6 type carbide. The M23C6 volume fraction increases by up to 18 %, and the γ-phase fraction reduces by up to 40 % by applying PDHT. The PDHT process significantly changed the texture from {110}<011> to {001}<110>. The PDHT process increases the dislocation density (1.974 × 10−15 m−2) than the as-deposited condition (0.924 × 10−15 m−2). The total low energy boundary (LAGB+CSL) contribution of the as-deposited sample is 19.5 %, whereas the PDHT sample demonstrated a higher fraction of low energy boundaries of 32.4 %. The PDHT sample showed a much smaller distribution of grains with an average grain size of 11 μm compared to the as-deposited condition. The overall hardness increases from 468 HV to 487 HV after PDHT compared to the as-deposited condition with lower inhomogeneity across the build direction. The mean 0.2 % proof stress, ultimate tensile stress, and elongation of the PDHT sample increased by 17 %, 5 %, and 60 %, respectively, compared to the as-deposited sample.