A Comparative Study on the Microstructure and Texture Evolution of L-PBF and LP-DED 17-4 PH Stainless Steel during Heat Treatment

This study aims to characterize the microstructure and crystallographic texture of 17-4 PH stainless steel (SS) manufactured with laser powder directed energy deposition (LP-DED) and laser powder bed fusion (L-PBF), in both non-heat treated and heat treated conditions. It is found that the non-heat treated LP-DED 17-4 PH SS possesses coarse columnar ferrite grains decorated with Widmanstätten ferrite grains, whereas the L-PBF counterpart has very fine and mostly equiaxed ferrite grains along with lath martensite. An identical stress relief (SR) temperature is obtained for both the L-PBF and LP-DED 17-4 PH SS samples based on the phase diagrams generated using Thermo-Calc. software. The SR step prior to CA-H1025 heat treatment resulted in texture weakening and slightly refined the grain structure. The non-heat treated L-PBF 17-4 PH SS sample possesses strong cube and γ-fiber textures, while the texture transfers to weaker γ-fiber components after performing SR-CA-H1025 heat treatment.