Study of multi-layer deposition in L-DED process for 15–5 PH stainless steel: A numerical and experimental approach

Abstract

The present work investigates the multilayer deposition of 15–5 Precipitation Hardening (PH) stainless steels via Laser based Direct Energy Deposition (L-DED). The laser power and scanning speed are kept constant at 450 W and 5 mm/s with energy density of 75 J/mm2. At present, very limited literatures are available on the thermal behavior of 15–5 PH multi-layer deposition in relation with its micro structural characteristics. The complex thermal phenomena include repetitive heating and cooling cycles were simulated using 3-D multi-physics model. Through this numerical investigation temperature data of the specific region was captured and correlated with the micro structural morphology. The 15–5 PH multilayer deposition showed clear columnar grains and ferrite transformation. The XRD result revealed that austenite (ɣ) phase fraction increased with the increase in layer deposition. The IPF phase fraction map shows 1.5 % increase in retained austenite phase fraction with each layer addition. In 15–5 PH multilayer deposition the grains are primarily oriented along the 〈101〉/〈001〉 direction and with addition of layer High angle grain boundary (HAGB) fraction increases. The detailed texture analysis shows that as the layer increases, there is formation of brass, copper, shear and rotated goss structure. Similarly, it exhibited proportional rise in hardness due to its δ-ferrite dominating phases and higher HAGB percentage.