Effect of construction angles on the microstructure and mechanical properties of LPBF-fabricated 15-5 PH stainless steel

In this study, 15-5 PH stainless steel were fabricated by laser powder bed fusion (LPBF) at different construction angles (0 degrees , 30 degrees , 45 degrees , 60 degrees , and 90 degrees ). Effects of construction angles on the microstructure, mechanical properties, electrochemical properties and surface characterization of 15-5 PH stainless steel were investigated. The LPBFfabricated 15-5 PH stainless steel exhibited a " track-track " overlap trajectory on the horizontal plane, and the vertical plane displayed the " layer -layer " overlap of the melt pool. All samples were composed of martensitic and austenite phases. Irregular grains and random grain orientation were found in each sample. In fact, the construction angle has an important role in the microstructure. The 0 degrees sample has the lowest martensite content (75.8%), since fewer deposited layers correspond to less number of thermal cycles. Due to the largest amount of martensite (90.1%), the 45 degrees sample exhibits the highest hardness of 308.9HV 0.2 . The similar tensile strength and yield strength are achieved for samples fabricated at different forming angles. Layer by layer melt pool boundary (MPBs) contributes to the ductile deformation, whereas track by track MPBs is favorable for brittle deformation. Samples with a larger construction angle have more layer by layer MPBs, resulting in the increased elongation. Therefore, the 0 degrees sample shows a minimum elongation of 20.1%, but the 90 degrees sample reaches a maximum elongation of 23.9%. The construction angle affects the corrosion resistance of the 15-5 PH SS by influencing the martensite content. As a result, the 0 degrees sample, with the highest austenite content (24.2%), shows the best corrosion resistance and lowest roughness.