Characteristics of a Martensitic Stainless Steel by Additive Manufacturing

The objective of this project is to evaluate the mechanical properties and microstructural characteristics of a martensitic stainless steel using Powder Bed Fusion using laser (PBF-L), also known as Direct Metal Laser Sintering (DMLS), an additive manufacturing process. This report also embraces the effect of stress relief and heat treatment on mechanical properties and case depth of carburizing and nitriding treatments. During PBL-F, metal powder is deposited on a substrate (the build platform) and a laser beam scans over the powder surface, melting the powder. In order to reduce residual stress and improve mechanical properties, stress relief treatment is commonly employed on PBL-F manufactured materials. In summary, the samples after stress relief could have achieved tensile strength > 250 ksi, yield strength > 150 ksi, elongation > 14%, hardness > 48 HRC, and Charpy impact energy > 27 ft-lbs. After stress relief + quench & temper treatment, the coupons could have achieved tensile strength > 250 ksi, yield strength > 200 ksi, elongation > 14%, hardness > 48 HRC, and Charpy impact energy > 10 ft-lbs. After quench and temper treatment, there is a significant increase of yield strength, however, a decrease of Charpy impact energy. The surface of hardness could achieve 63 HRC for carburized coupon and 54 HRC for nitrided coupon, respectively.