Effects of Heat Treatment on Microstructure and Properties of 347 Stainless Steel Alloy Prepared by Wire Arc Additive Manufacturing

Herein, 347 austenitic stainless steel parts are made by the wire arc additive manufacturing process. Then, the effects of solution heat treatment at 1150 degrees C for 3 h followed by NbC stabilizing heat treatment at 950 degrees C for 1 h on the properties of the alloy are investigated. Results show that after solidification, delta-ferrite and NbC carbide particles are formed in the gamma matrix while heat treatment eliminates the delta phase. Tensile test results show that for the as-prepared alloy, yield strength varies between 336 and 352 MPa, tensile strength between 559 and 589 MPa, and elongation between 50% and 58%. However, heat treatment results in a 20-22% decrease in yield strength, a 5-10% decrease in tensile strength, and a 5% decline in elongation. The potentiodynamic (PD) polarization test results show that the ICORR and the corrosion rate of the WAAM 347 stainless steel in the as-prepared condition are separately 4.9 and 5.6 times higher than the wrought alloy. After heat treatment, the ICORR increases from 5.84 x 10-6 A cm-2 in the as-prepared alloy to 6.68 x 10-6 A cm-2 and the corrosion rate from 0.0678 to 0.0776 mm y-1. This means that the heat treatment deteriorates the corrosion resistance of the WAAM 347 stainless steel alloy by about 14%. Microstructure, mechanical properties, and corrosion resistance of a 347 stainless steel alloy manufactured by wire arc additive manufacturing (WAAM) process in the as-prepared and heat-treated conditions are compared with a similar wrought alloy. The wrought alloy has the highest tensile strength and corrosion resistance, while heat treatment deteriorates both mechanical properties and corrosion resistance of the WAAM alloy.image (c) 2023 WILEY-VCH GmbH