Optimize the Corrosion and Mechanical Performance of Additive-Manufactured Nano-Size WC-Reinforced Stainless Steel Matrix Composites by Heat Treatments

Adding 200 nm WC can dramatically increase the mechanical properties of laser powder bed fusion (LPBF) 420 stainless steel, whereas the evolution of the microstructure, corrosion resistance, wear resistance, and tensile performance in LPBF 420 + 2 wt% WC MMCs is not researched yet. WC increases the hardness of the LPBF MMCs. WC offers W and C to the matrix during laser scanning, with C diffusing to the matrix to form austenite and Cr-rich carbides. The austenite content increases with higher tempering temperatures by up to 22% after heat treatment at 400°C. However, more numbers and large size Cr-rich carbides are formed after being tempered at 600°C. Austenite increases pitting corrosion resistance by a higher critical pitting potential and lower pit growth kinetics. Wear resistance is linearly related to the hardness value, with smaller grain and more austenite improving ductility without sacrificing tensile strength. Overall, LPBF 420 + 2 wt% WC MMCs has the best corrosion in 0.1 M NaCl, with optimized mechanical properties.