Sunil B. Badwe PhD, Chief Metallurgist, North American Hoganas
Somayeh Pasebani PhD, Assistant Professor, Oregon State University
17-4PH is a popular alloy, due to its high strength and corrosion resistance. When fabricated with L-PBF technique and treated with standard heat treatments, this alloy is still inferior in mechanical properties in comparison to wrought counterparts. This difference stems from the dramatic difference in the microstructures. Microstructure in L-PBF fabricated parts is dendritic and consists of Martensite along with retained Austenite; whereas wrought microstructure is fully Martensitic. An attempt has been made to modify the microstructure by incorporating higher carbon, 0.2% vs 0.07% in the composition and annealing parts at higher temperature 1315 C vs 1050 C. Increased carbon will lead to increasing % of Martensite in the microstructure and increased annealing temperature will help recrystallize the dendrites. Such a microstructure will give a proper platform for the further hardening heat treatment, where the precipitation of fine Cu rich intermetallic will occur in the matrix. The mechanical properties of such parts are found to be comparable with the wrought properties.