Homogenization on solution treatment and its effects on the precipitation-hardening of selective laser melted 17-4PH stainless steel

Abstract

17-4 precipitation-hardened (PH) stainless steel (SS) exhibits high strength and good corrosion resistance via Cu-precipitation hardening. Unlike conventional wrought 17-4PH SS, Cu segregation and ε-Cu precipitates are observed in additively manufactured (AM) 17-4PH SS owing to the repeated rapid cooling after heating, which characterizes the AM process. In this study, solution treatment was conducted under various temperatures (1,000, 1,050, 1,100, and 1,200 °C) and durations (1, 2, 4, and 8 h) to minimize the negative effects of Cu segregation and ε-Cu precipitates on precipitation hardening. The mechanical properties and microstructures of each condition for the Cu precipitation behavior were examined. Although the ε-Cu precipitates did not disappear after solution treatment, the average diameter of the ε-Cu precipitates tended to decrease with increasing solution treatment temperature and duration. Therefore, solution treatment at a temperature of 1,200 °C for 8 h was the best, resulting in improved strength compared to the conventional solution treatment at 1,050 °C. Solution treatment on at least 1,100 °C is effective in AM.