Effect of heat treatment variables on microstructure and mechanical properties of 15Cr–4Ni–0·08C martensitic stainless steel

Abstract

In order to understand the best regime of heat treatment for 15Cr–4Ni–0·08C martensitic stainless steel, different heat treatment procedures involving solution treatment and tempering were investigated. The solution treatment was performed at temperatures of 900–1100°C for different soaking times of 30, 60 and 120 min followed by air cooling. Optical and scanning electron microscopy observations revealed that grain growth commenced by dissolution of pre‐existing chromium carbides at ∼1000°C after 60 min soaking. Therefore, this regime was considered as the best solution treatment procedure. The tempering treatment was performed on the solution treated samples at temperatures of 250–600°C for 2 h followed by air cooling. Standard tensile test and Charpy impact tests were performed on the tempered specimens and showed that two secondary hardening steps at 450 and 550°C contribute in ductility loss and increment of strength and hardness. The fractography observations corroborated the mechanical testing results.