Effects of heat treatment parameters on the microstructure and mechanical properties of laser power bed fusion (LPBF) 316L stainless steel

• Main Author: Sun, Yuheng
• Other Authors: Upadrasta Ramamurty
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/181840
• Institution: Nanyang Technological University

The 316L austenitic stainless steel (just referred to as 316L here after) is widely used in chemical, biomedical, and marine engineering industries due to its excellent corrosion resistance and mechanical properties. Laser powder bed fusion (LPBF) significantly enhances the microstructure and mechanical properties of 316L compared to conventional manufacturing methods, owing to the rapid cooling rates and high energy input involved in the LPBF process. These conditions result in fine-grained structures with cellular structures and high density of dislocations that contribute to improved strength and ductility. However, post-processing is often required to modify the microstructure, enhance properties, relieve residual stresses, and reduce anisotropy. This study investigates the recrystallization mechanisms during heat treatment of LPBF 316L to achieve comparable mechanical properties and microstructures to conventionally manufactured (CM) 316L. The effect of annealing temperature and time on the microstructure and mechanical behaviors were investigated in this work. No obvious recrystallization was observed when the annealing temperature is below 1300 °C; annealing at 1200 °C for 30 minutes to 2 hours only led to partially recrystallization; full recrystallization was obtained at 1300 °C for more than 30 mins, where similar microstructure and mechanical properties were obtained to CM 316L. The mechanical properties of samples annealed at 1200 and 1300 °C with various holding times were further evaluated, and a wide property range is obtained, These findings contribute to optimizing thermal processing routes for the LPBF-manufactured components and ensuring their reliability in critical applications.