Influence of Annealing Heat Treatment on the Microstructure and Mechanical Properties of Multilayer 316L-TiC Composite Fabricated by Selective Laser Melting

Abstract

Selective laser melting (SLM) can induce residual stresses in components, especially those with multilayer structures and varying thermal properties. This study investigates the effect of annealing post-heat treatment on the microstructure and mechanical properties of multilayer 316L stainless steel composite reinforced with TiC particles. Three-layer composite samples of 316L/316L-5%TiC/316L-10%TiC (wt.%) were fabricated using the SLM method. One set of samples was then annealed at 1100 °C for 1 h followed by air cooling, while another set remained as-produced. Both sets were characterized using optical and electron microscopy. Additionally, the wear behavior and the hardness of samples were evaluated. Results reveal defect-free interfaces and increased hardness in TiC-reinforced layers after annealing, along with improved ductility. The microstructure, initially with fusion lines and elongated austenite grains, transitioned to an equiaxed grain microstructure after annealing, with no observable cellular structure. Annealing enhanced both the ductiliy of the pure 316L layer and the overall strength of the multilayer sample. Despite a slight decrease in wear performance after annealing treatment, the TiC reinforcement effectively improved wear performance for the layers. This study highlights the importance of annealing in optimizing the microstructure and mechanical performance of SLM-produced functionally graded composites for advanced applications.