Effects of annealing temperature on the microstructure, mechanical properties, and tribological performance of the Mn8/SS400 bimetal composite

Abstract

This study investigates the effects of annealing temperatures on the microstructure, mechanical properties, and tribological performance of Mn8/SS400 bimetal composite (BC) produced via hot-rolled bonding. Results show that annealing led to a microstructural transition in the Mn8 layer from a fully austenitic structure to a multiphase structure containing pearlite, ferrite, bainite, and retained austenite. The SS400 layer transformed from the bainitic ferrite (BF) and martensite/retained austenite (M/RA) to a more stable bainitic structure. Annealing at 600 °C resulted in optimal mechanical properties, with ultimate tensile strength (UTS) reaching 755.7 MPa and the best wear resistance. This enhancement is attributed to the synergistic strengthening provided by the multiphase microstructure and interfacial element diffusion across the interface. Higher annealing temperatures (700–800 °C) promoted the formation of intermetallic compounds (IMCs), reducing the interfacial diffusion layer width and consequently influencing wear behaviour. The study highlights that the multiphase strengthening and interfacial bonding between the Mn8 and SS400 layers are key to achieving superior mechanical and tribological performance, with the 600 °C annealed sample exhibiting the best overall properties.