Microstructure and properties of high-Si high-Mn bainitic steel after heat treatment

The transformation kinetics, microstructure, hardness, impact toughness and sliding wear properties of high-Si high-Mn bainitic steel containing 0.45C-2.50Si-2.20Mn(wt%) after austenitizing at 850, 880, 910, 940, 970 and 1000 °C were systematically studied by means of optical microscopy, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, laser confocal microscopy, x-ray diffraction, microhardness tester, Rockwell hardness tester and M-200 wear tester (Jinan Sida Testing Technology Co., LTD, China). The results show that the microstructure of the sample is mainly composed of acicular lower bainite, film-like retained austenite and martensite/austenite (M/A) after air quenching. As the austenitizing temperature increases, the microstructures refine first and then change little, the hardness increases first and then remains basically unchanged, the impact toughness decreases first and then increases, and the wear resistance first increases and then weakens, and increases again at 1000 °C. Under the same test conditions, the sample austenitizing at 910 °C shows higher hardness and toughness coordination before and after tempering at 250 °C, and the wear resistance is the best.