Experimental Analysis of Nano Carbide-Free Bainite Microstructure on Toughness

The aim of this study was to explore various heat treatment methods for producing nano carbide-free bainite (NCFB) in high-silicon spring steel. Silicon helps prevent carbide formation during austempering, promoting the development of NCFB. The steel composition used in this study was 0.55% C, 1.76% Si, 0.83% Mn, and 0.13% Cr. Heat treatments were carried out at different austempering temperatures of 300 °C, 350 °C, and 400 °C, with holding times of 10, 20, 30, and 40 min, after that shot peened all sample to achieve the desired microstructure. Analyze the toughness of the heat treated samples. The relationship between toughness and scanning electron microscopy were employed to analyze the phase composition and the stability of retained austenite.