Effect of vacuum carburizing-quenching parameters on the microstructure and properties of 20Cr2Ni4 Steel

This study systematically investigates the effects of vacuum carburizing and gas quenching parameters on the carbon distribution, microstructure, and properties of hot-rolled 20Cr2Ni4 structural steel. Experiments were conducted with carburizing temperatures of 1, 203 K, 1, 223 K, and 1, 243 K; diffusion times of 100, 114, and 140 minutes; and quenching pressures of 6, 8, and 10 bar. The results show that increasing the carburizing temperature significantly enhances carbon diffusion and deepens the effective case depth, but excessively high temperatures lead to grain coarsening and increased retained austenite. Longer diffusion times improve deep-layer carbon distribution and uniformity of the carburized layer. Higher quenching pressures effectively increase surface hardness and improve the core microstructure. The findings provide experimental and theoretical support for optimizing heat treatment processes of high-performance gears.