Study on microstructure and microhardness in surface layer of 20CrMnTi steel carburised at 880°C with and without RE

This paper deals with the effect of adding rare earth (RE) in 880°C drip-feed carburising atmosphere on the microstructure and microhardness profiles in carburised layer, carbon potential and kinetics of weight gain of 20CrMnTi steel. The results show that the incorporation of RE increases the carbon potential, flux of carbon and layer thickness. It is also found that compared with 880°C carburising, a good microstructure with a super fine martensite and less residual austenite were formed based on a lot of dispersed granular carbide precipitates in the surface layer during RE carburising, which resulted in a remarkable increase in microhardness.