Effects of niobium on network carbide in high-carbon chromium bearing steel by in situ observation analysis

The effect of Nb on the dissolution and precipitation behaviours of the network carbide in bearing steel, including the precipitation and dissolution temperature and the thickness of network carbide has been investigated in this paper. The precipitation and dissolution processes were carefully compared and analysed in bearing steels with different contents of Nb. The results showed that the presence of Nb has significantly reduced precipitation and dissolution temperatures of network carbide. The precipitation temperatures of Nb free, 0.018%Nb and 0.040%Nb steel are found to be 753°C, 723°C and 719°C, and the dissolution temperatures are 845°C, 785°C and 780°C, respectively. The average thicknesses of network carbide in 0.018%Nb steel and the 0.040%Nb steel are reduced by 21% and 27% compared with Nb-free steel, respectively.