Effect of Nb Content on Microstructure and Mechanical Properties of Hypereutectic High Chromium Cast Iron

The primary carbide in hypereutectic high chromium cast irons（HCCIs） was refined by the addition of Nb during air cooling, and the influences of Nb content on the microstructure and mechanical properties of hypereutectic HCCIs in cooling condition were investigated. The results show that Cr₂Nb forms firstly in the alloy by Nb addition during the solidification process, increase nucleation rate and refine the proeutectic carbide, then increase the hardness of Nb contained hypereutectic HCCIs. The hardness reaches 86.5 HRC, when 1.5%Nb content is added.