Effect of Nb Micro-alloying on Microstructure and Wear Resistance of Medium-carbon Wear-resisting Steel

The design of alloy composition and the optimization of heat treatment process for shield machine disc shaped hobring were studied. The as-cast and heat treatment state microstructure, and friction wear morphology of ring were analyzed by using optical microscope（OM） and scanning electron microscope（SEM）. The wear resistance experiments were performed using friction wear equipment. The results show that with the addition of Nb element, the solidification segregation of the as-cast microstructure decreases and the microstructure is obviously refined. After heat treatment, the grain refinement is uniform and segregation is basically eliminated. The friction and wear morphology of the sample without Nb is dominated by furrow wear, and that of the sample with 0.01wt%-0.02wt% Nb is dominated by adhesive wear. The friction and wear morphology of the sample with 0.04wt%-0.05wt%Nb is both furrow wear and adhesive wear, and the wear amount and depth of 3 sample change the least after friction and wear, and the wear resistance is relatively good.