Wear Resistance of the HT250 Brake Disk Treated by Gas Nitriding

HT250 the brake disk was treated by gas nitriding for improved wear resistance, corrosion resistance and prolong service lifetime. The microstructure and phase of the nitrided and unnitrided samples were analyzed and the wear mechanisms were discussed under dry sliding with a pin-on-plate configuration. The results indicate that the thickness of the nitriding layer treated by gas nitriding at the 530 ℃×10 h was 0.3 mm and the surface hardness was HV_0.11 140. The friction coefficient of the nitrided sample was higher than that of unnitrided sample under loads of 20, 50 and 100 N. However, the wear rates were reduced by 11.1% (20 N), 27.5% (50 N) and 38.3% (100 N) using unnitrided sample as reference. The wear mechanisms of the unnitrided sample was fatigue peeling wear accompanied by abrasive wear. The wear mechanism of the nitrided sample was peeling wear. The compressive residual stress of nitriding layer inhibited the crack propagation and improved the wear resistance.