Wear Performances of Hypereutectoid P/M Steels Subjected to Different Heat Treatments

Dry sliding wear test specimens of high-carbon powder metallurgy steels were performed in accordance with the ASTM G99-05 standard. Heat treatment of sintered specimens was carried out by the austenitization process at 950°C for 4 min, next quenching in a salt bath at 210, 350 and 400°C for 60–360 s. Wear performances of the specimens were carried out with a constant load of 10 N, at a sliding speed of 1.00 m s^–1 and up to a sliding distance of 1000 m. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used for microstructure analysis and phase identification. It was seen that the friction coefficient of the specimen was not directly related to the hardness. The friction coefficient of the specimen with the lowest hardness, which was treated isothermal at 400°C, is lower than the specimen with higher hardness. However, even though the friction coefficient is low in this sample, the increase in the wear rate was remarkable. In other specimens, the coefficient of friction and wear rate decreased proportionally with the increase in their hardness. The wear rate of the specimens was reduced by the decrease in isothermal holding temperature and time.