Effect of Silicon Content on Wear Behavior of Heat Treated Powder Metallurgy Steels

Three different steel compositions with 1, 3 and 5 mass% Si were prepared using atomized iron (ASC.100.29) and 0.35 mass% natural graphite powders. The mixed powders were cold pressed at 700 MPa and sintered at 1200 °C for 30 min under pure Ar gas atmosphere. Some of the sintered specimens was quenched from 850 °C and then tempered at 100 °C for 1 h. The other sintered specimens were annealed at intercritical heat treatment temperature of 750 °C for 10 min and rapidly water-quenched. The experimental results showed that in as-sintered specimens inhomogeneously dispersed typical pearlitic structure in the ferrite matrix formed and its amount decreased with increasing Si content. In intercritically annealed specimens, the microstructure obtained was a mixture of partially transformed martensite and ferrite + pearlite. In quenched plus tempered specimens, beside tempered martensite, ferritic structure formed and its amount increased with increasing Si content. The wear tests were carried out under dry sliding conditions using a pin-on-disk type machine at constant load, speed and sliding distance. It was seen that, in all specimens, the friction coefficient and the wear rate both increased with increasing Si content. The increase of these values was less in the heat treated specimen than the as-sintered specimen