DRY SLIDING WEAR OF AUSTEMPERED DUCTILE IRON

A series of austempered ductile iron samples were prepared at austempering temperatures of 370, 340, 300, and 270 degrees C. Their sliding dry wear behaviour was studied under applied loads of 110, 300, 500 and 800 N. The results obtained showed that the wear resistance is independent of austempering temperature with low applied loads, but shows a strong dependence on austempering temperature at high applied loads (500 and 880 N), reaching a maximum value at a temperature of 340 degrees C. Scanning electron microscopy observations show no evidence of transformation induced plasticity. Wear is explained as being due to subsurface fatigue, with cracks readily nucleated at plastically deformed graphite nodules, the wear controlling mechanism being the crack growth stage when wear shows a dependence on applied load and austempering temperature.