Wear resistance of Cu–Ni–Mo austempered ductile iron

A series of ductile iron samples alloyed with 0.66% Cu, 1.02% Ni, and 0.26% Mo were austempered at 315 and 370 °C for 5–240 min and then tested for wear strength. A block-on-ring wear testing machine was used for this purpose. The wear samples were tested under a load of 45 N and a displacement speed of 2.40 m/s. The experimental outcome indicates that the wear properties of the austempered ductile iron (ADI) are strongly influenced by the exhibited microstructure. In particular, optimal wear properties were found in samples austempered at 370 and 315 °C for 90 and 120 min, respectively. These heat treatment times are long enough to promote the development of a relatively high volume fraction of high carbon retained austenite concomitant with ferrite and a fine dispersion of carbides. After wear testing, scanning electron microscopy (SEM) observations on the wear samples did not show any evidence of a transformation-induced-plasticity (TRIP). Hence, the experimental evidence suggests that the dominant wear mechanism was delamination associated with sub-surface crack formation and final wear particle debris removal.