The wear of high-carbon metal-on-metal bearings after different heat treatments.

To study the tribological performance of metal-on-metal hip joint resurfacings, the wear performance of three pairs of Co-Cr-Mo alloy samples (pins and plates) were tested in a multidirectional pin-on-plate wear machine. An 'as-cast', a single-heat-treated, and a double-heat-treated set of specimens were tested to 3 x 10(6) cycles. The two heat treatments resulted in partial and full solution of the carbides into the matrix. An increasing trend in wear rate was found from 'as-cast' to the double-heat-treated specimens. The as-cast specimens showed the lowest wear rate (1.69 x 10(-6) mm3/N m), the reduced carbide samples had the next lowest wear rate (2.1 x 10(-6) mm3/N m), while the specimens without carbides wore the most (2.41 x 10(-6) mm3/N m).