Specimen-counterface bulk hardness effects in impact wear of 17-4 PH steel pairs

Impact sliding wear tests have been performed with 17-4 PH steel as both specimen and counterface material. Tests were designed to explore the influence of bulk hardness; this was done by contacting hard pins against soft discs and vice versa. Additional wear tests were conducted with specimen and counterface of equal hardness. The entire program employed four distinct microstructural conditions in the hardness range from 30 to 44 HRC. The results indicate that for the test conditions explored the wear rate of the specimens (pins) depends on the “hardness pair” while the counterface (disc) wear does not. It was further shown that changes in specimen geometry (mushrooming) are of major relevance. The subsurface sections from the pins and discs formed characteristic zones of plastic deformation and mechanochemical mixing. In this, the hardest pin-softest disc and softest pin-hardest disc pairs developed essentially the same near-surface zone on the counterface, irrespective of initial microstructural condition.