Positron Studies of Subsurface Zone in Pure Iron Induced by Sliding

Positron annihilation spectroscopy and microhardness measurements were performed for pure iron samples after dry sliding. Well-defined depth profiles of edge dislocations decorated by vacancies and vacancy clusters were observed in the subsurface zone (SZ) of the samples studied. The vacancy clusters contained more than ten vacancies and their concentration decreased with the depth from the worn surface. Like in other metals studied, the depth profile of the defects detected exhibited the exponential decay with the depth. The total depth of the SZ was correlated with the load applied during sliding but did not exceed 220 μm. The defect profile in the SZ was revealed also in raw iron samples after dry sliding and blasted iron samples. In the case of raw iron, the profile induced by sliding overlaps defect structure which already exists in a raw material.