Effect of the normal load on the sliding wear behavior of Hadfield steels

This work studies the tribological behavior of Hadfield steel under sliding wear conditions. Wear tests were performed on Hadfield steel in the pin-on-disk configuration. The pins were manufactured from Hadfield steel, and the discs were manufactured from H-13 (600 HV). The normal load varied in 6 levels between 50 N and 500 N, and the test time and sliding speed were 0.18 m/s and 60 min, respectively. The friction force was monitored during the tests, and the mass loss was obtained afterward. Microhardness profiles were taken in the cross section. The worn surfaces and subsurface were analyzed with scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that the mass loss increases with increasing normal load until the load reaches 100 N, but the mass loss decreases for subsequent increments until the load reaches 300 N. After increasing the normal load to 500 N, the mass loss increases again. The lowest and highest values of mass loss occur at loads of 50 N and 500 N, respectively. The peak mass loss is at a 100 N normal load, suggesting that some of the tests were conducted after the known severe–moderate wear transition. The coefficient of friction decreases monotonically with increasing normal load. Worn surface analyses show evidence of more severe wear after applying higher loads (300 N–500 N). The wear mechanisms of the higher loads are plastic deformation, abrasion, rupture, and oxidation of the oxide layer; the wear mechanisms of the lower loads are oxidation and adhesion. The area fraction of oxides on the worn surface increases with increasing normal load, justifying the reduction in the coefficient of friction. A martensitic transformation occurs in tests with normal loads between 300 N and 500 N, justifying the increase in hardness after the tests.