The friction and sliding wear of unlubricated 316 stainless steel in air at room temperature in the load range 0.5–90 N

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The reciprocating self-wear of 316 stainless steel in air and at room temperature has been investigated in the load range 0.5–90 N. Above approximately 40 N the debris was metallic, indicating a severe wear mode. The wear volume was a linear function of the sliding distance and the specific wear rate was independent of load. Below the 40 N load, after an initial severe stage, a transition occurred with a decrease in wear rate by up to an order of magnitude. The specific wear rate in both wear stages decreased with decreasing load, showing no indication of saturating at low loads. The load dependence of the wear volume V per unit sliding distance was of the form V = kL n where n ≈ 1.8 for both pre- and post-transition stages. The transition and the decreasing specific wear rates with decreasing load are thought to be associated with an increasing proportion of asperity interactions' being elastic rather than involving plastic deformation. It is proposed that wear occurs by a multistage mechanism of metal transfer to form prows, prow oxidation in the post-transition stage and prow breakdown. The transition is associated with a change in the rate-limiting step. This is believed to be the metal transfer step in the pre-transitional stage and the prow breakdown step in the post-transitional stage. Only a tentative correlation could be made between the onset of a wear transition and changes either in the friction behaviour or in the appearance of oxide in the wear debris. The friction data suggest that wear in the post-transition stage is a cyclic process of prow breakdown, prow re-formation by further metallic transfer, prow embrittlement by oxidation leading once again to breakdown and the formation of oxide-containing wear debris.