Mild Wear Transition by Supply of Powder on Sliding Surface

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When metals slide against each other, a transition from severe running-in wear to mild steady wear is observed. In mild wear, a metal surface is covered with a protective oxide layer that prevents intermetallic contact, resulting in a low wear rate.In this research, the effects of supplying iron-oxide or iron particles on rubbing steel surfaces were investigated by a pin-on-disc wear test method. Particularly, the influence of the size of supplied Fe_2O_3 oxide particles on the transition from severe running-in to mild steady wear with sliding distance was studied.It was found that the supply of fine oxide particles with diameters of 0.5 μm and less accelerated the severe-mild wear transition. In these wear tests, the worn surfaces of the disc were discolored to red, suggesting that compact oxide layers were formed on the rubbing surfaces. The sliding distance of the severe-mild wear transition was reduced when finer particles were supplied, suggesting that fine particles easily form compacted layers on the wear surface. On the other hand, employing oxide particles of 1 μm, no severe-mild wear transition was observed, producing a wear curve similar to that observed in the test where no particles were supplied. The present work is the first to show the critical size of oxide particles, which are considered to be responsible for the formation of protective compact oxide layers on the surface for mild wear; between 0.5 and 1.0 μm in diameter.