Wear mode transition of hard films on ai alloys under variable normal load

The purpose of this investigation was to analyse the microscopic wear mode transition of TiN, Cr, and anodic oxide films on Al alloys in reciprocating sliding under lubricated conditions. For this purpose, a CCD microscope tribosystem was developed. By using this system, the dynamic wear processes of hard films could be observed successively: the following results were obtained. There are two critical normal loads Wc₁ and Wc₂. where Wc₁ is the critical normal load below which there is no spalling of the coating film at any number of reciprocations and Wc₂ is the critical normal load for spalling or flake formation of the coating film after a single sliding passage. The TiN film showed higher wear resistance when W<Wc₁. When W<Wc₁, spalling of the coating film did not occur at any time during the sliding test. When Wc₁ ≤ W < Wc₂, spalling of the coating film occurred after a certain number of reciprocations. When W≥Wc₂, spalling or flake formation of the coating film occurred after a single passage. The specific wear rate also changed dramatically with the transition of the wear mode.