Self-lubrication mechanism via the in situ formed lubricious oxide tribofilm

Abstract

In situ formation of tribofilms is indispensable to reduce the wear volume and friction coefficient in dry. These tribofilms must be robust even in working at high normal pressure and sliding velocity between work materials and tools. Although TiN and TiC ceramic coating films are frequently utilized as a protective coating for dies and cutting tools, they often suffer from severe, adhesive wearing in dry forming and machining. Chlorine ion implantation assists lubricious oxide film to be in situ formed during wearing. At the presence of chlorine atoms in the inside of TiN or TiC films, in situ formation of lubricous intermediate titanium oxides with TiO and Ti n O 2 n−1 is sustained to preserve low frictional and wearing state. The fundamental process of this self-lubrication mechanism on the tribofilms, is discussed together with microscopic analysis and observation of worn surface and wear debris. The self-lubrication process works well in dry machining in order to reduce the flank wear of cutting tools even in the higher cutting speed range up to 500 m/min.