Boundary Lubrication Studies on Undulated Titanium Surfaces

It is customary in tribological research, and especially in practice, to employ smooth surfaces, for it is generally believed that smooth surfaces should have low sliding friction. However the wear particles produced during sliding get trapped at the interfaces, and plowing by the wear particles becomes the principal mechanism of friction. Through experimental and theoretical investigations, it is shown that the plowing friction component can be substantially reduced by means of surface undulations. Steel-titanium and titanium-titanium pairs were tested to investigate the role of surface undulations in boundary lubricated sliding. Compared with the experimental results of flat titanium surfaces, friction coefficient and wear rate were considerably reduced with the undulated titanium surfaces, especially when lubricants considered ineffective for titanium were used. In addition, the effects of pad width and cavity volume fraction of the undulated surface were also investigated. A plowing model proposed for...