Improving the tribological behavior of copper through novel Ti–Cu intermetallic coatings

In order to improve the tribological properties of copper substrate, Ti–Cu intermetallic coatings were formed onto the surface of an oxygen free high conductivity (OFHC) copper by a pack cementation process. Evaluation of coated and uncoated samples carried out by a laboratory tribo-tester under dry conditions indicated significant improvements in tribological behavior of the coated samples. It was observed that the coefficient of friction was decreased from 0.8 in the uncoated copper to about 0.15 for the coated samples. Microstructural examination revealed that the specimen surface zone consists of three layers; the outermost layer is the transformation product of β phase containing α-Ti and Ti2Cu, the intermediate layer is composed of intermetallic compounds including the TiCu and Ti2Cu phases, and the innermost layer is a solid solution of titanium in copper. Accordingly, plastic deformation of the wear surfaces in coated samples decreased due to the presence of these intermetallic coatings. Study of wear surfaces, wear debris and counterface surfaces suggested delamination and oxidation wear to be the predominant wear mechanisms in the coated samples.