Fretting study of an impregnated graphite bearing/nitrided stainless steel in a dry contact submitted to severe thermal-vibratory loading

Some industrial applications require the use of self-lubricating materials when fluid lubrication cannot be used. Carbon-based materials and in particular graphites are usually a used solution. However, the application of these materials is limited at high temperature; these materials are exposed to significant degradation and to high friction due to their high sensitivity to the air humidity and to the desorption phenomenon. This study determines the influence of a specific metallic impregnation on the graphite bearing, which is submitted to a severe thermo-vibratory loading by fretting against a stainless steel surface. The stainless steel surface has undergone a nitriding treatment by plasma. During the fretting contact, a strong transfer of the impregnant takes place from the impregnated graphite bearing to the steel conterface by adhesion; this deposit film allows a significant improvement in the tribological properties of the contact surfaces at high temperature.