A CONCEPT FOR FRICTION MECHANISMS OF COATED SURFACES

A comprehensive concept for friction mechanisms of coated surfaces is presented. The friction mechanisms are first classified broadly into macromechanical, micromechanical, tribochemical and material transfer mechanisms. The macromechanical mechanisms are classified on the basis of hardness relationships between coating, substrate and counterface, the film thickness, the surface roughnesses and the debris in the contact. The micromechanical mechanisms are studied on the basis of shear, fracture, elasticity and rolling effects. The tribochemical mechanisms include the formation of microfilms on asperity peaks of hard coatings and the oxidation of soft coatings. The mechanism of material transfer influences friction by changing the properties of the counterface as a transferred film is formed on it.