Characterisation of Self-Regenerative Dry Lubricated Layers on Mo-Basis by Nano Mechanical Testing

For the application in dry lubricated rolling bearings the development of self-regenerative molybdenum oxide layers is necessary. The self-regenerative coatings should provide a hard overcoat in the tribological contact due to oxidative processes. The application of the Mo-layers on the conventional bearing steel (AISI 52100) is carried out by means of physical vapour deposition (PVD). The characterisation of layers in the nanometre range is highly demanding and close the measurable limit. In the development of molybdenum layer systems, the behaviour of the individual layers on the substrate and among each other is of great importance. The coefficients of friction and the elastic and plastic material behaviour were determined by means of nano scratch tests. Moreover, the layer thickness, nano hardness and modulus of elasticity were determined by nanoindents. The measurements were made on a Hysitron TriboIndenter® TI 950. Based on these results the nano investigations are the basis for the further development of the Mo-layer systems.