EFFECT OF DIFFERENT A-C-H FILMS ON THE FRETTING BEHAVIOR OF BEARING STEEL

Two different types of DLHC coatings have been deposited on bearing st eel (M50). One was produced using a broad-beam ion source to apply fir st a 0.2 mu m thick amorphous silicon bond layer and then a 2 mu m DLH C layer. The second coating was a 2 mu m thick layer of DLHC deposited using r.f. plasma-assisted CVD. Both contain about 30 at.% hydrogen. The coatings have been tested under fretting conditions at 1 Hz. The i nfluence of load and displacement amplitude has been studied and is su mmarized on fretting maps. Degradation mechanisms which have been iden tified using optical or scanning electron microscopy are related to th e mechanical properties of the coatings. Particular attention has been given to coating adhesion which has been estimated on the basis of sc ratch tests. The influence of coating adhesion and associated test par ameters on the coating life is highlighted.