STUDY ON LOADING CAPACITY OF THE COATING-SUBSTRATE SYSTEM OF VAPOR-DEPOSITED TIN AND TIC ON BEARING BALLS .2. RUBBING METHOD IN EXPERIMENTSAND ANALYSIS

The critical load of failure L-c is an important index for the loading capacity of a coating-substrate system. In consideration of the fact that a coating-substrate system in practice may take any one form of t he four failure modes, coating failure, substrate yielding, interfacia l failure or the mixed failure, this paper defines the critical load o f failure of a coating-substrate system as the maximum normal load und er a certain friction coefficient before any failure occurs. It also p uts forward a new method the rubbing method, to measure L-c. A multifu nctional tester, Model CM-I, is developed on the basis of this method. The critical loads of bearing balls with physical vapor deposited (PV D) TiN or chemical vapor deposited (CVD) TiC or CVD TiC + Ti(CxNy) + T iN coatings under different friction coefficients are tested on this m achine and their failing processes are analysed. The results show that the rubbing method is a sound new method for the measurement of L-c, and the results agree well with the those of held effect microscopy. T he L-c of the CVD coating is greater than that of the PVD coating, and the L-c under smaller friction coefficient f is greater than that und er larger f. (C) 1997 Elsevier Science S.A.