Mechanical properties of thin ceramic coatings of the SiCN system deposited by reactive ion-plasma sputtering

Abstract

The paper deals with the influence of a partial nitrogen pressure on the adhesion strength and microhardness of SiC and SiCSi 3N 4 coatings as well as their interaction with substrates at the coating-substrate interface. The adhesion strength of the coatings was determined by indentation using the critical loading method. For the coatings deposited at 350°C this characteristic was found to be quite low and to undergo practically no changes with the increase in the partial nitrogen pressure, while for the coatings obtained at 450°C the adhesion strength grew with the partial nitrogen pressure. Microhardness tests have demonstrated the effect of variation of the partial nitrogen pressure. The maximum value of microhardness was measured to be 27.5 GPa. Interaction at the substrate-coating interface was studied using electron microprobe analysis. A diffusion zone of 3.5 μm in size was found to exist. Low adhesion strength of SiC coatings can be attributed to the interfacial pore formation due to the Kirkendall effect.