Scandium containing Ti(C,N,O) superhard coatings

The hardness in Ti-C-N-O system can be governed through composition changes, refining the structure or using slight addition of suitable metallic element. Our experimental results showed the increase of hardness from 22-32 GPa up to 45 GPa when the Ti-neighbouring element scandium was added, especially with magnetron sputtered coatings using Ti- and Sc-targets. This substance can be considered as the third or fourth most hard compound, following diamond types and cubic boron nitride. The contribution brings the discussion of structural features and some interesting properties of the (Ti,Sc)(C,N,O) system, eg. abrasive and oxidation resistance, which is several hundred degrees centigrade higher than that of lp-diamond or diamond-like coatings. The exploitation of the system described has been hindered untill now by the high price of scandium. Nowadays the strategic scandium resources have been released and the consumption of scandium in the mentioned coatings appears so low lying that its prices are competitive with other coating types.