Composition and phase stability upon annealing of gradient nitride coatings

Gradient Ti–Cr–N systems have been formed by cathodic arc vapour deposition in nitrogen atmosphere using simultaneous surface bombardment by metal ions. The deposition was carried out by combining titanium and chromium plasma flows with a variable density. shown that gradient by composition coatings with a variable content of metal components in depth are formed. It is established that coatings are mono-(a solid solution of variable composition) or two-phase (a solid solution and titanium nitride) systems. established that element and phase composition is stable up to 800 °C. Annealing to greatest temperatures leads to the crystallization processes of a solid solution that ensures the appearance of additional phases (CrN и σ–FeCr). Moreover, it results in the redistribution of chromium in the coating leading to an increase of a solid solution lattice parameter, migration of chromium into the substrate and σ–FeCr formation. The relationship between element and phase composition of coatings is discussed on the basis of a solid solution formation model.