Study of the High-Temperature Stability and the Heat Resistance of TiAlN–Cu and TiAlN–Ni Coatings by Analyzing the Diffusion Processes in Annealing

Resumo

The thermal stability and the heat resistance of TiAlN–Cu and TiAlN–Ni coatings are studied. The phase compositions of the coatings are found to be unchanged upon annealing at temperatures up to 700°C in a vacuum of 10^–5 Pa. As the annealing temperature increases to 800°C, the lattice parameter of the nitride phase increases to near-stoichiometric TiN_x, the microstrains decrease, and the coherent domain sizes increase. The calculated diffusion coefficients of oxygen in the coatings upon heating in the temperature range 600–800°C demonstrate higher protective properties (high-temperature oxidation resistance) of the TiAlN–Ni coatings as compared to the TiAlN–Cu coatings, which is caused by the formation of a barrier layer based on NiO, TiO₂, and TiNiO₃ oxides.