EFFECT OF VACUUM-ARC ANNEALING OF TiN COATINGS ON THEIR PEEL LOAD AND RESISTANCE TO FRETTING WEAR

The effect of vacuum-arc annealing of TiN coating on its wear resistance under fretting conditions and peel load is studied. It is found that the coating in the initial state contains TiN with a face-centered cubic lattice and Ti with a hexagonal close-packed lattice, and its phase composition does not change during annealing at 300–500 °C. After annealing the coating at 550 ℃, TiN, Ti and TiO2 are recorded in its phase composition. It is shown that annealing the coating at 350–400 ℃ contributes to an increase in fretting wear resistance by 10 % and an increase in the peel load. As a result of annealing at 450–500 ℃, the peel load remains at a high level, and after annealing at 550 ℃, it drops sharply. At the same time, the wear resistance of the coatings in the annealing temperature range of 450–550 ℃ decreases by 20 %. It is concluded that the increase in the coating peeling load after annealing at 350–500 ℃ is due to the formation of a film of lower titanium oxides on the coating surface, which act as a solid lubricant and prevent the nucleation of dislocations, as well as the appearance of microcracks at the coating-substrate boundary during scratch testing. The reduction of peel load as a result of annealing at 550℃ and wear resistance after annealing at 450–550 ℃ is caused by softening of the coating.