The effects of Si3N4 interlayer on the thermal stability and hardness of Ti/TiNx (x = 0.5–1) nanolayered coatings

The polycrystalline Ti/TiNx multilayer films were deposited by magnetron sputtering, and the as-deposited multilayer coatings were annealed at 500–800 8C for 2–4 h in vacuum. We investigated the effects of annealing temperature and annealing time on the microstructural, interfacial, and mechanical properties of the polycrystalline Ti/TiNx multilayer films. It was found that the hardness increased with annealing temperature. This hardness enhancement was probably caused by the preferred crystalline orientation TiN(1 1 1). The X-ray reflectivity measurements showed that the layer structure of the coatings could be maintained after annealing at 500 8C and the addition of the Si3N4 interlayer to Ti/TiNx multilayer could improve the thermal stability to 800 8C.