The structure and mechanical properties of multilayer TiN/(Ti0.5Al0.5)N coatings deposited by plasma enhanced chemical vapor deposition

The structure and the properties of multilayer TiN/(Ti0.5Al0.5)N coatings with a layer thickness of 50 nm and a film thickness of 3 μm, which were deposited on high-speed steel and Si wafer substrates using plasma enhanced chemical vapor deposition, were investigated. Continuous columnar growth was observed in the multilayer coatings without any interruption at the layer boundaries. The identical crystal structure and similar lattice parameter between TiN and (Ti0.5Al0.5)N layers made the continuous columnar growth possible. The multilayer coating exhibited a higher hardness, adhesion strength and wear resistance compared to either of the monolayer TiN and (Ti0.5Al0.5)N coatings. It is believed that the stress evolution at the layer boundaries increased the hardness of the coating. However, the stress evolution was interrupted at the layer boundaries, which positively affected the adhesion property of the coating. The higher hardness and adhesion caused a higher wear resistance of the multilayer coating compared to either of the monolayer TiN and (Ti0.5Al0.5)N coatings.