Effects of pulsed bias duty ratio on microstructure and mechanical properties of TiN/TiAlN multilayer coatings

► TiN/TiAlN multilayer coatings with excellent mechanical and tribological properties were deposited by arc ion plating method. ► The phase of TiN/TiAlN multilayer coatings exhibited preferred orientation along (1 1 1) plane with the increase duty ratio of pulsed bias. ► The surface morphologies were strongly influenced by duty ratio and the multilayer structure was clearer and denser with the increase duty ratio of pulsed bias. ► The TiN/TiAlN multilayer coatings showed higher hardness at 20% duty ratio of pulsed bias and excellent tribological properties at 50% duty ratio of pulsed bias. TiN/TiAlN multilayer coatings were deposited on M2 high speed steel by a pulsed bias arc ion plating system. The effect of pulsed bias duty ratio on the microstructure, mechanical and wear properties was investigated. The amount of macroparticles reduced with the increase of the duty ratio. The surface roughness was 0.0858 μm at duty ratio of 50%. TiN/TiAlN multilayer coatings were crystallized with orientations in the (1 1 1), (2 0 0) (2 2 2) and (3 1 1) crystallographic planes and the microstructure strengthened at (1 1 1) preferred orientation. At duty ratio of 20%, the hardness of TiN/TiAlN multilayer coatings reached a maximum of 3004 HV, which was 3.2 times that of the substrate. The adhesion strength reached a maximum of 77 N at 50% duty ratio. Friction and wear analyses were carried out by pin-on-disc tester at room temperature. Compared with the substrate, all the specimens coated with TiN/TiAlN multilayer coatings exhibited better tribological properties.