Effects of modulation ratio on microstructure and properties of TiN/TiAlN multilayer coatings

TiN/TiAlN multilayer coatings were deposited on M2 high speed steel by a pulsed bias arc ion plating system. The effect of modulation ratio on the microstructure, mechanical and wear properties was investigated. TiN/TiAlN multilayer coatings were crystallized with orientations at the (111), (200) (222) and (311) crystallographic planes and the microstructure was strengthened at (111) preferred orientation. The average atom ratio of N was about 0.39. With the increase of TiN modulation ratio from 50s:100s to 100s:50s, the atom ratio of Ti increased from 0.42 to 0.518 and the atom ratio of Al decreased from 0.193 to 0.084. At modulation ratio of 60s:90s, the hardness of TiN/TiAlN multilayer coatings reached the maximum of 40.7 GPa, which was 4.5 times that of the substrate. The adhesion strength reached the maximum of 74 N at modulation ratio of 100s:50s. Friction and wear analysis was 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.