Nano mechanical and wear properties of multi-layer Ti/TiN coatings deposited on Al 7075 by high-vacuum magnetron sputtering

Super-hard coatings are frequently applied to improve the mechanical properties and abrasive properties of light alloys such as titanium and aluminum. In this work, single-layer TiN and multi-layer Ti/TiN coatings are deposited on Al 7075 by ultra-high vacuum magnetron sputtering and the structure, morphology, and triobological properties are investigated. The impact of the Ti layer on the microstructure, mechanical, and abrasive properties are also studied in details. The coatings containing the single TiN layer and Ti/TiN multi-layer crystal have the (111) and (002) preferred orientations. The hardness values of the single-layer and multi-layer coatings are 45.93 and 35.54, which are about 25 and 19 times larger than that of the substrate, respectively. The coefficients of friction of the multi-layer and single-layer coatings are 0.48 and 0.54, respectively. In the multi-layer coating, the Ti interlayer has smaller shear strength and acts as a lubricant during the abrasion test to reduce the friction. The TiAlNxOy and TiNxOy tribolayers may be formed in the single-layer and multi-layer coatings, respectively and compared with the single-layer coatings, the multilayer ones have better tribological properties.