Mechanical property and tribological performance of AlTiSiN and AlTiBN hard coatings using ternary alloy targets

Abstract

Ternary transition metal nitrides, such as AlTiN, TiSiN and TiBN, have been attracting great interest as hard protective coatings due to their high hardness, wear resistance, and thermal stability. In this study, AlTiSiN and AlTiBN coatings were synthesized by cathodic-arc evaporation using ternary AlTiSi and AlTiB alloy targets. During the coating process of AlTiSiN and AlTiBN, TiN was deposited as an interlayer to enhance adhesion strength between the coatings and substrates. After deposition, the AlTiBN coating was conducted by an oxidation post-treatment at high temperature of up to 800 °C in vacuum and in a controlled atmosphere of Ar and air to synthesize a top oxide layer and improve the tribological performance. The microstructure of the synthesized coatings was studied by a field emission scanning electron microscope (FE-SEM) and a field emission gun high resolution transmission electron microscope (FEG-HRTEM). Ball-on-disc wear tests were conducted to evaluate the tribological properties of the coatings. The AlTiSiN and AlTiBN coatings possessed higher hardnesses and lower wear rates than AlTiN. After oxidation post-treatment, the AlTiBN coating contained an oxide layer composed of nanocrystalline Al2O3 and TiO2. The result of ball-on-disc wear tests showed that the lowest wear rate was obtained for the AlTiBN coating after oxidation post-treatment, which was significantly better than that of the AlTiN, AlTiSiN and AlTiBN.