The oxidation behaviors of TiB1.73, Al0.59Ti0.41N, and TiB1.73/Al0.59Ti0.41N coatings deposited by high-power impulse magnetron sputtering method

Abstract

Transition metal nitrides and diborides have high melting points, excellent chemical stability, and good thermal conductivity. However, these materials typically suffer from oxidation when served in high-temperature environment. In the present work, the single layer TiB1.73, Al0.59Ti0.41N, and bilayer TiB1.73/Al0.59Ti0.41N coatings with ~4–6 μm thickness have been deposited on cemented carbide inserts by high-power impulse magnetron sputtering (HiPIMS) method. The oxidation behavior and phase transition of these coatings at elevated temperatures (400–900 °C) are investigated by means of a hybrid approach of experiments and phase diagram calculations. TiB1.73 and Al0.59Ti0.41N coatings grow in columnar form. Anatase is the first generated product during TiB1.73 coating oxidation at 400°C for 1 h, then the amount of rutile phase gradually increases with the rise of oxidation temperature. Oxide layers for TiB1.73 coating are porous and show oxidation delamination phenomenon, which are related to the evaporation of B2O3 (g) and the transformation of anatase to rutile. Anatase is also firstly formed during the oxidation process at 700 °C for Al0.59Ti0.41N coating. Subsequently, a protective Al-rich oxide layer is generated and this layer is broken after oxidation at 900 °C. The initial oxidation behavior of bilayer TiB1.73/Al0.59Ti0.41N coating is similar to that of TiB1.73 coating, but aluminum oxides are observed after oxidation at 650 °C. The B element on TiB1.73/Al0.59Ti0.41N coating surface is gradually exhausted with the increase of oxidation temperature.