Thermal stability, mechanical properties, and tribological performance of TiAlXN coatings: Understanding the effects of alloying additions

In tribological applications, the degradation of metallic coatings due to oxidation and thermal softening at high temperatures is an issue of increasing concern. Recently, researchers have focused on the development of durable hard coatings that can perform well under elevated temperatures. The alloying of ternary TiAlN coatings with various elements has received considerable attention due to its ability to improve coating properties at high temperatures by solid solution hardening, grain refinement, formation of new phases, diffusion barriers, and self-lubricious tribo-oxides. This paper reviews the microstructure, thermal stability, oxidation behaviour, and mechanical and tribological properties of resultant quaternary TiAlXN coatings (X = Si, Cr, V, Ta and B). The effects of the deposition parameters, chemical composition, high-temperature annealing, and coating architecture on the coating properties are discussed in depth. The properties of quinary TiAlCrSiN coatings are also reviewed to provide a better understanding of the synergistic effects of Si and Cr additions to TiAlN. The maximum hardness and plastic deformation resistance (H/E and H3/E2) of TiAlXN coatings produced by various deposition techniques are compared. This paper provides useful insights into the challenges and future research perspectives of the reviewed coatings

A short review on the phase structures, oxidation kinetics, and mechanical properties of complex Ti-Al alloys

This paper reviews the phase structures and oxidation kinetics of complex Ti-Al alloys at oxidation temperatures in the range of 600–1000 °C. The mass gain and parabolic rate constants of the alloys under isothermal exposure at 100 h (or equivalent to cyclic exposure for 300 cycles) is compared. Of the alloying elements investigated, Si appeared to be the most effective in improving the oxidation resistance of Ti-Al alloys at high temperatures. The effect of alloying elements on the mechanical properties of Ti-Al alloys is also discussed. Significant improvement of the mechanical properties of Ti-Al alloys by element additions has been observed through the formation of new phases, grain refinement, and solid solution strengthening