Correlation between microstructure evolution and high temperature properties of TiAlSiN hard coatings with different Si and Al content

Highlights: • Microstructure and high temperature properties of TiAlSiN coatings are presented. • Si incorporation induced an obvious grain refinement effect. • The coating with smaller grain sizes shows superior oxidation resistance. • The coating with higher thermal and oxidation stability has better wear resistance. - Abstract: TiAlSiN coatings with different Si and Al content are synthesized by multi-plasma immersion ion implantation and deposition (MPIIID). The microstructure, oxidation resistance and wear resistance of as-deposited coatings are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nano-indentation, thermo gravimetric analysis (TGA) and friction tests. Studies show that TiAlSiN coating has nc-TiAlN/a-Si₃N₄ structure. The grain size of nc-TiAlN decreases gradually and the volume fraction of the interfacial a-Si₃N₄ increases with the increased Si level. The obvious reduction in grain size together with the increase in interfacial a-Si₃N₄ eventually leads to the superior oxidation resistance of TiAlSiN coating. In addition, TiAlSiN coating with low Si and Al content exhibits poor oxidation stability and thermal stability, which results in its unsatisfied wear resistance at 800°C. However, TiAlSiN coating with higher Si and Al content possesses better oxidation stability and thermal stability, and this coating shows excellent wear resistance both at RT and 800°C. The correlation between microstructure evolution and oxidation resistance and wear resistance of as-deposited coatings are systematically discussed