Investigation on oxidation behaviors of Ti-Si-N coating at high temperature

Ti-Si-N coating with nanocomposite structure is a promising protective coating for cutting tools which will be subject to high temperature oxidation during service. This study aims to investigate the thermal stability of Ti-Si-N coatings and lays the foundation for its application in high speed dry cutting.

Nanocomposite Ti-Si-N coating was deposited on stainless substrate and silicon wafer (100) by Ti90Si10 alloy target by using cathodic arc ion plating. The microstructure of Ti-Si-N coating had been detected by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).

The results suggested that the coating was TiN nanocrystals with a diameter of 6.3 nm surrounded by amorphous Si3N4. The oxidation test was conducted under 550, 650, 750, 800, 850, 900 and 950°C for 2 h. The structure evolution was observed by Scanning electron microscope (SEM), energy dispersive spectrum (EDS), XRD and XPS. The results indicated that rutile has been formed at 650°C, while Si3N4 began to oxidized at 800°C. The grain size of TiN increased from 6.3 to 13 nm as the samples oxidized from 550 to 800. Micro-crack also formed in samples oxidized over 900°C.

Ti-Si-N coating, in this study, was deposited by cathodic arc ion plating using alloy target at high-bias voltage. The oxidation temperature ranged from 500 to 950°C with TiN coating as reference.