Influence of deposition pressure on the microstructure and mechanical properties of CVD TiAlSiN coatings

Deposition pressure is one of the key factors affecting the quality of chemical vapor deposition (CVD) coatings. In this study, the influence of deposition pressure on the microstructure and mechanical properties of CVD TiAlSiN coatings was systematically studied for the first time. It is found that within the deposition pressure range from 400 to 2000 Pa, an increase in deposition pressure has a significant influence on the microstructure of the coating, but has a minimal effect on the properties. According to grazing incidence X-ray diffraction (GIXRD) measurement, as the pressure increases from 400 to 1000 Pa, the preferred face-centered cubic (fcc-) (200) orientation disappears. Full width at half-maximum (FWHM) of three coatings implies that the grain size of the coating decreases at first and then increases with the increasing deposition pressure. TEM results indicate that Ti0.09Al0.89Si0.02N coating is self-organized with a periodically alternating Al-rich (10-14 nm) and Ti-rich (2-5 nm) nanolamellae, while Ti0.22Al0.74Si0.04N and Ti0.10Al0.87Si0.03N coatings consist of nanocrystalline (Ti,Al)N embedded in amorphous SiNx matrix. There is basically no change for the hardness of three coatings, and all values are in the range of 28.6 +/- 1.2 GPa. The present work provides an inspiration for depositing CVD TiAlSiN coating with a specific microstructure by controlling the deposition parameters.