Influence of CH4 fraction on the composition, structure, and internal stress of the TiCN coatings deposited by LAFAD technique

TiCN coatings were deposited using a large area filtered arc deposition (LAFAD) technique from Ti targets in a mixture of N2 and CH4 gases. CH4 fraction was varied from 0 to 50% to change the C content in the coatings. Scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and substrate bending method were used to characterize the dependence of the CH4 fraction on the surface morphology, composition, bonding structure, crystalline structure, and internal stress in the deposited coatings. It was found that TiCN coatings consist of nano-sized clusters and the cluster size increases with CH4 fraction. XPS results show that with increasing CH4 fraction, the N content in the coatings decrease continuously, the C content increases to 9.3 at.% at a CH4 fraction of 30% followed by a slight decrease with the additional increase in the CH4 fraction. With an increase of the C content in the coatings, there is a decrease in the Ti–N bonding content and an increase in the Ti–C and C–N bonding contents in the coatings. XRD results indicate that with increasing CH4 fraction, the growth orientation of the TiCN coatings changes from (111) to (220) preferred orientation. The TiN (220) peak shifts to a lower diffraction angle, and the grain size decreases continuously. The internal stresses in all TiCN coatings are compressive and increase linearly with increasing C content in the coatings. The decrease in the grain size and the increase in the C content correspond to the continuous increase in the internal stress in the coatings.