Influence of CH 4 fraction on the composition, structure, and internal stress of the TiCN coatings deposited by LAFAD technique

Abstract

TiCN coatings were deposited using a large area filtered arc deposition (LAFAD) technique from Ti targets in a mixture of N 2 and CH 4 gases. CH 4 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 CH 4 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 CH 4 fraction. XPS results show that with increasing CH 4 fraction, the N content in the coatings decrease continuously, the C content increases to 9.3 at.% at a CH 4 fraction of 30% followed by a slight decrease with the additional increase in the CH 4 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 CH 4 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.