Work

On the reliability of Vegard's law in compositional analysis of chemical vapor deposited AlxTi1-xN

Year: 2025

Type: article

Abstract: Aluminum titanium nitride (Al x Ti 1 -x N, 0 < x < 1) is a critical hard coating material for cutting tools due to its exceptional hardness, thermal stability, wear resistance, and oxidation resistance, all of which are influenced by its Al content. A common method to swiftly estimate the Al content in production of such coatings is by the size of the Al x Ti 1 -x N unit cell – determined by standard θ-2θ X-ray diffraction – and the equilibrium cell size of the binary constituents AlN and TiN in the framework of Vegard's law. However, in most cases, the measured unit cell size does not merely depend on Al content as Al x Ti 1 -x N is a metastable phase that may exhibit crystalline defects, non-ideal mixing of the binaries, differences in bonding characteristics, strain relaxation, and phase separation. We seek to investigate the resulting uncertainty in Vegard's-law-based estimation by comparing estimated Al content with elemental composition of Al x Ti 1 -x N coatings – grown industrially by chemical vapor deposition on cemented tungsten carbide substrates – using energy-dispersive X-ray spectroscopy, hard X-ray photoelectron spectroscopy, time-of-flight elastic recoil detection analysis, and Rutherford backscattering spectrometry. Our results demonstrate that the uncertainties in Al content estimated by Vegard's law are relatively small, rendering this method a good first-order approach for compositional analysis of the metal sub-lattices in Al x Ti 1 -x N. Moreover, our data indicate that a multimethod strategy is required for precise composition determination that includes both the metal and the non-metal sublattices and impurity level.

Source: Surface and Coatings Technology

DOI: 10.1016/j.surfcoat.2025.132898