Detailed microstructure and the influence of post-treatment on CVD TiAlN wear-resistant coatings

Review article, 2025

In this work, the growth modes of low-pressure chemical vapour deposition (LP-CVD) nano-lamellar TiAlN coatings deposited on cemented carbide substrates and the influence of blasting post-treatment on the microstructure are investigated by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and transmission Kikuchi diffraction (TKD). Detailed information on the microstructure is revealed and gives insight into the growth mechanisms during deposition. Local information on the influence of blast-treatment on the micro- and nanostructure reveals how the material is influenced by external stresses on a microstructural level. Two distinct surface morphologies corresponding to specific grain orientations with <111> and <110> directions parallel to the coating normal are observed. Additionally, a growth mechanism is proposed, which suggests that the surface reaction kinetics are influenced by the detailed microstructure of the grains, leading to locally varying Al/Ti ratios. Blast-treatment of the TiAlN coatings leads to bending and intermixing of the nano-lamellae, where the direct visualization of the lamellae enabled the estimation of the deformation. Continuous lattice rotations were observed in the near-surface region, where the magnitude of the lattice rotation in areas with a high orientation density of <110> directions was more pronounced as compared to areas with a high orientation density of <111> directions. This could be related to the local Schmid factors.