Effect of cathodic current of Cr ion etching on the structure and properties of TiAlN coated cemented carbide

Abstract

Metal ion etching is an important pretreatment before the deposition of PVD coatings, which has a crucial effect on the bonding force. In this paper, Cr ion etching with different target current intensities was used to treat cemented carbide substrates, and then TiAlN was deposited on them. By studying the morphology and elements on the substrate surface after etching, it was found that the bombardment and deposition effects of the etching process are controlled by the target current intensity, and the bombardment will preferentially sputter Co while deposition will preferentially be on W. It would form droplet defects and greater roughness on the substrate surface, while transforming the residual stress to tensile. TiAlN grows in a different way because etching changes the morphology of the substrate surface and leaves Cr residues. 150 A etching results in a very rough surface, the substrate surface integrity was destroyed, and the final coating bond was unchanged. 200 A etching removes mainly the Co phase from the substrate and the coating bond is significantly improved due to the increased effective mechanical occlusion. The 250 A etching has a less efficient bombardment, mainly depositing Cr layers, which induced the competitive growth of TiAlN in multiple directions, causing the bonding force to be not effectively enhanced. In addition, the etched coatings were less subjected to adhesive wear in the ball-disk friction test, due to the high bonding force and roughness.