The mechanism of wearing of the hard alloy tool under ultrasonic reinforcing finishing treatment

Novosibirsk State Technical University, Faculty of Mechanical Engineering and Technologies, 630073 Prospekt K. Marks 20, Novosibirsk, Russia

^* Corresponding author: v.gileta@corp.nstu.ru

Abstract

The working capacity of indenters prepared from hard alloy VK8 under conditions of reinforcing finishing treatment by ultrasonic tools was investigated. It was found that under normal treatment conditions, normal wear of the hard alloy takes place. An electron microscopic study of the morphology of the surface of the wear area and its state after the etching of cobalt (Co) using replicas was performed. X-ray microanalysis of the wear area was performed. No obvious traces of adhesive, diffusion, abrasive wear were detected. It was shown that the deterioration of the hard alloy tool VK8 mainly occurs as a result of fatigue failure, which leads in the investigated speed range of the part 10...120 m/min to the precipitation of individual carbide grains and whole groups of them. The non-linear nature of the wear-velocity curve is due to allotropic transformations of cobalt. It was found that at cobalt speeds of 10...50 m/min, the first allotropic transformation from the initial β-Co state to α-Co occurs, and then the second partial allotropic conversion of α-Co to β-Co occurs at a velocity of more than 50 m/min. The presence of a β-Co phase, which is more brittle, leads to an intensification of wear. The WC-WC boundaries and the deformation of WC carbides are not responsible for the formation of the wear surface microrelief and the integral wear of the carbide tool.