Mechanism of material removal in tungsten carbide-cobalt alloy during chemistry enhanced shear thickening polishing

Abstract

The use of cemented carbides is ubiquitous in many fields especially for mechanical toolings, dies, and mining equipment. Surface finishing of cemented carbide down to atomic level has been a long-standing quest in manufacturing and materials community. For application of complex-shaped cemented carbide components, this work proposes a novel ‘chemistry enhanced shear thickening polishing’ (C-STP) process using Fenton's reagent to obtain sub 10 nm finished polishing at a rate twice that of the conventional STP. This work offers quantitative insights into the influence of the concentration of Fenton's reagent on the polishing performance. While the material removal rate was seen to be sensitive to the concentration, the surface roughness (Sa) was found to be insensitive to the concentration of Fenton's reagent. The electrochemical experiments proved that Fenton's reagent could effectively reduce the corrosion resistance of tungsten carbide-cobalt alloy. The characterization of polished carbides using XPS and EDS revealed that the cobalt binder gets removed preferentially during C-STP, which explains why the material removal rate during this technique becomes twice that of conventional STP. This study provides a promising method for high efficiency polishing of tungsten carbide-cobalt alloy parts with complex-shaped such as micro-drill.