Abrasion resistance of nanostructured and conventional cemented carbides

Abstract

The abrasion resistance of nanostructured WCCo composites, synthesized by a novel spray conversion method, is determined and compared with that of conventional materials. Scratching by diamond indenter and abrasion by hard (diamond), soft (zirconia) and intermediate (SiC) abrasives was investigated. The size of the scratch formed by the diamond is simply related to the hardness of the composite. Plastic deformation, fracture and fragmentation of the WC grains increase with their size. Nanoscale composites show purely ductile scratch formation. Nanocomposites possess an abrasion resistance approximately double that of the most resistant conventional material: this is a higher gain than the increase in hardness which is at most 23%. This large gain is due to a specific grain size effect on abrasion resistance in the case of diamond and SiC abrasive and to a very rapid increase of abrasion resistance with hardness in the case of the softer (SiC and ZrO 2) abrasives. The observation of the abraded surfaces of conventional composites reproduced the known mechanisms: plastic deformation and fracture of WC grains by hard abrasives; removal of binder phase and fall-out of WC by soft abrasives. Magnetic fields from the ferromagnetic Co prevent the observation of abrasion mechanisms in the very fine-structured nanocomposites.