Effects of extended punching on wear of the WC/Co micropunch and the punched microholes

The wear of the tungsten carbide-cobalt (WC/Co) micropunch (150 mu m diameter) and its effects on the microhole morphology in various periods of processing were investigated. Punching was performed using titanium as substrate. Effects of the punch number on the weight loss and the surface morphology of the micropunch had been studied by confocal microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, etc. The morphology of the punched microholes had also been investigated correspondingly. Results showed that the micropunch underwent distinct wear loss during the initial period of micropunching, which was linked to loss in Co. The diameter of the punched microholes was changed accordingly and some debris on the surface of the hole was observed. Then, the punch entered a period of quasi-stability: there was very little wear loss and the diameter of the punched holes was rather stable. The wear rate of the micropunch increased remarkably when the punch number exceeded about 1,500. The wear loss was due to loss in both Co and WC. Large bulk debris was attached to the punched hole, and the diameter of microholes was changed correspondingly. Further increase in the punch number showed more drastic punch wear, debris attachment, and hole's diameter reduction. The dominant was then mainly in WC.