DRILLING STUDIES OF AN AL2O2-AL METAL-MATRIX COMPOSITE .1. DRILL WEARCHARACTERISTICS

Comparative drilling studies have been carried out for a 20% Al2O3 mic rosphere reinforced Al metal matrix composite (MMC) using a (a) high s peed steel (HSS) drill, (b) tungsten carbide (WC) drill and (c) polycr ystalline diamond (PCD) drill. In this part of the paper, the flank we ar characteristics of the drills have been presented. It is found that for the HSS drill a flank wear of 1.00 mm is reached in drilling for as little as 12 s. In contrast, under similar conditions for the WC dr ill, a flank wear of 0.16 mm was observed after drilling for a period of 600 s and in the case of the PCD drill, after 2210 s of drilling a flank wear of only 0.12 mm was observed. The PCD drill, however, showe d some signs of chipping in the early stage, but this seemed to stabil ize later on. Scanning electron microscopic (SEM) observations of the worn drill tips revealed that in addition to flank wear the HSS exhibi ted margin wear, the WC drill exhibited both margin wear and chisel ed ge wear and the PCD drill displayed crater wear.