High speed continuous and interrupted dry turning of A390 Aluminum/Silicon Alloy using nanostructured diamond coated WC-6 wt. percent cobalt tool inserts by MPCVD

摘要

Nanostructured diamond films were grown to a thickness of approximately 35 mu m by a 30 kW, 915 MHz, microwave plasma-assisted chemical vapor deposition (MPCVD) on chemically treated WC-6 wt. percent Co tool inserts. Rockwell indentation tests were performed to evaluate the adhesion of the films and compared to that of traditional microcrystalline diamond. A series of high speed dry turning tests on high-silicon (18 wt. percent Si) aluminum alloy A390 under continuous and interrupted modes were performed and comparisons were carried out to investigate the wear behavior on tool inserts that were uncoated, coated with nanostructured diamond, and commercial PCD (polycrystalline diamond cutter) ones. The tests showed that nanostructured diamond coatings demonstrated excellent durability against the highly abrasive A390 aluminum-silicon alloys in high speed dry turning. Ultra fine grain structure of this coating produces workpiece surface finish comparable or even better than PCD tools in the range we studied. Excellent coating adhesion of nanostructured diamond on WC-6 percent Co substrates leads to reliable wear behavior. For the first time, we evaluated the performance of nanostructured diamond film coated insert under high speed interrupted turning mode. A "self-cleaning" mechanism was observed which can significantly improve the performance of nanostructured diamond films. Micro-Raman spectra were taken on tested tools to study the wear mechanism of the coating.