Wear Mechanisms During Sliding of Ti64 Balls Against Bare and HFCVD Polycrystalline-Diamond-Coated WC-Co Exchangeable Inserts

Diamond coatings present the state-of-the-art surface finish of tools for machining titanium and its alloys. However, the influence of this coating on the wear mechanism has not been elucidated yet. In this paper, ball-on-disc wear tests against 6-mm-diameter Ti6Al4V balls had been performed to characterize the wear performance of a polycrystalline diamond (PCD) coating produced by hot filament chemical vapor deposition and of bare tungsten carbide (WC-Co). The wear scars were evaluated by scanning electron microscopy and energy-dispersive X-ray spectrum. The PCD coating exhibited lower friction coefficient and mass loss than those of the WC-Co under same testing condition. The oxidation was inevitable in both PCD and WC-Co wear process. For WC-Co, abrasive wear was the main wear mechanism. In contrast to that, the PCD coating was worn by microcuts in the ball-on-disc test, and oxidized Ti64 debris also caused a great effect on its wear mechanism.