Wear Mechanism and Modeling of Tribological Behavior of Polycrystalline Diamond Tools When Cutting Ti6Al4V

Owing to its outstanding physical and mechanical properties, polycrystalline diamond (PCD) is ideal for cutting titanium alloys. However, the high temperature and stress caused by the interaction of tool surface and chip flow lead to different types of wear. This paper investigates the wear mechanisms of PCD tools in three different tribological regions: sticking zone, transition zone, and sliding zone, when machining titanium alloy Ti6Al4V. The tribological behavior of PCD tools in the wear processes were analyzed through both experiments and theoretical calculations. Analytical models of stresses and temperature distribution were developed and validated by turning experiments. PCD tools, consisting of diamond grains of different sizes: CTB002 (2 mu m), CTB010 (10 mu m), and CTM302 (2-30 mu m), were used to cut Ti6Al4V at the normal cutting speed of 160 m/min and high cutting speed 240 m/min. It was found that adhesion, abrasion and diffusion dominated the wear process of PCD tools in different worn regions. Microscopic characters showed that the wear mechanisms were different in the three tribological regions, which was affected by the distribution of stresses and temperature. Sticking of workpiece material was obvious on the cutting edge, abrasion was severe in the transition zone, and adhesion was significant in the sliding zone. The shapes and morphological characters in different worn regions were affected by the stresses distribution and the types of PCD materials.