Mechanisms and characteristics of direct cutting of tungsten carbide using a diamond-coated carbide end mill

This paper addresses the cutting mechanisms of cemented carbide using a diamond-coated carbide end mill at ultrasmall feed rates. The tool wear behavior, cutting force, and form and surface integrity of the machined groove were experimentally investigated. In addition, the cutting edge temperature, finished surface, and influence of feed rate on tool durability were investigated to determine the cutting characteristics. A large flaking of the coating film on the rake face occurred immediately after the cutting onset, and a sharp cutting edge evolved on the ridgeline of the section of the coating film that remained on the flank face. The cutting force decreased, and the removal volume increased because of the flaking of the coating film on the rake face, which resulted in the evolution of the sharp cutting edge. The temperature of the cutting edge increased with increasing the tool’s speed of revolution, similar to the case of hardened die steel materials, and reached 440–560 °C. No damaged layer was observed on the finished surface layer, as confirmed by compositional mapping of a section of the preliminary and finished surfaces. The durability of the cutting tool deteriorated significantly at feed rates higher than the cross-sectional thickness of the coating film. High wear resistance and cutting performance can be achieved by setting the feed rate to ultrasmall values, less than the thickness of the coating film.