Investigations on Milling Operations of AMPCO Using TIALN/DLC Coatings: Tool Wear and Surface Roughness

Abstract The development of new materials and alloys, techniques, and process optimization has rendered machining, particularly milling, a focal point of rigorous research and development. The machinability of AMPCOLOY® 83 is exceptional and very competitive compared to standard steels; nevertheless, the cutting speed is significantly influenced by the machining tools, the stability of the equipment, and the type of lubrication employed. The alloy's significant relevance in the plastic injection molding sector was a decisive factor in its selection. Furthermore, novel coating solutions have been researched and used for machining tools, offering a reduced coefficient of friction and enhanced lubrication, hence prolonging tool lifespan. Consequently, it is essential to examine the wear characteristics of cutting tools coated with thin films that provide reduced friction and enhanced self-lubrication, while also ensuring a superior oxidation resistance and fast machining speeds, attributes usually assigned to TiAlN/DLC coatings. The objective of this study was to investigate the impact of TiAlN/DLC coating on milling cutters in relation to their cutting performance during the milling of AMPCOLOY®83. The machined surface quality was assessed, and the cutting tool wear was analyzed. Milling experiments were conducted by altering the feed rate, cutting speed, and cutting length. The coated tools exhibited superior performance compared to the uncoated ones across all circumstances, and cutting settings employed. Moreover, the surface roughness achieved on the machined component consistently surpassed that seen in experiments with uncoated cutters. In fact, the wear of coated tools was less than that exhibited by the uncoated tools, while the main wear mechanisms identified were material adhesion and abrasion. Additionally, cutting edge breakage (chipping) was also observed in uncoated tools, while delamination occurred in coated tools.