Evaluation of the performance of DLC Coatings (ta-C) of WC-Co tools while machining Al7075 alloy

Abstract

This study investigates the performance of DLC-coated 3-flute Ø 12 mm WC-Co (10%) end mills in the high-speed machining (226 m/min) of Al7075 Aluminum alloy, with high-pressure (20 bar) cooling applied in all tests focused on the cutting zone. Rolled blocks with dimensions of 150 × 350 × 150 mm were used as workpiece material. Slot milling was preferred as a test method for machining tests. Each end mill machined 757 slots with a length of 350 mm at a depth of 3 mm, and a total volume of 9150 cm3 was removed with each tool. In total, three groups of endmills were tested. A1 is a specially designed endmill for aluminum machining and was tested in an uncoated state, while A2 has the exact same geometry as A1 and was coated with tetrahedral amorphous carbon (ta-C), which is a form of Diamond-Like Carbon (DLC) coating. Finally, the A3 endmill was tested as an industrial comparative designed for aluminum machining, which was also ta-C coated. Performance tests have shown that ta-C coating significantly prevented the formation of the built-up edge. In addition, it reduced the average bending moment on the tool by 20%–25% by acting as a lubricant. It has been observed that DLC coating reduces tool wear. It was determined that flank wear was reduced by 28% and rake wear by approximately 58% in the A2 tool compared to the uncoated tool. The DLC-coated tools also provided smaller chips and improved chip control.