Performance of High-Speed Steel Drills in Wet Drilling Inconel 718 Superalloy

Hole machining of nickel-based alloys has a wide application space in aerospace manufacturing industry, but the high cutting force, high cutting temperature, large plastic deformation, cold work hardening and severe tool wear during the cutting process of nickel-based alloys make them typical difficult-to-machine materials. Therefore, when drilling nickel-based alloys, the selection of cutting parameters is very important. Reasonable cutting parameters will help to control the chip shape and facilitate chip removal. In this paper, the cutting force, cutting temperature, and tool life of high-speed steels in drilling Nickel-based superalloy Inconel 718 was investigated through orthogonal cutting experiments. Then the empirical method of multi-factor line regression was used to establish the empirical models of drilling torque, thrust force, cutting temperature, and tool life of the drills with emulsion as the cutting fluid, and to verify the validity of the established model, and the significance of the regression method is tested to verify the effectiveness of the model. The tool wear morphology and wear mechanisms were examined by scanning electron microscope (SEM) and energy spectrum analysis (EDS). The results revealed that the major drill wear modes incorporate flank wear, peripheral wear, micro-chipping and chipping, and the tool failure mechanisms were comprehensively synergistic interactions among abrasive wear, adhesive wear, and oxidation wear. In addition, the cutting parameters of high-speed steels in drilling Nickel-based superalloy were optimized based on the response surface methodology of equivalent tool life-efficiency, and then the reasonable cutting parameters under the condition of using cutting fluid were recommended.