Research on chip mechanism of Inconel 718 with ultrasonic assisted drilling by step drill

Abstract

Abstract Nickel-based high-temperature alloys (Inconel 718) are considered to be difficult-to-machine materials with high yield strength and high-temperature strength properties and are widely used in the aerospace industry. Due to the low thermal conductivity of Inconel 718 material, it tends to cause severe tool wear. In this paper, three step drills with different second point angles are proposed and compared with common twist drills to analyze the effect of spindle speed on torque and thrust. The thrust and torque models of twist drill and step drill bits are firstly established, and then the critical burr generating state of the drill bit is analyzed. The experimental and finite element simulation analyses of the four types of drills show that the step drill has the advantages of lower drilling torque, lower thrust, less exit burr, less effective stress, and higher chip flow rate compared with the common twist drill, and the thrust and torque decrease as the second point angle of the step drill decreases. In addition, the step drill is then compared with conventional drilling (CD) and ultrasonic-assisted drilling (UAD) to analyze the differences in temperature and chip morphology, and the results show that the machining temperature is lower and chip breaking performance is better under ultrasonic-assisted drilling.