Study on Machining Mechanism and Wear Mechanism of Composite Coated Tools on CoCrFeNiAl0.6 High Entropy Alloy at High Speed

Abstract

This study investigates the cutting and wear mechanisms of coated tools on CoCrFeNiAl0.6 high entropy alloy during high-speed machining. CoCrFeNiAl0.6 alloy, known for its high strength and hardness, presents significant challenges in machining, causing severe tool wear and workpiece damage. This research aims to optimize machining parameters and tool coatings for improved performance and tool life. Finite Element Method simulations and experimental tests were conducted to analyze cutting forces, temperatures, deformation rates, and tool wear under varying cutting speeds, depths, rake angles, and coating types. Cutting forces increased with both cutting depth and coating thickness but decreased with rake angle and speed, with forces reducing up to 10% between 800  mm/s and 1200 mm/s. Multi-layer coatings significantly reduced cutting forces, with TiAlN+TiN+Al₂O₃ coatings experiencing forces around 83% of those with TiAlN coatings. Cutting temperatures rose with cutting depth but decreased with speed; increasing the rake angle or coating thickness initially lowered temperatures but raised them with greater depths, resulting in up to 60% increase in the 0.5–0.7 mm range. Temperature differentials also grew with additional coating layers, with three-layer coatings showing a temperature drop between TiAlN and TiN layers 2.6 times greater than in two-layer coatings. Chip thickness and deformation rates declined with speed and rake angle; TiAlN coatings exhibited the highest deformation rates, while TiN coatings were the lowest, with aluminum additions further raising deformation rates by up to 4%. At a cutting depth of 0.3 mm, wear rates were 1.2 times those at 0.1 mm, increasing with speed and rake angle. For wear rates, single-layer coatings followed the trend TiAlN > Al₂O₃ > TiN, while multi-layer coatings followed TiAlN+Al₂O₃ > TiAlN+TiN > TiAlN+TiN+Al₂O₃. Additional layers reduced wear rates, with three-layered tools achieving only 90% of TiAlN’s wear rate. These findings offer valuable insights into coating design and machining parameters, providing practical guidance for enhancing the efficiency and stability of high-entropy alloy machining.