Study on the wear mechanism of high-entropy alloy coated tools and grain evolution in micro-cutting of TC4 titanium alloy

Abstract

This study investigates the wear mechanisms and grain refinement patterns of CoCrFeNiAlX series high-entropy alloy-coated tools during the micro-cutting of TC4 titanium alloy. Three coatings were selected: CoCrFeNiAl (Al1), CoCrFeNiAl0.6 (Al0.6), and CoCrFeNi (Al0). Using DEFORM-3D for three-dimensional cutting simulations, the effects of coating type and thickness on tool wear and grain refinement in the cutting deformation zone were analyzed. Results show that at a coating thickness of 10 μm, all types of coated tools exhibited minimal wear depth. Al0.6 coating was significantly affected by thickness, with wear depth increasing by up to 10 %. Dual-layer coatings performed better in reducing wear and maintained good wear resistance even at higher thicknesses, whereas single-layer coatings showed a marked increase in wear depth and rate with increased thickness. As coating thickness increased, the number of dynamic recrystallization (DRX) grains at location P2 decreased for single-layer coated tools. Dual-layer coated tools showed stable DRX numbers, fluctuating between 400 and 600 at P2. Compared to single-layer coatings, dual-layer coatings exhibited higher DRX grain counts across all cutting deformation zones, especially in the third deformation zone, demonstrating superior mechanical properties and recrystallization effects. Dual-layer coated tools also displayed good stability with minimal grain size variation, with Al1 as the inner layer contributing to more stable grain sizes. The Al0.6+Al1 coating experienced significant grain size growth in the third deformation zone due to stress concentration.