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Orthogonal and single factor intermittent turning experiments of hardened AISI 1045 steel were conducted with two kinds of Al2O3-(W, Ti)C ceramic tools used, aiming to reveal the effects of cutting parameters on cutting forces, the influence of mechanical and thermal loads on tool wear mechanisms at different wear evolution stages. Empirical formulas for average cutting forces and tool lives (impact number of tools under two different flank wear limits 0.1 mm and 0.3 mm) were established respectively. The worn or fractured surfaces of the tools tested at different cutting speeds were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). It is found that feed rate and depth of cut had greater influence on the average cutting forces in cutting periods than cutting speed did. The amplitude of the vibration generated in the radial direction decreased with increasing cutting speed, while that of the vibration generated in the other two directions increased. The influences of mechanical and thermal loads on tool wear changed in different ways at different stages of tool wear evolution process. There existed critical cutting speeds above which adhesive wear of the ceramic cutting tools became less serious.

The failure progression of coated carbide tools in end milling of Inconel 718 superalloy was investigated. Tool wear was measured and failure mechanisms were discussed in the experimental process periodically. The experimental results indicated that the tool failure mechanisms were synergistic interaction among abrasive wear, adhesive wear, and fatigue wear. However, abrasive wear and adhesive wear were the main failure mechanisms at the beginning, fatigue wear prevailed the upper hand around the time when edge chipping appeared, and after edge chipping abrasive wear and adhesive wear dominated until the failure time. In addition, the macroscopic failure of the cutting tools is closely correlated to the nucleation and propagation of the crack under cyclic mechanical and thermal impact forces. Mechanical fatigue wear was the key form of fatigue wear at lower cutting speed, while at higher cutting speed thermal fatigue wear was the dominant fatigue wear.