Experimental study on the formation of TCR and thermal behavior of hard machining using TiAlN coated tools

Abstract

Thermal contact resistance (TCR) is formatted at tool-chip interface during metal cutting process, which will influence on cutting temperature distribution. This study analyzed the formation mechanism of TCR in initial and stable stages in H13 hardened steel cutting process. Dry orthogonal cutting experiments were carried out with TiAlN coated tools. The cutting temperatures at the tool-chip contact zone and tool substrate were investigated. Scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) were used to characterize the tool rake face and fracture cross-sectional morphology of TiAlN coated tool. By analyzing the experimental results, the TCR was caused by original defects of TiAlN coating such as particles and pits in the initial cutting stage. In the stable cutting stage, the TCR was generated by the Al2O3 oxide layer and the uneven adhesion of the chip material on tool rake face. A finite element (FE) model based on Arbitrary-Lagrangian-Eulerian (ALE) approach was applied to simulate the influence of TCR on cutting process. The FE simulation results indicated that the maximum cutting temperature of the tool rake face decreased with the increase of TCR. On the contrary, the maximum cutting temperature of tool-chip contact area increased with TCR. This proposed formation mechanism of TCR at tool-chip interface was helpful to better understand the cutting heat transfer in machining process.