Thermal contact resistance enhancement with aluminum oxide layer generated on TiAlN-coated tool and its effect on cutting performance for H13 hardened steel

Abstract

During metal cutting process, thermal contact resistance (TCR) generated at TiAlN-coated tool and chip contact interface is enhanced compared with that generated at uncoated tool and chip interface. However, the TCR enhancement mechanism need to be revealed and its effects on cutting process need to be discussed. In this research, enhancement mechanism of the TCR generated at TiAlN-coated tool and chip interface was analyzed by comparing with the TCR formation mechanism of uncoated tool. Then, effects of the TCR on cutting temperature, cutting forces and tool life were analyzed. It was found higher nanohardness and elastic modulus of TiAlN-coated tool decreased the deformation of rake face asperities. Lower thermal conductivity and greater specific heat of Al2O3 layer resisted cutting heat conducting into tool. Thermophysical properties of TiAlN coating and generation of Al2O3 oxide layer explained the enhancement mechanism of the TCR. Compared with uncoated tool, the enhanced TCR of TiAlN-coated tool caused more cutting heat to been trapped in chip. Meanwhile, the radial cutting force was reduced by 16.82% and the tool life was extended by 29.41%. Therefore, the enhanced TCR improved TiAlN-coated tool cutting performance when machining H13 hardened steel.