Cutting performance of CrN and Cr-Si–N coated end-mill deposited by hybrid coating system for ultra-high speed micro machining

In this paper, comparative studies on the properties and cutting performance between CrN and Cr–Si–N coated micro end-mill for ultra-high speed machining applications were conducted. Ternary Cr–Si–N coatings, in which Si was incorporated into CrN, were synthesized onto WC–Co substrates using a hybrid system of arc ion plating and sputtering techniques. In the hybrid coating system for Cr–Si–N coatings, the CrN coating process was performed substantially by a cathodic AIP technique using Cr target, and Si could be added by sputtering Si target during CrN deposition. The high hardness of Cr–Si–N coatings was related to the composite microstructure consisting of fine CrN crystallites and amorphous Si3N4. The average friction coefficient of Cr–Si–N coatings gradually decreased with increase of Si content in CrN coatings. Good oxidation resistance of the CrN film was further improved by the incorporation of Si into the CrN films. Cutting tests were carried out to evaluate the characteristics of micro tool in vertical machining center using ultrahigh-speed air turbine spindle. Especially, the reliable evaluation system of coated tools for micro machining, where the cutting force and tool wear were simultaneously measured, was introduced