Thermoelectric Characteristics of the Process of Steel Turning by Carbide Inserts with Combined Coatings

This work is dedicated to assessing the effect of TiN, ZrN, TiN + ZrN, (Ti–Zr)N, ZrN–(Ti–Zr)N–TiN nanostructured coatings, deposited on plates of hard alloy T15K6 by the PVD method, on tool wear and thermoelectric parameters of the process of turning work pieces from steels 45, 38HS, and 12H18N10T. The greatest decrease in temperature in the cutting zone was recorded during the processing of steels 45 and 38HS, characterized by high thermal conductivity coefficients, while the maximum effect was achieved due to TiN + ZrN and ZrN coatings, for low thermal conductivity steel 12H18N10T, the lowest temperature was provided by the ZrN, (Ti–Zr)N and ZrN + (Ti–Zr)N + TiN compositions. Analysis of the variable component of the thermo-EMF signal during cutting shows a decrease in the amplitude of oscillations for coatings that provide the greatest wear resistance of the tool. According to the results of the experiments, such an effect when turning steels 45 and 38HS at optimal speeds was demonstrated by ZrN + (Ti–Zr)N + TiN and TiN + ZrN coatings, and for stainless steel 12H18N10T, ZrN, ZrN + (Ti–Zr)N + TiN and TiN. The established relationship between the wear resistance of carbide inserts and the amplitude of fluctuations of the variable thermos-EMF component makes it possible to use it as an indirect criterion for selecting the optimal composition of the wear-resistant coating from the point of view of thermophysical compatibility with tool and machined materials.