Study on coating performance of CVD coated cermet tools for 4340 steel cutting

Abstract For the coating/substrate combination, the substrate and the coating influence each other. Different coating combinations have different effects in cutting processing. Therefore, studying the cutting characteristics of different coating combinations will help guide the design of tool coatings for machining 4340 steel. In the paper, three different composite coatings were deposited on the cermet substrate. The comprehensive cutting performances of the three coating/substrate systems were discussed. During the process of cutting 4340 steel, the wear morphology of the flank surface and the rake surface, the cutting force and temperature were recorded and analyzed. The microstructure observation, cutting performances test and mechanical properties characteristic of three CVD coating system show that the TiCN/Al2O3 coating has the best overall performance in the process of cutting 4340 steel. The surface morphology of the coating is related to the structural design of the coating, that is, it is related to the nucleation and growth of each coating. The surface of the coated tool not only affects the friction coefficient between the tool and the chip, but also affects the temperature distribution of the chip-tool contact interface. The simulation results show that the intermediate coating between the coating and the substrate is different, and the thermal conductivity of the entire coating/substrate system is also different, which will affect the temperature distribution during the heat transfer process. The selection of the intermediate layer of the coating is very important for the design and selection of the coating tool, especially the thickness and thermal physical properties of the coating