Oleksandr Gutnichenko

Tool wear and tool life of PCBN, binderless cBN and wBN-cBN tools in continuous finish hard turning of cold work tool steel

The paper presents the results of comparative study of performance of cutting tools made of ceramic-bound, binderless cBN, and wBN-cBN tool materials. The tool performance was assessed by tool wear-resistance, values of cutting forces, parameters of machined surface quality, and the state of sub-surface layer generated in continuous turning of hardened cold work tool steel. The tests were carried out under conditions of high speed machining (vc = 120–180 m/min) both with and without a coolant. The best tool performance by the above-mentioned criteria is provided by a low-cBN material with ceramic binder.

EFFECTS OF CUTTING SPEED WHEN TURNING AGE HARDENED INCONEL 718 WITH PCBN TOOLS OF BINDERLESS AND LOW-CBN GRADES

Application of polycrystalline cubic boron nitride (PCBN) tools as an alternative for ceramic and cemented carbide tools in machining superalloys has been frequently identified as a solution for enhancing process efficiency but only a limited number of studies has been done in this area. The current study explores the effect of the cutting speed, which was varied in a wide range (2–14 m/s), on machinability of age hardened Inconel 718 with PCBN tools. Performance of binderless PCBN grade and grade with low-cBN content was evaluated in terms of tool life, tool wear, cutting forces and surface quality. Chip formation and process dynamics were analyzed as well. It was found that low-cBN grade provided 70–90% better surface finish and tool life than the binderless at moderate speeds (5–8 m/s). Performance of both grades at low and high speed ranges was non-satisfactory due to notching and flaking respectively. At low cutting speed adhesive wear plays a major role while as the speed increases a chemical wear becomes dominant.

Influence of tool material and tool wear on tool temperature in hard turning reconstructed via inverse problem solution

In this work the cutting tool temperature distribution that develops during turning of hardened cold-work tool steel is modeled on the basis of experimental data. The data obtained from a series of thermocouples, placed on a PCBN insert, into an anvil, and into a toolholder, were used as the input for the model. An inverse problem was solved, where the heat fluxes were computed. The temperature distribution was modeled for the case of new tools, as well as for the case of its development in the course of a tool wear. The reconstructed temperature distributions were in good agreement with the measured data. The heat flux through rake face was found to be reducing with the decrease of thermal conductivity of the tool material.

Dynamic stability of the process of turning nickel superalloys using a toolholder produced by selective laser sintering

The paper presents the results of a comparative analysis of dynamic stability of SiC whisker reinforced alumina tools used in a conventional and prototype toolholders when turning a nickel-based superalloy Inconel 718. The use of the prototype toolholder with a cellular spatial structure is shown to significantly suppress vibrations during the machining operation and stabilize the cutting process within the cutting speed range between 200 and 500 m/min. Considering the identical nature of tool wear rate and the analytical ellaborations regarding the process dynamics, the above-mentioned benefits are related to damping properties of the proposed toolholder.