Tribooxidation as a Way to Improve the Wear Resistance of Cutting Tools

Dmitry Wainstein,Anatoly Kovalev

doi:10.3390/coatings8060223

Abstract

This paper generalizes the results of our research, which was aimed at the development of adaptive cutting tool coatings for high speed dry cutting, from the inception of the idea to complex multilayer coatings for processing tough metals. Typically, the streams of external energy and matter during high speed cutting are causing damage to the tool materials and to the hard, protective coatings through multiple mechanical and chemical processes including oxidation, however these oxidation processes could be used to improve the tools’ lifetime. The structure and the phase transformations on the wear surface in the nanostructured single layer and nanolaminated multilayer PVD coatings were investigated by a set of electron spectroscopy methods. The dynamics of the secondary phase formation on the various stages of tool life is demonstrated. The obtained results show that the enhancement of non-equilibrium processes during friction leads to a dominating formation of protective triboceramics on a base of sapphire-like, tungsten, and niobium polyvalent oxides with a structure which decisively improves the wear performance. The mechanisms of the formation of non-equilibrium protective oxides at high speed dry cutting and the non-equilibrium thermodynamics approaches for the tribooxidation description are discussed. Polyvalent metals and multilayer coatings provide a wider set of protective oxide nanofilms.

Highlights

The present series of researches were aimed at increasing the wear resistance of tools operating at severe tribological conditions of high speed dry cutting, with temperatures of up to 1000 ◦ C, high local stresses in the “tool-chip” contact area, the interaction of the tool surface with processing material, and atmosphere
physical vapor deposition (PVD) is realized at lower temperatures (
It is necessary to emphasize that the application of the above-mentioned coatings for high speed dry cutting is limited by the heat resistance of the substrate

Summary

Introduction

The present series of researches were aimed at increasing the wear resistance of tools operating at severe tribological conditions of high speed dry cutting, with temperatures of up to 1000 ◦ C, high local stresses in the “tool-chip” contact area, the interaction of the tool surface with processing material, and atmosphere. At cutting C45 steel (HB 180–200) have demonstrated the formation of secondary non-equilibrium non-stoichiometric amorphous oxide films on the tools surface: TiC and BN were transformed to simple and complex oxides on the wear hollow surface as a result of tribooxidation. These processes were developed at a depth less than 0.5 μm. One can clearly see the lack of long range order in the atomic coordination, which evidences the amorphous structure of oxide films

Methods

Discussion

Conclusion