Improvement of Wear Performance of Nano-Multilayer PVD Coatings under Dry Hard End Milling Conditions Based on Their Architectural Development

Shahereen Chowdhury,Bipasha Bose,Myriam Aguirre,Kenji Yamamoto,Ben Beake,Stephen Veldhuis,German Fox-Rabinovich

doi:10.3390/coatings8020059

Abstract

The TiAlCrSiYN-based family of PVD (physical vapor deposition) hard coatings was specially designed for extreme conditions involving the dry ultra-performance machining of hardened tool steels. However, there is a strong potential for further advances in the wear performance of the coatings through improvements in their architecture. A few different coating architectures (monolayer, multilayer, bi-multilayer, bi-multilayer with increased number of alternating nano-layers) were studied in relation to cutting-tool life. Comprehensive characterization of the structure and properties of the coatings has been performed using XRD, SEM, TEM, micro-mechanical studies and tool-life evaluation. The wear performance was then related to the ability of the coating layer to exhibit minimal surface damage under operation, which is directly associated with the various micro-mechanical characteristics (such as hardness, elastic modulus and related characteristics; nano-impact; scratch test-based characteristics). The results presented exhibited that a substantial increase in tool life as well as improvement of the mechanical properties could be achieved through the architectural development of the coatings.

Highlights

It is well known that high hardness, low thermal conductivity and high adhesion to the substrate are the key properties of wear resistant coatings helping them to sustain the heavy loads/high-temperature operating conditions during cutting [1]
Mirror polished cemented carbide WC-Co substrates (SPG 422, SPGN12 03 08) were selected for coating characterization and Mitsubishi C-2SB ball nose end mills were chosen for cutting-tool life studies
For the given cutting conditions and coating deposition parameters, multilayer behavior is exhibited by the bi-multilayer coatings

Summary

Introduction

It is well known that high hardness, low thermal conductivity and high adhesion to the substrate are the key properties of wear resistant coatings helping them to sustain the heavy loads/high-temperature operating conditions during cutting [1]. This is especially true for severe/extreme frictional conditions associated with dry high-performance machining of hardened steels [2]. The introduction of more complex coatings which combine nano-columnar and nano-laminated structures [5] critically improves the multi-functionality of Coatings 2018, 8, 59; doi:10.3390/coatings8020059 www.mdpi.com/journal/coatings

Objectives

Methods

Results

Conclusion