Crater wear mechanism of TiAlN coatings during high-speed metal turning

Maiara Moreno,Jon M Andersson,Robert Boyd,Mats P Johansson-Jöesaar,Lars J.S Johnson,Magnus Odén,Lina Rogström

doi:10.1016/j.wear.2021.204016

Abstract

The influence of the aluminium content (x) on crater wear mechanisms of Ti1-xAlxN coated WC-Co inserts in high-speed turning of 316L stainless steel was investigated. Electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the wear behaviour. Ti1-xAlxN coatings with x ≤ 0.53 showed, after 1/3 of the tool life, a thick adhered layer composed of oxides and metallic species from the steel, and no diffusion of workpiece material into the coating. These coatings presented the best wear resistance and least abrasive wear. The high aluminium content Ti0·38Al0·62N coating showed the worst crater wear resistance. This is assigned to interdiffusion of workpiece elements and oxygen into the coating as a consequence of spinodal decomposition of the cubic TiAlN-phase, resulting in more severe abrasive wear.

Highlights

TiAlN is a hard coating and since the 1980s it is extensively used in the cutting tool industry [1]
The hot-hardness of these coatings stem from age hardening at high temperatures due to spinodal decomposition, a condition pro moted by high pressures at the interface between the coated tool and chip during metal machining [1,3,4,5,6,7]
Henry et al [12] studied TiAlN coatings with different Al-content and found that cracking was the main reason for wear at room temperature

Summary

Introduction

TiAlN is a hard coating and since the 1980s it is extensively used in the cutting tool industry [1]. Its excellent properties at high tempera ture, such as resistance to oxidation and high hardness, make this coating suitable for high temperature environments such as high-speed turning [2]. Staia et al [9] studied commercial TiAlN coatings They conducted ball-on-disc sliding tests using alumina ball up to 700 ◦C and observed the best wear behaviour for nanostructured coatings. Henry et al [12] studied TiAlN coatings with different Al-content and found that cracking was the main reason for wear at room temperature. They noted that the coating toughness varied with Al-content. Scratch experiments revealed that the crack resistance for Ti-rich coat ings was better than for Al-rich ones due to different texture and the presence of hexagonal (h) AlN the coatings [12]

Results

Discussion

Conclusion