Structural changes in Ti1-xAlxN coatings during turning: A XANES and EXAFS study of worn tools

TL;DR

This study investigates the structural evolution of Ti1-xAlxN coatings during turning of stainless steel using advanced spectroscopic techniques, revealing TiN domain formation, phase changes, and steel adhesion effects.

Contribution

It provides detailed insights into the microstructural changes and chemical states of Ti1-xAlxN coatings during machining, utilizing XANES, EXAFS, EDS, and STEM analyses.

Findings

TiN-enriched domains form during turning due to spinodal decomposition.

Structural changes occur in the w-TiAlN phase during machining.

Cr oxidizes while Fe adheres to the tool surface during cutting.

Abstract

Structural changes in Ti1-xAlxN coated tool inserts used for turning in 316L stainless steel were investigated by XANES, EXAFS, EDS, and STEM. For coarse-grained fcc-structured Ti1-xAlxN coatings, with 0 \leq x \leq 0.62, the XANES spectrum changes with Al-content. XANES Ti 1s line-scans across the rake face of the worn samples reveals that TiN-enriched domains have formed during turning in Ti0.47Al0.53N and Ti0.38Al0.62N samples as a result of spinodal decomposition. The XANES spectra reveal the locations on the tool in which the most TiN-rich domains have formed, indicating which part of the tool-chip contact area that experienced the highest temperature during turning. Changes in the pre-edge features in the XANES spectra reveal that structural changes occur also in the w-TiAlN phase in fine-grained Ti0.38Al0.62N during turning. EDS shows that Cr and Fe from the steel adhere to the tool rake face during machining. Cr 1s and Fe 1s XANES show that Cr is oxidized in the end of the contact length while the adhered Fe retains in the same fcc-structure as that of the 316L stainless steel.