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On wear of TiAlN coated tools with and without NbN overlayer in machining titanium alloys

Lindvall, Rebecka LU ; Lenrick, Filip LU orcid ; Andersson, Jon M. ; M'Saoubi, Rachid LU and Bushlya, Volodymyr LU (2024) In International Journal of Machine Tools and Manufacture 198.
Abstract

Finding a wear resistant coating for cemented carbide cutting tools in the machining of difficult to cut Ti alloys is a challenge due to their high strength and chemical reactivity. Tool manufacturers recommend physical vapor deposited (PVD) TixAl1-xN (x = 0.4–0.7), and an extra NbN overlayer has shown promising potential. This study explores wear mechanisms of PVD Ti0.45Al0.55N with and without NbN overlayer and its WC-Co substrate in machining Ti alloys. To achieve an accurate understanding of tool-chip-workpiece interaction and related wear mechanisms, several approaches were employed. Tests with controlled variation of cutting speeds were complemented by process freezing experiments using... (More)

Finding a wear resistant coating for cemented carbide cutting tools in the machining of difficult to cut Ti alloys is a challenge due to their high strength and chemical reactivity. Tool manufacturers recommend physical vapor deposited (PVD) TixAl1-xN (x = 0.4–0.7), and an extra NbN overlayer has shown promising potential. This study explores wear mechanisms of PVD Ti0.45Al0.55N with and without NbN overlayer and its WC-Co substrate in machining Ti alloys. To achieve an accurate understanding of tool-chip-workpiece interaction and related wear mechanisms, several approaches were employed. Tests with controlled variation of cutting speeds were complemented by process freezing experiments using the quick stop method and imitational experiments of diffusion couples. Advanced microscopy techniques were employed for accurate detection of wear products and phenomena across length scale. Findings reveal that any new design of coatings for Ti machining must combine both high mechanical integrity and resistance to diffusional dissolution and oxidation. Observed diffusional loss of Al and N from the coating results in a TiN layer which is mechanically weaker than the original coating, while the NbN overlayer reduces the Al diffusion rate, but NbN is subjected to diffusional dissolution itself. On dissolution, Nb stabilizes β-Ti and thus facilitating loss of Al, but the observed formation of intermetallic Nb3Al at the NbN–Ti interface works as a diffusion barrier. However, brittle Nb3Al can be more easily removed during machining. It was found that the coating retains longest on the edge line and protects the tool edge from failure because substrate cemented carbide wears at a faster rate than the coating with outward diffusion of C from WC grains and Co binder.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Cemented carbide, NbN, TiAlN, Titanium, Tool wear
in
International Journal of Machine Tools and Manufacture
volume
198
article number
104148
publisher
Elsevier
external identifiers
  • scopus:85189093319
ISSN
0890-6955
DOI
10.1016/j.ijmachtools.2024.104148
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2024 The Authors
id
babc29e7-46fc-4294-a324-cdae35b8b9a5
date added to LUP
2024-04-08 10:43:03
date last changed
2025-04-04 14:21:36
@article{babc29e7-46fc-4294-a324-cdae35b8b9a5,
  abstract     = {{<p>Finding a wear resistant coating for cemented carbide cutting tools in the machining of difficult to cut Ti alloys is a challenge due to their high strength and chemical reactivity. Tool manufacturers recommend physical vapor deposited (PVD) Ti<sub>x</sub>Al<sub>1-x</sub>N (x = 0.4–0.7), and an extra NbN overlayer has shown promising potential. This study explores wear mechanisms of PVD Ti<sub>0.45</sub>Al<sub>0.55</sub>N with and without NbN overlayer and its WC-Co substrate in machining Ti alloys. To achieve an accurate understanding of tool-chip-workpiece interaction and related wear mechanisms, several approaches were employed. Tests with controlled variation of cutting speeds were complemented by process freezing experiments using the quick stop method and imitational experiments of diffusion couples. Advanced microscopy techniques were employed for accurate detection of wear products and phenomena across length scale. Findings reveal that any new design of coatings for Ti machining must combine both high mechanical integrity and resistance to diffusional dissolution and oxidation. Observed diffusional loss of Al and N from the coating results in a TiN layer which is mechanically weaker than the original coating, while the NbN overlayer reduces the Al diffusion rate, but NbN is subjected to diffusional dissolution itself. On dissolution, Nb stabilizes β-Ti and thus facilitating loss of Al, but the observed formation of intermetallic Nb<sub>3</sub>Al at the NbN–Ti interface works as a diffusion barrier. However, brittle Nb<sub>3</sub>Al can be more easily removed during machining. It was found that the coating retains longest on the edge line and protects the tool edge from failure because substrate cemented carbide wears at a faster rate than the coating with outward diffusion of C from WC grains and Co binder.</p>}},
  author       = {{Lindvall, Rebecka and Lenrick, Filip and Andersson, Jon M. and M'Saoubi, Rachid and Bushlya, Volodymyr}},
  issn         = {{0890-6955}},
  keywords     = {{Cemented carbide; NbN; TiAlN; Titanium; Tool wear}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{International Journal of Machine Tools and Manufacture}},
  title        = {{On wear of TiAlN coated tools with and without NbN overlayer in machining titanium alloys}},
  url          = {{http://dx.doi.org/10.1016/j.ijmachtools.2024.104148}},
  doi          = {{10.1016/j.ijmachtools.2024.104148}},
  volume       = {{198}},
  year         = {{2024}},
}