Enhanced steel machining performance using texture-controlled CVD alpha-alumina coatings : Fundamental degradation mechanisms
(2024) In International Journal of Machine Tools and Manufacture 197.- Abstract
Cemented carbide inserts coated with CVD α-alumina, particularly those exhibiting a (0001) texture, have proven highly effective in steel turning. Despite the established superior performance of (0001) textured alumina coatings, the underlying reasons remain unclear. This study explores the influence of the crystallographic texture of alumina on wear mechanisms in various chip-tool contact zones on the insert rake face. The objective is to establish a fundamental understanding of the active degradation mechanisms and machining performance by relating coating texture to the orientation and deformation of individual Al2O3 grains. Two multilayered coatings, Al2O3 on Ti(C,N), featuring (0001)- and... (More)
Cemented carbide inserts coated with CVD α-alumina, particularly those exhibiting a (0001) texture, have proven highly effective in steel turning. Despite the established superior performance of (0001) textured alumina coatings, the underlying reasons remain unclear. This study explores the influence of the crystallographic texture of alumina on wear mechanisms in various chip-tool contact zones on the insert rake face. The objective is to establish a fundamental understanding of the active degradation mechanisms and machining performance by relating coating texture to the orientation and deformation of individual Al2O3 grains. Two multilayered coatings, Al2O3 on Ti(C,N), featuring (0001)- and (112‾0)-textured CVD α-alumina, were assessed in dry turning of a bearing steel. The wear rate of the (112‾0) coating was double that of the (0001) coating. Worn coatings exhibit nano-terrace formation at the insert edge, likely due to chemical etching. In the sticking zone, plastic deformation leads to larger facets for grains oriented with the chip flow direction, while rounded surfaces result if this condition is not met. In the transition zone, both (0001) and (112‾0) textured coatings undergo increased plastic deformation accompanied by sub-surface dislocations. (0001) texture deforms more by basal slip creating a wavy coating pattern with steps present at larger misalignments of the lattice planes in neighboring grains while (112‾0) texture deforms by several slip systems creating elongated ridges and ruptured-like areas resulting in rougher surface. This difference in surface morphology is then inherited by the abrasion of submicron coating fragments embedded in the chip (more in (112‾0) texture) in the sliding zone resulting in an even rougher surface. Chemical reaction with the hot chip may also contribute to wear acting as an additional mechanism. This fundamental understanding contributes to the potential enhancement of steel machining using texture-controlled CVD alumina coatings, ultimately improving coated cutting tool performance.
(Less)
- author
- Shoja, S. ; Bäcke, O. ; Fazi, A. ; Norgren, S. LU ; Andrén, H. O. and Halvarsson, M.
- organization
- publishing date
- 2024-04
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Chemical vapor deposition, Hard coatings, Machining, Schmid factor, Transmission kikuchi diffraction, Wear mechanisms
- in
- International Journal of Machine Tools and Manufacture
- volume
- 197
- article number
- 104137
- publisher
- Elsevier
- external identifiers
-
- scopus:85188519688
- ISSN
- 0890-6955
- DOI
- 10.1016/j.ijmachtools.2024.104137
- language
- English
- LU publication?
- yes
- id
- 6b32846c-b80a-4a29-afe0-069264786ad6
- date added to LUP
- 2024-04-15 16:10:56
- date last changed
- 2024-04-15 16:11:59
@article{6b32846c-b80a-4a29-afe0-069264786ad6,
abstract = {{<p>Cemented carbide inserts coated with CVD α-alumina, particularly those exhibiting a (0001) texture, have proven highly effective in steel turning. Despite the established superior performance of (0001) textured alumina coatings, the underlying reasons remain unclear. This study explores the influence of the crystallographic texture of alumina on wear mechanisms in various chip-tool contact zones on the insert rake face. The objective is to establish a fundamental understanding of the active degradation mechanisms and machining performance by relating coating texture to the orientation and deformation of individual Al<sub>2</sub>O<sub>3</sub> grains. Two multilayered coatings, Al<sub>2</sub>O<sub>3</sub> on Ti(C,N), featuring (0001)- and (112‾0)-textured CVD α-alumina, were assessed in dry turning of a bearing steel. The wear rate of the (112‾0) coating was double that of the (0001) coating. Worn coatings exhibit nano-terrace formation at the insert edge, likely due to chemical etching. In the sticking zone, plastic deformation leads to larger facets for grains oriented with the chip flow direction, while rounded surfaces result if this condition is not met. In the transition zone, both (0001) and (112‾0) textured coatings undergo increased plastic deformation accompanied by sub-surface dislocations. (0001) texture deforms more by basal slip creating a wavy coating pattern with steps present at larger misalignments of the lattice planes in neighboring grains while (112‾0) texture deforms by several slip systems creating elongated ridges and ruptured-like areas resulting in rougher surface. This difference in surface morphology is then inherited by the abrasion of submicron coating fragments embedded in the chip (more in (112‾0) texture) in the sliding zone resulting in an even rougher surface. Chemical reaction with the hot chip may also contribute to wear acting as an additional mechanism. This fundamental understanding contributes to the potential enhancement of steel machining using texture-controlled CVD alumina coatings, ultimately improving coated cutting tool performance.</p>}},
author = {{Shoja, S. and Bäcke, O. and Fazi, A. and Norgren, S. and Andrén, H. O. and Halvarsson, M.}},
issn = {{0890-6955}},
keywords = {{Chemical vapor deposition; Hard coatings; Machining; Schmid factor; Transmission kikuchi diffraction; Wear mechanisms}},
language = {{eng}},
publisher = {{Elsevier}},
series = {{International Journal of Machine Tools and Manufacture}},
title = {{Enhanced steel machining performance using texture-controlled CVD alpha-alumina coatings : Fundamental degradation mechanisms}},
url = {{http://dx.doi.org/10.1016/j.ijmachtools.2024.104137}},
doi = {{10.1016/j.ijmachtools.2024.104137}},
volume = {{197}},
year = {{2024}},
}