Fatigue crack propagation in 15-5PH/316L bi-material steels fabricated by laser powder bed fusion
Fatigue crack propagation in 15-5PH/316L bi-material steels fabricated by laser powder bed fusion
Multi-material laser powder bed fusion (MM-LPBF) offers the possibility of components with material and compositional complexity, as well as the geometric complexity for which additive manufacturing is known. LPBF materials are susceptible to fatigue failures due to stress concentrating roughness and porosity defects. Understanding fatigue failure processes is therefore important to enable adoption of multi-material parts, and suitable combinations of materials may offer a strategy to enhance fatigue performance by resisting crack propagation. This study focused on fatigue crack propagation in 316L/15-5 precipitation hardened (PH) bi-material stainless steels (SS), and the effect of residual stress distribution and yield stress gradient on fatigue crack propagation through the interface. The expected yield stress gradient effect in bi-materials (soft to hard interface) was simulated using FE models, showing a slight shielding effect with a drop in J-integral value. Contour cutting measurements detected a residual stress distribution near the bi-material interface that was tensile in 316L layer and compressive in 15-5PH layer. Fatigue crack propagation rates in bi-materials deviated from those in the corresponding single-material specimens. A relatively small shielding effect due to the yield stress gradient was detected within a short distance of the crack tip from the interface. However, the effects of residual stress were more pronounced and inhibited the crack growth rate by up to 77.8 % in regions of 15-5PH SS under residual compression, which suggesting that MM-LPBF parts can be designed such that the compressive residual stress is positioned to intercept and suppress propagating cracks to improve damage tolerance.
Liang, Anqi
25257f89-cc17-42b8-81ac-fbf89b37738e
Lu, Songsong
179a342f-28f8-4181-8767-f5be79806578
Leering, Mitchell
ffb90f18-bc6d-4e1f-b2a2-a0b271473669
Ahmed, Bilal
7eba6d9e-223d-48df-80da-7c05e9cc1fb5
Fitzpatrick, Michael E.
b926f6e7-c189-4ad6-8a63-b783ebc4423d
Reed, Philippa A.S.
8b79d87f-3288-4167-bcfc-c1de4b93ce17
Polcar, Tomas
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2
Hamilton, Andrew R.
9088cf01-8d7f-45f0-af56-b4784227447c
15 July 2025
Liang, Anqi
25257f89-cc17-42b8-81ac-fbf89b37738e
Lu, Songsong
179a342f-28f8-4181-8767-f5be79806578
Leering, Mitchell
ffb90f18-bc6d-4e1f-b2a2-a0b271473669
Ahmed, Bilal
7eba6d9e-223d-48df-80da-7c05e9cc1fb5
Fitzpatrick, Michael E.
b926f6e7-c189-4ad6-8a63-b783ebc4423d
Reed, Philippa A.S.
8b79d87f-3288-4167-bcfc-c1de4b93ce17
Polcar, Tomas
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2
Hamilton, Andrew R.
9088cf01-8d7f-45f0-af56-b4784227447c
Liang, Anqi, Lu, Songsong, Leering, Mitchell, Ahmed, Bilal, Fitzpatrick, Michael E., Reed, Philippa A.S., Polcar, Tomas and Hamilton, Andrew R.
(2025)
Fatigue crack propagation in 15-5PH/316L bi-material steels fabricated by laser powder bed fusion.
International Journal of Fatigue, 201, [109165].
(doi:10.1016/j.ijfatigue.2025.109165).
Abstract
Multi-material laser powder bed fusion (MM-LPBF) offers the possibility of components with material and compositional complexity, as well as the geometric complexity for which additive manufacturing is known. LPBF materials are susceptible to fatigue failures due to stress concentrating roughness and porosity defects. Understanding fatigue failure processes is therefore important to enable adoption of multi-material parts, and suitable combinations of materials may offer a strategy to enhance fatigue performance by resisting crack propagation. This study focused on fatigue crack propagation in 316L/15-5 precipitation hardened (PH) bi-material stainless steels (SS), and the effect of residual stress distribution and yield stress gradient on fatigue crack propagation through the interface. The expected yield stress gradient effect in bi-materials (soft to hard interface) was simulated using FE models, showing a slight shielding effect with a drop in J-integral value. Contour cutting measurements detected a residual stress distribution near the bi-material interface that was tensile in 316L layer and compressive in 15-5PH layer. Fatigue crack propagation rates in bi-materials deviated from those in the corresponding single-material specimens. A relatively small shielding effect due to the yield stress gradient was detected within a short distance of the crack tip from the interface. However, the effects of residual stress were more pronounced and inhibited the crack growth rate by up to 77.8 % in regions of 15-5PH SS under residual compression, which suggesting that MM-LPBF parts can be designed such that the compressive residual stress is positioned to intercept and suppress propagating cracks to improve damage tolerance.
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Accepted/In Press date: 7 July 2025
e-pub ahead of print date: 7 July 2025
Published date: 15 July 2025
Identifiers
Local EPrints ID: 504369
URI: http://eprints.soton.ac.uk/id/eprint/504369
ISSN: 0142-1123
PURE UUID: 86dd376c-cc12-454f-858f-c3d2445d8b5a
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Date deposited: 08 Sep 2025 16:53
Last modified: 09 Sep 2025 01:58
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Author:
Anqi Liang
Author:
Songsong Lu
Author:
Mitchell Leering
Author:
Bilal Ahmed
Author:
Michael E. Fitzpatrick
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