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Volume 8
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Article

Diffusion Barriers for Electrodes in Resistance Spot Welding of Aluminum Alloys—Investigation of Coating Characteristics Using Nanoindentation and SEM Analysis

by
Sascha Brechelt
1,*,
Henning Wiche
1,
Jochen Junge
1,
René Gustus
1,
Harald Schmidt
2 and
Volker Wesling
3
1
Clausthal Center of Materials Technology, Clausthal University of Technology, Leibnizstraße 9, D-38678 Clausthal-Zellerfeld, Germany
2
Institute of Metallurgy, Clausthal University of Technology, Robert-Koch Straße 42, D-38678 Clausthal-Zellerfeld, Germany
3
Institute of Welding and Machining, Clausthal University of Technology, Agricolastraße 2, D-38678 Clausthal-Zellerfeld, Germany
*
Author to whom correspondence should be addressed.
Surfaces 2025, 8(4), 81; https://doi.org/10.3390/surfaces8040081
Submission received: 10 October 2025 / Revised: 9 November 2025 / Accepted: 14 November 2025 / Published: 17 November 2025
(This article belongs to the Special Issue Surface Engineering of Thin Films)
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Abstract

Resistance spot welding of aluminum alloys causes the electrode materials to degrade rapidly. This is due to diffusion processes occurring between the sheet materials and the copper electrodes at process temperatures of up to 600 °C. This significantly limits the electrode life, resulting in less than 60 weld cycles before the joint quality becomes insufficient. Thin-film diffusion barriers can increase electrode life and improve joint quality. This article describes the generation of barrier layers of nickel and tungsten using physical vapor deposition. These layers directly influence the welding process by altering the electrical resistance and friction coefficients in the contact area. Nanoindentation is used to determine the specific properties of the barrier layers within the 2.5–3 µm layer thickness range. Hardness and modulus of elasticity are determined by indentation tests. Scratch tests determine the friction coefficients and adhesion strength of the coating against plastic deformation. Nanoindentation is also used to investigate the degradation process of the electrode base material and barrier layers. This reveals which damage mechanisms occur with uncoated electrodes and demonstrates how thin-film diffusion barrier coatings can prevent aluminum diffusion.
Keywords: resistance spot welding; electrode degradation; CuCr1Zr; diffusion; nanoindentation; SEM; SIMS resistance spot welding; electrode degradation; CuCr1Zr; diffusion; nanoindentation; SEM; SIMS
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MDPI and ACS Style

Brechelt, S.; Wiche, H.; Junge, J.; Gustus, R.; Schmidt, H.; Wesling, V. Diffusion Barriers for Electrodes in Resistance Spot Welding of Aluminum Alloys—Investigation of Coating Characteristics Using Nanoindentation and SEM Analysis. Surfaces 2025, 8, 81. https://doi.org/10.3390/surfaces8040081

AMA Style

Brechelt S, Wiche H, Junge J, Gustus R, Schmidt H, Wesling V. Diffusion Barriers for Electrodes in Resistance Spot Welding of Aluminum Alloys—Investigation of Coating Characteristics Using Nanoindentation and SEM Analysis. Surfaces. 2025; 8(4):81. https://doi.org/10.3390/surfaces8040081

Chicago/Turabian Style

Brechelt, Sascha, Henning Wiche, Jochen Junge, René Gustus, Harald Schmidt, and Volker Wesling. 2025. "Diffusion Barriers for Electrodes in Resistance Spot Welding of Aluminum Alloys—Investigation of Coating Characteristics Using Nanoindentation and SEM Analysis" Surfaces 8, no. 4: 81. https://doi.org/10.3390/surfaces8040081

APA Style

Brechelt, S., Wiche, H., Junge, J., Gustus, R., Schmidt, H., & Wesling, V. (2025). Diffusion Barriers for Electrodes in Resistance Spot Welding of Aluminum Alloys—Investigation of Coating Characteristics Using Nanoindentation and SEM Analysis. Surfaces, 8(4), 81. https://doi.org/10.3390/surfaces8040081

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