Localised surface modification of high-strength aluminium–alumina metal matrix composite coatings using cold spraying and friction stir processing

ABSTRACT

This study presents a novel approach for surface repairs of high-strength, cold-worked aluminium (Al) alloys, without negatively affecting the base material strength. Low-pressure cold spraying was used to fabricate Al–Al₂O₃ metal matrix composite overlays, with varying concentrations of Al₂O₃ deposited on an Al alloy. Friction stir processing (FSP) was employed to disperse and consolidate the overlay coating on the base material. The FSP was found to improve the Al₂O₃ particle distribution in the coating and reduce the mean free path between Al₂O₃ particles. The coating hardness increased after FSP. The post-FSPed overlays also exhibited lower wear rates compared to the as-sprayed condition. Remarkable improvement was observed in the tensile properties of the coatings, which were attributed to the improved dispersion of Al₂O₃ particles in the matrix, while the enhanced ductility was attributed to the possible grain refinement that occurred due to the recrystallisation of Al during FSP.

KEYWORDS:

• Alumina
• aluminium alloy
• cold spray
• friction stir processing
• mechanical properties
• metal matrix composite
• repair overlays
• coatings

Acknowledgements

The authors would like to thank Mr. Kapil Bhagavathula for hardness testing training and DIC training and Dr. Chenwei Shao for assistance with SEM imaging. The authors extend their gratitude to Mr. David Parlin for assistance with wire EDM, Mr. Mitul Patel for assistance with the tensile testing, and Mr. Maxime Guerin for assistance with the FSP.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Natural Sciences and Engineering Research Council of Canada under a Discovery Grant [Number RGPIN-2018-04298].