Microstructural investigations on bonding mechanisms of cold-sprayed copper with SS316L steel

ABSTRACT

The purpose of the study was to understand the adhesion mechanism between cold-sprayed copper and SS316L steel substrate. Coatings of 3-mm thickness were deposited by cold-spraying on steel substrates prepared with different roughness values. To understand the bonding mechanism of the coating with substrates, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analyses were done on interfacial surfaces; exposed after the adhesion testing. Additionally, cross-sectional as-well-as top surface deformation behaviour of single copper particles deposited on steel substrates was investigated by using SEM/EDS, to elucidate the mechanism behind bonding. The results of the study validated that the adhesion is governed by both metallurgical bonding, as-well-as, mechanical interlocking, owing to the jetting formation. The mirror-polished surface resulted in a better adhesion strength as compared to the as-received and semi-polished surfaces, which was further validated by ultrasonic testing. Also, smaller-sized particles were found to be favourable for good adhesion strength.

KEYWORDS:

• Cold-spray
• bonding
• copper
• deformation
• microstructure
• adhesion strength
• roughness

Acknowledgements

Author acknowledges Dr Eklavya Calla from General Electric Bengaluru India for helping in the deposition work.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Department of Atomic Energy (DAE), Board of Research in Nuclear Sciences (BRNS), through the project entitled ‘Development of thick pure Cu cladding/coating on SS304/SS316 substrates with cold spray technology’ bearing sanction number [39/19/2015-BRNS], which is gratefully acknowledged. Also, the authors would like to thank the Department of Science and Technology-Funds for Improvement in Science and Technology (DST-FIST) INDIA, Grant number: SR/FST/ETI-379/2014 for the financial support which helped in creating facilities to carry out this work.