Cold-Sprayed Bell Metal: Improving Adhesion by Substrate Laser Surface Texturing

Historical bells are worn and damaged by the ravages of time. The repair and restoration of these heritage masterpieces could be attempted using cold technology, provided a sufficient adhesion is reached. In this paper, the improvement of Cu20Sn bell metal repair adhesion by various substrate surface treatments was studied: grinding, polishing, cold spray grit-blasting, and laser texturing using five different patterns. The adhesion was tested by a new, simple glue-less method tailored for testing thick cold spray deposits. It was shown that while the cold spray grit-blasting provides a good adhesion of around 70 MPa, even better results of approximately 120 MPa could be obtained by the laser patterning. The detailed three-dimensional fractographic analysis allowed us to describe the failure mechanism of all specimens. For the best-performing laser texturing, this was a combination of interfacial debonding at the original substrate surface and the deposit cohesive fracture inside the pattern recessed areas.