Adhesion of Cold Sprayed Brass Coatings for Lead-Free Bearings

State-of-the-art for manufacturing sliding bearings is soldering brass components to respective parts, which is costly and energy-intensive. Furthermore, up to now most bearings still contain lead, which has to be omitted due to associated health risks by EU regulations for new parts. Cold spraying can be employed as additive manufacturing technique and opens the perspective to deposit the requested bearings where needed. Aside deposit cohesion and tribological behaviour, the adhesion of the coating is very important for application. The present study aims to systematically elucidate the influence of surface roughness on adhesion.

The surface roughness was adjusted by varying the grit material, - size, blast pressure, - distance and substrate material with the aim to study influences by impact conditions, surface topography on particle deformation and bonding. The results show that the adhesion strength reaches a maximum for a certain roughness. The ideal surface roughness seems to be dependent on specific spray conditions related to the substrate material strength, the powder material strength and particle size distribution, - temperature and velocity. By systematic tuning, coating adhesion can be increased up to 200 % as compared to common grit blasted substrates, thus meeting the requirements for new benign and lead-free bearings.