Effect of water environment on particle deposition of underwater cold spray

(a) Cross-sectional and surface morphologies contrast SEM photographs of CS and UCS coatings (b) Microhardness and etched cross sectional images of CS and UCS coatings (c) Simulation results of PEEQ and Mises stress of CS and UCS particles (d) Schematic of particle deposition mechanism under different water film thickness. [Display omitted] •A newly underwater remanufacturing-manufacturing method based on gas-dynamics underwater cold spray (UCS) was proposed.•Microscale effect of water thin film was numerical simulated and deformation mechanism of UCS coating was investigated.•The value of PEEQ and Mises stress of UCS particles compared with CS was studied.•The Al/SS304 water film thickness threshold was given through systematic study. Underwater in-situ repair and maintenance are focused by more and more researchers. In this paper, an effective underwater coating preparation method is proposed and preliminarily clarifies its deposition mechanism. AA1050 pure aluminium is deposited onto the SS304 substrate by underwater cold spray (UCS), substrate and nozzle completely immersed in the water. The UCS coating in this research has a similar structure to the conventional CS coating, while it has a lower porosity and lower surface roughness than CS coating. Porosity of UCS is 5.05% while CS is 6.86%, and surface roughness is 20.8 μm and 24 μm, respectively. Effect of water environment on deposition process is revealed by analysis of finite element using Eulerian model. Compared with conventional CS, the presence of water film increases the equivalent strain and Mises stress of particle during the deposition, while reduces the velocity. The hardness of UCS coating is slightly higher than CS. When the thickness of the water film exceeds 1.25 μm, the deposition spot will accumulate moisture and affect bonding between particles and substrate. The UCS coating deposition mechanism contains direct deposition from plastic deformation of high-velocity particles and secondary tamping of low-velocity particles.