Quantitative assessment of critical velocity in cold-spray using a peridynamics-based numerical framework incorporating adhesion

Cold spray (CS) is a promising technology for applications spanning structural repair, advanced coating and additive manufacturing. For CS of metal powders, though successful deposition is generally recognized to depend on rupture of native oxide films to enable intimate metallic contact, the exact mechanism of oxide rupture and its role in particle deposition remain insufficiently understood. Based on the peridynamics method, a new numerical framework incorporating an adhesion model and explicitly accounting for oxide layers on the particle and/or substrate was developed to predict the critical onset velocity for particle adhesion in cold sprayed Cu-on-Cu system. Numerical simulations were then performed to reveal the oxide rupture mechanism and oxide removal process, showing that oxide removal occurs mainly during the initial impact stage with jet initiation, while subsequent penetration primarily redistributes fragmented oxides with negligible further removal. Furthermore, the role of oxide in contact formation, particle adhesion, and rebounding-bonding competition was quantitatively clarified, and subsequently the critical velocity was predicted as a function of oxide thickness. These results agree well with experimental data and demonstrate that the proposed new framework enables realistic and accurate numerical investigation of particle impact and bonding behaviors for better mechanistic understanding of the CS process.