Cold gas dynamics spraying (CGDS) is a process employing aerodynamics particle acceleration and high-speed impact dynamics surface-coating technology. The main advantages of CGDS include : (1) A low level of residual stresses; (2) CGDS can collect and reuse the undeposited particle more efficient than thermal spray processes; (3) Coatings can be deposited on materials that are temperature-sensitive; (4) Thick coatings can be produced to allow for free-standing structures or for rapid prototyping; (5) CGDS is safer because it is operated in low temperatures and low noise levels (6) Easy implementation due to its simplicity of technical design; (7). CGDS could produce high thermal and electrical conductivity of coatings.
In the CGDS process, a high-pressure gas stream (generally 20–30 atm) carries metal particles (usually 1–50 μm in diameter) through a DeLaval type nozzle to reach a supersonic velocity before impact on the substrate. Typically, the impact velocities in the CGDS process range from 300 to 1200 m/s. When the particle exceeds the minimum deposition speed, adiabatic shear instabilities occur. This minimum deposition speed is also called critical velocity. In this paper, single particle impact simulations were performed to investigate the critical velocities of different particle sizes on the bonding process. This paper presents a three-dimensional numerical analysis of the particle critical velocity on the bonding efficiency in Cold Gas Dynamic Spray (CGDS) process by using ABAQUS/CAE 6.9-EF1. The particle impact temperature in CGDS is one of the most important factors that can determine the properties of the bonding strength to the substrate. In the CGDS process, bonding occurs when the impact velocity of particles exceed a critical velocity, which can reach minimum interface temperature of 60% of melting temperature in °C. The critical velocity depends not only on the particle size, but also the particle material. Therefore, critical velocity should have a strong effect on the coating quality. In the present numerical analysis, impact velocities were increased in steps of 100 m/s from the lowest simulated impact velocity of 300 m/s. This study illustrates the substrate deformations and the transient impact temperature distribution between particle(s) and substrate. In this paper, an explicit numerical scheme was used to investigate the critical velocity of different sizes of particle during the bonding process. Finally, the computed results are compared with the experimental data. Copper particles (Cu) and Aluminum substrate (Al) were chosen as the materials of simulation.