Modeling of cold spray gas flow dynamics for off-axis gun/ substrate hole geometries

Cold spray has been proved to be an economic spraying technique while being green and eco-friendly. Thanks to its remarkable deposition rate, flexibility, and low process temperature, it is particularly popular for fast and low thermal impact part repairs. Despite cold spray advantages, deposition in discontinuous geometries such as steps, corners, and holes remains a challenge as the understanding of the gas jet interaction with these geometrical features is still limited. Experimental works have shown that it is difficult to completely fill the hole as some areas inside the hole and near its entrance remain undeposited or exhibit poorly-bonded coating. In this work, we studied the effect of introducing an offset between the gun main axis and the center of the hole. With the aid of numerical modeling, we simulated this configuration and monitored the particle velocity and distribution upon impact. The effects of inlet pressure, hole diameter, particle size, and offset distance were investigated. The results show that by choosing the right offset distance and by increasing the inlet pressure, the particles can be accelerated and deposited to completely cover the inside surface of the hole and fill the regions that remained undeposited in the on-axis geometry.