Critical Velocity for Cold-Sprayed Coatings

The cold-spray technology has been rapidly gaining in popularity, especially over the last two decades, due to its ability for depositing coatings at relatively low temperatures in contrast to other thermal spray methods. A key challenge for this technique lies in optimization of process parameters. Particle deposition occurs by plastic deformation of the particle and the substrate, which requires a high kinetic energy of impact. This calls for a minimum threshold velocity called the critical velocity and happens to be a key factor affecting process efficiency. In this review, we focus on numerical, theoretical and experimental approaches towards measuring the critical velocity (v_cr) and subsequently elucidate the factors affecting v_cr.