Critical velocity and deposition efficiency in cold spray: A reduced-order model and experimental validation

Abstract

Deposition efficiency (DE) in cold spray additive manufacturing (CSAM) is a key indicator for evaluating process efficiency. Here we develop a reduced-order model to predict DE of metals during CSAM by simultaneously calculating the critical velocity and impact velocity using the gas temperature, gas pressure, and particle size as inputs. The impact velocity must exceed the critical velocity to achieve particle adhesion. Since both the critical and impact velocities vary with particle size, DE can be derived from the intersection of these curves. An equation for calculating critical velocity is proposed based on the hydrodynamic spall mechanism with the support of experimental data. The impact velocity is determined using a parametric expression that accounts for the bow shock effect. The model is first calibrated for aluminum to create process design maps. Ten validation experiments are then conducted using two different cold spray systems. The experimental DE values show close agreement with the predicted results. The model can be used to rapidly identify optimal process parameters for achieving high DE of metals, contributing to improved process efficiency and product quality during CSAM.