Deposition mechanisms of metallic glass particles by Cold Gas Spraying

The deposition mechanisms of metallic glass particles impacting a substrate at high velocity (385-485 m/s) and temperatures near and above the glass transition are studied using finite element modeling. The deformation mechanisms of the metallic glass particles in these conditions are extremely dependent on their Reynolds number only leading to deposition and bonding at high Reynolds number. Unlike early works, this study includes the homogenous flow deformation under Newtonian and non Newtonian regime modeled using the constitutive equations of the free-volume model. The computed results are compared against experimental data of metallic glass coatings build-up by Cold Gas Spray. A critical value of the Reynolds number is found by both experiments and simulation, showing that it is a useful parameter to control the activation of viscoplastic deformation and bonding of metallic glass particles. Interestingly, this work demonstrates that deposition of metallic glass particles is governed by a cooperative movement of the liquid instead of a simple shear instability effect at the particle-substrate interface unlike polycrystalline metals. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.