Cold spray as an innovative process to develop leak tight aluminum coatings for ultrahigh vacuum applications in a large particle high-energy collider

摘要

Vacuum chambers used in high-energy particle accelerator experiments are conventionally made of bulk beryllium, which shows significant drawbacks due to cost and toxicity. An alternative solution could be to develop cold sprayed Al-coated chamber. This requires that cold sprayed Al behaves as a perfect vacuum barrier. The study focuses on the relation between porosity in the cold sprayed aluminum coatings and leak tightness. Coatings from 0.18% to 9% porosity were achieved, and related to their tightness through helium leak testing. Multiscale porosity was studied, in 2D, by SEM and TEM. Porosity rates are discussed in the light of those from leak tests. In addition, numerical 3D Finite Element (FE) analyses of single and multi-particle impacts were led to go into mechanisms involved in the creation of porosity in cold spray coatings. This study involved different approaches to be compared: an Arbitrary Lagrangian Eulerian method and a coupled Eulerian-Lagrangian one.