EFFECTS OF SHOCK WAVES ON THE PARTICLE ACCELERATION FOR COLD GAS DYNAMIC SPRAY

摘要

The particle velocity in cold gas dynamic spraying (CGDS) is one of the most important factors that can determine the properties of the bonding to the substrate. In this paper, the acceleration process of micro-scale and sub micro-scale copper (Cu) and platinum (Pt) particles inside and outside De-Laval-Type nozzle is investigated. A numerical simulation is performed for the gas-particle two phase flow with particle diameter ranging from 100nm to 50μm, which are accelerated by carrier gas Nitrogen in a supersonic De-Laval-type nozzle. The carrier gas velocity and pressure distributions in the nozzle and outside the nozzle are illustrated. The center-line velocity for two types of particles, Pt and Cu, are demonstrated. It is observed that the existence of the bow shocks near the substrate prevents the smaller size particles (less than 0.5 μm) from penetrating, thus leads to poor coating in the actual practices.