A New Concept of the Application of Shock Wave Technology in the Cold Gas Dynamic Spray Process

Abstract

Abstract A new cold spray process for a combustion-free spraying is studied experimentally and by modeling and simulation. The high particle velocity at the front of the substrate is achieved by using the shock tube technology. The particles have been injected downstream of the nozzle throat into a supersonic nozzle flow. The shock tube of 6.5 m length and 56 mm inner diameter provides the necessary reservoir conditions for the nozzle flow. The measurements of the particle velocity made by a laser Doppler anemometry (LDA) setup showed that the maximum velocity amounts to 1220 m/s for stainless steel particles of 15 µm diameter. The CFD-Code (Fluent) is first verified by a comparison with available numerical and experimental data for gas and gas-particle flow fields in a long Laval-nozzle. The good agreement implied the great potential of the new dynamic process concept for cold gas coating applications. Then the flow fields in the short Laval nozzle designed and realized by the Shock Wave Laboratory (SWL) have been investigated. The gas flow for experimentally obtained stagnation conditions has been simulated. The gas-particle flow without and with the influence of the particles on the gas flow has been calculated by the Surface Engineering Institute (IOT) and compared with experiments. The influence of the injection parameters on the particle velocities has been investigated as well.