Optimization of a laval nozzle for energy-efficient cold spraying of microparticles. Issue 2 (25th January 2018) - Buhl, Sebastian
ABSTRACT: An application of cold spraying is the microstructuring of surfaces by particles in the size range of 1–10 µm, for example, to improve tribological properties. Since the particle acceleration is crucial for the cold spray process, this work is focused on the optimization of a Laval nozzle. Therefore, a nozzle was designed using analytic models for the fluid and particles behavior. The new nozzle design was improved by CFD simulations considering the effects of friction between the gas and the inner nozzle wall. Moreover, the effects of the distance between the nozzle outlet and the sample, as well as the particle position by entering the nozzle on the particle trajectories and impact velocity were studied numerically. The optimization of nozzle design has been validated experimentally by cold spraying small TiO2 particles with mean size of 1 µm and larger Ti particles with the mean size of 10 µm. The optimized nozzle showed an improved spray performance. This work has been presented at the conference SMT30 (ID 267)