Microstructuring of Component Surfaces with Fine Particles by Cold Spraying

The creation of a defined surface morphology of components plays an important role in many technical applications like reduction of friction and wear or change of the adhesion of particles. In this contribution, a surface treatment process for the precise modification of the surface topology was developed on the basis of the cold spray technology. In this process, fine particles are accelerated in a gas stream by a Laval nozzle to supersonic velocities and sprayed on the surface. The particles can be embedded into the substrate surface by impact forming hills or rebound from the surface forming a crater-like surface. The influence of the process parameters on the microstructure formation was studied for fine steel and titanium particles colliding on the steel and titanium surfaces by experiments and numerical simulations. The particle acceleration in the Laval nozzle and the jet was simulated by Computational Fluid Dynamics and measured with high-speed Particle Image Velocimetry. The deposition of particles was described by a model for the critical impact velocity. The mechanical properties of surfaces and particles were measured by high temperature nanoindentation method and used for the determination of the regime diagram of the process.