Influence of the Injector Head Geometry on the Particle Injection in Plasma Spraying

In plasma spraying the particle velocity at the injector outlet has significant influence on particles’ penetration into the plasma jet. The geometry of the injector and the flow rate of the carrier gas determine the particle velocities. Based on numerical simulations, it is evident that higher particle velocities and thus, deeper penetration of the particles into the plasma jet can be realized with an injector geometry, which is significantly longer than the standard injector. This leads to a higher melting degree of the particles in the numerical investigations, especially for operating parameters leading to high-speed plasma jets.

In order to verify the results of the simulations, injectors with different diameters and lengths are manufactured and its influence on the particle velocities at the injector head is measured via particle diagnostics. The injectors are furthermore used to apply coatings with the TriplexPro-210. Alumina (AMDRY 6062) is used as feedstock material. The resulting deposition efficiencies are determined. By measuring the relative intensities of the α- and γ-alumina peaks in the X-Ray diffraction spectrum, the different melting degrees are compared qualitatively. As a result, it seems feasible to influence the injection behavior of the particles positively with small changes in injector geometry.