Comparison of fine (-10 +2 µm) and conventional(-45 +20 µm) WC-CoCr 86-10-4 feedstock powders:Influence of the HVOF spraying parameters on theparticle and coating properties

The composition, morphology, shape and size of the powder feedstock significantly influences the subsequent properties of every HVOF-sprayed coating. For example, the inherent porosity or grain size of the particles is directly reflected in the microscopic and macroscopic structure of the coating and determines the mechanical and physical properties of the coating at the same time. Particularly in relation to the coating homogeneity and the contour accuracy, totally new possibilities are offered with fine (≤ 10 μm) feedstock powders. For instance, complex component structures and linings can be put into effect in a better way and costs can be saved due to a smaller scope of post-processing. Within the framework of this research paper, the technical possibilities, limits and potentials of these fine powders are considered employing WC-CoCr 86-10-4. A direct comparison is made between fine (−10 +2 μm) feedstock powders and the conventional (−45 +20 μm) powder fraction. Investigations are conducted determining the influence of the particle grain size on the particle properties in flight (particle temperature, velocity and trajectory) as well as on the coating properties (porosity, application efficiency / coating thickness and hardness).