Influence of Parameter Variations on WC-Co Splat Formation in An HVOF Process Using DOE (design of experiments)

During the last 20 years, numerous scientists have studied the formation of thermally sprayed WC-Co coatings. Most of them focused on the direct connection between parameter variations and coating properties, like the microstructure, wear or hardness. Due to various modeling attempts of the interconnection between the spray parameters and coating properties, the formation of single splats as the most basic process was observed, as well. The aim of single splat interpretation is to determine the influence of different spray parameters on the morphological distribution of particles inside the flame. This distribution is indispensable to understand the formation of each coating layer during the process. Unfortunately, most of the methods presently used for generating single splats do not allow an assignment of each splat to its radial position in the flame.

A method to create a footprint of a spray beam with an extremely short exposure time was used in this paper. The resulting field of splats enables the assignment of the splats on the specimen to their radial position in the cross-section of the spray beam. The footprints were analyzed by correlating the quantities and morphology of the splats to measurements of the spray beam properties and the splat’s radial position inside the beam.