Influence of powder feed rates at mechanical properties and microstructure of tungsten carbide based powder

Producers of thermally sprayed coatings are currently forced to spray coatings with extremely precise final coating thickness. The reason for such demand is fact, that there is rising number of applications using thermally sprayed coatings without final grinding. This fact makes standardly optimized powder feed rates unusable, because the requested coating thickness tolerance is maximally up to 0.05mm. The possible way how to achieve such precision at coating layer deposition is to adjust the feeding rates. Such change of optimized feed rates results in change of mechanical properties and microstructure of final layer. This paper aims to characterize and quantify the changes. Tested WC-Co-Cr coating was prepared using HP/HVOF technology by pre-optimized parameters and with different powder feed rates. Micro and macro hardness was measured for each sample together with microstructure and furthermore evaluated. The results show final dependency of mechanical parameters and microstructure of selected feed rates and defines the relationship between them.