Investigation of the microstructure and adhesionof warm sprayed WC-Co(Cr) coatings with smallcarbides (400-500 nm)

For decades, the deposition of WC-Co and WC-CoCr wear protective coatings by means of thermal spraying has been well investigated and established. These coatings exhibit a high hardness and a high toughness and thus superior wear resistance. In other application fields, WC-Co is used extensively as a cutting tool material. These cemented carbide tools are made by means of forming and sintering. In a final process step, the cutting edge is prepared by means of grinding processes. Solid cemented carbide tools are complex in manufacturing and hence, comparatively expensive. This paper focusses on an alternative process route for the manufacturing of cemented carbide cutting tools. WC-Co and WC-CoCr coatings are applied on a high-speed steel cutting tool base body by means of warm spraying (WS). The idea is to substitute the initial forming and sintering process and use less WC-Co by thermal spraying techniques. For this purpose, a fine WC-Co (−10+2 μm) powder and a coarser WC-Co-Cr (−30+5 μm) powder with fine WC-particles (400-500 nm) are used for spraying in order to achieve similar properties as sintered cemented carbide tools. In an initial step, the particle velocity and temperature are investigated along the spray plume for different N2 flow rates and two different nozzle lengths. With higher N2 flow rate the in-flight particle temperature is decreased and the in-flight particle velocity increases. Coatings are sprayed with different spray parameters and the coating morphology and properties are investigated extensively.