Characterization of cold-sprayed multimodal WC-12Co coating

In present work, the deposition behaviors of individual bimodal WC-12Co particles impacting on stainless steel and WC-12Co substrates were investigated. The microstructure and properties of the cold-sprayed WC-12Co coating were characterized. The results showed that the WC-12Co particles partially penetrated into the stainless steel substrate. Flattening of the particles occurred with splashes at its periphery when impacting on the WC-12Co substrate. A movement of small WC particles accompanied with a plastic flow of the Co binder occurred during the impacting and flattening process of the powders. The sprayed coating exhibited a characteristic microstructure with a wide range of WC particle sizes varying from less than 100 nm up to a micron scale. The obtained multimodal coating exhibited both a high hardness and high fracture toughness, e.g. the microhardness is similar to that of a cold sprayed nano WC-12Co coating and the fracture toughness is comparable to that of a bulk material of micro WC-12Co. The cold sprayed coating exhibited a greatly enhanced wear resistance in comparison to the conventional high-velocity oxy-fuel (HVOF) sprayed WC-12Co coating.