The coatings of tungsten carbide with cobalt or cobalt alloys reveal high microhardness and an excellent wear resistance. The hard WC grains form a wear resistant constituent of a coating. The coatings microstructure is determined by the processing parameters of the torch and the powder used to spray. The modern online particle monitoring systems allows even deeper insight in the mechanism of coating formation. The integrated optical monitoring system DPV2000, used in this paper, enables a simultaneous of powder particles velocity, temperature, and size. These in-flight parameters, depending on operational processing parameters, are directly influencing the coatings microstructure. In this paper, the hardness of the HVOF sprayed two types of WC composite powders is related to the coatings microstructure and to the different processing conditions. These conditions are monitored by an DPV2000 optical system that enabled determination of the in-flight particles velocity and temperature. Paper includes a German-language abstract.