This paper compares the coating characteristics of two HVOF processes: air-cooled converging-nozzle Diamond Jet (DJ) spraying and Hybrid 2600 air/water-cooled converging/diverging technology. WC-Co coatings were deposited on steel substrates using different combinations of spray parameters, gas flow ratios, and cooling gas types. The coatings were then examined and tested to determine the extent to which microstructure, hardness, surface roughness, wear resistance, and deposition efficiency can be controlled. In addition to investigating process relationships, the paper also addresses the issues of practicality and cost.

HVOF-sprayed stainless steel coatings are potential candidates for protection against water corrosion. However, the process parameter "window" leading to acceptable corrosion behavior has yet to be determined. With potentiodynamic tests, this paper examines the corrosion behavior of metallic, thermally sprayed coatings under carefully controlled conditions in order to gain an insight into their performance "in service". The influence of the variations in the fuel:oxygen ratio, in the total gas volume and in the spraying distance, on the corrosion process of HVOF-sprayed stainless steel coatings on steel substrates with a low carbon content is determined by means of potentiodynamic measurements. The results are correlated with a characterization of the microstructure to understand the influence and role of oxide content, porosity, and coating morphology. Some comparisons with VPS coatings are also made. Paper includes a German-language abstract.