Erosion–corrosion resistance of microcrystalline and near-nanocrystalline WC–17Co high velocity oxy-fuel thermal spray coatings

Cermet based coatings are being increasingly used to combat erosion–corrosion in oil sands pipelines and pumps where the degradation is caused by a slurry mix of sand particles and aqueous solution. This research assesses the erosion–corrosion resistance of cermet composite coatings obtained by HVOF thermal spraying of microcrystalline and ‘duplex cobalt coated’ near-nanocrystalline WC–17Co feedstock powders. Electrochemical measurements, surface characterization, and the extent of weight loss were studied through an impingement jet system. Results suggest that the erosion–corrosion mechanism in the coatings was dominated by pure erosion in the microcrystalline coating and corrosion-enhanced erosion in the near-nanocrystalline coating.

► Prevention of WC decarburization during spraying by use of Duplex Co coated powder.
► Impingement slurry jet test for erosion–corrosion behaviour of WC–17Co coatings.
► Microgalvanic cell, crevice corrosion site formation in microcrystalline coating.
► Absence of oxide scale fracture in near-nanocrystalline coating.
► Erosion–corrosion synergism in the coatings dominated by two distinct mechanisms.