Tribocorrosion behaviour of thermally sprayed cermet coatings in paper machine environment

Tribocorrosion behaviour of thermally sprayed cermet coatings: WC-CoCr deposited by HVOF and HVAF and Cr₃C₂-WC-NiCrCo applied by HVAF, was examined in paper machine environment in a pin-on-disc tribometer under the load of 20 N in electrolyte containing chlorides and sulphates, pH 4.5. Wear was the dominant degradation mechanism for all coatings, followed by corrosion-induced wear, the importance of which increased with rising potential. The overall material losses were lowest for HVAF WC-CoCr and highest for HVAF Cr₃C₂-WC-NiCrCo, the latter being related to the evident abrasive wear of the Cr₃C₂ phase and cracking along Cr₃C₂-matrix interface in the near-surface areas. Among the three coatings, contribution by corrosion to the damage was greatest in HVOF WC-CoCr, likely due to high degree of porosity.