Hot corrosion behavior selected thermally sprayed based alloy coatings

Corrosion resistance of coatings deposited by thermal spraying technology HVOF (High Velocity Oxygen Fuel) requires high density in coating and good adhesion to the substrate. The majority of thermally sprayed materials meet the requirements for high corrosion resistance in terms of their composition. NiCoCrAlYHfSi, NiCoCrAlY NiCoCrAlTaReY and CoCrAlYTaCSi coatings were deposited on substrate material 1.4923. All evaluated coatings were deposited using HVOF (High Velocity Oxygen Fuel) thermal spraying technology. The evaluation of high temperature corrosion resistance was conducted for all selected thermally sprayed coatings. All evaluated coatings were exposed to corrosive-aggressive environment in the form of molten salts mixture with composition of 60% V2O5 and 40% Na2SO4 at the selected temperature of 750 °C. Further, all coatings were exposed to cyclic conditions. Each cycle included one hour exposure of coated specimens with salts mixture layer on the surface at 750 °C in silicon carbide furnace. 20 minutes cooling in air followed the exposure period. Weight changes of individual specimens were measured after every cycle and the results were recorded in a diagram. After the corrosion tests, all coatings were analyzed using scanning electron microscope (SEM), analysis of elemental composition (EDS) and X-Ray diffraction was also conducted.