High temperature hot corrosion behavior of selected thermally sprayed coatings in an aggressive environment at 690 °C

This study is focused on hot corrosion evaluation of selected thermal sprayed coatings. Cr₃C₂-25%NiCr, Stellite 6, NiCrBSi and Hastelloy C-276 was sprayed to the substrate material 1.4923. This material is used as an efficient construction material for components of power equipment. All tested coatings were sprayed using HP / HVOF (High Pressure / High Velocity Oxygen Fuel) technology.

Hot corrosion studies were performed in a molten salt environment typical for coal-fired boilers. All coatings was exposited Na₂SO₄ 82 % Fe₂ (SO₄)₃ environment at 690 °C under cyclic condition. Each cycle consisted 1h heating in silicon carbide tube furnace followed by 20 min of cooling. The weight change measurement was performed after each cycle to establish the corrosion kinetics. Scanning electron microscopy (SEM), elemental analysis (EDS) and optical microscopy (OM) technique were used to analyse the corrosion mechanism.