Chlorine induced high-temperature corrosion mechanisms in HVOF and HVAF sprayed Cr3C2-based hardmetal coatings

•High temperature corrosion properties of HVOF and HVAF Cr3C2-based coatings.•Synergistic use of TGA and furnace corrosion tests.•A corrosion mechanism for chloritizing-oxidizing condition was proposed.•Temperature ranges were identified for the onset of chlorine corrosion.•Fine secondary carbide precipitates were highly detrimental in the test conditions. A novel method that combines thermal analysis and traditional furnace corrosion tests was used to study the corrosion behaviour of thermally sprayed Cr3C2-based hardmetal coatings at 450 °C and 550 °C under a KCl deposit. This method enabled the identification of the onset temperature of chlorine-induced oxidation to be within 450–500 °C. Two corrosion mechanisms were suggested for these temperatures. At 450 °C, the corrosion rate was slow and mainly controlled by the formation of K2CrO4. Exposure at 550 °C caused the formation of fine interconnected secondary-carbide precipitates in the metal matrix. Their fast corrosion was identified as the major cause of degradation.