Chromium-titanium carbide cermet coating for elevated temperature erosion protection in fluidized bed combustion boilers

摘要

The elevated temperature erosion resistance of one high-velocity oxygen-fuel (HVOF) chromium-titanium carbide cermet coating on mild steel was investigated in a laboratory blast nozzle-type erosion tester. Erosion tests were carried out at 300 and 450℃, at particle velocities of 30 and 60 m/s and at impact angles of 30° and 90°, using bed ashes and fly ashes retrieved from operating fluidized bed combustion (FBC) boilers. The elevated temperature erosion behavior of HVOF chromium-titaniumcarbide cermet coating was compared with that of two reference materials, mild steels (AISI 1018, ASTM SA213 T22) and other thermal sprayed coatings including an HVOF chromium carbide cermet coating, an HVOF tungsten carbide cermet coating, and anarc-sprayed FeCrSiB metallic coating. The morphology of specimens was examined by light microscopy and scanning electron microscopy. The thermal shock resistance of the coatings specimens was measured. It was found that the HVOF chromium-titanium carbidecermet coating exhibited high erosion resistance with similar level to that of the HVOF tungsten carbide cermet coating, but with a much higher thermal shock resistance. The erosion behavior of the coatings is closely related to their microstructurecomposition and the properties of erodent particles. However, the effect of these factors on the erosion behavior varied with erosion test conditions.