Erosion–corrosion behaviour of HVOF NiAl–Al2O3 intermetallic-ceramic coating

Erosion–corrosion (E–C) tests of a high velocity oxygen fuel (HVOF) NiAl–40Al2O3 intermetallic-ceramic coating were carried out in a laboratory, elevated temperature erosion tester. Bed ash and fly ash retrieved from operating boilers were used as erodent materials. The influence of the test temperature, velocity and impact angle on the erosion–corrosion behavior was investigated. E–C behavior of this coating was compared with that of AISI 1018 low carbon steel and other thermal sprayed coatings. The hardness and thermal shock resistance of the coatings were also measured. It was found that the HVOF NiAl–40Al2O3 coating exhibited excellent thermal shock resistance and high erosion resistance, especially at high impact angles and high temperatures. The erosion behavior of the HVOF NiAl–40Al2O3 coating was found to be less sensitive to the test temperature and impact angle as compared with chromium carbide cermet coatings. The elevated temperature erosion wastage of this coating increased with particle velocity following a power law with a lower velocity exponent than chromium carbide cermet coatings.