Hot corrosion resistance of NiCr based cermet coatings for the protection of boiler heat exchanger tubes

摘要

In large coal-fired boilers, boiler tubes, such as waterwall tubes, superheater tubes, economizer tubes and reheater tubes are exposed to very severe environment, and are subjected to corrosion and erosion. Nowadays thermally sprayed coatings offer an effective solution for extending the tubes service life. In the study, three kinds of NiCr-Cr{sub}3C{sub}2 cermet coatings were designed and deposited with subsonic velocity flame spraying, their performance of hot corrosion resistance was evaluated in comparison with 1020, 200 boiler tube steel, and FeCrAl, NiCrTi, Ni50Cr and NiCrAlMoFe-Cr{sub}3C{sub}2 coatings which are used widely at present for protection of boiler tubes. Meanwhile, the influences of sealer on the various coatings' hot corrosion resistance and the mechanisms of coating corrosion were explored. The research results showed that the NiCr-Cr{sub}3C{sub}2 cermet coating containing 50% Cr{sub}3C{sub}2 possesses excellent hot corrosion resistance and its hot corrosion performance is sixty to seventy times as high as that of 102G, 20G steel; the influence of sealer on the corrosion performance of NiCr-Cr{sub}5C{sub}2 cermet coatings is not obvious.