Laser surface remelting to improve the erosion–corrosion resistance of nickel–chromium–aluminium–yttrium (NiCrAlY) plasma spray coatings

Abstract: The chapter deals with the role of NiCrAlY plasma spray coatings and subsequent laser surface remelting to improve the characteristics of these coatings. NiCrAlY plasma spray coating has been formulated on boiler tube steels, namely low carbon steel ASTM-SA210-Grade A1, 1Cr–0.5Mo steel ASTMSA213-T-11 and 2.25Cr–1Mo steel ASTM-SA213-T-22. The coated steels have also been laser remelted by Nd: YAG (yttrium aluminium garnet) laser. The coatings have been characterised and the degradation behaviour of as-sprayed and laser remelted coatings have been evaluated in actual conditions in a coal-fired boiler for 1000 h at 755 °C. The laser remelting was found to be effective at increasing the degradation resistance of plasma sprayed boiler steels. The decrease in porosity and better surface structure after laser remelting probably contributed to improve the performance of the laser remelted coatings.

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