Characterisations of plasma sprayed and laser remelted NiCrAlY bond coats and Ni3Al coatings on boiler tube steels

NiCrAlY and Ni3Al coatings were obtained on boiler tube steels namely ASTM-SA210-Grade A1, ASTM-SA213-T-11 and ASTM-SA213-T-22 through shrouded plasma spray process. NiCrAlY was also used as a bond coat before applying Ni3Al coatings. The coatings were subjected to metallography, XRD and SEM/EDAX analysis. The microhardness of the coatings has been measured along the cross-section. Considerable reduction in the hardness values has been observed after laser remelting in case of NiCrAlY bond coats. The laser remelting has resulted in significant dilution of coating due to inter diffusion of atoms. Very dense and homogeneous structures have been obtained by laser remelting of coatings.