Microstructural and mechanical properties of CNT-reinforced ZrO2-Y2O3 coated boiler tube steel T-91

The main purpose of this study was to fabricate carbon nanotubes (CNTs) reinforced zircon­nium yttrium coatings on boiler tube steel and to investigate the microstructural and mechanical properties of these coatings. Plasma sprayed conventional ZrO2-Y2O3, ZrO2-Y2O3 and 1 wt.% CNT and ZrO2-Y2O3 and 4 wt.% CNT were prepared and deposited successfully on boiler tube steel material T-91 (ASTM SA-213) by plasma thermal spray technology. Microhardness, porosity, XRD (X-ray diffraction), SEM/EDAX (scanning elec­tron microscopy/energy dispersive X-ray spectroscopy), X-ray mapping and cross-sectional analyses were used to analyse the specimens. The hardness of CNT reinforced ZrO2-Y2O3 increased with the increase in the percentage of CNT, whereas the porosity of the composite coatings decreased with the increase in the CNT percentage. The observed increase in hardness may be attributed to the content of CNT in the composite coating. The present research gives important information related to the fabrication and physical characteristics of CNT-reinforced ZrO2-Y2O3 coatings deposited on T-91 boiler tube steel.