Improving the high-temperature oxidation resistance of ASME-SA213-T11 boiler tube steel by plasma spraying with CNT-reinforced alumina coatings

Abstract

Purpose This paper aims to discuss that a conventional Al2O3, 1.5 Wt.% carbon nanotubes (CNTs)-Al2O3, 2 Wt.% CNTs-Al2O3 and 4 Wt.% CNTs-Al2O3 composite coatings were deposited with the help of Plasma spray process. Design/methodology/approach To better understand the effect of CNT reinforcement on oxidation resistance, high-temperature oxidation behaviour of conventional Al2O3, 1.5 Wt.% CNTs-Al2O3, 2 Wt.% CNTs-Al2O3 and 4 Wt.% CNTs-Al2O3 composite coatings at 900°C was compared with the performance of the uncoated ASME-SA213-T11 boiler tube steel substrate. Findings The results showed that the CNT-reinforced alumina coatings exhibited better oxidation resistance and thermal stability than uncoated ASME-SA213-T11 boiler tube steel. The coated steel substrates had a lower mass gain rate than the substrate after different oxidation times. Originality/value Limited literature is available where the CNT have been reinforced into the composite alloy powders and has been thermally spray-deposited for various surface engineering applications. This research showed that with the increase in the percentage of CNTs into the alloy powder mixture, there is a significant reduction in weight gain and hence higher resistance to oxidation.

Behaviour of carbon nanotubes-Cr2O3thermal barrier coatings in actual boiler

“…Because CNTs helped bridging between splat boundaries which further resulted in reduced weight and volume loss of plasma sprayed hydroxyapatite-carbon nanotubes composite coating. Goyal et al [29] investigated hot oxidation performance of alumina, 1.5, 2 and 4 wt-% CNT-Al 2 O 3 composite coatings deposited by the plasma spraying method on T11 (ASTM-SA213-T-11) boiler steel at 900°C. It was observed that CNT reinforced coatings enhanced high-temperature corrosion resistance compared with conventional alumina coatings.…”

Hot corrosion behaviour of CNT-reinforced ZrO2-Y2O3 composite coatings on boiler tube steel at 900°C

“…But, during the subsequent cycles of exposure, the oxide layer could not bear the strain and peeled off followed by cracks from the surface of the substrate as clearly visible in the macrograph [Figure 2 (b)]. The molten salt enters through the perpendicular cracks to reach towards the substrate, as observed by Goyal et al (2018a, 2018b), Chatha et al (2012) and Mehta et al (2017). The formation of un protective oxide was confirmed by XRD and EDS analysis followed, by the EPMA technique, which revealed that the thermal spallation and cracks in the scale might be attributed to formation of un protective Fe 2 O 3 and Cr 2 O 3 oxide scale.…”

“…The iron-based materials experienced extensive attack and more weight in the molten salt (Na 2 SO 4 – 60 Wt.% V 2 O 5 ) conditions as observed by Goyal (2018a) and Sidhu and Prakash (2005). Due to weight gain, the formation of oxides of Na and V caused penetration of oxygen towards the substrate, resulting in severe corrosion of base material (Goyal et al , 2018a; Rani et al , 2017). The corrosion rate of un-coated T-91 steel specimen increased during the initial cycles of study, which could be attributed to the formation of cracks in the upper layer of substrate.…”

Hot-corrosion behaviour of CNT reinforced Cr3C2-NiCr coatings working under high-temperature sprayed by HVOF method

“…30 Goyal et al reported CNT additions in aluminium dispersed homogeneously in coatings, chemically stable properties and decreased porosity with increasing CNT percentage deposited by plasma spray. 31…”

“…30 Goyal et al reported CNT additions in aluminium dispersed homogeneously in coatings, chemically stable properties and decreased porosity with increasing CNT percentage deposited by plasma spray. 31 Bhatia et al reported on the 65Cr 3 C 2 -35(Ni-20Cr) coatings, working under incinerated elevated situations. The Cr 3 C 2 hard phase in the NiCr matrix enhances erosioncorrosion resistance.…”