Analysis of phase transformation in plasma sprayed alumina coatings using Rietveld refinement

Sabiruddin, Kazi; Joardar, J.; Bandyopadhyay, P.P.

doi:10.1016/j.surfcoat.2010.03.026

Cited by 63 publications

(24 citation statements)

References 17 publications

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“…For many conventional APS alumina coatings deposited with Ar/H 2 plasmas, a content of γ-Al 2 O 3 of 90% or more is reported, e.g., (Ref 29 , 47 ). This is also valid for many conditions in the systematic study of Sabiruddin et al (Ref 10 ) when using a N 2 /H 2 plasma, but several conditions can also produce a higher α-Al 2 O 3 content. Remarkably, the heights of the γ-Al 2 O 3 peaks in the XRD pattern for parameter sets 1-4 in this work were not higher than for α-Al 2 O 3 .…”

Section: Discussionsupporting

confidence: 63%

“…Each of the single oxides shows a specific material behavior during spraying, which is detrimental to the processing and/or coating properties (Ref [1][2][3][4]. For alumina, the detrimental phase transformation from a-Al 2 O 3 (corundum) existing in the feedstocks, to predominantly metastable c-Al 2 O 3 in the coatings, is well known (Ref [5][6][7][8][9][10]. The retained a-Al 2 O 3 was originally accounted for by McPherson by the appearance of unmolten cores of the feedstock particles (Ref 6).…”

Section: Introductionmentioning

confidence: 99%

“…The retained α-Al 2 O 3 was originally accounted for by McPherson by the appearance of unmolten cores of the feedstock particles (Ref 6 ). Sabiruddin et al (Ref 10 ) have shown that for conventional APS with an N 2 /H 2 plasma, the retained content of α-Al 2 O 3 depends on many process parameters, like spray distance, primary and secondary plasma gas flow rate, nozzle size, etc. However, alumina is very stable regarding its oxygen content, irrespective of the spray process conditions.…”

Section: Introductionmentioning

confidence: 99%

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Changes in the Coating Composition Due to APS Process Conditions for Al2O3-Cr2O3-TiO2 Ternary Powder Blends

et al. 2020

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Thermally sprayed coatings from the single oxides and binary compositions of the Al2O3-Cr2O3-TiO2 system show multifunctional properties. Ternary compositions are promising for further improvement in their performance. The stability of the composition during coating formation is an important issue for blended feedstock powders in order to obtain the desired properties. This work focuses on the compositional changes of a ternary blend of Al2O3, Cr2O3 and TiOx powders of equal content by mass in a conventional atmospheric plasma spraying (APS) process using an Ar/H2 plasma gas mixture. By increasing the argon flow rate at constant hydrogen flow rate, the total plasma gas flow rate and the Ar/H2 ratio were varied. For the highest argon flow rate, this resulted in an average particle velocity of 140% and an average particle temperature of 90% of the initial values, respectively. Coating composition and microstructure were studied by optical microscopy, SEM, including EDS analyses, and XRD. In addition, the coating hardness and electrical impedance were also measured. Differences in the “difficulty of melting factor” (DMF) and the thermal diffusivity of the three oxides appear to be responsible for the dramatic change of the coating composition with an increasing argon flow rate. For the highest argon flow rate applied, besides TiO2, the coating contains only 8 wt.% Al2O3, while the Cr2O3 content remained almost constant. At the same time, the change of the Ar/H2 ratio resulted in the formation of stoichiometric TiO2 in the coating by oxidation of TiOx in the feedstock powder. Moreover, a small content of titanium was found in the Cr2O3 splats, showing that there are only limited interactions between the large oxide powder particles. Thus, the study has shown that stability of the chemical composition during spraying of ternary powder blends is strongly influenced by the process conditions.

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Section: Discussionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Changes in the Coating Composition Due to APS Process Conditions for Al2O3-Cr2O3-TiO2 Ternary Powder Blends

et al. 2020

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“…5). This probably depends, on the one hand, on the low crystallinity of rapidly solidified Al 2 O 3 (which turns from the thermodynamically stable α-phase into γand glassy-phases after thermal spraying[39,40]) and, on the other hand, to a matrix effect due to the fact that Al 2 O 3 particles are surrounded by the Ni-based alloy.…”

mentioning

confidence: 99%

Tribology of NiCrAlY+Al2O3 composite coatings by plasma spraying with hybrid feeding of dry powder+suspension

Bolelli

Candeli

Lusvarghi

et al. 2015

Wear

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NiCrAlY layers containing different amounts of Al2O3 (0, 3, 6, 12, 18 wt.%) were deposited onto stainless steel substrates by a “hybrid” plasma spray process whereby the NiCrAlY powder was fed in dry form whilst fine Al2O3 powder, dispersed in ethanol, was injected through a suspension feeding system.\ud The Al2O3 reinforcement, consisting of fine, rounded particles interspersed within larger NiCrAlY lamellae, only causes marginal changes in hardness, due to the limited particles-matrix cohesion. Nonetheless, at room temperature, ball-on-disk dry sliding wear rates against sintered Al2O3 counterparts decrease from ≈5⁎10−4 mm3/(Nm) for pure NiCrAlY to ≈5⁎10−6 mm3/(Nm) with 18 wt.% Al2O3 addition. Pure NiCrAlY indeed suffers adhesive wear, whereas, on the composite coatings, the pull-out of some Al2O3 particles triggers the formation of a tribo-layer of smeared oxide fragments, which mediates the contact with the counterbody.\ud At 400 °C and at 700 °C, all wear rates are levelled to ≈8⁎10−5 mm3/(Nm) and ≈2⁎10−5 mm3/(Nm), respectively. An oxide layer grows on the NiCrAlY matrix upon high-temperature exposure, resulting in a tribo-oxidation wear mechanism, which makes the addition of Al2O3 irrelevant. At 700 °C, coatings are further strengthened by partial healing of interlamellar defects and by fine-grained β-NiAl precipitating within the metal matrix

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“…However, very little published data is available on this subject. In one such rare publication, Sabiruddin et al [14] discussed quantitative phase analysis of plasma sprayed alumina coating using Rietveld refinement. The effects of some parameters like primary & secondary gas flow rate, nozzle diameter, SOD on retention of α-alumina in the coating were investigated.…”

Section: Introductionmentioning

confidence: 99%

The effect of parametric variation on the mullite content of plasma sprayed zircon-alumina powder mixture

Hazra

Bandyopadhyay

2016

Surface and Coatings Technology

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Analysis of phase transformation in plasma sprayed alumina coatings using Rietveld refinement

Cited by 63 publications

References 17 publications

Changes in the Coating Composition Due to APS Process Conditions for Al2O3-Cr2O3-TiO2 Ternary Powder Blends

Changes in the Coating Composition Due to APS Process Conditions for Al2O3-Cr2O3-TiO2 Ternary Powder Blends

Tribology of NiCrAlY+Al2O3 composite coatings by plasma spraying with hybrid feeding of dry powder+suspension

The effect of parametric variation on the mullite content of plasma sprayed zircon-alumina powder mixture

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