Synergistic effect of CeO2 and Al2O3 nanoparticle dispersion on the oxidation behavior of MCrAlY coatings deposited by HVOF

Rouhaghdam

2021

Sci Rep

Conventional and nanocrystalline MCrAlY coatings were applied by the high-velocity oxy-fuel (HVOF) deposition process. The ball-milling method was used to prepare the nanocrystalline MCrAlY powder feedstock. The microstructure examinations of the conventional and nanocrystalline powders and coatings were performed using X-ray diffraction (XRD), high-resolution field emission scanning electron microscope (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). Williamson–Hall analyzing method was also used for estimation of the crystalline size and lattice strain of the as-milled powders and sprayed coatings. Owing to the investigation of the oxidation behavior, the freestanding coatings were subjected to isothermal and cyclic oxidation testing at 1000 and 1100 °C under static air. The results showed that the conventional as-sprayed MCrAlY coating had a parabolic behavior in the early stage and prolonged oxidation process. On the contrary, in the case of the nanocrystalline MCrAlY coating, the long-term oxidation behavior has deviated from parabolic to sub-parabolic rate law. Moreover, the results also exemplified that the nanocrystalline MCrAlY coating had a greater oxidation resistance following the creation of a continuous and slow-growing Al2O3 scale with a fine-grained structure. The nucleation and growth mechanisms of the oxides formed on the nanocrystalline coating have also been discussed in detail.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A comprehensive study on the microstructure evolution and oxidation resistance of conventional and nanocrystalline MCrAlY coatings

Rouhaghdam

2021

Sci Rep

“…Advanced ceramics and protective coatings for high temperature applications have been recently attracted [1][2][3][4][5][6][7][8][9][10][11] . With a high melting point (about 3380 °C), high thermal and electrical conductivity, excellent strength at the severe environment, and brilliant thermal shock resistance, HfB 2 is one of the ultra-high temperature ceramics (UHTCs).…”

Section: Effect Of In Situ Vsi 2 and Sic Phases On The Sintering Behamentioning

confidence: 99%

Effect of in situ VSi2 and SiC phases on the sintering behavior and the mechanical properties of HfB2-based composites

Taheri-Nassaj

Baharvandi

et al. 2020

Sci Rep

In situ HfB2–SiC–VSi2 composite was fabricated by reactive pressureless sintering at the temperature of 2150 °C for 4 h under a vacuum atmosphere. In situ SiC and VSi2 reinforcements were formed using VC and Si powders as starting materials according to the following reaction: VC + 3Si = SiC + VSi2. Microstructural studies and thermodynamic calculations revealed that in situ VSi2 and SiC phases were mostly formed and homogeneously distributed in HfB2 skeleton. The results showed that the density of in situ HfB2–SiC–VSi2 composite was 98%. Besides, the mechanical properties of the composite were effectively enhanced by the formation of in situ second phases. The Vickers hardness and the fracture toughness of the composite reached 20.1 GPa and 5.8 MPa m−1/2, respectively.

“…In fact, the composition and growth rate of the TGO layer varies according to the coating properties such as the chemical composition, microstructure, and oxides content [8]. These coatings have been manufactured by methods of physical vapor deposition (PVD) [9], magnetron sputtering [10], arc ion plating (AIP) [11], thermal spraying [12][13][14][15] and laser powder deposition (LPD) [16]. The MCrAlY coatings deposited using the HVOF process often have better properties in comparison to the other thermal spraying methods and in some cases provided higher oxidation resistance [17,18].…”

Section: Introductionmentioning

confidence: 99%

Study on production of modified MCrAlY powder with nano oxide dispersoids as HVOF thermal spray feedstock using mechanical milling

Zakeri

Rouhaghdam

et al. 2020

Mater. Res. Express

This paper investigates NiCoCrAlY-CeO 2 nanocomposite powders prepared by mechanical milling process. At first, micron-sized ceria powder was pre-milled to obtain nano-sized powders and then 1 wt% CeO 2 was mixed with the conventional NiCoCrAlY powder and milled under three sets of parameters. The conventional and milled powders were deposited on low carbon steel substrates by HVOF thermal spray technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), fieldemission scanning electron microscopy (FESEM) and image analyzing method were used to characterize the prepared powders and coatings. Microstructural characterization showed that the milled powders underwent morphological and phase transitions. Through the microstructural and compositional analyses, it was found that a homogeneous distribution of CeO 2 nano-dispersoids in the NiCoCrAlY matrix was obtained. The resulting coatings showed that by using optimized milling parameters, required particle size and suitable morphology for thermal spray can be achieved.