Development and oxidation resistance of air plasma sprayed Mo–Si–Al coating on an Nbss/Nb5Si3 in situ composite

A Mo ( Si , Al )2 coating is developed to protect Nb ss/ Nb 5 Si 3 in situ composite by plasma spraying. The binary layers of this coating consist of an inner interdiffusion layer surrounded by Mo ( Si , Al )2 layer with C40 crystal structure. After oxidation at 1250°C for 100h, Mo ( Si , Al )2 coating exhibited an excellent protection against oxidation and good adherence to substrate. The oxidation curve followed parabolic law and even after oxidation at high temperature for 100h, the weight gain per unit area of Mo ( Si , Al )2 coating is 8.24mg/cm2. No evident spalling of coating to substrate was observed but a continuous and compact layer of Al 2 O 3 was formed on coating surface to prevent oxidation below coating and substrate.

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Suppression of molten salt corrosion by plasma sprayed Ni3Al coatings

Emergent Materials ◽

10.1007/s42247-021-00334-y ◽

2021 ◽

Author(s):

Sarah Yasir ◽

Jose Luis Endrino ◽

Elena Guillén ◽

Adrianus Indrat Aria

Keyword(s):

Stainless Steel ◽

Corrosion Rate ◽

Corrosion Behaviour ◽

Stainless Steel Surface ◽

Air Plasma ◽

Oxide Layers ◽

Salt Corrosion ◽

Plasma Sprayed ◽

Steel Substrates ◽

Al Coating

AbstractCorrosion behaviour of stainless steel 347 was investigated in a molten nitrate salt (60 wt% NaNO3 + 40 wt% KNO3) immersion at 565 °C for up to 3000 h. A growth of stratified oxide layers consisting of NaFeO2, Fe2O3 and Fe3O4 was observed on the stainless steel surface with a constant gravimetric corrosion rate of ~ 0.4 µm/year. The feasibility of using Ni3Al coatings deposited by means of air plasma spray for suppression of corrosion was investigated. Ni3Al coatings were observed to undergo a fast oxidation with a corrosion rate of ~ 2.7 µm/year in the first 500 h, and subsequently stabilise between 500 and 3000 h with no observable changes in microstructure, composition and weight at a corrosion rate of ~ 0.02 µm/year. The results presented in this study strongly suggest that Ni3Al coating suppresses the formation of oxide layers on the surface of stainless steel substrates and can be used as protection against corrosion in the presence of molten nitrate salts, which is of relevance to thermal energy storage applications.

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HOT CORROSION OF CERIA-YTTRIA STABILIZED ZIRCONIA PLASMA SPRAYED THERMAL BARRIER COATING BY EUTECTIC VANDIUM PENTAOXIDE-SODIUM SULFATE

THE IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING ◽

10.32852/iqjfmme.vol18.iss1.83 ◽

2018 ◽

Vol 18 (1) ◽

pp. 182-192 ◽

Cited By ~ 1

Author(s):

Mohammed J Kadhim ◽

Mohammed H Hafiz ◽

Maryam A Ali Bash

Keyword(s):

Thermal Barrier Coating ◽

Hot Corrosion ◽

Monoclinic Phase ◽

Volume Fraction ◽

High Volume ◽

Thermal Barrier ◽

Air Plasma ◽

Plan View ◽

Barrier Coating ◽

Plasma Sprayed

The high temperature corrosion behavior of thermal barrier coating (TBC) systemconsisting of IN-738 LC superalloy substrate, air plasma sprayed Ni24.5Cr6Al0.4Y (wt%)bond coat and air plasma sprayed ZrO2-20 wt% ceria-3.6 wt% yttria (CYSZ) ceramic coatwere characterized. The upper surfaces of CYSZ covered with 30 mg/cm2 , mixed 45 wt%Na2SO4-55 wt% V2O5 salt were exposed at different temperatures from 800 to 1000 oC andinteraction times from 1 up to 8 h. The upper surface plan view of the coatings wereidentified for topography, roughness, chemical composition, phases and reaction productsusing scanning electron microscopy, energy dispersive spectroscopy, talysurf, and X-raydiffraction. XRD analyses of the plasma sprayed coatings after hot corrosion confirmed thephase transformation of nontransformable tetragonal (t') into monoclinic phase, presence ofYVO4 and CeVO4 products. Analysis of the hot corrosion CYSZ coating confirmed theformation of high volume fraction of YVO4, with low volume fractions of CeOV4 and CeO2.The formation of these compounds were combined with formation of monoclinic phase (m)from transformation of nontransformable tetragonal phase (t').

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