A Study on Thermal Spray Coatings of Recuperators

1996 ◽  
Author(s):  
B.G. Seong ◽  
S.Y. Hwang
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Molten Salt ◽  
High Temperature Corrosion ◽  
Maximum Temperature ◽  
Corrosion Mechanism ◽  
Spray Coatings ◽  
Arc Spray ◽  
Salt Corrosion ◽  
Hvof Spray

Abstract High temperature corrosion is a serious problem on tlie heat exchanger tubes of recuperators because they encounter an corrosive environment at maximum temperature around 900°C. These tubes were found to be corroded via oxidation, sulfidation and molten salt corrosion. Particularly molten salt corrosion could be the most severe corrosion mechanism. As a protective coating for recuperators, nickel and cobalt based self-fluxing alloys, iron based amorphous alloy and chromium carbide cermet coatings were considered. These coatings were prepared by an arc spray and or/not fusing or a HVOF spray. Their molten salt corrosion resistance was tested, and the high temperature corrosion resistance in a SO2 containing atmosphere was examined. Also microstructures of the coatings were studied after corrosion tests.

Electrochemical Studies on High-Temperature Corrosion of Silicon-Iron Coatings and Iron Aluminide Intermetallic Alloys by Molten Salts

CORROSION ◽  
2001 ◽  
Vol 57 (6) ◽  
pp. 489-496 ◽  
Author(s):  
M. Amaya ◽  
J. Porcayo-Calderon ◽  
L. Martinez
Keyword(s):  
High Temperature ◽  
Molten Salt ◽  
Electric Power ◽  
Molten Salts ◽  
Corrosion Current ◽  
High Temperature Corrosion ◽  
Iron Aluminide ◽  
Fuel Oil ◽  
Silicon Iron ◽  
Salt Corrosion

Abstract The performance of Fe-Si coatings and an iron aluminide (FeAl) intermetallic alloy (FeAl40at%+0.1at%B+10vol%Al2O3) in molten salts containing vanadium pentoxide (V2O5) and sodium sulfate (Na2SO4) is reported. Corrosion and fouling by ash deposits containing V2O5 and Na2SO4 are typical corrosion problems in fuel oil-fired electric power units. High-temperature corrosion tests were performed using both electrochemical polarization and immersion techniques. The temperature interval of this study was 600°C to 900°C, and the molten salts were 80wt%V2O5-20wt%Na2SO4. Curves of corrosion current density vs temperature obtained by the potentiodynamic studies are reported, as well as the weight loss vs temperature curves from molten salt immersion tests. Both Fe-Si coatings and FeAl40at%+0.1at%B+10vol%Al2O3 showed good behavior against molten salt corrosion. The final results show the potential of these coatings and alloys to solve the high-temperature corrosion in fuel oil-fired electric power units.

Stress Evolution and Element Diffusion in Bi-Layered Yb2SiO5/ Mullite Environmental Barrier Coatings under High-Temperature Molten Salt Corrosion

2018 ◽  
Vol 281 ◽  
pp. 478-486
Author(s):  
Hong Fei Chen ◽  
Ya Xiong Du ◽  
Juan Feng ◽  
Guang Yang ◽  
Yan Feng Gao
Keyword(s):  
Residual Stress ◽  
High Temperature ◽  
Molten Salt ◽  
Corrosion Mechanism ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Substrate Interface ◽  
Layered Coatings ◽  
Salt Corrosion

Yb2SiO5/mullite bi-layered coatings are promising environmental barrier coatings, but its molten salt corrosion mechanism is unclear. In this work, Yb2SiO5/mullite bi-layered coatings are fabricated by combining plasma spraying and dip-coating techniques. Residual stresses in the coatings caused by thermo-mechanical interaction are investigated by a nondestructive Raman spectrum method under high-temperature molten salt corrosion. In the as-deposited coatings, the stress in the mullite layer is compressive and the value near Si3N4 substrate is minimum. During high-temperature corrosion test, the residual stress near mullite-substrate interface changes sharply while the stress near mullite-Yb2SiO5 interface is concentrated without large fluctuation. An interfacial phase, YbAlO3, which is formed because of the inter diffusion of Al in the mullite layer and Yb in the Yb2SiO5 layer, causes the stress concentration. The change of SiO2 component in the mullite layer leads to the sharp change of residual stress near the mullite-substrate interface.

scholarly journals High-Temperature Corrosion Behaviour of HVOF Sprayed Cr3C2- 25NiCr Coated on Alloy X22CrMoV12-1 at 600o C

2018 ◽  
Vol 1 (1) ◽  
pp. 7-12
Author(s):  
P. Akshay Prasanna ◽  
◽  
P. Subramani ◽  
V. Sreenivasulu ◽  
N. Arivazhagan ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Molten Salt ◽  
Hot Corrosion ◽  
Corrosion Behaviour ◽  
High Temperature Corrosion ◽  
Spinel Oxide ◽  
Good Resistance ◽  
Good Corrosion Resistance ◽  
Temperature Environment

The present study investigates the hot corrosion behaviour of high-velocity oxy-fuel sprayed alloy X22CrMoV12-1 with Cr3C2-25NiCr coating at 600oC. The study was carried out by air and molten salt environment for both coated and uncoated substrates for 50 cycles. Thermogravimetry analysis was carried out to evaluate the hot corrosion by calculating the mass changes in each cycle. The results show that coating provides the marginally good corrosion resistance than the uncoated alloy. The formation of Fe2O3 and MoO3 phases in the uncoated substrates in both air and molten salt environments reduces the corrosion resistance at the high-temperature environment. The formation of Ni2Oand spinel oxide NiCr2O4 provided good resistance to corrosion in the coated substrates in the air and molten salt environment.

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