HIGH TEMPERATURE CORROSION STUDIES OF HVOF SPRAYED COATINGS IN MOLTEN SULPHATE SALTS ENVIRONMENT

1 LENCOVÁ Kateřina
Co-authors:
2 ČESÁNEK Zdeněk 3 HOUDKOVÁ Šárka 4 MUŠÁLEK Radek 5 LUKÁČ František
Institutions:
1 Research and Testing Institute Pilsen, Plzeň, Czech Republic, EU, lencova@vzuplzen.cz
2 Research and Testing Institute Pilsen, Plzeň, Czech Republic, EU, cesanek@vzuplzen.cz
3 Research and Testing Institute Pilsen, Plzeň, Czech Republic, EU, houdkova@vzuplzen.cz
4 Institute of Plasma Physics of CAS, Praha, EU, musalek@ipp.cas.cz
5 Institute of Plasma Physics of CAS, Praha, EU, lukac@ipp.cas.cz
Conference:
28th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, May 22nd - 24th 2019
Proceedings:
Proceedings 28th International Conference on Metallurgy and Materials
Pages:
1079-1085
ISBN:
978-80-87294-92-5
ISSN:
2694-9296
Published:
4th November 2019
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
29 views / 3 downloads
Abstract

The generally applied requirements on lowering of emission production in the field of power industry have led, among others, into the application of low-emission combustion process of coal fired power plants. Besides the emissions reduction, this process has led to an increase of boilers parts corrosion degradation due to the reducing atmosphere in low-emission boilers, responsible for sulphide corrosion and molten salt attack. In such environment, the protection of the exposed surfaces gains importance. Among others, the thermal spraying technology can offer a suitable way of surface corrosion protection. In the present work, the high temperature corrosion behaviour of CoCrAlYTaCSi and Cr3C2-25%NiCr High Pressure/High Velocity Oxygen Fuel (HP/HVOF) sprayed coatings is evaluated and compared to the behaviour of bare structural steel (SPT360) substrate. The specimens were exposed to a molten salt environment, i. e., 12% Na2SO4 + 82% Fe2(SO4)3 at 690 °C under cyclic condition, simulating the working environment in low-emission boilers of coal-fired power plants. The thermogravimetric method was used to establish the kinetics of corrosion. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the corrosion products and determine the corrosion mechanism. The thermogravimetric measurement shows high oxidation rate of SPT360 steel. Cr3C225%NiCr coating provides slightly better performance compared to CoCrAlYTaCSi coating. Based on the obtained results, both coatings were found to have higher corrosion resistance than the SPT360 steel substrate, offering a sufficient surface protection in a given environment.

Keywords: High temperature corrosion, low-emission boilers, coal fired boilers, HVOF, thermal spraying, CoCrAlYTaCSi, Cr3C2-25%NiCr
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