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| Abstract No.: |
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Scheduled at:
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Thursday, May 22, 2014, Hall A 11:20 AM
HVOF- / HVAF-Spraying
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| Title: |
Thermal spray coatings for high temperature corrosion protection in biomass boilers
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| Authors: |
Maria Oksa* / VTT Technical Research Centre of Finland, Finland
Jarkko Metsäjoki / VTT Technical Research Centre of Finland, Finland
Janne Kärki/ VTT Technical Research Centre of Finland, Finland
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| Abstract: |
There are over 1000 biomass boilers and about 500 plants using waste as fuel in Europe, and the numbers are increasing. In many of them there are serious problems with high temperature corrosion due to detrimental elements such as chlorides, alkali metals and heavy metals. By HVOF spraying it is possible to produce very dense and well adhered coatings, which can be used as protection against severe material wastage of heat exchanger surfaces in biomass and waste-to-energy power plant boilers.
Four HVOF coatings and one arc sprayed coating were manufactured on metallic test rings, which were exposed to actual biomass boiler conditions in superheater area as a probe measurement. The coating materials were Ni-50Cr, Fe-25Cr-15W-12Nb-6Mo, IN625 and Ni-45Cr-1Ti. Both CJS and DJ Hybrid spray guns were used for HVOF spraying to compare the corrosion resistance of Ni-50Cr coating structures. Substrate and reference materials were ferritic steel T92 for test temperature 550 °C and nickel super alloy A263 for 750 °C. The circulating fluidized bed (CFB) boiler used wood, peat and coal as fuel. The duration of the measurement was 5900 hours. All the coatings showed excellent corrosion resistance at 550 °C compared to the ferritic steel. At higher temperature, NiCr sprayed with CJS had the best corrosion resistance. IN625 was consumed almost completely during the exposure at 750 °C.
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