Nickel- and iron-based HVOF thermal spray coatings for high temperature corrosion protection in biomass-fired power plant boilers: Dissertation

    Research output: ThesisDissertationMonograph

    Abstract

    Biomass burning for production of electricity and heat has been increasing due to legislation in Europe. Growing awareness of environmental problems has led to strict restrictions on greenhouse emissions in the energy sector, and increased demand for higher use of renewable energy sources and carbonneutral fuels, such as biomass. There are over 1000 biomass boilers in Europe, and the number is increasing. These plants often face serious problems due to high temperature corrosion. Fouling and corrosion in biomass boilers can lead to tube failure and leakage. In addition, demand for higher efficiency of electricity and heat generation requires an increase in steam temperatures, which raises the material temperatures of boiler tubes and may result in more severe corrosion problems. To overcome corrosion damages to boilers, commonly used low-alloyed steels are being replaced by higher-alloy tube materials. However, the high price and sometimes difficult machinability of these materials hinders their adoption. Thermal spray coatings can offer an attractive solution for corrosion protection of boiler tubing. The objective of this work was to determine the corrosion resistance of thermal spray coatings in biomass combustion conditions. The overall research aim wasto enhance the lifetime of the heat exchanger surfaces of biomass power plant boilers. The research focused mainly on improving the high temperature corrosion resistance of thermal sprayed HVOF (high velocity oxy-fuel) coatings by optimizing their structure and verification of corrosion performance in biomass boiler conditions. Focus was also placed on determining the corrosion mechanisms of nickel- and iron-based coatings. The corrosion performance of the selected coatings was validated in both laboratory conditions and real biomass boiler conditions. According to this research, the tested HVOF sprayed nickel- and iron-based coatings can offer protection for low-alloy substrates in biomass boiler conditions. The results of the present study will help optimize the coating process for high temperature corrosion applications, and in adopting the use of thermal spray coatings for protection of the heat exchanger surfaces of biomass boilers.
    Original languageEnglish
    QualificationDoctor Degree
    Awarding Institution
    • Aalto University
    Supervisors/Advisors
    • Hannula, Simo-Pekka, Supervisor, External person
    • Turunen, Erja, Advisor
    Award date23 Jan 2015
    Place of PublicationEspoo
    Publisher
    Print ISBNs978-951-38-8206-8
    Electronic ISBNs978-951-38-8207-5
    Publication statusPublished - 2015
    MoE publication typeG4 Doctoral dissertation (monograph)

    Keywords

    • thermal spray
    • coating
    • process optimization
    • high temperature corrosion
    • biomass burning
    • corrosion protection

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