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

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 carbon-neutral 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 was to 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.

Department dc:contributor.department

Materiaalitekniikan laitos

Grantor dc:publisher

VTT Technical Research Centre of Finland

Year dc:date.issued

2015

Author dc:creator

• Oksa, Maria

Advisors dc:contributor.advisor

• Turunen, Erja, Prof., VTT Technical Research Centre of Finland, Espoo, Finland
• Hannula, Simo-Pekka, Prof., Aalto University, Department of Materials Science and Engineering, Espoo, Finland

Contributors dc:contributor

• Aalto-yliopisto
• Aalto University

Language dc:language.iso

en

Repository record dc:identifier.uri

https://aaltodoc.aalto.fi/handle/123456789/14943

OAI record oai:identifier

https://aaltodoc.aalto.fi/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aaaltodoc.aalto.fi%3A123456789%2F14943