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|Regional Outlook: Thick Ceramic Coatings in Tampere Region|
Ceramic coatings are widely used in the Finnish paper and pulp industry. The coatings on centre press rolls of modern paper machines have large surface areas of several tens of square meters. Tungsten carbide or chromium carbide based cermet coatings are also used in many roller applications. In addition to the rolls, ceramic coatings are used to increase wear and corrosion resistance of other components in the paper and pulp industry. The ceramic coatings used in these applications are typically alumina and chromia based compositions, often with some other oxide additives, such as titania or silica. Tungsten carbide and chromium carbide based cermets are also widely used in many wear and corrosion applications in the wood and paper industries.
Other applications for thick ceramic coatings include Thermal Barrier Coatings (TBC) for gas turbine and diesel engine applications. The materials currently used in this application include a number of zirconia based coating formulations.
The main companies in the Tampere region producing thermally sprayed coatings are:
Thick ceramic-metal composite coatings can also be produced by powder metallurgy utilising HIP technology. Metso Powdermet Oy in Tampere supplies these materials for demanding applications such as power generation, pulp and paper industry, metallurgy and mining, offshore structures and the chemical and petrochemical industries.
Thermal spray research in the region and in Finland as a whole is concentrated in Tampere University of Technology. The Surface Engineering Laboratory in the Institute of Materials Science has been involved in research and development of thermal spraying and thermal sprayed coatings. The laboratory has different spray units including plasma spray gun (Plasma Teknik A3000S), detonation gun (Perun P), HVOF spray system (Sulzer Metco 2600 & 2700 Hybrides) and flame spray guns. In addition to its spraying capability, the Institute has facilities for basic structural and compositional characterisation of the coatings as well as for mechanical testing including wear and corrosion testing. The research includes all aspects of the coatings starting from powder development and spray parameters to coatings and advancing coating applications in industry. The most recent projects related to thick ceramic coatings are:
The recently established Laser Application Laboratory in Tampere University of Technology is offering new possibilities to study the preparation of large area ceramic and cermet coatings by laser cladding. The laboratory has two fully robot controlled high power laser facilities; continuous wave 6 kW HPDL and 4 kW Nd-YAG units.
SHS process (Self-Propagating High Temperature Synthesis) for producing cermet powders for thermal spraying and laser cladding is being studied in VTT Processes Tampere (former VTT Manufacturing Technology Tampere).
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