Abstract
The main limiting factor for P92 steel, in power plant at high temperature, is the increased oxidation damage on the inside surface which causes enhanced damage of components. Industry have attempted to address this problem by applying oxidation resistant coatings to the inside surface of the P92 pipework to prevent damage. Aluminide diffusion coatings have been a particular focus for research to date, however they have been found to have a number of detrimental effects on the creep properties and coating-substrate integrity. This paper introduces a Co-Cr-C type coating, composed of Cr3C2 particles electro-deposited within a cobalt matrix. On exposure to high temperature oxidation conditions the coating is shown to form a cobalt and chromium rich oxide which is slow growing, adherent and ideal for oxidation resistance. When applied to P92 substrate and exposed at service relevant temperatures the coated system retains its integrity and appears suitable for long term service. The coated P92 system is also shown to retain its integrity during high temperature creep testing and coating application does not have a negative effect on the mechanical properties of P92. Overall the Co-Cr-C coating has a number of superior properties compared to previously investigated coatings.
Acknowledgments
The funding is provided through the Efficient Fossil Energy Technologies Engineering Doctorate Centre based at the University of Nottingham, UK, and the Biomass and Fossil Fuel Research Alliance (BF2RA). Thanks also to Doosan Babcock Ltd and Praxair Surface Technologies Ltd for materials provided and technical support. Thanks also to RWE Generation UK for their continued support of the completion and presentation of this paper.