Abstract

In many industrial processes, metallic materials are submitted to very aggressive environment because of high temperature corrosion and erosion mechanisms. Such conditions occur especially in thermal energy advanced systems using tube bundles of fluidised bed boilers. For these types of plants, availability and low costs determine the choice of materials and in most cases this choice is not optimised for middle or long-term behaviour. Moreover, few data exist to estimate material lifetime under such aggressive conditions. Such is the case for low carbon steel grades which constitute the basic materials for these plants. New FeAl intermetallic alloys have been developed in the framework of a European collaboration, and it has been seen that these materials have good corrosion and erosion resistance properties at high temperature. Heat exchanger tubes in low carbon steel have been coated by thermal-spray then tested in a new industrial plant burning a very poor fuel (coal residues). After 5000 hours of operation in a rich erosive high temperature environment (850-900°C), no significant wear was observed on coated tubes whereas the other tubes, without protection, showed an appreciable diameter reduction.

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