Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

New materials for water turbines and pumps

Water turbines and pumps are often susceptible to severe erosion and cavitation action in service. Among the various coatings applied for the protection of working surfaces, only metallic alloys of amorphous structure can meet the requirements. The metal alloy grades that give an amorphous structure after fast cooling, have been determined.
The characteristics of such grades are high ultimate tensile strength, ductility and resistance to corrosion under various physical conditions. The crystallisation temperature is greater than or equal to 400 C.
It has been shown that the plasma spraying procedure under controlled atmosphere conditions and temperature allows 0.5 mm thick depositions of amorphous structure to be obtained on large surfaces.
The characterisation and optimisation of deposition conditions with respect to the chemical analyses specified have been conducted, and the coatings obtained comply satisfactorily with the contradictory properties required.

The results have considerable economic potential but technical difficulties associated with treatment of large components have to be overcome. The technology may be of interest to various sectors dealing with corrosion, erosion and cavitation problems, such as the naval and mining industries. The development of a dedicated plasma spraying torch is important.

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