Improving the Surface Properties of a Pelton Turbine Bucket via Centrifugal Casting Technique

Abstract

This study examines the possibility of fabricating a complex, non-cylindrical, Pelton turbine bucket by centrifugal casting technique. Oil hardening non-shrinking die steel material was selected for the permanent mould production, machined with computer numerical control and heat treated to a hardness of 432BHN. Aluminium alloys, A390 and A390-5%Mg, were considered as the Pelton turbine bucket materials, cast and characterised. The effects of centrifugal casting technique and thermal treatment on the mechanical properties and corrosion resistance of A390 and A390-5%Mg alloys were studied. A hardness of 150BHN (maximum) was recorded near the inner surface of the bucket and 157BHN (maximum) was recorded at the outer periphery of the cylindrical cast. It was observed that A390-5%Mg by gravity casting shows higher corrosion resistance than the A390 alloy. Furthermore, the specimen from the outer zone of the circular cast shows a higher corrosion resistance than the specimen from the inner periphery.