5.6   Blading materials

 

Turbine blading alloys are chosen for their ability to provide properties particular to the mechanical and environmental service which they must endure.

One of the first considerations of LP blading, for example, is the ability to resist corrosion and scaling in fast-flowing wet steam. This generally rules out low alloy steel and blades are made from either stainless steel or titanium alloys. A second requirement is adequate tensile strength to resist steady centrifugal and bending stresses. Strength without ductility is not desirable; ductility is needed to accommodate stress peaks and concentrations. Ductility also is needed to resist rubbing, and, in the case of shrouded blades, to permit the peening of tenons to secure the shroud. Impact strength is also necessary, since contact with foreign objects is sudden. Water slugs can produce impact loading.

      5.6.1  12% Cr steels

      5.6.2  Titanium

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