Material Selection for Power Recovery Turbines

In analyzing these data it is necessary to go beyond the curves and determine the expected behavior of the material with respect to notch sensitivity. Problems with notch sensitivity can often be corrected by modifying the processing steps and/or heat treatment. 

While evaluating the mechanical properties of materials, attention must also be given to availability. Sometimes an alloy of attractive properties is not commercially available. It may be possible to obtain special heats for large parts such as appreciable quantities of plate, large forgings, and so forth, but it may be difficult to contain smaller quantities required for incidental pieces. 

HOT CORROSION OF WASPALOY MATERIAL IN GAS EXPANDER ROTATING COMPONENTS 

Typical chemical analysis of some alloys used in power recovery turbines 

Some manufacturers have experienced die above mentioned Ni3S2 scale formation phenomenon under certain gas conditions, which led to die failure of a rotating blade. One such experience involved a fracture dial was distinctly intergranular with evidence of secondary intergranular cracks or grain separation across die fracture. Intergranular facets of die fracture were sharp and distinct with little evidence of any ductile mode. The fracture appeared to have occurred in a brittle intergranular mode. 

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