Treatment process for a centrifugal compressor wheel to extend low-cycle fatigue life

A process for producing a centrifugal compressor wheel, comprising the steps of:

• providing an as-manufactured centrifugal compressor wheel fabricated of a ductile metal having a tensile yield strength, the compressor wheel comprising a hub and a back disk, and a plurality of blades joined to the hub and the back disk, the plurality of blades defining an inducer portion of the compressor wheel configured for axial entrance of air into the compressor wheel and defining an exducer portion of the compressor wheel configured for radially outward discharge of air from the compressor wheel, each blade having a blade root fillet where the blade joins with the hub, the compressor wheel having a first face and an opposite second face, the compressor wheel defining a bore that extends centrally through the hub and the back disk along a downstream axial direction;
• and
• treating the as-manufactured compressor wheel by:
• (a) a bore treatment step comprising forcibly expanding a diameter of the bore, thereby cold working the metal at an inner surface of the bore beyond the tensile yield strength in a hoop-wise direction about the bore, so as to induce compressive residual hoop stresses in the metal adjacent the inner surface of the bore;
• and
• (b) a back disk treatment step comprising surface peening at least a portion of the back disk of the compressor wheel.