Treatment process for a central bore through a centrifugal compressor wheel to create a deep cylindrical zone of compressive residual hoop stress on a fractional portion of the bore length, and compressor wheel resulting therefrom

An article produced by a process comprising the steps of:

• providing a centrifugal compressor wheel fabricated of a ductile metal having a tensile yield strength, the compressor wheel comprising a hub and a plurality of blades joined to the hub and extending radially outwardly from the hub, each blade having a blade root fillet where the blade joins with the hub, said blade root fillets each having a leading edge, the compressor wheel having a first face and an opposite second face, the hub of the compressor wheel defining a bore that extends centrally through the hub along a downstream axial direction, the bore having an axial length;
• selecting a fractional portion of the axial length of the bore defined between a starting point and an ending point of said fractional portion, wherein the starting point is spaced axially downstream from the leading edges of the blade root fillets and the ending point is spaced axially downstream from the starting point, and providing the bore to have a counterbore located upstream of the starting point of the fractional portion of the bore, the counterbore having a diameter exceeding an initial diameter of the fractional portion of the bore;
• disposing a mechanical tool in the counterbore, the tool having a diameter that exceeds the initial diameter of the fractional portion of the bore;
• and
• cold working the metal at an inner surface of the bore beyond the tensile yield strength in a hoop-wise direction about the bore, along only said fractional portion of the bore, by drawing the tool along the downstream axial direction through the fractional portion of the bore, the bore not being cold worked outside said fractional portion, so as to induce compressive residual hoop stresses in the metal adjacent the inner surface along said fractional portion.