The effects of structure control available from the precipitating phases in wrought superalloys were demonstrated in a recent review. It was shown that criteria for selection of superalloys should be reviewed periodically to establish that they reflect the state of the art. For example, expensive materials may have been specified where lower cost alloys could do a job equally well. This is especially true for superalloys in applications where properties up to about 1200°F are critical. This paper reviews some results of the continuing study by superalloy metallurgists to reveal means of “retrograding” elevated temperature requirements to lower cost compositions that, combined with proper processing, will meet property requirements. It is shown that microstructure studies, combined with knowledge of phase relationships, prove to be an invaluable tool. Recent examples of improved hot-work behavior, heat-treat response, and property development are reviewed. Effects of thermomechanical processing are also discussed.

Wrought superalloys that are capable of high strengths at room and elevated temperatures are characterized by complex alloy compositions and phase relationships. Alloy composition establishes which phases will occur, and composition control is critical to assure consistent phase boundary relationships. This presentation discusses the metallurgy of several important superalloys including: A-286, Alloy 901, Alloy 718, Waspaloy and René 95; and two new wrought superalloys, Pyromet CTX-1 and Pyromet 31. The achievement of property goals in these alloys, for various applications, is shown to be related to proper selection of process parameters with respect to phase relationships.