W. D. Cao, R. Kennedy, ATI Allvac, Monroe, NC; E. T. McDevitt, Allegheny Technologies Incorporated (ATI), Monroe, NC
Allvac 718Plus is a newly developed Ni-Fe-Nb superalloy with a 100°F higher temperature capability than alloy 718. It has much better processing characteristics than other 1300°F capable superalloys. Thermal stability is much superior to alloy 718, which permits the application of this alloy at higher working temperatures.
Thermal degradation of alloy 718Plus occurred by the coarsening of precipitates and transformation to more stable delta phase. Microstructural changes during thermal exposure were followed by various tools and the degradation in mechanical properties was also studied in detail. It was found that the chemistry of this alloy has a significant influence on thermal stability. Co and Fe levels are important in retarding the growth of precipitates and the contents of Al and Ti, especially the Al/Ti ratio, are very critical to both retarding precipitate growth and decelerating the transformation of precipitates to delta phase.
Summary: Allvac 718Plus is a newly developed Ni-Fe-Nb superalloy with a 100ºF higher temperature capability than alloy 718. It has much better processing characteristics than other 1300ºF capable superalloys. Thermal stability is much superior to alloy 718, which permits the application of this alloy at higher working temperatures.
