T. D. Bayha, Allegheny Technologies Incorporated (ATI), Monroe, NC; W. D. Cao, R. A. Jeniski, R. L. Kennedy, Allvac, Monroe, NC
Summary: Applications of the widely used Alloy 718 are restricted to about 1200°F. Above this temperature the ý (Ni3Nb) precipitation hardening phase responsible for the alloy’s outstanding characteristics rapidly overages and properties, particularly creep resistance, fall dramatically. This has led to a long-standing desire for an alloy that maintains the excellent properties and processing characteristics of 718 up to a temperature of at least 1300°F.
Allvac® 718Plus™, was developed to meet the need described above. Extensive work at both laboratory and production levels has demonstrated that this alloy has essentially met the requirements for a “718 + 100°F” type alloy. The new alloy shows excellent hot-workability and weldability similar to that of Alloy 718. Allvac® 718Plus™ alloy shows much better stress rupture and creep properties at 1300°F than Alloy 718 or Waspaloy. It has excellent thermal stability, and in contrast with Alloy 718, only a small drop in mechanical properties is observed after long-term thermal exposure up to 1400°F.
ATI Allvac has ongoing product development efforts for 718Plus in billet, bar, rolled sheet, investment castings, forgings and rolled. In this presentation, the chemistry, microstructure, mechanical properties and processing characteristics of Alloy 718Plus will be described and compared with those of alloys 718 and Waspaloy for the various products of interest.
