Development of Isothermally Forged P/M Udimet 720 for Turbine Disk Applications

Abstract

Udimet 720@ nickel-base superalloy is in current use as the material for the stage-two power turbine disk for the T800 engine. This alloy was selected because of its attractive level of tensile strength and resistance to low cycle fatigue (LCF). Advancements in novel isothermal forging technology have enabled the production of complex disk forgings called cluster forgings.A single cluster forging produces seven PT2 disks in a single forging operation. Coupled with recent advances in powder metallurgy (P/M) billet production featuring consolidation by HIP followed by extrusion, turbine disk forgings can be produced at a significant cost reduction as compared to single-piece hot die forged disks made from conventional cast/wrought billet. P/M Udimet 720 material displays excellent mechanical properties, competitive with other high strength disk alloys.Turbine disks produced from isothermally forged P/M Udimet 720 passed component test requirements established for the T800 engine. A significant cost reduction resulted from the use of this process.

Ni-based superalloys for turbine discs

“…Based on comparisons of tensile strength properties versus temperature for U720 and U720LI in the literature 68,69,[72][73][74][75][76][77] with results from a current study, U720LI is slightly stronger than U720. The results from the current study match well with the best U720LI properties.…”

Review of Microstructure–Mechanical Property Relationships in Cast and Wrought Ni‐Based Superalloys with Boron, Carbon, and Zirconium Microalloying Additions

“…A comparison between Udimet 720 and Udimet 720LI allows to further rationalize the roles of B and C. Both superalloys contain γ ′ precipitates, MC, and M 23 C 6 carbides, and M 3 B 2 borides have been reported occasionally. [ 175,176 ] Cr, C, and B are reduced in Udiment 720LI to remove carbide and boride stringers and thus improve hot workability and high‐temperature strength. [ 176,177 ] However, C and B additions in PM Udimet 720 can improve the creep rupture life.…”

Changes of γ′ precipitate characteristics in damaged superalloy IN738LC during different stages of rejuvenation heat treatment cycles

“…Nickel based superalloys are of the most complex materials that have been primarily utilised for manufacturing high performance components, such as discs and blades of either land base or aerospace gas turbines. [1][2][3] Components made from nickel based alloys are susceptible to various types of damage due to the effect of high temperatures and stresses during service. Severe service condition inevitably causes various microstructural changes in these alloys.…”