Development of Hot-Isostatically Pressed and Forged P/M Rene 95 for Turbine Disc Application

Previous studies had demonstrated the economic and technical feasibility of producing high-quality forgings for aircraft turbine engine parts from hot-isostatically pressed (HIP) Rene 95 powder billets. The present program was aimed at developing a production practice for making HIP + forged turbine discs. The major goal was improved product fabricability and reliability with minimum cost.

The program was conducted using argon atomized Rene 95 powder. Experimental studies were conducted to evaluate the effect of powder characteristics, HIP parameters, preform design, and forging conditions on forgeability, microstructure, and mechanical properties. The results of these studies were incorporated into a pilot production run in which 10 disc forgings were made and evaluated.

The selected process involved the consolidation of -60 mesh powder to full density by hot-isostatic pressing at a temperature above the γ' solvus temperature. This compaction process develops a desirable starting microstructure. Subsequent forging below the γ' solvus temperature develops the required “necklace” (partially recrystallized) microstructure. The properties of the resulting product were found to exceed specification requirements. Furthermore, pilot production has demonstrated the reliability and reproducibility of the process.