|About this Abstract
||10th International Symposium on Superalloy 718 and Derivatives (2023)
||Superalloy 718 and Derivatives
||The Effect of Microstructure on the Strength of VDM Alloy 780
||Mark C. Hardy, Masood Hafez, Christos Argyrakis, Ross Buckingham, Andrea La Monaca, Bodo Gehrmann
|On-Site Speaker (Planned)
||Mark C. Hardy
Nickel-base alloys have been developed, which offer higher temperature capability from ingot metallurgy than Alloy 718. However, these alloys have higher volume fractions of gamma prime precipitates, require further processing steps and consequently, have higher material processing costs, show a greater propensity for freckle and are not readily electron beam (EB) welded. There is an appetite for an alloy that shows improved forgeability, that is EB weldable and can be used at temperatures of up to 700°C.
This study examines VDM Alloy 780, first using laboratory compression tests and heat treatment experiments to determine suitable thermo-mechanical processing (TMP) conditions. Subsequently, pancakes that were 18-20 mm in height and 137-144 mm in diameter were forged from 70 mm in diameter x 76 mm high bars, which were extracted from mid-radius locations of 8-inch diameter billet. From these, test piece blanks were extracted, and heat treated for tensile tests at temperatures between 20 and 750°C. Results from these tests were compared with microstructure and data from 30 mm thick pancake forgings that received different TMP conditions from earlier work at VDM Metals International. The combined experiences provide an insight into the effect of forging and heat treatment conditions on the microstructure and tensile test properties of VDM Alloy 780. They show that strength levels for fine grain Alloy 720Li can be achieved if specific sizes of gamma grains and gamma prime precipitates can be produced.
||Definite: At-meeting proceedings