Study on multi stage forging process with combination of different strain rate and temperature region in IMI685 aero engine compressor disc forging

Abstract

IMI 685, a near alpha Ti alloy has been used in high pressure compressor discs for aero engine application due to its high strength to weight ratio and high creep resistance. Manufacturing process plays an important role in obtaining the required mechanical properties for the highly complex and critical products. The suitable manufacturing process is not available in open literature. Hence, in this paper non-isothermal approach of manufacturing compressor disc combining hydraulic press and pneumatic hammer at different temperature for different stages of forging has been explored. Mechanical and metallurgical analysis of processing in partial α-β/β temperature range resulted in higher creep resistance with acicular/needle alpha platelets with a basket weave structure. This experiment has proven that with a proper selection of thermo mechanical processing parameters (combination of different forging temperature and strain rates in forging sequence), required creep properties can be met with the non-isothermal processing route.