Microstructure Control and Mechanical Properties of New Developed C&W Superalloy GH4175 at 800°C

Abstract

As the thrust-weight ratio continues to increase, the aero-engine turbine disk material required both high strength and high temperature resistant properties which were often not compatible; Besides the working temperature of the turbine disk rim had reached 800 °C, the existing superalloys can not to meet the requirements, which was the reason that GH4175 alloy was produced. GH4175 was derived from Russian BK175 alloy, and the volume content of γ' was over 58%. For the new GH4175, the low-segregation melting ingot with diameter of as large as 508mm could be prepared by the Double vacuum melting or Triple metlting process, in which the macro segregation and various metallurgical defects could be effectively controlled, then the conversion of as-cast microstructure and fine-grained billets were achieved on open-die hydraulic press by multi-times upsetting and drawing process and the novel temperature control technology with high efficiency, next, with the multi-cycle thermos-mechanical processing technology, the full-size turbine disks with a diameter of 600mm or more could be produced on hot die forging or isothermal forging. After standard heat treatment, the alloy combines high strength and high temperature characteristics, and balances the relationship between fatigue and creep. The long-term working temperature of the alloy reaches 800 °C.