Isothermal forging process design for spray-formed FGH95 superalloy turbine disk based on numerical simulation

Based on the experimental data from hot compression tests on Gleeble 1500 thermal simulator, the revised constitutive equations of spray-formed FGH95 superalloy considering the effect of strain on the material constants were established. The average absolute relative error （AARE） was employed to verify the validity of the constitutive equation, and the value of AARE is 3.85 %. Subsequently, the revised constitutive equations were successfully used to simulate and analyze the deformation behavior, stress distribution, forming loads and temperature distribution in both dies and billet during the isothermal forging process of turbine disk of large dimension （about 400 mm in diameter） by the means of finite element method （FEM）. Moreover, the optimum process parameters are 1,120 ℃ of forging temperature and 0.01 s^-1 of strain rate for the spray-formed FGH95 superalloy turbine disk.

Surface characteristics of rapidly solidified nickel-based superalloy pow-ders prepared by PREP

The surface microstructure and the surface segregation of FGH 95 nickel-basedsuperalloy powders prepared through plasma rotating electrode processing (PREP) have beeninvestigated by using SEM and AES. The results indicate that the surface microstructure of powderschanges from dendrite into cellular stricture as the particle size of powders decrease, and thepredominant precipitates solidified on the particle surfaces were identified as MC' type carbidesenriched with Nb and Ti. It was also indicated that along with the depth of particle surfaces, thesegregation layer of S, C and O elements are thick, and that of Ti, Cr elements are thin for largesire powders while they are in reverse for median size particles.

Flow Behavior and Numerical Simulation of Spray-Formed FGH95 Superalloy Under Hot Compression

The flow behavior of spray-formed FGH95 superalloy （similar to Rene 95） was investigated at tempera- tures ranging from 1050 to 1 140 ℃ and strain rate ranging from 0.01 to 10 s-1. At a given temperature and strain rate, flow stress increases quickly with increasing strain and then reaches a peak, then gradual decreases until high strain, and dynamic softening is observed. Utilizing the hyperbolic sine {unction and introducing the strain with non- linear fitting, the revised constitutive equations incorporating the effects of temperature, strain rate and strain for high temperature flow stress prediction of superalloy were established. The revised constitutive equations were im- planted into finite element software by second development to simulate the hot compression process successfully, and the effective stress and load stroke curves obtained by numerical simulation are good agreement with the experimen- tal results.

Creep Behaviors of FGH95 Powder Ni-Base Superalloy

This article makes an investigation into the creep behavior and deformation features of FGH95 powder Ni-base superalloy by means of creep curves and microstructural observation. Results show that this superalloy exposes obvious sensibility to the applied temperature and stresses in the experimental range. Microstructure of the alloy consists of γ＇ phase of various sizes and dispersed carbide particles precipitated in the wider crystal boundaries between the powder particles. During the creep, the deformation of the alloy occurs in the form of singleor double-oriented slipping inside the grains, and some of the finer carbide particles are precipitated near the slipping traces. The wide grain boundaries might be broken into the finer grains due to severe deformation. The deformation mechanism of the alloy during creep is thought to be the activation of dislocations of double-oriented slipping, including （1/2）〈 110〉 dislocation inside the γ matrix phase and 〈110〉 super-dislocation inside the γ＇phase. The formation of the stacking faults and （1/3）〈112〉 super-Shockleys partial dislocation configuration is attributed to the decomposition of 〈 110〉 super-dislocation in the γ＇ phase.

Microstructure,Tensile Properties and Heat Treatment Process of Spray Formed FGH95 Superalloy

The potential of spray forming for microstructural refining can be attractive to the production of superalloys.A200mm spray formed FGH95superalloy round billet that was produced using a single atomizer has considerably homogeneous,small,equiaxed grains.The measured oxygen content is 2×10-5,and the measured porosity is only 0.6%.The achieved yield of deposit is in a good range of about 73.6%.The microstructure and tensile properties of nickel-based spray formed FGH95superalloy are analyzed.Also,effects of heat treatment on microstructure were discussed.The results show that the spray formed FGH95superalloy has higher isotropy in tensile property due to itsγ′phase homogeneous distribution and less defects in the microstructure.Regarding processing procedures,the different heat treatment processes affect the microstructure andγ′phase homogeneous distribution of spray formed FGH95superalloy.