Superplasticity And Application Research Of Superalloy GH4169

As a age hardening Ni-Cr-Fe-based wrought superalloy, GH4169 has stable structure property and excellent mechanical properties until 650℃, which has been dominant in the production of wrought superalloys. High intensity and good weldability are the outstanding advantage of this alloy and it is more widely used than ordinary superalloy. However, it is very difficult to process the alloy at room temperature and only can be formed by methods of forging,extrusion,welding,machining etc., and the manufacturing cost is very high. This limits the application of the alloy. With superplastic forming, the force of forming can reduce, the size of deformation can increase, and precision parts can be produced, so superplastic forming is an ideal process for less-deformable materials. The superplastic phenomenon of superalloys was found later than aluminum, titanium alloys. Moreover, the superplastic research and its application of Ni-base superalloy GH4169 are even more late. Therefore, it is meaningful to carry on the superplastic research of superalloy GH4169 and then instruct its engineering application.In this paper, the grain-refining treatment on superalloy GH4169 was carried out, and then the high temperature tensile tests by the methods of Maximum m value and deformation-induced superplasticity were implemented. The main results are as follows:1. As for the grain refining processe of superalloy GH4169, the best treatment in this paper is: forging heat deformation + 890℃×10hδ-phase precipitation treatment + 950℃×3h recrystallization annealing. The non-uniform microstructure of the alloy was eliminated by heat treatment and the equiaxial uniform small grains can be obtained. Theδ-phase precipitated would help to control the grain size of recrystallization annealing during the follow- up high temperature tensile test.2. After given grain-refining treatment, the elongation of the superalloy GH4169 has a significant improvement and the flow stress reduces, comparing with the original superalloy GH4169.3. The paper has carried out the high temperature tensile test on GH4169 at different temperatures. It indicated that this alloy has good superplasticity in a wide range of deformation temperatures (T=950℃～1020℃), the best deformation temperature is 950℃.4. The deformation-induced method tensile test has a certain degree of pre-tensile deformation that makes the grain size of superalloy GH4169 refining. Especially for the samples which have had heat treatment, the uniformly distributedδ-phase limit crystal boundary migration of recrystal grains, which promotes grain refining. Therefore, as to superalloy GH4169, the high temperature tensile test by the deformation-induced method is better than by the Maximum m method. The Max elongation reached 340% by the Maximum m method, whereas the deformation-induced method achieved 566%. Most of the strain rate sensitivity (m value) are between 0.15 and 0.4 and the corresponding strain rate changes from 2×10-4 to 6×10-4 s-1 When the high temperature tensile test is carried out by the Maximum m method.This paper has developed a feasible and effective fine grain processing technique for the superalloy GH4169 in theory and practice and successfully applied the Maximum m method and deformation-induced superplasticity method to this alloy. So this paper has broken a new path for the study on superplasticity of GH4169 and its application.