Effect of hot extrusion on microstructure for nickel-based superalloy FGH96
YANG Jie, LIU Guang-xu, WANG Wen-ying, ZHANG Jing, WANG Xiao-feng, ZOU Jin-wen
Science and Technology on Advanced High Temperature Structural Materials Laboratory, AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China
Abstract：The influences of hot extrusion temperature, extrusion ratio, extrusion rate and pretreatment before extrusion on microstructure for nickel-based superalloy FGH96 were studied. The hot extrusion method for obtaining superplastic fine grain structure with grain size less than 10 μm was determined. The results showed that the FGH96 superalloy recrystallized after hot isostatic pressing, and the powder was fully densified. However, the grain size was extremely uneven, and there were obvious previous particle boundary (PPB) defects. The pretreatment process before hot extrusion not only ensured that grain size of the alloy did not grow up, but also coarsened the γ' phase, which significantly reduced the deformation resistance of hot extrusion. With the increase of extrusion temperature, the grain size of FGH96 superalloy tended to grow up. The fully recrystallized superplastic structure with average grain size less than 10 μm was obtained when the extrusion temperature was 1 080 ℃. With the increase of extrusion temperature, grain size grew up obviously. With the increase of extrusion ratio, the extrusion loading increased obviously. The fully recrystallized superplastic structure with average grain size less than 10 μm could be obtained when the extrusion ratio was greater than 6∶1. The loading increased with the increase of hot extrusion rate, thus the lower extrusion rate should be selected as far as possible under the condition of fine grain structure. There was no obvious orientation due to the fully dynamic recrystallization of FGH96 superalloy during hot extrusion. The results of mechanical properties test also showed that the properties in both parallel and vertical direction for the extrusion were equivalent and the micro texture in different extrusion directions had no obvious effect on the properties.
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