Study on fatigue fracture characteristics of powder metallurgy superalloy FGH4113A
The fatigue origins and fracture characteristics under different test conditions and heat treatments of a third generation nickel-based powder metallurgy superalloy FGH4113A prepared by hot isostatic pressure(HIP)+hot extrusion(HEX)+isothermal forging(IF)were studied.The results show that the mean grain size of FGH4113A alloy prepared by extrusion and forging with fine powder reaches grade 12 or more,no PPB defects are found,and the size of inclusions is effectively controlled.The mean size of the alloy is maintained at about grade 12 after sub-solvus heat treatment.The dissolution of primary y'phase under super-solvus heat treatment leads to the growth of mean grain size up to ASTM 7.8.The inclusion fatigue origins at 650 ℃ stress-controled tests and 700 ℃/0～0.8％strain controled tests of the super-solvus specimens are less than 15％,but more than 85％in the sub-solvus specimens.The fatigue origins of sub-solvus specimens are mainly small size inclusions,and the fatigue properties are not weaken.The fatigue origin type of the specimens under the control of 700 ℃with large strain(strain≥ 1.0％)is not decided by heat treatment process,the fatigue cracks only initiate on the surface and extremely sensitive to the inclusions nearby.
powder superalloyheat treatmenttype of fatigue sourcefatigue lifeinclusionsgrain size
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