Creep Damage Repair of a Nickel-Based Single Crystal Superalloy Based on Heat Treatment

Abstract

Taking nickel-based single crystal superalloy DD6 as the research object, different degrees of creep damage were prefabricated by creep interruption tests, and then the creep damage was repaired by the restoration heat treatment system of solid solution heat treatment and two-stage aging heat treatment. The results show that with the creep time increasing, the alloy underwent microstructure evolution including γ′ phase coarsening, N-type rafting and de-rafting. After the restoration heat treatment, the coarse rafted γ′ phase of creep damaged specimens dissolved, precipitated, grew up, and became cubic again. Except for the specimens with creep interruption of 100 h, the γ′ phase can basically achieve the same arrangement as the γ′ phase of the original sample. The comparison of the secondary creep test shows that the steady-state creep stage of the test piece after the restoration heat treatment is relatively increased, and the total creep life can reach the same level as the primary creep life. The high temperature creep properties of the tested alloy are basically recovered, and the restoration heat treatment effect is good.

Methods for Improving the Quality of Forgings and Blanks Obtained by Forging through Intensifying Shear or Alternating Strain in the Bulk of Deformable Metal

“…To reduce casting defects in large forgings, such as solidification segregation, a new technology for deformation of semi-solid liquid forging has been developed [21][22][23][24]. The deformation of the semi-solid liq-uid core is more uniform, the performance of the equipment is also improved.…”