4.8 Article

Rafting-Enabled Recovery Avoids Recrystallization in 3D-Printing-Repaired Single-Crystal Superalloys

期刊

ADVANCED MATERIALS
卷 32, 期 12, 页码 -

出版社

WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.201907164

关键词

3D-printing; heat treatment; Ni-based superalloys; recovery protocols; recrystallization; single crystals

资金

  1. National Natural Science Foundation of China [91860109, 51901026]
  2. National Key Research and Development Program of China [2016YFB0700404]
  3. International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technologies
  4. Office of Science, Office of Basic Energy Sciences, Materials Science Division, of the U.S. Department of Energy at LBNL [DE-AC02-05CH11231]
  5. NSF [CMMI-1922206]
  6. [NSF-DMR-1804320]

向作者/读者索取更多资源

The repair of damaged Ni-based superalloy single-crystal turbine blades has been a long-standing challenge. Additive manufacturing by an electron beam is promising to this end, but there is a formidable obstacle: either the residual stress and gamma/gamma ' microstructure in the single-crystalline fusion zone after e-beam melting are unacceptable (e.g., prone to cracking), or, after solutionizing heat treatment, recrystallization occurs, bringing forth new grains that degrade the high-temperature creep properties. Here, a post-3D printing recovery protocol is designed that eliminates the driving force for recrystallization, namely, the stored energy associated with the high retained dislocation density, prior to standard solution treatment and aging. The post-electron-beam-melting, pre-solutionizing recovery via sub-solvus annealing is rendered possible by the rafting (i.e., directional coarsening) of gamma ' particles that facilitates dislocation rearrangement and annihilation. The rafted microstructure is removed in subsequent solution treatment, leaving behind a damage-free and residual-stress-free single crystal with uniform gamma ' precipitates indistinguishable from the rest of the turbine blade. This discovery offers a practical means to keep 3D-printed single crystals from cracking due to unrelieved residual stress, or stress-relieved but recrystallizing into a polycrystalline microstructure, paving the way for additive manufacturing to repair, restore, and reshape any superalloy single-crystal product.

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