Formation of needle-like MC carbide at or near incoherent twin boundary in IN740H Ni-based superalloy

During aging at 900 degrees C for 100 h of IN740H Ni-based superalloy, unexpected needle-like MC carbide formed at or near incoherent twin boundary having a twin relationship with surrounding matrix. Similar to the known needle-like M23C6 precipitation, the nucleation and growth of MC carbide in needle-like morphology resulted from emission of Shockley partial dislocations and inherent directional stress field originated from incoherent twin boundary, respectively. Also, this precipitation process essentially gave rise to the twin relationship with its surrounding matrix. (C) 2019 Elsevier B.V. All rights reserved.