DOI QR Code
HIP diffusion bonding of Ni-based superalloys, cast Mar-M247 (MM247) and Udimet 720 (U720) powder, was experimentally and numerically studied. Subsolvus HIP treatment was optimized by investigating the variations of high temperature tensile properties of HIP-bonded specimens with powder size, HIP'ing time, etc. While the tensile strength at high temperatures showed no detectable changes, the tensile elongation and reduction in area were slightly increased as the powder size decreased from -140 mesh to -270 mesh. While as-HIP'ed U720 showed a high tensile strength comparable to that of lorded U720 alloy, the HIP diffusion-bonded specimen showed a strength lower than the forged U720 alloy and the cast MM247 alloy The increase of HIP'ing tune from 2 hours to 3 hours resulted in a rapid risc of tensile strength and elongation due to the disappearence of microvoids in the cast MM247. FEM simulation for HIP process was conducted by applying the McMeeking micromechanical model, which uses power-law creep model as constitutive equations. ABAQUS user subroutine CREEP with an implemented microscopic model was used for the simulation. Numerical simulation was shown to be essential for the near-net shape manufacturing as well as the HIP process optimization.
