Transient-Liquid-Phase Bonding of H230 Ni-Based Alloy Using Ni-P Interlayer: Microstructure and Mechanical Properties

Transient-liquid-phase bonding using Ni-P as an interlayer has been developed for H230 Ni-Cr-W solid-solution-strengthened Ni-based alloy. Two process parameters—composition of the interlayer and bonding time—have been varied to optimize the mechanical properties. H230 has been bonded into two sets of stacks (set I and II) for 8 and 4 hours using Ni-12P and Ni-6P interlayer, respectively, (wt pct) at 1423 K (1150 °C) and 12.7 MPa. The microstructure of both the stacks has three distinct regions—the joint centerline which showed the presence of pores, an isothermally solidified zone (ISZ) which did not have any carbide precipitates and base H230. Transmission electron microscopy and atom probe tomography showed a uniform microstructure, and an absence of any deleterious phases at the joint and in ISZ. Set I and set II had a yield strength of 76 and 86 pct of that of the H230 sheet, tested at 1023 K (750 °C). The measured elongation at fracture was negligible, but the fracture surfaces revealed a ductile cup-and-cone-type fracture occurring through the ISZ/joint region. Examination of broken tensile samples revealed that the plastic strain was constrained to within one joint region through which fracture occurred.