High temperature shear and thermal aging behavior of dissimilar transient liquid phase bonded Hastelloy X to Ni3Al intermetallic compound

Nickel super alloys and intermetallic compounds (IMCs) are candidate as strategic materials for turbine industry, because of its excellent high temperature properties. In this study, mechanical properties and thermal aging behavior (post thermal exposure) of the transient liquid phase (TLP) bonds between Hastelloy X to Ni3Al IMC at temperature range of 800-900 degrees C were investigated. The microstructure and fracture surfaces of the joints were examined by optical and scanning electron microscopes as well as XRD analysis. The optimum joint bonding strength was achieved for the sample treated at 1100 degrees C-180 min equaling to 355 +/- 4.5 MPa. XRD patterns of semi-cleavage fracture surfaces revealed nickel solid solution matrix containing BNi3 and Ni3Si compounds generated at ASZ/ISA interface. The ultimate tensile strength reaches 36.5 +/- 1 and 20.5 +/- 1 MPa at tempera-tures of 800 degrees C and 900 degrees C, respectively. Fracture occurred in the IMC substrates for both temperatures were due to shrinkage porosity during solidification of IMC and mismatch of crystal lattice constants with the matrix. The thermal aging process at 900 degrees C for 50-500 h had a minor effect on the joint microstructure but generated TCP phases in the Hastelloy X.

Automated summary

This study investigates the mechanical properties and thermal aging behavior of nickel super alloys and intermetallic compounds as candidate materials for the turbine industry. The optimum joint bonding strength was achieved at 1100 degrees C-180 min, and XRD analysis revealed the presence of nickel solid solution matrix containing BNi3 and Ni3Si compounds. The ultimate tensile strength at 800 degrees C and 900 degrees C was 36.5 +/- 1 MPa and 20.5 +/- 1 MPa, respectively. Fracture occurred in the IMC substrates due to shrinkage porosity and lattice mismatch with the matrix. Thermal aging at 900 degrees C generated TCP phases in Hastelloy X.