Investigation on the effect of bonding time on microstructure and mechanical properties of transient liquid phase bonding between Inconel 718 and Inconel 600

In this paper, transient liquid phase (TLP) bonding process between Inconel 718 alloy and Inconel 600 alloy using a BNi-2 interlayer with 50 μm thickness was investigated. Transient liquid phase bonding process was performed at 1050 °C for 5, 25 and 45 min. Microstructure evaluation was carried out through optical microscopy, field emission scanning electron microscopy (FE-SEM). Also, bonding shear strength was measured. The results showed that the joint microstructure was formed of three zones including isothermal solidification zone (ISZ), thermal solidification zone (ASZ) and diffusion affected zone (DAZ). At the time of 5 min, boride intermetallic compounds in thermal solidification zone were formed. Isothermal solidification was completed and thermal solidification zone was vanished by increasing the bonding time from 5 to 45 min. Diffusion affected zone of the Inconel 718 alloy was persistent and expanded by increasing the time and diffusion of B element to parent metals, but this region in Inconel 600 alloy was vanished and the homogenization process was occurred by increasing the bonding time. Also, because of remove of boride intermetallic compounds, changes of hardness in joint region were more smoothly and the hardness value of joint region was about 280 HV. The results of shear strength showed that the bonding strength was increased from 250 MPa to 410 MPa with increasing the bonding time from 5 to 45 min, respectively.