Effect of Bonding Temperature on Microstructure and Mechanical Properties during TLP Bonding of GH4169 Superalloy

Qing He,Anpeng Wang,Mengjia Xu,Qiancheng Sun,Duo Dong,Dongdong Zhu

doi:10.3390/app9061112

Abstract

The effect of bonding temperature on the microstructure and mechanical properties of transient liquid phase (TLP) joints of GH4169 superalloy was investigated. Joining processes were carried out at 1040–1100 °C for 30 min using BNi-2 solder paste. The results showed that three distinct microstructural zones were formed in the joint region: an athermal solidification zone (ASZ), consisting of eutectic compounds; an isothermal solidification zone (ISZ), consisting of γ solid solution; and a diffusion affected zone (DAZ), consisting of Ni-Cr rich boride and Cr-Nb-Mo-rich boride compounds. With increasing bonding temperature, the amounts of eutectic compounds in ASZ first decreased and then increased. A eutectic-free joint centerline was obtained at 1080 °C. The maximum bonding shear strength reached 728.03 MPa due to the completion of isothermal solidification. Fractographic studies revealed that the boride compounds in ASZ and the intermetallic compounds in DAZ were the main causes for the failure of joints. The fracture mode of the sample bonded at 1040 °C was brittle, and the fracture path was along the ASZ. However, the fracture mode of the sample bonded at 1080 °C was ductile, and the fracture occurred along the DAZ.

Highlights

GH4169 is a precipitation-strengthened nickel-base superalloy with excellent fatigue resistance, radiation resistance, oxidation resistance, and corrosion resistance below 650 ◦ C [1,2,3]
The intensive dimples in the fracture surface (Figure 6d) indicated that the fracture mode of the sample bonded at 1080 °C was ductile fracture. This can be attributed to the completion of isothermal solidification
For the joints brazed at 1040 °C, the athermal solidification zone (ASZ), the isothermal along the diffusion-affected zone (DAZ) of the joint where the intermetallic compounds existed

Summary

Introduction

GH4169 is a precipitation-strengthened nickel-base superalloy with excellent fatigue resistance, radiation resistance, oxidation resistance, and corrosion resistance below 650 ◦ C [1,2,3]. In order to solve the problems during the welding process, some researchers have tried transient liquid phase (TLP) bonding technology to join nickel-base alloys. The cutting process is time-consuming, and the rate of material utilization is low Another issue is that the intermetallic compounds in the joint center which deteriorate the shear resistance cannot be eliminated completely, which makes the quality of GH4169 weldments unstable. In order to find a new method for batch welding GH4169 with high efficiency, reliability, and low consumption, the TLP welding of GH4169 alloy was studied by using BNi-2 solder paste in this paper. The TLP method has proved to be an effective technique for obtaining excellent nickel-based alloy joints at relatively low temperatures. The effect of bonding temperature on the microstructure and mechanical properties of the GH4169 joints was investigated

Materials and Methods

Discussion

The Effect of Bonding Temperature on the Joint Microstructure

Shear and Fractography

Conclusions