Rapid Joining of Commercial-Purity Ti to 304 Stainless Steel Using Joule Heating Diffusion Bonding: Interfacial Microstructure and Strength of the Dissimilar Joint

K T Suzuki,S Tokita,Y S Sato

doi:10.3390/met10121689

Abstract

A new solid-state bonding technique, Joule heating diffusion bonding, was used for the dissimilar bonding of commercial-purity Ti to 304 stainless steel within a short time without macroscopic deformation of the workpieces. The tensile strengths of the joints produced at various bonding parameters were examined at room temperature, and the microstructures of the joints and the fracture surfaces were analyzed to clarify the effect of the microstructural factors on the tensile strength of the joints. The tensile strength of the joints increased with the increase in the fraction of the sufficiently bonded interface. In the joints with the well-bonded interface, the tensile strength decreased with the increase in the thickness of the brittle Fe-Ti-type intermetallic compound layers at the joint interface. This study suggested that the high tensile strength could be achieved in the Joule heating diffusion bonded joints with the well-bonded interface where the thickness of the Fe-Ti-type intermetallic compound layers was thinner than 0.5 µm.

Highlights

Dissimilar joining of titanium (Ti) to stainless steel is an effective method to fabricate the cost-effective and high-performance parts and structures for the offshore industry [1].the conventional fusion welding techniques, such as arc welding, cannot be utilized for the dissimilar bonding of Ti to stainless steel [2]
Satoh et al demonstrated that the joints that were fabricated by the laser welding of commercial-purity titanium (CP-Ti) and austenitic 316 stainless steel exhibited low tensile strengths owing to the formation of intermetallic phases occupying the weld metal entirely [4]
The present study demonstrated the application of Joule heating diffusion bonding (JHDB) for the dissimilar bonding of CP-Ti to 304 stainless steel for various sets of bonding parameters and examined the microstructure and the tensile strength of the joints

Summary

Introduction

The conventional fusion welding techniques, such as arc welding, cannot be utilized for the dissimilar bonding of Ti to stainless steel [2]. These methods result in the fabrication of joints with poor mechanical properties owing to the formation of diverse brittle intermetallic compounds (IMCs) at the interface [3]. The conventional fusion welding techniques involve the melting and solidification of the base metals. This induces high residual stresses, owing to the difference in the coefficients of thermal expansion [3], and crack formation during cooling. The joining of Ti is hindered by the easy dissolution of oxygen and nitrogen from the welding atmosphere during melting [5]

Objectives

Discussion

Conclusion