Evolution of Interface Microstructure and Mechanical Properties of Titanium/304 Stainless Steel Diffusion Bonded Joint Using Nb Interlayer

Abstract

In the present investigation, the evolution of interface microstructure and mechanical properties of diffusion bonded joints of titanium to Type 304 stainless steel with a niobium interlayer were studied. The joints were processed in the temperature range of 800 to 1 000°C for 0.5 h in vacuum. The stainless steel/niobium interface was free from intermetallic phase up to 900°C; however, Fe 2 NbϩFe 7 Nb 6 phase mixture was observed at and above a processing temperature of 950°C. The niobium/titanium interface was free from intermetallic compounds at all processing temperatures. A maximum tensile strength of 297 MPa (ϳ93 % of Ti) and shear strength of 217 MPa (ϳ75 % of Ti) along with a 6.9 % ductility were achieved, when processed at 900°C processing temperature. The failure of bonded samples took place through the stainless steel-niobium interface at all processing temperatures during loading.KEY WORDS: diffusion bonding; niobium interlayer; electron probe microanalyser; scanning electron microscope; X-ray diffraction.

Laser joining of NiTi to Ti6Al4V using a Niobium interlayer

“…It is a refractory metal with a melting point of 2477 C and, when pure, it is malleable and ductile so can conform easily to any joint configuration [23,24]. The melting point of Niobium is significantly higher than that of NiTi (1310 C [25]) and Ti6Al4V (1660 C [26]), so Niobium would be an excellent diffusion barrier between NiTi and Ti6Al4V; with previous proven use as a diffusion barrier between Ti and stainless steel [27]. Niobium has been successfully laser welded to Ti6Al4V [28], and joined with a eutectic reaction to NiTi [23] without the formation of brittle intermetallics, which are not present in these systems [29].…”

The Determining Role of Nb Interlayer on Interfacial Microstructure and Mechanical Properties of Ti/Steel Clad Plate by Vacuum Rolling Cladding

“…Therefore, C element in steel and Ti diffused through Nb interlayer and then produced easily stable and discontinuous TiC. The previous studies [ 19 , 24 ] showed that discontinuous TiC and FeNb have a strong influence on the performance of clad plate. Therefore, the fractural surface of Ti side was divided into three parts, including the contact region between Nb and Ti, Nb interlayer and the contact region between Nb and steel in Figure 10 c.…”

“…During hot-rolling cladding Ti/steel clad plate, the oxides and nitrides at the interface can be effectively controlled by VRC, but TiFe and TiC compounds are easily produced at the interface of Ti and steel at elevated temperature, which reduce the interfacial bonding property in Ti/steel clad plate. In order to reduce the contents of TiC and TiFe and increase interfacial bonding strength, intermediate layer metals are commonly applied [ 19 ]. Recent some studies focused on mechanical properties of Ti/steel clad interface with various interlayers.…”

Interfacial microstructure and properties of a vacuum hot roll-bonded titanium-stainless steel clad plate with a niobium interlayer

“…In a prior study, when the diffusion-bonding (DB) process was carried out between pure Ti and 304 SS using a Nb interlayer with the same heating process parameters as the present study, the maximum shear strength obtained was ∼216 MPa at bonding temperature of 900 • C [19] . The bonding strength of the same interface produced by VHRB is significantly high.…”

“…However, intermetallic compounds can form between Fe and Nb at high temperatures. Diffusion bonding process between pure Ti and 304 SS with a Nb interlayer led to a maximum shear strength of 216 MPa at a bonding temperature of 900 • C [19] . However, majority of the above studies were limited to diffusion bonding to produce joints between Ti and SS rather than clad plates.…”