Abstract
In a dissimilar welded joint between Ni base alloys and titanium, creep failure is a potential concern as it could threaten to undermine the integrity of the joint. In this research, the mechanical heterogeneity of a Pulsed TIG welded joint between commercially pure titanium (CpTi) and Inconel 718 (IN718) with a vanadium (V) interlayer was studied through a nanoindentation technique with respect to hardness, elastic modulus, and ambient temperature creep deformation across all regions (fusion zones and interfaces, mainly composed of a dendritic morphology). According to the experimental results, a nanohardness of approximately 10 GPa was observed at the V/IN718 interface, which was almost 70% higher than that at the V/CpTi interface. This happened due to the formation of intermetallic compounds (IMCs) (e.g., Ti2Ni, NiV3, NiTi) and a (Ti, V) solid solution at the V/IN718 and V/CpTi interfaces, respectively. In addition, nanohardness at the V/IN718 interface was inhomogeneous as compared to that at the V/CpTi interface. Creep deformation behavior at the IN718 side was relatively higher than that at different regions on the CpTi side. The decreased plastic deformation or creep effect of the IMCs could be attributed to their higher hardness value. Compared to the base metals (CpTi and IN718), the IMCs exhibited a strain hardening effect. The calculated values of the creep stress exponent were found in the range of 1.51–3.52 and 2.52–4.15 in the V/CpTi and V/IN718 interfaces, respectively. Furthermore, the results indicated that the creep mechanism could have been due to diffusional creep and dislocation climb.
Highlights
The current trend in industry is toward making multifunctional components by integrating several similar and dissimilar materials
The TIG arc facing side depicts the common melt zone where the melting and dissolution of the commercially pure titanium (CpTi) and Inconel 718 (IN718) plates with the V foil is shown by an energy dispersive spectroscopy (EDS) line scan
The mixing of Ti, Ni and V triggered several metallurgical reactions which led to the formation of intermetallic compounds (IMCs)
Summary
The current trend in industry is toward making multifunctional components by integrating several similar and dissimilar materials. Along with IN718, due to its higher strength and excellent corrosion resistance, commercially pure titanium (CpTi) has been extensively used in the airframes of aircrafts and in the petrochemical industry Due to these special properties, titanium- and nickel (Ti/Ni)-based dissimilar alloy joints can afford significant advantages in many industries [8,9,10]. In designing the compressor section of aero engines, one strategy to reduce the net weight of the engine is to use a transition joint between the titanium alloys and the nickel-based super alloys [11]. These joints, making efficient use of both alloy properties, can improve the performance of equipment, save on material cost, and improve design. This problem can be overcome, by the choice of a proper welding process, input process parameters, and the insertion of a suitable metallic interlayer between the base alloys [18,19,20]
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