Dissimilar Welding of Titanium - and Nickel Alloys with High Entropy Fillers

Basic data for this project

Description

Dissimilar joining Ni-based to Ti-based alloys is required for the fabrication of components in many industries such as aerospace, offshore, oil & gas, chemical, and in the field of carbon capture and storage (CCS). Yet obtaining a quality joint between Ti- and Ni-based alloys remains problematic due to several reasons, including a strong tendency for the formation of intermetallic phases. A promising strategy is the usage of a filler metal that can suppress or limit the formation of intermetallics. However, the selection of the proper filler materials and corresponding welding conditions remains a challenging task. In this joint project, we aim to produce quality joints between pure Ti/Ni and between the two most widely used Ti and Ni alloys for high-temperature applications, namely Ti-6Al-2Sn-4Zr-2Mo and Inconel 718, by using specifically designed high entropy alloy (HEA) filler metals and optimization of the laser beam welding (LBW) and/or diffusion bonding (DB) conditions. HEAs are multicomponent alloys specifically introduced with the intent to suppress intermetallic phase formation. This feature, together with their multicomponent nature, which allows for the varying of different physical and mechanical properties, makes them highly attractive candidates as filler materials. In this work, we aim to develop new HEAs to be used as a filler material between Ti-/ Ni-based alloys using a combination of experimental analyses and CALPHAD calculation that will allow us to estimate the equilibrium and non-equilibrium phases in potential joints. Promising HEAs will be selected, fabricated, and tested as filler materials in the welding processes. Scale-bridging microstructure characterization and mechanical – as well as diffusion analyses spanning a wide range in temperature will be performed, including time-resolved phase analysis during LBW using a high-energy X-ray beam. Finally, specific attention will be paid to the optimization of the welding conditions (laser power, welding speed, pre-heating temperature, etc.). In addition, due to its unique capacity to join complex parts, DB between Ti-6Al-2Sn-4Zr-2Mo and Inconel 718 alloys using the developed HEA filler will be investigated. As a result of this joint project, new filler material and LBW or DB conditions will be developed for obtaining quality joints between Ti-6Al-2Sn-4Zr-2Mo and Inconel 718 alloys free from welding defects such as pores or cracks. The results from the proposed work will promote technological advancements in many industries and offer a scientific basis for the development of HEAs that can be utilized as a filler for dissimilar welding between other pairs of materials.