Analysis of Microstructure Evolution and Mechanical Properties of Inconel 718/TC4 Dissimilar Metal Welding by Cold Spraying

Titanium alloy/nickel-based alloy composite structures are widely used in lightweight designs in aerospace applications. This study introduces cold spray technology for manufacturing titanium alloy/nickel-based alloy composite structures, offering a solution that effectively prevents the formation of brittle intermetallic compounds in conventional welding of titanium alloy/nickel-based alloy. Three types of powders (Inconel 718, TC4, Ti) are used to weld Inconel 718/TC4 via the cold spray process. The results indicate that a well-bonded interface is formed using pure Ti and Inconel 718 powders, and the welded joints (CS Inconel 718) have low porosity, only 0.96 ± 0.11%. The dissimilar materials interface (CS Inconel 718/TC4 base material) demonstrates superior bonding property compared to the same material interface (CS Inconel 718/Inconel 718 base material). The dynamic recrystallization occurred in the dissimilar materials interface region, leading to an increase in β-phase content and the formation of nanocrystals in the intersection of interface and TC4 base metal. The microstructure of the bonding zone (CS Inconel 718) is primarily composed of γ-phase, with a minor fraction of Laves phase resulting from the metallurgical bonding between Inconel 718 particles in cold spray deposition. The mechanical properties of the joint are mainly related to the interface bonding quality and porosity. In the case of well-bonded interface, the mechanical properties of cold spray-welded joints are primarily influenced by porosity. The tensile strength of the joints improves as porosity decreases, but the microhardness shows a declining trend. Tensile tests indicate that the welded joints (CS Inconel 718) possess a room-temperature strength of 433.63 ± 30.9 MPa and retains a stable value of 390.7 ± 19.58 MPa at 600 °C, demonstrating excellent high-temperature property stability. In summary, the Inconel 718 powder is identified as the optimal filler material for cold spray welding of titanium alloy/nickel-based alloy.