Advanced conformal welding via Ni nanoparticle sintering for high-temperature applications

Purpose Titanium–zirconium–molybdenum (TZM) alloy exhibits exceptional mechanical properties, rendering it a promising material for utilization in aerospace and nuclear energy systems. However, its poor machinability gives rise to the formation of unstable interstitial cavities in complex assemblies, thereby compromising mechanical integrity and reducing heat transfer efficiency. The purpose of this study is to eliminate interstitial cavities in TZM using low-temperature nanoparticle sintering technology. Design/methodology/approach Ni nanoparticles (NPs) with an average diameter of 55.8 nm were synthesized via oleylamine-assisted reduction of metal salts, and a conformal low-temperature welding strategy for TZM assemblies was developed based on pressureless sintering of these NPs. Findings By applying Ni NPs onto the surface of TZM substrates and sintering at 450°C, TZM/Ni NPs/TZM sandwich joints with a shear strength of 1 ± 0.09 MPa were successfully fabricated. After subsequent high-temperatures treatment at 1,200°C, the shear strength of these sandwiched joints increased to 76.57 ± 0.86 MPa, while maintaining a thermal conductivity of 60.74 ± 0.34 W·m−1·K−1. The method’s capability for low-temperature fabrication and reliable high-temperature performance is primarily attributed to the formation of interfacial NiMo and Ni3Mo phases at low temperatures, which promote metallurgical bonding between the Ni sintered layers and TZM alloys. These interfacial intermetallics subsequently transform into the NiMo2 phase and Mo-based solid solution phases at elevated temperatures, ultimately resulting in a dense and robust sintered joint. Originality/value This work proposes a conformal welding technique based on the sintering of Ni NPs, offering an effective strategy for achieving high-performance and reliable service of TZM assemblies under demanding high-temperature conditions.