Optimization design and interface characteristics research of high damping NiTi - Nickel-Aluminum Bronze functional gradient composite coating additively manufactured by high-speed laser-directed energy deposition

• Published in: Surface & coatings technology Vol. 493; p. 131280
• Main Authors: Li, Jiaxuan, Liu, Zongde
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2024
• Subjects: Additive manufacturing; Damping performance; Interface; Interlayer; NiTi alloy; Additive manufacturing; Interlayer; NiTi alloy; Damping performance; Interface
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2024.131280

The near-equatomic NiTi shape memory alloy demonstrates exceptional damping performance due to its distinctive low-temperature self-cooperative martensitic internal friction. This study successfully fabricated NiTi-NAB (Nickel-Aluminium bronze shape memory alloy) functionally graded composite coatings with excellent metallurgical bonding between layers on Q235 steel substrates by designing an appropriate interlayer structure and employing the high-speed laser-directed energy deposition (LDED). Through comprehensive evaluation of the composite coating's performance and the numerical simulations of heat transfer within the molten pool, we elucidated the impact of process parameter levels on the microstructure and phase transformation characteristics of the NiTi alloy coating (NTC). The phase composition and phase interface characteristics of the NTC surface and bonding interface were analyzed using an electron probe microanalyzer and transmission electron microscopy, while dynamic thermomechanical analysis was employed to evaluate the damping performance of the NTC. The results indicate that an optimal parameter combination area still exists within the NTC-LDED process parameter window, even with equal laser energy density. Insufficient parameter levels can lead to an increase of micro-defects within the NTC, consequently causing a deterioration in both the cohesion and deformation resistance of the coating. Excessively high parameter levels can lead to significant element loss and residual stress, which in turn contributes to an increase in microcracks within the coating. A considerable quantity of reaction product mixture phases was formed at the interface between NTC and NAB, tending to align coherently with the NAB phase interface. The NTC, prepared with optimal process parameters, exhibits exceptional damping performance with a damping ratio of 0.498 at internal friction equilibrium, rendering it highly promising for applications in surface erosion protection for fluid machinery. •The NiTi alloy coating stabilizes in the B19′ phase at ambient temperature.•The impact of molten pool traits on NiTi alloy coatings' properties was uncovered.•The atoms at the NiTi-NAB interface tend to arrange themselves coherently.•The damping ratio of the NiTi alloy coating hits 0.498 post-internal friction balance.