Microstructure and mechanical properties of Ni nanoparticle-bonded Inconel 718. (15th July 2019)

• Record Type: Journal Article
• Authors: Bridges, Denzel; Xu, Raymond; Hu, Anming
• Is Part Of: Materials & design. Volume 174(2019)
• Publication Date: 2019-07-15
• Subjects: Transient liquid phase bonding -- Nanoparticles -- Nickel -- Inconel -- Superalloy -- Brazing; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2019.107784
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Ni nanoparticles were successfully used as a melting point depressant-free filler metal to join Inconel 718 via transient liquid phase (TLP) bonding in a vacuum environment. Ni nanoparticles of 22, 29, and 42 nm in diameters were synthesized by controlling the reducing agent injection rates and the TLP bonding was carried out at up to 1050 °C with heating rates of 2–15 °C/min. Based on the Gibbs-Thomson equation and surface melting models, bonding using Ni nanoparticles occurs due to competing solid-state sintering and surface melting processes. It was found that larger particle size, faster heating rate, and higher maximum temperature resulted in higher bonding strength due to less grain boundary contamination, smaller crystallite size, and more robust metallurgical bonding, respectively. Using a faster heating rate limits the amount of solid-state nanoparticle-nanoparticle sintering that occurs at lower temperatures. The suppression of nanoparticle-nanoparticle sintering as a function of nanoparticle diameter is also discussed. The maximum bonding strength achieved is 243 MPa. According to digital image correlation, the strain is mostly sustained in the Ni-Inconel interfacial region. The fractography of Ni nanoparticle-bonded joints is also discussed in detail. Graphical abstract: Unlabelled Image Highlights: Ni nanoparticle bonding strength up to 243 MPa in a lap shear configuration Heating rate, temperature, and particle size identified as key factors Ni nanoparticle hardness up to 231 HV Dense Ni NP joint achieved over 300 °C below the particle melting point