Development of a Novel Ni-Based Multi-principal Element Alloy Filler Metal, Using an Alternative Melting Point Depressant

Abstract

Brazing is a crucial joining technology in industries where nickel-superalloy components must be joined. Nickel-based brazing filler metals are extensively employed, possessing excellent mechanical properties, corrosion resistance, and retained strength at elevated temperatures. To function as a filler metal, the alloy melting point must be reduced to below that of the materials being joined, but the addition of melting point depressants (MPDs) such as boron, silicon, and phosphorus can, however, lead to the formation of brittle intermetallics, potentially compromising the joint performance. In the present work, a novel multi-principal element brazing alloy (in the style of a high entropy alloy), utilizing Ge as an alternative MPD along with a reduced B addition, is investigated. The design process considered binary phase diagrams and predictions based on Thermo-Calc software and empirical thermodynamic parameters. The alloy was used to vacuum braze nickel-superalloy Inconel-718, and microstructural and mechanical investigations are reported. The maximum shear strength achieved was 297 MPa with a brazing temperature of 1100 °C and 60-minute hold time, with isothermal solidification completed. Shear strength was only slightly reduced with increased joint width. Assessments are made of the ability to accurately predict properties of multi-principle element alloys using Thermo-Calc software and empirical thermodynamic parameters.

Advanced 3D Through-Si-Via and Solder Bumping Technology: A Review

“…Many studies have been conducted on connecting techniques and the use of appropriate fillers for Ni-and Ti-base alloys [313,314]. It is important to remember that Ni-base alloys may not be optimum for joining during fabrication or repair, even if they are created for maximum performance.…”

Archives of Metallurgy and Materials

“…However, addition of melting point depressants (MPD) such as boron, silicon or phosphorus can lead to formation of hard, brittle phases concentrated in the centreline area of the joint, which might result in reduction of its strength and durability [17,18]. Industrial popularity of this BFM group provides an incentive for continuous search for improvement, focused either on replacement of currently used MPD in filler alloy [19][20][21] or investigation of the brazing process parameters impact on microstructure and properties of the joint [22][23][24].…”