Study of the Ni–Si–Be system as a base to create boron-free brazing filler metals

Abstract

The investigation results of alloys of the Ni-Si-Be system with a various content of Si and Be are presented. Two low-melting eutectics with melting temperatures of the order of 1100 and 915°C have been found out by the methods of differential thermal and X-ray phase analysis and metallography. Two alloys have been selected for the development of brazing filler metals: Ni-5Si-3Be and Ni-6Si-5Be alloys. Three phases have been shown to be components of the binary and ternary eutectics in the Ni-Si-Be system from the side of the nickel angle of the phase diagram. A Ni-5Si-3Be ribbon and fragments of the Ni-6Si-5Be ribbon have been obtained from the selected alloys by rapid quenching. Filler metal of the Ni-5Si-3Be system has been used for brazing samples of the 12Cr21Ni5Ti austenitic-ferritic corrosion-resistant steel at 1150°C for 30 min.

Recent Advances in Brazing Fillers for Joining of Dissimilar Materials

“…The formation of borides in boroncontaining brazing fillers at the interface results in increased brittleness and eventually leads to complete failure during application. Recent developments in boron-free brazing fillers include Ni-Si-Be alloys for joining austenitic-ferritic steels [100].…”

Brazing filler metals

“…Recent reports of brazing research include sapphire-sapphire joining for use in aircraft windows and scratch resistant engineering components [3], joining of bulk metallic glasses to steel [4], gold-based filler metals to join graphite to superalloy in the petrochemical and nuclear industries [5], boron free-filler metals for joining corrosion-resistant steel in rocket nozzles and heat exchangers [6], indium-containing alloys for SiO 2f /SiO 2 composite materials in antenna radomes [7], and filler metals free of radiation sensitive elements (e.g. Ni and Co) for use with tungsten in fusion reactor diverters [8].…”

“…The incorporation of phosphorus allowed the development of the first iron-based amorphous brazing foil (VITROBRAZE® VZ2099 (Vacuumschmelze) [77]). Other elements have also been investigated as additions including: zirconium and hafnium [78] (which demonstrate homogeneity after brazing as well as desirable capillary characteristics); germanium [79]; and beryllium [6]. The principal advantage for phosphorus is its superior melting point suppression compared to silicon or boron.…”

“…Steel samples brazed with these alloys showed tensile strengths of 587 MPa, comparable to conventional Ni-based fillers (although due to the oxygen affinity of hafnium, a vacuum greater than 2×10 −4 mbar was required) [82]. The use of boron-containing nickel-based filler metals to join steels similarly results in deleterious intermetallic phases, but replacement with beryllium avoids phases which reduce joint strength [6].…”