Designing brazing filler metal for heat-resistant alloys based on NI3AL intermetallide

Abstract

One of the most promising structural materials in gas turbine engineering is the alloys based on an intermetallide, the type of Ni 3 Al, with an equiaxial and directional columnar structure. These materials make it possible to increase the working temperature of blades to 1,220 °C. The blades are made by the method of precise casting in a vacuum; in this case, it is necessary to technologically join the nozzle blades into blocks, to fix the signal holes in cooled blades, to correct casting defects. Welding by melting intermetallide materials, as well as other cast heat-resistant nickel alloys (HNA), does not yield positive results. Therefore, various brazing techniques are used such as TLP-Bonding (Transient Liquid Phase Bonding). Filler metals' melting point is lower than that of the main metal. The key issue related to the technology of brazing HNA, including the design of appropriate filler metals, is the improvement of the physical-mechanical and operational properties of brazed joints. This paper reports the established rational doping of a filler metal base, as well as depressants, the critical temperatures and surface properties of filler metals, their chemical composition, the structure and properties of brazed joints, the mode parameters, and brazing technology.To improve the stability of the structure and the high-temperature strength of the brazed joints, the filler metal was alloyed with rhenium and tantalum. Mechanical tests of brazed joints at 900 °C were conducted in Ukraine; at a temperature of 1,100 °C -in the People's Republic of China. The test results showed that the short-term strength of alloy compounds with an equiaxial structure based on the Ni 3 Al-type intermetallide at 1,100 °C is 0.98 of the strength of the main metal. The long-lasting strength at the same temperature meets the requirements for the strength of the main metal

Designing brazing filler metal for heat-resistant nickel alloys of new generation marine gas turbines

“…The working temperature of aviation HNAs reaches more than 1100 °C. Alloys based on Ni 3 Al intermetalide are also used [3,14]. For their brazing, multicomponent brazing filler metals with a brazing temperature of 1260-1300 °C have been developed, for example, VPr36, VPr37, VPr44, BH2.…”

“…For alloys CM93-VI and CM96-VI it is necessary to develop a new brazing filler metal called SBM-4. Work [3] proposed a method of brazing filler metal development in two stages. At the first stage, the chemical composition of the brazing filler metal base is determined, taking into account the peculiarities of the operating conditions of the blades of ship's GTE and the achievements of the materials science of HNAs using the PHACOMP software.…”

“…With capillary brazing with a gap of 0.1 mm, depending on the permissible concentration in the center of the interlayer, the time of homogenization high-temperature processing is tens of hours. It increases in proportion to the square of the interlayer thickness [3].…”

“…It includes research into the formation of SSS, development of brazing filler metal taking into account the conditions and resource of work and properties of the base metal under operating conditions. An example of such an approach is the development of SBM-3 brazing filler metal for aviation HNA based on Ni 3 Al [3]. But the operating conditions of aircraft and marine gas turbines are significantly different.…”

Using the linear damage summation hypothesis in determining the endurance limit of titanium alloy

“…The transformed value x = F(σa) is selected as an independent value. The form of the function x = F(σa) is set so that the dependence y = f(x) is linear (Kvasnytskyi et al, 2020;Razavi et al, 2020;Shojaei & Volgers, 2017). The fatigue curve equation has the form:…”