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The influence of silicon on the properties of brazed joints of high-chromium nickel-based superalloys
Svitlana Maksymova, Vitalii Voronov and Petro Kovalchuk
For the manufacture of gas turbine engines and power plants, multi-component nickel alloys with a high concentration of chromium (16–20%) are used. Chromium enhances resistance to high-temperature corrosion caused by the aggressive environments of diesel and gas fuels and salts from seawater. These alloys are known for their poor weldability and tendency to form hot cracks during both welding and subsequent heat treatment. Therefore, high-temperature brazing is a promising method for joining such alloys, as it can help avoid crack formation in brazed joints when the correct temperature regime and chemical composition of the brazing filler metal are selected.
This paper presents the results of metallographic and micro-X-ray spectroscopic studies of brazed joints made of heat-resistant nickel alloy CM104-VI (containing 20% chromium), obtained by high-temperature vacuum brazing using a Ni-Cr-Co-(Me)-B-Si filler metal. The effect of silicon on the structure and mechanical properties of the joints at room and elevated temperatures was investigated. By reducing the concentration of silicon (or excluding it from the filler metal composition), it was possible to reduce the amount of the silicide phase and avoid eutectic formation.
Mechanical tests at room and elevated temperatures demonstrate the potential of a silicon-free brazing filler metal, providing high tensile strength at both room temperature and 1173 К, with values of 739 MPa and 424 MPa, respectively. This corresponds to 75–80% and 85–90% of the strength of the base metal.
Keywords: high-temperature brazing, filler metal, structure, strength, nickel alloy containing 20 % chromium
DOI: 10.32908/hthp.v54.1901