DIFFUSION WELDING IN VACUUM THIN SHEET OF NICKEL ALLOY
Falchenko Yurii, Paton Electric Welding Institute of NAS of Ukraine (11 Bozhenko Str., 03680 Kiev, Ukraine)
Petrushynets Lidiia, Paton Electric Welding Institute of NAS of Ukraine (11 Bozhenko Str., 03680 Kiev, Ukraine)
Ustinov Anatolii, Paton Electric Welding Institute of NAS of Ukraine (11 Bozhenko Str., 03680 Kiev, Ukraine)
Melnichenko Tatiana , Paton Electric Welding Institute of NAS of Ukraine (11 Bozhenko Str., 03680 Kiev, Ukraine)
Novomlinets Oleg, Chernihiv National University of Technology (95 Shevchenka Str., 14027 Chernihiv, Ukraine)
Gusarova Irina, M. K. Yangel Yuzhnoye State Design Office (3 Krivorozhskaya Str., 49008 Dnipro, Ukraine).
Urgency of the research. Nickel alloys are widely applied in manufacture of gas turbines, in space vehicles, rocket engines, etc.
Target setting. Complexity of producing nickel alloy joints by diffusion welding consists in presence of a thermally-stable oxide layer on their surfaces and low ductility of this group of materials.
Actual scientific researches and issues analysis. Performed analysis showed that combination of high parameters of diffusion welding with application of interlayers allows producing sound joints ofhigh-temperature nickel alloys.
Uninvestigated parts of general matters defining. Described technologies are designed for joining massive items and are not suitable for thin foils.
The research objective. Study the possibility of producing welded joints of foils of powdered nickel alloys.
The statement of basic materials. Vacuum diffusion welding of nickel foils of thickness δ = 25 μm was performed.
In welding without interlayers the defectiveness of the joint zone is reduced with increase of welding temperature. However, even at Тw = 1200 °С a string of oxides and pores in the joint zone is preserved.
Cu, Co, Ni interlayers were used for activation of diffusion processes. Application of interlayers with Co leads to formation of chemical inhomogeneity in the joint zone and development of considerable porosity in the butt. Application of Ni interlayers leads to formation of a zone with a low chromium content in the butt zone. Microstructure of this zone is similar to that of the initial alloy, but is less defective. Welding with Cu interlayer ensures a uniform nature of distribution of elements in the butt and minimum number of defects.
Average strength of samples produced with Ni interlayer is equal to σв = 108 MPa, with Co – σв = 233 MPa, and with Cu – σв = 317 MPa.
Conclusions. Conditions for producing joints of thin foils of a nickel alloy by vacuum diffusion welding at application of Cu, Co, Ni interlayers were studied. It is shown that foils produced by thetechnology of electron beam evaporation and condensation in vacuum promote intensification of diffusion processes in the butt and ensure formation of welded joints.
diffusion welding in vacuum, Ni-Cr, multilayer foil, microstructure, microindentation
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