N. V. Sachkova

SHS joining in the Ti-Si-C system: Structure of transition layer

Explored was SHS joining in sandwiches of (Ti + yC)/(Ti + xSi) powder compacts, and the transition layers were characterized by SEM, EDS, XRD, and optical microscopy. The transition layers were found to contain titanium carbides, titanium silicides, and Ti3SiC2. The results suggest that, in the systems under study, the weld seam is formed due to convective interpenetration of melted combustion products.

Simultaneous synthesis and joining of a Ni-Al-Based layer to a Mo foil by SHS

Explored was the simultaneous synthesis and joining of a Ni-Al-based layer to a Mo foil by SHS in Al-Ni and Al-NiO mixtures. It has been demonstrated that variation in reaction conditions can be used as a tool for regulating a thickness of a deposited coating and its phase composition. Under some certain conditions, a Mo foil can be fully consumed in the reaction with combustion products to yield a product of desired composition.

Deposition of composite metallic coating onto Al through mechanical impregnation followed by thermal treatment

Investigated were the processes taking place in thermally treated Al plates mechanically impregnated with a mixture of metallic particles. Vibratory treatment of an Al surface in a powder mixture of metals was found to result in destruction of the surface Al2O3 film and formation of extensive physical contacts between the Al matrix and the metallic particles mechanically impregnated into the near-surface layer of Al. Subsequent thermal treatment was then used to launch chemical reaction yielding intermetallides within the impregnated layer. Performing SHS reactions yielding melted intermetallides in the coatings (or pellets) deposited (or placed) onto the surface of thus treated Al plates, one can obtain strong weld joining between solidified SHS products and Al. This approach can also be used for deposition of coatings with a desired composition onto Al substrates.

Interaction of SHS-produced melt with a Ti surface in microgravity conditions

In this paper, we report on the SHS reaction 3NiO + 5Al → 3NiAl + Al2O3 carried out aboard International Space Station (Flight Mission 18) with special emphasis on the effect of the composition of reaction products on the composition of coatings formed on a Ti substrate.

SHS welding by thermal explosion: Ti-Ti and Ti-NiAl joints

Ti-Ti and Ti-NiAl joints were obtained by thermal explosion in the Ti-Ni-Al system. The bulk Ti samples used as a substrate were preliminary coated with mechanically activated Ni-Al powders by the method of mechanical cold working. The Ti-Ti joints were found to have the NixAlyTiz composition and lower porosity compared to that of Ti-NiAl joints.

SHS joining of intermetallics with metallic substrates

SHS-produced Ti-Al and Ni-Al intermetallics have been successfully joined to mechanically activated Ti and Ni substrates by SHS reactions under moderate pressure.

High-porosity TiAl foam by volume combustion synthesis

Preparation of high-porous TiAl foam by volume combustion synthesis (VCS) was investigated. It is shown that the optimum conditions for pore formation are attained when gas evolution coincides in time with melting of the reactants.

Peculiar features of interaction of intermetallic compounds based on Ti-Al, Ni-Al with Ti and Ni metallic substrates in the mode of self-propagating high-temperature synthesis

Self-propagating high-temperature synthesis (SHS) is applied for production of titanium and nickel aluminides with various operating properties, which is important for deformation of items in the SHS mode and application of coatings on intermetallic and metallic substrates (for instance, Ti, Ni, Al, and others). The possibilities of application of intermetallic coatings and joining (welding) of such materials in the SHS mode are studied.

SHS joining by thermal explosion in (Ni + Al)/Nb/(Ni + Al + Nb) sandwiches: Microstructure of transition zone

Thermal explosion in (Ni + Al)/Nb/(Ni + Al + Nb) sandwiches was found to results in formation of (a) NiAlNb composite containing NiAl, NiAlNb, and trace amounts of Nb5Ni and (b) good joining with a transition zone.

Load-assisted SHS joining of NiAl to Ni

The joining of NiAl to Ni substrates was carried out through load-assisted SHS reaction. The process of bonding between liquid reaction products and Ni substrate was studied. A transition layer at the NiAl/Ni interface was found to form mainly due to the diffusion of Al. The components of Ni-rich phases were found to undergo diffusion into the reaction products. Microstructural observations showed the formation of excellent bonding at the NiAl/Ni interface.