Department of Welding, Material Forming and Allied Processes, Togliatti State University, Togliatti, Russia:

A. I. Kovtunov, Professor, Doctor of Technical Sciences
Yu. Yu. Khokhlov, Head of Laboratory, e-mail: y.y.khokhlov@rambler.ru
P. N. Selyanin, Lecturer

Titanium aluminide- and nickel aluminide-based alloys are distinguished by a unique set of mechanical and performance properties and can be successfully used as heat-resistant coatings on products made of titanium, nickel and their alloys. The simplest, most productive and versatile method of coating formation is liquid-phase dipping into aluminum melt followed by diffusion annealing. During dipping, an aluminum layer is formed on the surface of the products, which transforms into a layer of aluminides during high-temperature soaking. This paper describes a study that looked at the formation of titanium aluminide- and nickel aluminide-based coatings on titanium and nickel by liquidphase aluminizing followed by diffusion annealing. To achieve adhesive bonding between aluminum and nickel and titanium, the surfaces of the latter were pre-activated with a KF – AlF₃ flux of eutectic concentration (Nocoloc flux). The paper demonstrates the effect of high-temperature soaking on the kinetics of phase and structural transformations in titanium aluminide- and nickel aluminide-based coatings. The study helped establish how the time of high-temperature soaking of aluminized samples at 950 ^оС influences the weight and the oxidation rate of titanium and nickel samples with aluminide coatings. The aluminized nickel samples were found to have higher heat resistance than the aluminized titanium ones. The nickel aluminide-coated nickel samples tend to change their weight and oxidation rate 20 times less than the aluminized titanium samples.

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