The dissertation is devoted to solving an important scientific and technical problem of establishing the regularity of the reaction sintering of metal compositions that contain
non-interacting compounds, and the development of heat-resisting dispersion-hardened nichrome and the technology of obtaining products of them.
For the first time, thermokinetic models of irreversible processes initiated by contact melting of components based on theoretical analysis taking into account collective interactions in the Ni-Al and Ti-Al reaction systems of and the representation of the flow reactor were constructed.
Different kinds of thermokinetic trajectories of interaction process development were established. It was revealed that thermal radiation plays a particularly important role in the transmission of energy, which made it possible to effectively apply a direct thermal analysis for reacting mixtures.
The experimental thermokinetics of reacting systems (Ni-Al, Ti-Al, Ni-Ti, Ni-Sn, Cu-Ti, Cu-Sn), which are the basis of industrial alloys were studied. It is shown that the behavior of these systems is characterized by a complex non-monotonic change in temperature and occurs in the regimes of thermal explosion and self-propagating high-temperature synthesis.
Such thermokinetic behavior confirms the synergistic nature of the reaction interaction, as was shown in the simulation of these processes. This became the basis of the experimental study of the regularities of sintering.
The analysis of shrinkage curves and the comparison of the relative density of raw and sintered powder blanks from metal mixtures showed that the reaction sintering process is initiated (along) with the appearance of a peritectic or eutectic fluid.
It has been found that samples of almost all investigated powder double systems with a relative density of more than 80% give a significant increase in volume during the sintering process.
However, the introduction of a certain amount of chemically inert impurities localizes the reaction processes throughout the volume of the presses and prevents small pores from being coagulated into cavities.
This contributes to the slowing of the growth of the raw powder blanks and, eventually, leads to significant shrinkage. Small pores in each small local volume take part in the mass transfer and activate the shrinkage process in the late stages of sintering. Heat-resistant dispersion-hardened alloys based on nichrome with an aluminum content of up to 6% and yttrium oxide (Y2O3) up to 1,5% were developed using reaction sintering, as well as developed technologies for producing products from them, in particular, the modes of rolling thick billets and thin sheets with a thickness of up to 0.1 mm. Solder compositions and thermo-reaction soldering conditions for thick blanks were developed, which are used in the manufacture of the air intake of a hypersonic aircraft. Soldering regimes and other technological operations for the manufacture of heat-protective panels for hypersonic and reusable spacecraft were also worked out. The obtained physical-mechanical and functional properties of dispersion-strengthened nichromes provide in aggregate the necessary performance of reusable space systems at the temperatures up to 1200 0C.
Key words: synergetic model, thermokinetics, reacting sintering, self-propagating high-temperature synthesis, thermal explosion, intermetallics, dispersed-strengthened nichroms, heat resistance, refractory, fatigue strength.
