Combustion in layered Ni + Al and Ti + Al + C powder mixtures

This study is devoted to the technology of producing cermet coatings using self-propagating high-temperature synthesis (SHS). The importance of the study is related to the universal usage of flat electric heaters and protective coatings intended for various purposes. A technique is proposed to obtain electrically conductive coatings by the SHS in powdered Ni + Al and Ti + Al + C mixtures. Specific features of the evolution of the autowave SHS in these mixtures are investigated. The mixture is deposited on a ceramic base as a layer of a suspension in isopropyl alcohol (0.2–2.0) × 10–3 m in thickness using a stencil. The effect of the thickness of the powdered mixture layer on the velocity of front propagation and maximum temperature is studied. These parameters are shown to naturally increase with an increase in thickness. The coating based on the Ni + Al mixture is found to consist of NiAl and Ni3Al intermetallic compounds, while that based on Ti + Al + C is found to consist of TiC and MAX phases of Ti2AlC and Ti3AlC2. The coating based on intermetallic compounds consists of rounded particles that are fused together and contains NiAl and Ni3Al phases. The coatings obtained from the Ti + Al + C mixture contain needle-shaped crystals of MAX phases and interspersed rounded particles of titanium carbide. The content of the NiAl and Ti2ALC target phases increases with the increasing layer thickness. Coatings based on NiAl, Ni3Al, and Ti2AlC, Ti3AlC2 heat-resistant phases (0.2–1.2) × 10–3 m in thickness with a specific electrical resistance of 0.1–0.6 μOhm m are obtained.