SHS-aided joining of ceramics with Ta substrate

The possibility of joining ceramic materials with a Ta substrate was explored in the conditions of self-propagating high-temperature synthesis (SHS). The sample used in experiments consisted of Ta foils, Ti + 0,65C pellet, 5Ti + 3Si pellet, and a Ti + 2B igniting tape laid between them. The sample was installed onto a BN base and covered by a chamotte brick (SiO2+ Al2O3) plate with a weight of 3,36 kg placed on top in order to reduce heat sink. Experiments were performed in a closed reactor under 1 atm of Ar. Samples were preheated from the bottom, after which SHS reaction was initiated from the butt. Temperature was monitored with three W/Re thermocouples. Depending on heating rate, temperature gradient along the sample depth had a value of 50–150 deg/mm. The samples obtained exhibited strong joining between Ta foil and Ti + 0,65C and also between the two pellets. The upper foil did not stick to the 5Ti + 3Si pellet, which can be explained by low temperature at the interface (1600 °C). At the Ta–TiC interface, the formation of Ti–Ta and (Ti, Ta)C interlayers was observed. The studies conducted demonstrate the possibility of Ta foil joining with ceramic materials under SHS conditions. Main conditions for this joint are the presence of a liquid phase and Ti + 0,65C combustion temperature matching the Ta substrate melting temperature. The results may be useful for deposition of multilayer functional coatings and functionally graded materials.