Participation of gases in the surface formation during self-propagating high-temperature synthesis of porous nickel titanium

The participation of gases in the product surface formation during self-propagating high-temperature synthesis (SHS) of porous nickel titanium (TiNi) alloys has been studied. The alloy-surface structure was analyzed by optical and scanning electron microscopy techniques. A dense surface layer formed under the action of dual-origin gases has been found. It is established that impurity gases involved in heat transfer from the reaction zone to porous alloy structure formation region cause liquation and the appearance of Ti-reach surface melt. It is suggested that chemical inertness of porous alloy samples studied is ensured by a surface layer of fine-grained refractory carbooxynitrides formed as a result of the interaction of the surface melt with impurities of the protective gas atmosphere in the reactor.