Long-term oxidation resistance of titanium materials for hybrid fuel cells

Abstract

Hybrid SOFC-MGT systems, which combine a solid oxide fuel cell (SOFC) and a gas microturbine (MGT) are capable of generating clean energy with high efficiency. Compared to large turbines in aviation and other areas of mechanical engineering and energetics, the requirements for mechanical properties of MGT materials in SOFC may be less strong, but one of the most important is resistance to long-term oxidation. For SOFC materials it is considered that oxidation resistance test duration must be not less than 1000 h. In addition, today there is a tendency to developing average-temperature (550—650 oC) SOFC modifications. Physical and mechanical properties, the long-term (1000 hours) oxidation resistance at 600 °C in particular, for a number of titanium alloys and composites depending on their chemical and phase composition and production method have been studied. These materials are promising for gas microturbines of a hybrid system “solid oxide fuel cell — gas turbine”. Cast, thermally deformed (forging, rolling), and heat-treated titanium alloys and also sintered and hot-pressed titanium composites have been investigated. They were compared to the most widely used in mechanical engineering and other industries Ti—6Al—4V alloy. It was shown that materials of the Ti—Al—X system (X = C, Nb, Mo) based on titanium MAX phases with nanolaminate microstructure have an advantage. At the same time, alloys based on titanium aluminides γ-TiAl / α2-Ti3Al in the cast state have the highest long-term heat resistance, as well as the best complex of physical and mechanical characteristics among the studied materials. Keywords: titanium alloys, chemical and phase composition, mechanical properties, long - term heat resistance, fuel cell.