Space propulsion components based on Gamma TiAl based alloys by combustion synthesis + compation route

Intermetallic compounds of Ti-Al system and alloys based on such compounds are materials of rapidly growing technological importance. Such alloys have relatively high yield strength at elevated temperatures, advanced creep characteristics, and good oxidation/corrosion resistance. Several methods have been utilized in the synthesis of Ti-Al intermetallic compounds. These include conventional melting and casting processes and powder metallurgical techniques. The latter include mechanical alloying, plasma-rotating electrode processes, and inert gas atomization (which all have been recently proposed as methods of preparing titanium aluminides in powder form). In all of these approaches, a subsequent step is required to obtain products with the desired density and shape. Over past years, a search for new synthetic approaches to intermetallides (including titanium aluminide and related materials) has led, among others, also to the technique of Self-propagating High-temperature Synthesis (SHS). This is an alternative powder technique for the production of intermetallics. This process requires a large exothermic enthalpy of formation for the desired intermetallic compound. Because of a low caloricity of reaction between Ti and Al, the classical SHS reaction between these metals can be initiated only upon preliminary heating of a green mixture. For this reason, the best results in synthesis of titanium aluminides were attained by combining SHS with some kinds of internal influence, such as heating up to the ignition temperature, mechanoactivation of green mixture, SHS followed by hot isostaic pressing (HIP), SHS in electromagnetic field, etc. This work studied and optimized the SHS-densification route for the synthesis of Gamma TiAl based Intermetallic (GE alloy: 48Ti-48Al-2Cr-Nb) using two different combustion modes: forced SHS + compaction and thermal explosion + compaction. A complete metallurgical characterization of the product was done: phase analysis, density, chemical analysis, microstructure and mechanical properties (tensile strength). The developed material and manufacturing process is a potential candidate to be used as turbine blades for ARIANNE VULCANE engine.