NICKEL-BASED SUPERALLOYS FOR SINGLE-CRYST AL TURBINE-BLADES

The development of the single crystal casting technology has authorise d the design of new nickel based superalloys for turbine blades suitab le for this manufacturing process. The absence of grain boundaries, th e preferential (001) growth orientation and the microstructural homoge neity give to these alloys a set of properties significantly higher th an for the conventionally cast superalloys. Some alloys were developed at ONERA and are now used in the high-temperature turbines of the fre nch engine manufacturers SNECMA and TURBOMECA. Other single crystal su peralloys were also developed for applications in land-based industria l gas turbines and in rocket engines. The studies of the relationships between the microstructure and the mechanical properties of these all oys have revealed some very significant effects of the solidification parameters, of the size of the strengthening gamma' phase precipitates and of the cristallographic orientation.