PROCESSING AND MICROSTRUCTURE OF INVESTMENT-CASTING TURBINE BLADE NITAC IN-SITU COMPOSITES

Directional solidification was used to produce turbine blades by the B ridgman method. NITAC alloys with various carbon contents were investi gated; the optimum range was found to be 0.40 to 0.48%. Within this ra nge, except for the blade locking piece edges, the blade structure con sisted predominantly of aligned eutectics. The in-situ eutectics were aligned tantalum fibers embedded in a gamma-phase matrix. The blades w ere produced using an alloy displacement rate of 1.86 x 10(-6) m/s. Me asurements of fiber spacings along the blade height indicated that the rate of displacement of the solidification front exhibited some varia tions. These variations were closely associated with dimensional chang es in the turbine blade cross sections.