Transient and steady-state erosion of in-situ reinforced silicon nitride

Relative to most other materials silicon nitride is very erosion resistant. However, the resulting surface flaws degrade strength - a serious concern for component designers. AlliedSignal Ceramic Components GS-44 in-situ reinforced silicon nitride was eroded in a slinger apparatus. Both transient (extremely low level) and steady-state erosion regimes were investigated. Alumina particles with effective average diameters of 140 Jim and 63 {mu}m were used at velocities of 50 m/s, 100 m/s, and 138 m/s. Biaxial tensile strength was measured. Strength decreased by about 15% after a very small erodent dosage and then remained virtually constant with further erosion. In-situ reinforcement produces R-curve behavior in which the fracture toughness increases with crack size. The effect of this is quite dramatic with strength loss being significantly less than expected for a normal silicon nitride with constant fracture toughness

REPORT ON CORE AND BLANKET DESIGN AND TECHNOLOGY

A summary is presented of the information developed to date on the core and blanket fuel materials for the Fermi Fast Breeder Reactor. The specification requiremente for the core and blanket subassembly fabrication are discussed, along with special materials accountability and shipping problems. (W.L.H.