EFFECT OF CASTING GEOMETRY ON MECHANICAL PROPERTIES OF TWO NICKEL-BASE SUPERALLOYS

摘要

An investigation was performed to determine mechanical properties of two rhenium-free modi¬fications of alloy TRW-NASA VIA to evaluate the suitability of the alloy for use in a small integrally cast turbine rotor. The two alloys (TRW-R and TRW-S), which differ from each other by having small variations in carbon and in reactive and refractory metals, were initially developed using stress rupture properties of specimens machined from solid gas turbine blades. Properties in this investigation were determined from cast-to-size bars and bars cut from 3.8 by 7.6 by 17.8 cm blocks. Specimens machined from blocks usually had inferior tensile strength and always had markedly poorer rupture lives than cast-to-size bars. At about 1000° C the cast-to-size bars had shorter rupture lives than those machined from blades. Alloy R generally had better properties than alloy S in the conditions evaluated. The results show the importance of casting geometry on mechanical properties of nickel-base superalloys and suggest that the geometry of a component be simulated when developing alloys for that component.