Development of Titanium Alloys for Cast Gas Turbine Engine Components.

摘要

A two phase problem definition program was conducted to determine the need for development of titanium alloys for casting high speed rotating components, e.g.,compressor impellers. (U) Four commercially available alloys,Ti-6A1-4V, 5621S, IM1700and Beta III were appraised with respect to castability and end-item casting performance potential. Phase 1screening studies involved casting a stylized shape in refractory metal face coated ceramic shell molds by skull melting and bottom pour induction melting. Castings were subjected to non-destructive inspection,and after appropriate heat treatment,to tensile,high cycle reverse bending fatigue,ballistic impact and metallographic tests. On the basis of tensile and fatigue test data,Ti-6A1-4V alloy was considered the optimum alloy for high speed rotating component application. This alloy was further evaluated in Phase 2via low cycle fatigue tests of skull melted stylized castings. In addition,tensile properties and destructive spin test behavior were determined for skull melted compressor impeller castings of T63engine configuration. Ceramic molds were instrumented in an attempt to correlate cooling curves with microstructure and mechanical properties. It was concluded that castability of the alloys evaluated is essentially identical,and that there is no apparent need to develop new alloys for the purpose of producing complex titanium castings for visualized high speed rotating component applications. (Author)