Fiber-Reinforced Superalloys For Rocket Engines
High pressure turbopumps for advanced reusable liquid propellant rocket engines such as that for the Space Shuttle Main Engine (SSME) require turbine blade materials that operate under extreme conditions of temperature, hydrogen environment, high-cycle fatigue loading, thermal fatigue and thermal shock. Such requirements tax the capabilities of current blade materials. Based on projections of properties for tungsten fiber reinforced superalloy (FRS) composites, it was concluded that FRS turbine blades offer the potential of a several fold increase in life and over a 200 C increase in temperature capability over the current SSME blade material. FRS composites were evaluated with respect to mechanical property requirements for SSME blade applications. Compared to the current blade material, the thermal shock resistance of FRS materials is excellent, two to nine times better, and their thermal fatigue resistance is equal to or higher than the current blade material. FRS materials had excellent low and high-cycle fatigue strengths, and thermal shock-induced surface microcracks had no influence on their fatigue strength. The material also exhibited negligible embrittlement when exposed to a hydrogen environment.
Tungsten wire/FeCrAlY matrix turbine blade fabrication study
The objective was to establish a viable FRS monotape technology base to fabricate a complex, advanced turbine blade. All elements of monotape fabrication were addressed. A new process for incorporation of the matrix, including bi-alloy matrices, was developed. Bonding, cleaning, cutting, sizing, and forming parameters were established. These monotapes were then used to fabricate a 48 ply solid JT9D-7F 1st stage turbine blade. Core technology was then developed and first a 12 ply and then a 7 ply shell hollow airfoil was fabricated. As the fabrication technology advanced, additional airfoils incorporated further elements of sophistication, by introducing in sequence bonded root blocks, cross-plying, bi-metallic matrix, tip cap, trailing edge slots, and impingement inserts.
Deformation of composite material during alternate heating and cooling. Report 1
The structural and dimensional changes in composite materials of EI435 alloy sheets reinforced with W or Mo wires during thermal cycling were investigated. It was found that during thermocycling irreversible deformation occurs in a fibrous composite due to the difference between the coefficients of expansion of the material of the fiber and base. In particular, this difference causes a greater deformation of the composite with tungsten fiber than with molybdenum. With an increase of the upper temperature of the cycle and range of temperature variations the dimensional instability of the composite increases. During thermocycling the Nichrome base experiences alternating plastic deformation. However, recrystallization processes leading to weakening occur in Nichrome during high-temperature heating. (JRD)