Layer Build of Titanium Alloy Complex-Geometry Components for Rocket En-gines

摘要

Liquid rocket engine performance has historically been constrained by the limitations of materials and processes used for component fabrication. Traditional manufacturing processes, such as machining from forgings, are capable of producing reliable components;however, such processes are expensive because of the materials needed,the complexity of designs and the low production quantities typically associated with liquid rocket en-gines. In particular, titanium alloy components,such as shrouded pump impellers with their complex flow passages,are exceedingly expensive to machine. This high machining cost offers considerable room for cost savings by alternative fabrication processes. Recognizing these cost drivers, Pratt & Whitney Rocketdyne has been exploring various additive manufacturing processes as a potential approach to lower costs for low-volume production components. Since additive manufacturing does not require tooling, it allows for complex shapes to be produced directly from CAD files,and it has an economic order quantity of one. If components can be produced with the quality and reproducibility of wrought materials,then additive manufacturing offers the potential of significantly reducing the cost of the next generation of liquid rocket engines. This paper provides the results of initial work performed to fabricate demonstration titanium-6Al-4V alloy impellers from powder metal by a layer-build additive manufacturing process. Evaluations of process results, microstructural examination, and mechanical property testing are presented.