The thin, inner iridium layer provides high-temperature oxidation protection for the remainder of the materials system. A thicker, structural layer of rhenium metal with a melting point of 3,180 degrees Celsius is then deposited by CVD over the iridium. Additional outer layers to facilitate joining of the structure to other components and to provide desired high-temperature emissivity characteristics are finally deposited onto the outer surface. The mandrel is removed using a proprietary process that does not adversely affect the iridium liner. The overall structure has a net-shape inner diameter.
External surfaces are ground when needed to meet dimensional or other requirements.
This immediate application is only one of the potential commercial and government applications of this SBIR-initiated technology. The possibility of enhancing the performance of Space Shuttle maneuvering thrusters by use of this technology is currently under study. And the inside-out fabrication method is not limited to thrusters. In some cases, the technology is being extended to the development of refractory metal lined, ceramic or composite overwrapped structures that maintain the benefits of long life at high temperature while providing reduced weight through the use of lightweight composites. For more information, contact Dr. Steve Schneider at Glenn Research Center.