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U.S. Department of Energy
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Consumable arc-melting, extruding, and rolling process for iridium sheet

Technical Report ·
DOI:https://doi.org/10.2172/5702073· OSTI ID:5702073
An iridium alloy has been used as cladding for the /sup 238/PuO/sub 2/ fuel in radioisotope thermoelectric generators (RTGs) for recent interplanetary spacecraft such as Voyagers 1 and 2 and will be used for the Galileo and Ulysses spacecraft. The iridium alloy sheet for the fuel cladding used on these missions was fabricated by hot and cold rolling of arc-melted and drop-cast 0.5-kg ingots. Upon completion of production for these spacecraft, an opportunity was taken to conduct process improvement studies that would increase processing batch sizes, develop a more uniform product, decrease rejections due to internal delaminations and surface defects, and reduce costs. The studies to scale up and improve the fabrication process are described. In the new process, iridium is electron beam melted, alloyed by arc melting, and then consumable arc melted to form a cylindrical ingot of approximately 7 kg for extrusion. The ingot is extruded to sheet bar and hot and cold rooled into sheet. Sheet evaluated from the first two ingots showed 100% acceptance with no defects on inspection. An improved uniformity of microstructure was obtained, and chemistry was controlled within specification limits.
Research Organization:
Oak Ridge National Lab., TN (USA)
DOE Contract Number:
AC05-84OR21400
OSTI ID:
5702073
Report Number(s):
ORNL-6270; ON: DE86013524
Country of Publication:
United States
Language:
English