Chemical vapor deposition of thoriated tungsten protective cups Page: 31 of 45
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It had been reported that some pure tungsten parts fabricated from CVD tungsten
tubing exhibited various degrees of diametral growth or swelling after a high temperature heat '
treatment. Metallographic analyses revealed appreciable porosity in the grain boundaries of
the pure tungsten as shown in Figure 13. It was determined that this dimensional growth was '
related to the fluoride content of the material. Above 20 ppm fluorine, diametral growth
was reported which increased with increasing fluorine content. Dimensional measurements of
the OD, ID, length, and bottom flat wall thickness were made on 5 finish-machined CVD
thoriated tungsten cups before and after a 2200 C heat treatment for one hour. No change in '
the dimensions was detected, and no porosity was observed metal lographically.
.- i . U - o =. , - I
Figure 13. Porosity in 22000C Stress Relieved Thoriated Tungsten
( .~ < 7.
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Blay, J.S. Chemical vapor deposition of thoriated tungsten protective cups, report, January 1, 1968; Pittsburgh, Pennsylvania. (https://digital.library.unt.edu/ark:/67531/metadc1026564/m1/31/: accessed March 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.