Chemical vapor deposition of thoriated tungsten protective cups Page: 28 of 45
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4. PRODUCT EVALUATION
The thoria content was calculated from the thorium analysis by emission spectrography.
Metallic impurities were also determined by emission spectrography.
Carbon was determined bycombustion techniques using a Leco 50-second analyzer.
Hydrogen content was determined by vacuum extraction techniques at 12000C; and oxygen,
by vacuum fusion in graphite oxidized with copper oxide and analyzed as CO2. Nitrogen
was determined by the difference of total gas volume minus the oxygen and hydrogen. Four
typical analyses are shown in Table 1.
The as-deposited parts were a dull matte gray on the outside surfaces deposited last
and highly reflective and smooth on the inside surfaces deposited first. An occasional nodule
was present on the outside as shown in Figure 11. The nodules were visible and were
eliminated during the grinding operation. Water immersion densities varied from 19.05 to
19. 15 gm/cc; this is estimated to be 99.9 percent of theoretical density.
The 20000C recrystallized material was found to remain stable and equiaxed when
heated to 22000C and held for three hours. Material heat treated to 23000C for five hours
showed only a 10 percent increase in grain size. The material showed no grain growth when
heated 5 times to 22000C for a total holding time of five hours at this temperature. The grain
growth blocking ability of the super fine CVD thoria dispersion was dramatically illustrated
during the early phases of this program when the thoriated tungsten was being plated on pure
PM tungsten mandrels. This super fine equiaxed plated thoriated tungsten after a 20000C heat
treatment is shown in Figure 12 on the large grain pure tungsten mandrel.
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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/m1/28/: accessed March 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.