M. Kawakami and N. Ogasawara
The effects of the various factors in carburizing conditions on the carburization of Th-W filament were investigated by the method of ``Hydrogen Carburization'' heated in hydrogen gas flow mixed with carburizing gas such as benzene. To know the degree of carburization, the measurements of the cold electric resistance and the microscopic investigations were carried out. The amount of carbon diffusing into W in hydrogen atmosphere increases parabolically with elapse of time at constant temperature, but generally, the degree of carburization obtained by the microscopic study is at variance with the one obtained by measuring cold electric resistance. Under the influence of the convection in the carburizing atmosphere, the thickness of the carbide layer on the filament is not uniform. The effect of the concentration of benzene is smaller than the one of the speed of hydrogen gas flow. From the results above mentioned, the filaments with the uniform thickness of carbide layer were obtained by us.
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