Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Special medium during sintering
Patent
1985-04-25
1986-04-01
Lechert, Jr., Stephen J.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Special medium during sintering
419 59, 419 60, 75239, 75240, 423439, 423440, 501 87, 501 94, B22F 900
Patent
active
045797137
ABSTRACT:
The present invention provides a method for controlling the carbon content of dewaxed carbide preforms in a carbon containing furnace. The method includes the steps of placing the preforms in a carbon containing furnace and then heating the furnace to a predetermined temperature range between 800 and 1100 degrees Centigrade. At that temperature, a mixture of methane and hydrogen is introduced into the furnace chamber such that the amount of methane is between 10 and 90 percent of the amount of methane present at equilibrium for the reaction C.sub.solid +2H.sub.2 .revreaction.CH.sub.4. The furnace chamber is maintained at its temperature for a first time period sufficient for the chemical reaction XC+2H2.revreaction.X+CH.sub.4 (where X is selected from the group of W, Ti, Ta, Hf and No) substantially reaches equilibrium but shorter than the a second time period in which the reaction C.sub.solid +2H2.revreaction.CH.sub.4 reaches equilibrium or the resident time of the gaseous mixture is less than the second time period.
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patent: 4153485 (1979-05-01), Ogata et al.
patent: 4190439 (1980-02-01), Gortsema
patent: 4225344 (1980-09-01), Fujimori et al.
patent: 4436696 (1984-03-01), Buck et al.
Lechert Jr. Stephen J.
Ultra-Temp Corporation
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