APPLICATION OF PROPANE GAS TO PLASMA CARBURIZING

This work was initiated to study the influences of treatment time, pla sma current and plasma voltage on the carbon content of specimens in a plasma carburizing process with propane as a carburizing gas. Low car bon steel foil with a thickness of 0.25 mm was used. The number of car bon atoms dissociated from the premixed propane by heat and plasma ene rgy is about 2.5 times higher than that dissociated from the premixed methane. Thus, for the same treatment time, the carbon content of a sp ecimen when using propane is 2.6 times higher than that in methane. Th e carbon content increases with increasing plasma current, plasma volt age and treatment time. For a 1.9 approximately 7.4 vol% premixed prop ane ratio, however, the carbon content is saturated with 1.75 approxim ately 1.90 mass%. Also, the increasing rate of carbon content in propa ne is higher than that in methane. But the carbon content of saturatio n when using propane is the same as that in methane. The carbon conten t is obtained using an equation containing the treatment time variable , the average obtained plasma voltage, the standard voltage and the pl asma current. Using this equation, the carbon content can be predicted by the treatment parameters prior to the actual plasma carburizing pr ocess.