Influence of hydrogen on the carburizing of steel in nitrogen-hydrogen mixtures with the addition of pure methane

Conclusions

• 1. An increase in hydrogen partial pressure in an N₂−H₂−CH₄ gaseous mixture promotes an increase in the flow of carbon into the steel as a result of the increase in the diffusion mobility of methane in the Nernst layer.

• 2. The effective diffusion coefficient of carbon in unalloyed austenite in carburzing of steels in nitrogen-hydrogen mixtures with pure methane significantly exceeds the actual diffusion coefficient of it and increases with an increase in the partial pressures of hydrogen and methane.

• 3. In carburizing in an N₂−H₂−CH₄ mixture there is observed the mutual influence of carbon and hydrogen on the kinetics of establishment of equilibrium with the steel with respect to hydrogen, which is probably caused by the existence of C−H complexes.

• 4. Carburizing in nitrogen-hydrogen mixtures with additions of pure methane may be intensified by increasing the partial pressures of methane and hydrogen and also by increasing the frequency of change as the result of the use of higher capacity centrifugal blowers.