Experimental and theoretical studies of gas consumption in the gas carburizing process

Chemical Potentials and Activities of Nitrogen and Carbon Imposed by Gaseous Nitriding and Carburising Atmospheres

“…1s For a discussion of these observations, see Refs. 18-20. In calculations involving nitrocarburising atmospheres, it has hitherto been assumed that the water gas reaction (see Table 1) is (practically) in equilibrium (sometimes, in particular with new, catalytically less active furnace systems, this may not be the case 13 ). On this basis the values for the nitrogen and carbon activities in the surface layer can be calculated if local equilibrium at the surface can be assumed.…”

“…Equation (13) requires only that the reference state of the nitrogen dissolved in the (iron) matrix is equated with the reference state of nitrogen gas. The reference state is now selected: nitrogen gas at 1 atm at the temperature concerned.…”

Thermodynamics and kinetics of solution nitriding

“…The flux of N-absorption, J N abs , can be expressed by Eq. (2) [9]. The diffusion flux from the surface into the specimen, J N diff , is given by Fick's first law expressed as Eq.…”

Measurement of the mass transfer coefficient at workpiece surfaces in heat treatment furnaces

“…Edenhofer (1995) and Sommer (1987) have calculated the carbon transfer coefficient from the gas composition (CO and H 2 ) according to the carburizing reaction in the H 2 /CH 4 /H 2 O-CO/CO 2 -N 2 system reported by Neumann and Wyss (1970). Several expressions for the mass transfer coefficient have been reported (Collin et al, 1972;Mikhailov, 1978;Chernov et al, 1980;Gyulikhandanov et al, 1981;Sproge and Agren, 1988;Andreev and Chernyakhovskii, 1989;Andryushechkin et al, 1989;Gao et al, 2002;Gupta et al, 2002;Gao et al, 2004), although, * Corresponding author.…”