KINETIC-MODEL OF MASS-TRANSFER THROUGH GAS-LIQUID INTERFACE IN LASER-SURFACE ALLOYING

In laser surface alloying from gas atmosphere neither surface concentr ation nor the flux of the alloying elements are known beforehand, They should be determined from the combined solution of heat and mass tran sfer equations with an account for the kinetics of interaction of a ga s with a melt. Kinetic theory description of mass transfer through the gas-liquid interface is applied to the problem of laser surface alloy ing of iron from the atmosphere of molecular nitrogen. The activation nature of gas molecules dissociation at the surface is considered, It is shown that under pulsed-periodic laser action the concentration pro files of the alloying element have maxima situated close to the surfac e of the metal. The efficiency of surface alloying increases steeply u nder laser-plasma conditions which results in the formation of highly supersaturated gas solutions in the metal.