Influence of some bulk and surface processes on strengthening and wear resistance under ion implantation

Abstract

A theoretical study has been made of some bulk and subsurface processes accompanying the ion implantation of mobile impurities with relatively high doses under technical vacuum conditions in order to modify the material properties, as well as of processes occurring at wear of bombarded surfaces. A mathematical model has been formulated for mobile impurity implantation in a sample containing a surface layer (“film”) with properties differing from the “base” and with mobile boundaries (ion-enhanced oxidation; disorder, involving amorphization; growth of carbon contaminations; bombardment of surface-coated targets; film condensation with simultaneous ion bombardment, etc). Numerical calculations and a comparison with experiment have been made for, primarily, ion nitriding of iron and steels. The possibility of impurity migration into the vacuum with kinetics of the first and second order has been taken into account; a general expression for the maximum dose for a homogeneous target and one of several possible versions for an inhomogeneous one has been obtained. The possible influence of subsurface layer “contaminations” upon the maximum dose of the mobile impurity has been analyzed in detail. A model for wear induced “ tribodiffusion” of the implanted impurity is offered. The possibilities for impurity redistribution depending on initial conditions and test regimes have been analyzed.