A model of the thermochemical polishing of CVD diamond films on transition metals with emphasis on steel

A model of thermochemical polishing, namely the conversion of diamond into non-diamond carbon at elevated temperatures and the subsequent dissolution of the non-diamond carbon into a transition metal polishing plate is investigated. Equations of the conversion rate k1, the dissolution rate k2, the diffusion constant of carbon in steel D, and the concentration profile of carbon in steel N(x,t)are derived. The rate constants are calculated for four diamond films polished at varying temperatures. Elastic recoil detection analysis (ERDA) measured carbon depth profiles in steel agree well with theoretical calculations. However, the calculated value of D = 1,16 x 10-14 cm2/s is far below the value of D = 1,19 x 10-7 cm2/s for gamma-iron. The discrepancy between the two values is related to oxygen-enhanced segregation of carbon in the near surface region of steel and to the incorporation of elements which act as trap centers of carbon in steel.