The effect of alloying elements on the rate of ostwald ripening of cementite in steel

Abstract The thermodynamic basis for the effect of ternary additions on the rate of coarsening of cementite in steel is considered in detail and a rate equation for the change in size of individual particles is derived using a crude model to estimate the rate of diffusion. The rate equation can be interpreted analytically for long times yielding a cube law for the rate of coarsening. The rate constant is predicted to be inversely proportional to the alloy content and to (1 − K)2 where K is the distribution coefficient for the element between cementite and ferrite. The theoretical predictions are compared with experimental information and fair agreement is found regarding the rate of coarsening. The agreement is somewhat less satisfactory regarding the rate by which the alloying element is distributed between the two phases.