Analysis of nucleation of carbide (Cr, Fe)7C3 in the Cr3C2/Fe-CrNiBSi composite coating

The nucleation of carbide (Cr, Fe)7C3 on the Cr3C2 particle in the Cr3C2/Fe-CrNiBSi composite coating was studied. It was found that there were a great deal of craters on the surface of half-dissolved Cr3C2 particle, and plenty of carbide (Cr, Fe)7C3 buds nucleated and grown out there. The analysis of crystallographic relationship shows that the lattice misfit between 013Cr3C2 and 101−0CrFe7C3 is 8.66%, indicating Cr3C2 can efficiently act as the heterogeneous nuclei of (Cr, Fe)7C3. The thermodynamic analysis indicates that the Cr3C2 surface craters can promote forming (Cr, Fe)7C3 nucleus, and the size of (Cr, Fe)7C3 buds grow on the craters was influenced by the shape factor x = R/rc (R: crater concave radius and rc: critical (Cr, Fe)7C3 nucleus radius) and the contact angle θ between (Cr, Fe)7C3 embryo and Cr3C2 crater surface.