Change of Secondary-Carbides' Nanostate in 14.5% Cr Cast Iron at High-Temperature Heating

The evaluation of changes of the state (amount, shape, size, distribution) of dispersed secondary carbides precipitated from primary austenite of complex-alloyed high-chromium cast iron during long-term destabilizing heating in the temperature range from 800 to 1050 C is fulfilled. As revealed, the rate of precipitation process reaches maximum at 950 C; that is the consequence of competing influence of two factors the rate of diffusion of atoms of alloying elements and the solubility of carbon in austenite. The influence of soaking time on amount, size of the secondary carbides, and the ratio of the carbide inclusions of various shapes is determined. As shown, the nanosized state of carbides is retained only at temperatures close to the critical point A(1); at higher temperatures, quite rapid coarsening of carbides occurs that ending after prolonged soaking by their coagulation and even by reversed dissolving (at 1050 degrees C).