THERMODYNAMIC CALCULATION AND PRECIPITATION OF CARBIDES IN THE FE-CR-NI-C SYSTEM

A series of calculated isothermal and vertical sections of the Fe-Cr-N i-C phase diagrams have been presented, and some of them are compared with experimental observations available. These diagrams can provide a n important basis for heat treatments and for further developments of stainless steels. Effects of the alloying elements on the phase relati ons and on the precipitation of the Cr-rich carbide (M23C6) have been examined by means of thermodynamic calculation. After introducing prop er assumptions, the critical condition for M23C6 precipitation from th e austenite were calculated from the thermodynamic properties of the F e-Cr-Ni-C system, and such conditions predict the loss of corrosion re sistance of austenitic stainless steels.