Publication details
ACTIVITIES OF INTERSTITIAL ELEMENTS INSIDE HEAT –RESISTANT STEELS, FILLER ALLOYS, AND WELDING ELECTRODE MATERIALS
| Authors | |
|---|---|
| Year of publication | 2006 |
| Type | Article in Proceedings |
| Conference | E-MRS 2006 Fall Meeting |
| MU Faculty or unit | |
| Citation | |
| Field | Physical chemistry and theoretical chemistry |
| Keywords | DICTRA;ThernoCalc;phase;diffusion;CALPHAD |
| Description | The iron-based materials are the most popular engineering alloys for industrial use. Very successful materials are the steels. The element bases of the modern steels are very complex. They are usually alloyed with the other transitions metals (Me: Cr, Mo, V, Nb, W,...) and interstitial elements (i.e. carbon and also recently nitrogen) in order to improve the mechanical and corrosion resistance properties. The steels are very important material also for high temperature engineering applications. The modern high-resistant steels (P91, P92, E911, VM12) [05Van] reached the high strength up to 100Mpa at 575-650oC. It is no rare case that these modern steels have to be weld joined with other steels, which have different compositions (T/P22, T/P23, T/P24,...). In the case of dissimilar weld joints [04Bha], the mechanical properties usually take a turn for the worse because the phase microstructure changes caused by long-time diffusion during exploitation at high temperature [01Sir]. The most important diffusing elements are the carbon and the nitrogen for the steels. The diffusion flux of these light elements (i.e. C, N) is in close relation to their thermodynamic activities. The heat-resistant steels, filler alloys, and welding electrodes can be thermodynamically treated as Fe-Me-N-C based closed systems. Phase diagrams and temperature dependent carbon and nitrogen activities of the steels can be calculated using CALPHAD approach [98Sau], which is based on semiempirical thermodynamic model of the multicomponent/multiphase system and thermodynamic condition of phase equilibrium. The activities of the carbon and nitrogen can be thus obtained. In this contribution, the CALPHAD method is applied for different steels, fillers, and electrodes. Examples of phase diagrams, temperature dependences of the carbon and nitrogen activities are calculated, plotted, and discussed. |
| Related projects: |