AN EXPERIMENTAL AND THEORETICAL INVESTIGATION OF DIFFUSION ACROSS A JOINT OF 2 MULTICOMPONENT STEELS

Diffusion across a joint of a stainless steel and a low alloy steer ha s been studied experimentally at 1 100 and 1250 degrees C. Precipitate s that formed as a result of the interdiffusion have been identified a s M23C6. Concentration profiles have been measured and the microstruct ure has been studied. The experimental results are compared with compu ter simulations based on thermodynamic calculations of phase equilibri um (CALPHAD) and driving forces for diffusion combined with a numerica l solution of the multicomponent diffusion equations. Despite the fact that no adjustable parameters have been introduced in the simulation the agreement between experimental results and simulations is satisfac tory. It is thus concluded that the structural changes close to the jo int may be essentially predicted from fundamental thermodynamic and di ffusivity data even for the present combination of alloys involving 6 major components which were all included in the simulations.