An Experimental and Theoretical Investigation of Diffusion across a Joint of Two Multicomponent Steels.

Diffusion across a joint of a stainless steel and a low alloy steel has been studied experimentally at 1100 and 1250°C. Precipitates that formed as a result of the interdiffusion have been identified as M23C6. Concentration profiles have been measured and the microstructure has been studied. The experimental results are compared with computer simulations based on thermodynamic calculations of phase equilibrium (CALPHAD) and driving forces for diffusion combined with a numerical 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 satisfactory. It is thus concluded that the structural changes close to the joint may be essentially predicted from fundamental thermodynamic and diffusivity data even for the present combination of alloys involving 6 major components which were all included in the simulations.