Characteristics of Interdiffusion between 17-4 PH Steel and Nickel

The characteristics of interdiffusion between precipitation-hardened 17-4 PH grade stainless steel and nickel were studied in the temperature range of 900 °C to 1100 °C, using diffusion couples of these two materials. The diffusion coefficients of the major diffusing elements Fe, Ni, Cr, and Cu were evaluated for this multicomponent system. The diffusion paths plotted on the Fe-Ni-Cr isotherm showed a flat “S” shape, suggesting insignificant interaction among the diffusing species. The temperature dependence of the diffusion coefficients for each element was evaluated, and the activation energies for diffusion were determined. The asymmetric nature of concentration variation of the elements at the diffusion zone was observed and was explained by the difference in diffusivities of the diffusing species. The activation energy for diffusion of Ni was found to be lower than that of Fe and Cr.