Diffusion bonding of stainless steel (SS) has been attempted in temperature range of 623 -773 K using multiple inter-layers of nickel, copper and silver. The intermediate layers were electro-deposited taking care to avoid oxidation at the interfaces. The bonded area was examined for the formation of any intermetallic compound through electron probe micro-analyzer (EPMA) and nano-indentation technique. Results indicate the absence of brittle intermetallics at the interfaces and the strength of the bonding was found to be satisfactory. The bond strength was found to be 130 ± 10 MPa and the bond was found to be leak tight with negligible leak rate.

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.

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