This paper deals with the solid state diffusion bonding of X70 steel to duplex stainless steel. Microstructure and mechanical properties of the welded dissimilar steels were investigated. Optical microscopy, Electron Backscatter Diffraction, energy dispersive spectrometry, Vickers hardness measurements, and X-Ray Diffraction were the main techniques of characterization. Microtructural variation was observed in the X70 steel side compared to duplex stainless steel. The diffusion coefficient of iron, chromium, and nickel across the interface X70 steel/duplex stainless steel was also measured. The diffusion coefficient of iron and chromium is higher than that of nickel. The Vickers microhardness profile across the bond joint showed an abrupt decrease in hardness from duplex stainless steel to X70 steel. In addition, a dynamic recrystallisation reaction was observed close to the interface in the X70 steel side.

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