Diffusion Control and Metallurgical Behavior of Successive Buttering on SA508 Steel Using Ni–Fe Alloy and Inconel 182

The metallurgical deterioration and carbon diffusion caused during welding in the vicinity of the fusion interfaces between dissimilar metals have been investigated in case of gas tungsten arc and shielded metal arc welded SA508Gr.3Cl.1 steel substrate with Ni–Fe alloy and Inconel 182. The study was conducted to investigate the effect of Ni–Fe matrix as buffer layer and SMAW process for buttering deposition on the carbon diffusion and metallurgical changes. Quantitative measurement and validation of carbon/alloying elements distribution in as-welded, thermally aged, and postweld heat-treated conditions were performed in buttering deposits by using optical emission spectrometry and electron probe microanalysis. The extent of carbon diffusion has been estimated using Groube’s diffusion couple and confirmed with microstructure microhardness and X-ray diffraction. Martensite formation has been estimated for its thickness and validated with metallurgical properties. The effect of buffer layer is significant for carbon diffusion and tempering of martensite with thermal aging, PWHT, and multipass deposition. The concentration and activity gradient of carbon has been established due to Ni–Fe matrix as buffer layer and higher dilution for buttering. The obtained results are confirming the control of carbon diffusion and lesser metallurgical deterioration in suggested buttering procedure.