Effect of Surface Roughness on the Friction Welded Austenitic-ferritic Stainless Steel Dissimilar Joints

摘要

In certain engineering applications austenitic-ferritic stainless steel dissimilar joints are preferred because a ustenitic stainless steels provide good ductility and toughness e ven in cryogenic conditions while ferritic stainless steel exhibits better aqueous corrosion resistance. Friction welding a process in which fine grain size and better mechanical properties is obtained' due to the thermo-mechanical working of the weld, is chosen for welding of such dissimilar metal combinations. The effect of roughness on faying surfaces of austenitic stainless steel on friction welded dissimilar joints has been studied. It has been observed that improvement in strength and toughness was observed up to a roughness value of Ra of 5. O mu m in austenitic stainless steel. However, roughness value beyond this resulted in layered structure on the ferritic stainless steel leading to lower toughness. Further more, the interface contains delamination defects preferably due to the differences in thermal conductivity, strength and ductility between the two materials.