Friction stir welding of nuclear grade material Cu-Cr-Zr and SS 304

Abstract

Dissimilar metal joints are used in several industries sectors like petrochemical, thermal, nuclear, hydrolytic pairs and refrigeration and air conditioning. Dissimilar weld joints between copper and SS are demanded in different units of air refrigeration and air conditioning system. Particularly in nuclear industries, the cold leg condenser units of reactor pressure vessel system demands the joint between Cu-Cr-Zr alloy and SS 304 L materials. Owing to varying and distinctive metallurgical and material properties joining of these alloys remain a big challenge. In thick section arc welding processes are the conventional option to weld them together lower joints could exhibit with metallurgical deterioration caused by arc welding process. Solid-state welding process are low heat input processes and can be used for joining these type of material to address the issue of metallurgical deterioration of weldment region. In present study, low heat input solid state welding process, friction stir welding process have been used to investigate the feasibility of joint on comparatively thin sections of 3 mm thickness. Significant amount of trial experiments were performed as preliminary investigation to decide the root map for investigation the failure of tool and its causes and effects were recorded and analysed in the study. The virtually inspected and qualified as welded joint between SS 304 and Cu-Cr-Zr allow has been used in this study. The specimen fabrication and experimentation procedure is described along with the welding and testing procedure. Several mechanical and metallurgical test were performed and the results were described in the study. The results of mechanical, metallurgical and fractography test were analysed and correlated with each other in weld qualification test (cross-weld tensile test), the specimen fractured from the HAZ /TMAZ regions of Cu-Cr-Zr alloy and the present investigation analyse the failure case of HAZ/TMAZ zone. The analysis of test result validated by other test also elaborated in this study. Heat produced in the FSW influences the Cu-Cr-Zr alloy side in through thickness in metallurgical aspect and resulted in different mixed mode fracture failure. However, study suggest the feasibility of joint using friction stir solid state welding process.