This study demonstrates the feasibility of producing defect-free weld joints in one pass by orbital friction stir welding. The pipes used are composed of API X65 PSL II steel pipes (6 mm thick) with a clad layer of Inconel 625 (3 mm thick). A PCBN (polycrystalline cubic boron nitride) 30% W-Re tool was chosen for these experiments due to the high strength of this material and the resulting high temperatures. This study investigates the influence of the process parameters in terms of material flow, microstructural evolution and mechanical properties. After the FSW process, sound joints were obtained, leading to good tensile properties. Correlation of characteristics of the welds, such as size of the hook on the advancing/retreating side, lack of bonding on the root face or lack of bonding on the weld face, with the mechanical properties are established.