Orbital friction stir welding (FSW) has recently been applied for clad pipes made of API X65 steel and Inconel 625 using polycrystalline boron nitride (pcBN) tools. However, degradation of the very expensive pcBN tools during FSW of high melting point and strength alloys has continuously occurred. In this investigation, four pcBN tools were employed for the orbital FSW of clad pipes, and the performance of these tools was evaluated by means of failure analysis. It was observed that premature tool failure occurred with low heat input due to inadequate plasticization of the clad pipes. Conversely, welds produced at excessively high temperatures promote thermal softening of the W-Re binder and subsequent diffusion, which also contributes to tool failure. Finally, optimal FSW process parameters should consider adequate heating to guarantee full plasticization of the clad pipes while excessive heat might bring unwanted thermal softening of the binder phase. The results of the study showed that the tools failed under conditions where the heat input generated by the combination of parameters was either too high (above 3 kJ/mm) or too low (below 1.8 kJ/mm). SEM and EDS analyses revealed that at high heat input values, the main degradation mechanism of the tool was the thermal softening of the binder phase, while at low heat input values, the material exhibited insufficient plasticization and fractured prematurely due to high loading.