Iridium Welding Process Improvement

An investigation is underway to evaluate an improvement to an iridium welding process. A pulsed gas tungsten arc welding (GTAW) process is being evaluated to replace the existing GTAW process which uses a magnetic arc oscillator. The magnetic arc oscillator has been credited with refinement of the weld grain structure and improved fracture toughness, which is critical to this iridium alloy as it is susceptible to rapid grain growth during welding, however, the actual magnetic deflection of the arc cannot be measured, thus this aspect of the process cannot be calibrated and the appropriate operating conditions cannot be confirmed and maintained. A pulsed current GTAW process, developed for a tantalum alloy with grain growth issues similar to iridium, has shown improved grain refinement and ductility compared to a conventional constant current GTAW process, so this pulsed current approach is being investigated for the iridium welding process. The discussion includes background of iridium welding issues, the development approach and results from the tantalum pulsed weld, and the results to date on the iridium weld investigation.