Alloy L-605 (also referenced as HAYNES® 25) is the strongest of the fabricable cobalt alloys, useful for continuous service to 1800°F. Because of its long and widespread use, this alloy has been the subject of many investigations to determine its properties over a wide range of conditions, thus making it an unusually well characterized material. When exposed for prolonged periods at intermediate temperatures, alloy L-605 exhibits a loss of room temperature ductility in much the same fashion as other superalloys, such as alloy X or alloy 625.

L-605 is welded using gas tungsten arc, gas metal arc, shielded metal arc, electron beam and resistance welding. Submerged arc welding is not recommended. Use good joint fit-up, minimum restraint, low interpass temperature and cool rapidly from welding. For maximum ductility, fabricated components should be annealed 2150-2250°F, rapid cool.