Hastelloy X electron beam (EB) weld metal shows higher creep rate and slightly lower rupture strength, and the tungsten inert gas (TIG) weld metal shows remarkably lower creep rate and rupture strength as compared with the base metal. Creep behavior for welded joint is determined mainly by the relation between the welding direction and the loading one, the creep rupture times, and the secondary creep rates of base and weld metal. In applying TIG and EB welding to joints of the shell or tubes, there are few problems for EB welding, but for TIG welding it is necessary to improve the weld metal.