Abstract: A laser welding apparatus and method are used to weld the inner surface of small diameter tubes such as nuclear heat exchanger tubes. A weld filler metal carried by a rotatable laser weld head is fed into the weld zone to produce deeply penetrating weldments of low profile. The apparatus and method can effectively be used to repair cracks in heat exchanger tubes to thereby provide extended service life.

Abstract: The wall of a pressure vessel tube having stress-corrosion cracks or the like is repaired by localized melting using laser welding, for fusing over defects by melting and re-solidifying the metal. A high powered laser beam is focused at a limited area or spot on the internal wall of the tube. The welding head is operated at sufficient power and is relatively moved in the tube at a sufficient rate to melt the spot while advancing along a line on the internal surface of the wall. The wall is melted to a depth of part or all of the thickness of the wall. Points at which the tube has been melted by the focused beam cool following passage of the welding head. The welding head is also advanced laterally of the line, either continuously or stepwise. Localized melting and cooling of the tube material continues progressively, line by overlapping and/or adjacent line, to melt and reform the degraded area.