Abstract: A nickel-base superalloy article which is susceptible to strain-age cracking and has a directionally oriented, single crystal, or equiaxed grain structure is repaired with minimal welding heat input into the article. The article is first heated to a welding temperature of from about 1650.degree. F. to about 2000.degree. F. in an inert atmosphere. A damaged area of the article is weld repaired using a plasma-transferred arc welder which vaporizes a filler metal in a plasma arc and deposited the vaporized metal onto the article to form a weld overlay. Minimal additional heat is added to the article during welding, as the weldment metal is vaporized remotely from the article.

Abstract: Direct electric current arc welding between an electrode and a workpiece surface is accomplished in the electric current range of about 0.5-45 amps while reversing the polarities between the electrode and the workpiece surface at a low frequency rate in the range of about 1-1000 cycles per second, in a series of polarity cycles. The workpiece surface, in at least some of the cycles, is positive for a time less than that surface is negative to result in anodic cleaning of the workpiece surface. If the arc is extinguished during a polarity reversal, the arc is maintained, for example, by restriking.

Abstract: A variable polarity device reverses the polarity of an electrically conductive workpiece and an electrode, having opposite polarities, between positive and negative in a low D.C. range of about 0.5-45 amps. Combined with the device is a control means which schedules a frequency of time rate of the reversing in the low time frequency of about 1-1000 cycles per second as well as the electric current at each polarity to provide a series of time and current defined polarity cycles for D.C. arc welding apparatus.