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.

Abstract: A gas turbine engine air cooled vane assembly which includes inner and outer platform members and an airfoil member therebetween is repaired by removing from the vane assembly a vane assembly segment comprising at least a portion of the leading edge wall, a portion of the airfoil body wall and a portion of at least one platform member connected with the leading edge wall. The vane assembly segment is removed along a preselected path which, during operation of the vane assembly in a gas turbine engine, experiences relatively low mechanical stresses. A replacement member of substantially the same type of material and of a size and shape which matches the removed vane assembly segment is placed into registry with the vane assembly and then metallurgically bonded to the vane assembly.