Steam control valves often used in nuclear and fossil fuel power plants typically include a cylindrical outer housing including a bottom muffler portion, and a moveable plug, typically made from carbon or low alloy steel, which is co-axially aligned within this outer housing and which is slidable within the interior diameter of the housing. The plug typically includes grooves about its circumference in predetermined positions for receiving circular sealing rings and a valve seat, which are sized to be inserted into the grooves. The valve seat of the steam control valve is typically protected from high temperature wear and abrasives by coating its sealing surface with STELLITE-6. Unfortunately, after machining the hardfacing to final tolerances, small imperfections, such as cracks and pores, can often be found in the deposit. To repair these defects, the area is typically mechanically gouged in the area of the defect. The component is then preheated, the gouged surface is repaired with hardfacing weld wire, and then the welded component is stress relieved at about 1200.degree. F., 649.degree. C.
While this technique has proved to be somewhat adequate in preparing valve seats for plugs, it is time-consuming, expensive, often distorts the plug, and creates more defects in both the repaired area as well as the surrounding metal. A large number of such defects can lead to entirely scrapping the valve plug.
Accordingly, a need exists for a manufacturing method and repair procedure for hardfaced valve seats which minimize welding defects. There also remains a need for a welding process which minimizes the necessity of subsequent stress relief operations, reduces the probability of producing cracks in the hardfaced seat area upon cooling from welding temperatures and eliminates the chore of removing the valve seat from the plug to make the repair.