Electrospark Deposition for Depot- and Field-Level Component Repair and Replacement of Hard Chromium Plating

摘要

Military components are frequently damaged in service through corrosion, impact, or wear. They must be either repaired in the field (operational-level repair) or shipped back to the depot. When a localized repair is possible, it is usually done by brush plating nickel (Ni) or chromium (Cr) (using a Cr6+ solution). If the component cannot be repaired in the damaged area alone, the entire surface and any coating on it must be removed and rebuilt, usually by chrome plating or sulfamate Ni to reclaim dimensions followed by chrome plate for wear. When chrome plate is damaged, the only recourse for a permanent repair is to strip and replate. All these processes create hazardous waste and expose personnel to toxic materials. In addition, there are many components that suffer significant damage and for which there is neither a field nor depot-level repair currently available. At present, these components must be condemned, resulting in costs associated with their replacement and disposal. A technology that could replace brush plating and provide field repair on currently nonrepairable parts would reduce waste generation, personnel exposure, and cost while improving readiness by returning components to service more rapidly. Electrospark deposition (ESD), also known as electrospark alloying (ESA), is a microwelding technique that has demonstrated capability for filling damaged areas and restoring coating damage. It uses short-duration, high-current electrical pulses to weld a consumable electrode material to a metallic substrate. Since almost any alloy can be deposited, the method is ideal for filling damage over small areas, as in the case of localized wear or corrosion, using the same alloy as the parent metal. The heat generated in the process is very small, eliminating thermal distortion and allowing the process to be used on heat-sensitive materials. The equipment is small and portable and can be manually operated with a simple shroud to remove any fumes.