Final Report - Strategic Environmental Research and Development ...

EXECUTIVE SUMMARY
Background: Military components are frequently damaged in service through corrosion,
impact or wear. They must be either repaired in the field (O-level repair) or shipped back
to the depot. Where a localized repair is possible it is usually done by brush plating of Ni
and/or Cr (using a Cr 6+ solution). Where 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. Where chrome plate is damaged the only recourse for a
permanent repair is to strip and replate. All of 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 both with replacing them
and with their demil 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, such as 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 heatsensitive
materials. The equipment is small and portable and can be manually operated
with a simple shroud to remove any fumes. The simplicity and cleanliness of the process
allows it to be safely used by operators without extensive training, for both D-level
overhaul and O-level in-place repair.
The process is used industrially, including its use by Rolls Royce for dimensional
restoration of non fatigue critical areas of turbine engine components. It is being used at
ASAP for a number of certified aircraft repairs, including:
1. Single crystal turbine blade for two gas turbine engines ( FAA approved repair)
2. Second stage gas turbine blade sulfidation corrosion repair (DER repair)
3. Helicopter flap restraint for main rotor (DER approved repair).
Objectives of the Demonstration: The objective was to demonstrate ESD as a
technically feasible and commercially viable production-scale process for localized repair
of weapons systems components, and to transition ESD repairs for use on DoD
components for gas turbine engines, vehicles and ships.
Demonstration sites were Oklahoma City Air Logistics Center (OC-ALC) and Anniston
Army Depot (ANAD) (working with the Army Research Laboratory (ARL). ESD units
were acquired and placed in each of these facilities, and candidate components identified.
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