Repair of HighTemperature RAM Coatings

A coating system is proposed comprised of1. Gradient pigment particles having an iron core encapsulated with a mixed intermetallic-oxide layer and a further silicon-based layer for enhanced bonding to the matrix2. A matrix raw material that is thermally-sprayable using conventional technology that partially cures to an oxide during application and becomes fully cured on first use3. Thermal spray equipment with separately-controlled feeders for matrix and pigment feed, to permit application of gradient coatings having superior bond at the interface and maximum pigment content at the surface. Feature 1: Increase iron content inthe coating, as a percentage of total coating weight, by reducing the amount of dielectric-forming elements (e.g. Al, Si) required in the pigment.Benefit 1: Option to improve signature reduction, reduce coating weight, or bothFeature 2: The system uses no solvents or liquid carriers.Benefit 2: Application is simplified with no VOC or other vapor discharges to control. Further, system avoids problems associated with coating distortion during bakeout of large liquid fractions, as with slurries.Feature 3: Pigment preparation system utilizes chemical vapor deposition (CVD) of elements onto surface of individual particles, creating ability to formulate unique alloys and gradients at the particle level.Benefit 3: Can quickly screen candidate formulations for improved coupling at high temperature, creating metamaterials that cannot be produced by conventional means. Can optimize the content and location of dielectric layer.Feature 4: Pigment and matrix will be applied by commercially-available thermal spray system, equipped with proposed dual-hopper feeder. System is field-proven, has no moving parts, easily transported and stored, can utilize multiple energy sources.Variant currently in use at multiple NSA manufacturing sites. Can be used in either manual or robotic modes.Benefit 4: Transport and operation require no additions to current infrastructure at repair sites, could be used on emergency basis at any location worldwide. Training has typically been less than 40 hours for equipment use AND repair.