Feb_March_AMP_Digital

iTSSe TSS A D V A N C E D M A T E R I A L S & P R O C E S S E S | F E B R U A R Y / M A R C H 2 0 1 8 3 9 iTSSe TSS suffered from deep grooving. The KM-coated shaft suffered no grooving, including after an additional 40 hours of testing. This part could not be coated using HVOF thermal spray because the high jet temperatures would degrade the substrate and its heat-treated properties. Performance of the component repaired using KM is su- perior to that of the uncoated OEM component (Fig. 2) and the chrome-plated component, and the KM-coated part is current- ly in service on F-18s. This coating solution is currently being tested on all rotating and stator components of the AMAD gearbox to qualify the repair method for general use on worn aircraft components such as those shown in Fig. 3. Efficient use of powder . The width of the KM spray jet im- pinging on the part being coated is about 10% that of HVOF, which enhances target efficiency (TE), or deposition efficiency (DE), the percentage of feedstock that deposits on an actual productionpart. Further, the low-temperatureprocess enables the spray jet to remain on the part throughout the coating pe- riod, eliminating the need for powder-wasting pauses to limit part heating. Simplicity and safety . KMdoes not require extra hardware or safety equipment. The process uses only inert gas and be- nign feedstock powders. There are no chemical reactions, so there are no toxic byproducts. Release of particulates is easily prevented by using a single-cartridge dust collector equipped TABLE 1 – COMPARISON OF PROCESS CHARACTERISTICS Characteristic Kinetic metallization WC-Co High velocity oxygen fuel (HVOF) WC-Co Electrolytic hard chrome (EHC) Byproducts Inert powder Heat, oxides, overspray Toxins, carcinogens Target efficiency Same as DE* Much lower than DE N/A Wear resistance Better than EHC Better than EHC Good Noise, dBA 74 140 N/A Deposition temperature, ° C <200 >1500 <100 As-deposited surface roughness (Ra), µin. 63 Rough Edge buildup Time to produce coating Minutes Minutes Up to 1 day Mobility Mobile system offered Varies No Unit footprint 6 × 6 ft >10 × >15 ft Varies by part size Substrate degradation No Likely Varies Worker protection Some respiratory, minor skin protection Significant respiratory and auditory, minor skin protection Significant respiratory, skin protection Hardness (HV 300g ) 800-1500 800-1200 700-1000 *DE is deposition efficiency, the percentage of feedstock that deposits on a standard flat surface. Fig. 2 — Wear damage on hydraulic pump gearshaft (left); repaired shaft using KMWC-Co coating (right). Fig. 3 — NAVAIR F/A-18E/F Super Hornet jet fighter AMAD gearbox showing gearshafts repaired using the KM production coating system. Courtesy of NAVAIR Fleet Readiness Center Southwest, San Diego. FEATURE 5