Specific Coating System Parameters

The coating system studied in this work, United Protective Technologies P51M, is a nanocomposite coating system comprised of a metallic adhesion layer and multiple nanocomposite functional layers. Its applied thickness is 3–5 microns.

Application

This work was funded as an SBIR project (Ref. 5) entitled “Super Lubricity Interface Coatings (SLIC)”, under topic AF203-DCS01, and was formulated to study and improve the performance of aerospace service gears used in the J85 turbine engine deployed on T-38 aircraft, shown in Figure 2, in service with the US Air Force. The current coatings used on many high friction aircraft components are outdated, and due to the low temperature final stage deposition of the UPT coating item configuration can remain the same, allowing the Air Force an economically viable method of improving the properties of these key components. The T-38 aircraft continues to be the quintessential training jet in the Air Force fleet, however, with the T-7 Redhawk positioned to take its place the need to develop economically viable improvements are of key importance for keeping the aging fleet performing in the interim.

System Description
The gears are part of a gearbox assembly designed by Northrop NORAIR division in 1961, which pulls power from the main turbine shaft to drive hydraulics and provide electrical power to aircraft systems in flight. Due to the hydraulic pump and electrical generator needs, the gearbox utilizes an oil-based hydraulic/centrifugal mechanism to shift between a disk clutch and a sprag clutch for low-speed and high-speed conditions, respectively. Most gearboxes are produced through the repair and overhaul procedure, refurbishing and reusing key components, including all gears where possible.