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Case Studies

Case 1 – CVI expertise provides unique friction brake
Parker Hannifin Corporation, Aircraft Wheel and Brake Division approached the Pyrogenics Group to collaborate towards creating a new coating material to support the V-22 Osprey revolutionary new tiltrotor aircraft.

The V-22 is a fixed-wing plane with rotors that tilt so the aircraft can take off and land like a helicopter. A tiltrotor combines the speed, range and fuel efficiency normally associated with turboprop aircraft with the vertical take-off/landing and hover capabilities of helicopters. The tiltrotor aircraft represents a major technological breakthrough in aviation that meets long standing military needs.

The tiltrotor brake pad and system must stand some of the harshest design criteria faced for an aircraft including hold and takeoff in support of mission operations and maneuvers on aircraft carriers and assault ships. The brake material must stand up to highly resistant wear, heat and fracture specifications and have a very high and uniform friction coefficient across ranges of operation.

 


The Challenge: Develop a cost effective material coating that can withstand the severe operational conditions and longevity requirements of the mission planners for the V22 Osprey.

The Pyrogenics Group worked closely with Parker Hannifin in developing a special SiC coating that satisfied the quality, performance, and schedule requirements set by the mission planners. This cost effective coating bonds to a carbon-carbon preform and under high temperature furnace conditions. Unlike superalloys and ceramics, the resultant brake material is light weight, self lubricating, and retains its strength at high temperatures. In addition, it possesses a very low coefficient of thermal expansion (CTE), low residue, and withstands the thermal shock of the mission profile. The extremely wear resistant material makes it ideal for this application, and with a friction coefficient as high as 0.70, is an ideal friction material for high performance clutches and other brake applications.

On September 29, 2005 United States Defense Department for Full Rate Production (FRP) of the Bell Boeing V-22 Osprey tiltrotor aircraft.

 


Case 2 – Pyrolytic Graphite Provides Optimum Erosion in MoCVD

MoCVD System photo courtesy Johannes Keppler University

A leading electronics manufacturer of Metal Organic Chemical Vapor Deposition (MoCVD) in looking to increase productivity has used SiC coated graphite and solid SiC susceptors.

In MoCVD, a laminar carrier gas with precursor molecules of metal-organic compounds flow over a wafer placed on hot graphite based susceptor inside a reactor vessel. The atoms are deposited by decomposing the metal-organic molecules while passing over the hot substrate. The undesired remnants are removed or deposited on the walls of the reactor.

The Challenge: Test materials to determine the best selection for new resistance to ammonium offering material stability and consistent long life.

The manufacturer undertook a detailed duration test under temperature (800 °C) for 40 hours with GaN cleaning media under a N2 and 0.3-0.5% levels of CL2 and HCl at flow rates of 0.33 to 1.095 SLM.

 

The results indicated that Pyroid® pyrolytic graphite provided the most erosion resistance of all the materials (2.5X times that of CVD SiC and 8X greater than SiC coated graphite).