Modern carbon-graphite self-lubricating materials

12 May 2016

Metallized Carbon offers materials ideal for mechanical seals in aircraft shaft applications, including main shaft seals for aircraft turbine engines and aircraft auxiliary power units (APUs).

The self-lubricating materials are impregnated with proprietary inorganic chemicals that improve their lubricating qualities and oxidation resistance. Experts consult with customers to recommend grades with the properties that will work best in new seal designs.

These modern carbon-based materials are an excellent option for use in aircraft applications because of their high thermal conductivity, which means they excel at handling and dissipating the high temperatures found in aerospace engines. The materials also feature a low coefficient of friction, a low wear rate at high sliding speed, and resistance to oxidation in high temperature air. The materials are also strong and dimensionally stable.

“Metcar’s modern carbon-graphite materials are an excellent option to help aerospace designers meet fuel efficiency requirements,” said President and CEO, Matthew Brennan, “Since more fuel efficient engines run hotter, they need higher temperature, more thermally conductive materials in the engine.”

Both mechanical face seals, with carbon-graphite primary rings, and circumferential seals, with carbon-graphite seal rings, are used in aircraft engines to seal the oil in the main shaft bearing sump. Lifting wedges and machined configurations are used to create lift, so that these seals run on a hydrodynamic film. Rotating speed over 10,000rpm and temperatures as high as 427°C are accommodated. M-45 is used to reduce the seal face temperature because of its superior thermal conductivity.

Metcar Grade M-595 type materials are recommended for aircraft turbine engines and auxiliary power unit main shaft seals, because the chemical additive in these grades prevents oxidation at high temperature and provides improved lubricating qualities at the required operating conditions.