Seals survive tungsten carbide surfaces

A Trelleborg Sealing Solutions UK product story

Edited by the Engineeringtalk editorial team Nov 13, 2006

Nonabrasive material optimises seal performance and gives exceptional integrity against tungsten carbide coated moving parts in primary flight controls and utility actuation systems.

The newly engineered Turcon M30 nonabrasive material from Busak+Shamban is proven to optimise seal performance and give exceptional integrity against tungsten carbide coated moving parts in primary flight controls and utility actuation systems.

Tungsten carbide coating is being used as an alternative to chrome plating to fulfil environmental requirements.

The harder and less malleable surface of tungsten carbide coating can in some cases lower seal life significantly but the improved friction characteristics of Turcon M30 counteracts this problem.

New regulations set forth by the US Environmental Protection Agency (EPA) and Occupational Safety and Health Agency (OSHA) are leading to a reduction in the use of chrome in aerospace applications.

The EPA now lists chromium as one of the 17 most toxic chemicals while OSHA has identified it as a carcinogen.

Due to this, there is a trend for replacement of chrome-plated components with tungsten carbide coated ones in primary flight control and utility actuation systems.

This has dramatically reduced usage of hazardous chemicals but the harder, denser surface of tungsten carbide makes sealing more challenging.

The inherent porosity of chrome plated mating surfaces makes them able to store lubricant.

This in conjunction with their malleability prolongs seal life.

Tungsten carbide however, is extremely hard and can cause significant seal wear, reducing seal life.

To counter this, improved sealing performance can be achieved by specifying seals with better friction and wear characteristics.

Turcon M30, a newly engineered proprietary material developed in the material laboratories of Trelleborg Sealing Solutions, is a high pressure, nonabrasive PTFE (polytetrafluoroethylene) based compound specifically for aerospace applications.

Its formulation offers enhanced friction characteristics along with superior wear resistance and improved leakage control.

This makes seals manufactured in this compound well suited for use against tungsten carbide coated mating surfaces.

In addition, seals in this material are capable of meeting the demanding performance criteria of primary flight control and utility actuation systems.

In these applications, seals must be able to operate effectively in a wide temperature range and withstand high pressures.

In flight controls, they are subject to short stroke movement and high frequency with side loads.

While utility actuation systems, such as landing gear support actuators, travel a relatively long distance rapidly, so seals must operate in long stroke, rapid displacement situations.

The effectiveness of Turcon M30 against tungsten carbide mating surfaces has been proven in controlled tests.

The Turcon M30 material surpassed a target leakage rate of one drop per 1000 cycles.

Leakage was recorded at only one drop per 30,000 cycles.

Other research supports the overall performance of Turcon M30.

In one series of tests, the material was compared with a selection of compounds commonly used in aerospace applications.

At high pressures of 345bar and velocity of 9m/min over 5 million cycles, it demonstrated better wear rates than the other compounds.

In a lubricated environment a wear rate of only 0.55 x 10e-10 was recorded.

In another development program, a Turcon VL seal was combined with an Excluder, both in Turcon M30.

Leakage measured at 345bar was zero, insufficient to form a drop.