Diamond idea to defeat cruel sea

August 4, 1995

The cruel sea can soon wear out even the hardest of industrial materials used by the oil industry such as tungsten carbide, used to make seabed valves.

Engineers at Southampton, Oxford and South Bank universities are about to launch a three-year project to develop diamond coatings to prolong the life of the valves.

Sand and gravel, carried by sea currents, can quickly wear away these valves which control flow from the oil well to platform.

Robert Wood of Southampton's Department of Mechanical Engineering explained: "The general aim of the project is to increase valve life. Even with solid tungsten carbide the erosion rates can be two millimetres per hour."

Diamond, the hardest material on Earth, was the obvious choice to provide protection. The challenge is to get a thin diamond coating to stick on to the tungsten carbide. The plan is to use chemical vapour deposition (CVD) to deposit carbon atoms.

"We would be growing a very thin diamond film using the deposition process. We generate a plasma environment, controlling the temperature and products present; the film would only be about 20 microns (millionths of a metre) thick," said Dr Wood.

The project will also be looking at lower temperature methods for coating steel. "The diamond coating is done at 800 degrees Celsius, which destroys steel. We're hoping to use a ceramic coating to halve the temperature to about 400 degrees. Then we could coat pumps, mining equipment and general industrial applications," he said.

In the third year of the project, treated valves will be placed offshore in Alaska and the Gulf of Mexico, to compare them with existing valves and to complement the materials testing at Southampton.

"Downsizing" of research capability in the oil industry has meant that industry alone cannot foot the bill for this work. About half of the project's money has come from the Department of Trade and Industry/Engineering and Physical Sciences Research Council LINK scheme, with British Petroleum, Asea Brown Boveri and other companies providing the rest of the support.

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