The so-called <<STELLITAGE>> operation consists of welding on the scrolls of the valves and on their seats a cobalt-chromium-tungsten alloy, which keeps its hardness when hot, and which therefore withstands the high temperature of the exhaust gases and their corrosive action.

The ordinary method of melting the stellite on the valve is more like a collage as shown in the first photograph. There is no bond between the metal of the valve and the stellite layer.

The S.N.C.M. succeeded in achieving a perfect bond between the stellite layer and the metal of the valve, using an intermediate metal which also diffuses into the two metals.

The second photograph represents a valve micrograph stellated by this method. This method also has the advantage of facilitating stellitage operations and thus increases production.