D-GUN PROCESS D002
A metal spray process used to put a hard wear surface on a softer metal.
This is the normal method of applying nickel base tungsten carbide to stainless steel.
The other common spray process is called the plasma spray process, but unlike the D-gun, it is described more as a mechanical rather than chemical bonding.
It should be noted that although these processes apply a reliable hard wear surface they do not provide a chemical resistant surface. You need a much thicker layer for chemical resistance.
Newer hard face materials have just about eliminated the need for these coated or plated seal faces. The API (American Petroleum Institute) specification allows the use of these materials only if they are being put on a solid base of the same material to provide added wear resistance.