Properties of a Newly Developed Concave Nickel Gasket for the ConFlat-type Sealing System

Nickel gaskets for large-bored vacuum flange systems remain virtually nonexistent in practical use, despite strong demand for a gasket invulnerable to both oxidation and reduction atmospheres in vacuum application processes. Nickel gaskets would seem preferable in these processes, which are characterized by sensitivity to copper contamination and in which highly corrosive gases could wear away copper gaskets. In working to develop a nickel gasket for the ConFlat-type sealing system with a seal reliability and handling impression comparable to conventional copper gaskets, the authors found that nickel-plated copper gaskets could not attain secure sealing because the nickel layer was too hard to form a tight fit with the flange face. In earlier developmental stages, seven types of prototype nickel gaskets were produced and subjected to a tightening test. These prototype gaskets varied in their respective annealings and/or applied surface finishes. In the tightening test, deep penetration of the flange knife...