Diamond coatings applied to mechanical face seals

Abstract

The desired properties of a mechanical face seal are low friction and low wear rate. To fulfil these requirements the seal material needs a low friction coefficient, high hardness, high corrosion resistance, high thermal conductivity and a high thermal shock resistance. Diamond displays a low friction against almost all materials. Furthermore, diamond shows the highest hardness of all materials, is extremely corrosion resistant, has the highest thermal conductivity (four times that of copper) and has a high thermal shock resistance. Therefore, diamond has the potential of becoming a very competitive seal material. The use of diamond in this kind of application has not yet been realised since it is an expensive material and very difficult to shape into complex geometries. However, it has recently become possible to deposit diamond coatings onto various substrate materials with the desired shape and thereby give the component diamond properties. The objective of this study is to investigate the performance of diamond coated cemented carbide as a face seal material. Laboratory dry sliding tests have been performed as well as component tests with water as the pressure medium. Commercial face seals were used as reference. The results show that diamond coatings considerably lower the friction in mechanical face seals and are therefore an interesting alternative to seal materials commercially available today. The benefits from using diamond coatings include lower running cost, increased reliability and the possibility to use a more simple seal design.