SBIR Phase I: Ultrananocrystalline Diamond as Wear Resistant and Protective Coating for Mechanical Shaft Seal Applications

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This Small Business Innovation Research (SBIR) Phase I project proposes to develop wear resistant and protective coatings for mechanical shaft seals based on a novel material called Ultrananocrystalline (tm) diamond. Diamond, because of its hardness, chemical inertness and low friction coefficient is an obvious candidate for coating mechanical shaft seals. Conventional CVD diamond technology (based on H2/CH4 gas chemistry), which produces microcrystalline (or nanocrystalline) diamond is not suitable because of large grain sizes and high internal stresses. The new process based on Ar/CH4 gas chemistry produces diamond with small grain sizes (2-5 nm) and a surface roughness of about 20-30 nm which is ideally suited for such applications.Mechanical shaft seals are used in almost every industry. The main functions of these seals are to ensure that the pumping fluid does not escape the system and to protect the fluids from contaminants. Presently, silicon carbide (SiC) is the material of choice for most of the seals used in these industries. However, several studies have shown that due to poor friction properties of this material, almost 20% of the energy is lost due to friction. By improving the efficiency of shaft seals in these devices by just factor of two, it is estimated that a worldwide energy savings of 6x109 Kw-hr/year could be achieved.