Molybdenum Disulphide used as Boundary Lubrication

Molybdenum disulphide is a solid lubricant comes under the classification of an inorganic compound, its chemical formula is MoS2. Where ‘Mo’ stands for Molybdenum and S2 for disulphide. The molecular weight of molybdenum disulphide is about 160.07 g/mol, density is 5.06 g/ cm3, melts at the temperature 1185oC where it starts decomposing, Generally available in black coloured powder. Molybdenum disulphide has a sandwich-like structure in which a layer of Mo atoms lies between two layers of sulphur atoms, which has the crystal structure in the form of hexagonal.

In nature, it exists in the form of molybdenite mineral ore. Molybdenum disulphide possesses a very low coefficient of friction and is stable in air up to 400oC and do not react with dilute acids. Its fine powder is spread on the surfaces sliding at high velocities, it fills up low spots in metal surface leading to smooth film formation. It can also be used along with solvents and in greases.

Besides the more important graphite and molybdenum disulphide, other substance like soapstone, talc, mica etc., are also used as solid lubricants. Molybdenum disulphide containing lubricant comes under the class of boundary lubrication type which can be used for a situation where the pressure and loads are high and the surface of contact metal is not well polished. For heavy vehicles and sports vehicles, the bearings should observe heavy thrust and load due to a sudden stop and start operations. To lubricate such bearings molybdenum disulphide mixed lubricant is preferred. Molybdenum disulphide treated solid lubricants packings are generally used in the mechanical seal, to prevent the leak between the moving and rotating surface. Molybdenum Disulphide used as boundary lubrication can withstand pressure and temperature for moderate levels of operations.

Nanofluid technology enhanced the process of making molybdenum disulphide nanoparticles.

It is done by the method called wet chemical synthesis. A chemical reaction between ammonium sulphide and ammonium molybdate in liquid phase produce molybdenum disulphide nanocrystals and ammonia gas.