*2.3.2 Boundary lubrication*

*Tribology in Materials and Manufacturing - Wear, Friction and Lubrication*

occurred while starting and ending up with lesser sliding speeds. The behavior of the interaction is directed through the lubricant bulk properties i.e., viscosity, and the frictional force can be developed based on the shearing of the viscous lubricant. Besides, the corrosive wear can be occurred on the bearing surfaces due to the presence of lubrication. The adhesive wear also was possible while initial and ending up the processes. The corrosive wear can be reduced through lubricant precipitation

*Coefficient of friction and lubricant film parameter as a function of Stribeck curve showing various* 

*lubrication regimes observed in fluid lubrication without an external pumping agency.*

and formation of film on the bearing surface.

**192**

**Figure 6.**

While increasing the load, the fluid viscosity or speed is decreased in the Stribeck graph as shown in **Figure 6**. In this situation, the friction coefficient can be increased as high as 0.1 or higher than this. This situation may also arise in a starved contact. When the solid surfaces are nearby that surface contact between the multimolecular or monomolecular films of gases or liquids and the dense solid asperities may rule the contact. For more understanding, the cross section of the films and the asperity area contacts is shown in **Figure 6** [21]. Further, with the absence of gases and boundary lubricants (without oxide films), the produced frictional forces may be higher than one. In case with failure in boundary lubrication, causes corrosive and adhesive wear. Generally, the boundary lubricants can easily form the sheared film on the bearing surfaces. Therefore, this formed shear film can be reduced the corrosive and adhesive wear. The major physical properties of the films are hardness, melting point and shear strength. The other properties are cohesion, tenacity or adhesion and formation rates. Also, the viscosity of the lubricant can show a minor impact on the wear and friction behavior [22, 23].
