**6. Other applications**

Bearings have been used in various industries in a variety of forms and shapes. They are crucial in tribology to reduce friction between objects. For oil and gas drilling operations, different types of bearings are used, from the surface to the bottom of the wellbore. There are several types of bearings in which surface-to-surface rubbing is involved, such as thrust bearings (as shown in **Figure 14**) and plain bearings, as shown by examples in **Figure 15**. In these examples, the surface-to-surface contact between the counterparts prevailed. Such types of bearings are used in drilling rotary control device (RCD), mud motors, rotary steering system (RSS), powder generating turbines, mud pulse tools, coring tools, electric submersible pumps, etc.

One of the tools is shown as an example in **Figure 15**. The materials of the thrust and plain bearings include bronze, brass, lead-based metal, cast iron, zirconia, tungsten carbide, silicon carbide, and PCD.

The PCD materials currently used in these applications are made of PCD grains bonded by metallic binders, such as cobalt, nickel, iron, or silicon. These metallic binders (Co, Ni, or Fe) are used as catalysts to facilitate diamond manufacturing so that the diamond grains can be obtained at traditionally high temperatures and high pressure. In the above-mentioned bearing applications, PCD materials typically outperform the rest of the materials, mainly due to their high hardness, high compression strength, high thermal conductivity, and very low coefficient of friction.

Electric Submersible Pumps (ESPs) are one of the primary artificial lift methods for oil and gas industry. The system is a complex electro-hydraulic system consisting of a centrifugal pump, a protector and an electric motor in addition to a sensory unit and a power delivery cable. The pump is used to lift well fluids to the surface. The motor converts electric power to mechanical power to drive the pump via the shaft. The power delivery cable provides a means of supplying the motor with the needed electrical power from the surface. The protector absorbs the thrust load from the

#### **Figure 14.** *Thrust bearings using catalyst-free and ultra-strong PCD materials [22].*
