About

Tribology is a coined word combining the Greek word “tribos” meaning “rubbing” and “ology” meaning “study,” and is an academic and technological field that deals with the science and technology related to “friction and wear phenomena” that occur between two objects in relative motion and “lubrication and surface technology to control them. Tribology is a field of science and technology that deals with the science and technology related to “friction and wear phenomena” and “lubrication and surface technology to control them” that occur between two objects in relative motion.

Tribology is an interdisciplinary field that requires knowledge of not only mechanical engineering but also chemistry and materials, and chemical engineering as a “comprehensive engineering” is needed.

In the various machines used in daily life, there are sliding surfaces such as bearings and gears that are in relative motion with other solids. Increased friction and wear usually cause a reduction in the life and durability of the machine and an increase in energy loss. Therefore, lubrication, which provides smooth motion between solids in relative motion, is an important technology not only to reduce friction and wear, but also to control and utilize friction effectively.

Lubricant is the most important means of lubrication. Lubricant is a liquid mixture consisting of a base oil, mainly mineral oil, and polar compounds called additives. Viscosity and additives are two of the most important properties required of lubricants. Especially under severe contact conditions, such as increased contact pressure, decreased velocity, and decreased base oil viscosity, the nanometer-scale molecular film (tribofilm) generated by various additives (oiliness improvers, anti-wear agents, extreme pressure agents, etc.) added to the lubricating oil prevents direct contact between solids in relative motion and reduces shear resistance of the solid surface. The tribofilm prevents direct contact between solids in relative motion and lowers the shear resistance of the solid surfaces. The state in which lubricity is provided by the tribofilm is called boundary lubrication.

Boundary lubrication is still difficult to theorize because it is affected by various factors such as the physical properties of the contact interface and the viscosity effect of the lubricant, in addition to the friction chemical reaction between the additive agent that contributes to tribofilm formation and the solid surface. The development of appropriate lubricants for each application and the establishment of technology to control friction under boundary lubrication are very important themes toward the realization of resource and energy conservation.