Influencing factors of graphite lubrication effect

Overview of graphite powder lubricants

Graphite has a flaky crystal structure with good lubricating properties. It also has good electrical conductivity, thermal conductivity, wear resistance, pressure resistance, temperature resistance (temperature up to 450 ℃) and chemical stability, so graphite is widely used in the machinery industry to make various lubricants.

The carbon atoms are held together firmly in the flakes. Since the bond between the thin plates is weak, graphite exhibits lower shear strength under frictional force. Therefore, it can be used as a solid lubricant and has become one of the traditional and main solid lubricating materials.

Application of graphite lubricant

Used as a lubricant, mainly to distribute fine graphite particles evenly in water, oil or other media to form a stable colloid. It can be directly applied to parts that need lubrication by spin coating, dip coating or spraying. Can be added to various lubricants and used together. Contact with the metal surface can not only form a strong lubricating film, but also improve the wettability of the metal surface to other lubricants, thereby maintaining long-term lubrication. In addition, because graphite exists in the form of extremely fine particles, it is easy to penetrate into tightly fitting sliding or rotating parts, thereby providing good lubrication.

Influencing factors of graphite lubrication effect

Graphite is a traditional solid lubricating material. Due to its special layered crystal structure, graphite materials have good lubricating properties. As early as the 1950s, many graphite lubricating products were developed one after another. For example, the world-famous German Leica camera uses graphite powder as a lubricating material for mechanical parts. In the 1960s, my country also produced bronze oil-impregnated graphite bearings. In recent years, domestic "Chikai" brand energy-saving antifriction king additives and "Metro" series lubricants have also come out one after another. Many studies and practices have shown that graphite used in lubricating oil has huge economic benefits and has many advantages of its own. With the development of science and technology and the deepening of scientific research, graphite lubricating materials have been extended to appear in the form of graphite derivatives, such as flake nano graphite, expanded graphite, fluorinated graphite, elemental or composite intercalated graphite, etc. This article comprehensively discusses the types, dispersion stability and lubricating effect of graphite lubricating additives, and provides references for the development and application of new graphite lubricating materials.

Influencing factors of graphite lubrication effect

Graphite particle size

The lubricating properties of graphite are affected by the particle size. Some scholars have shown that graphite powder with an average particle size of 4~5μm will produce a good lubricating effect, which can minimize the friction and wear of the specimen. However, more scholars have shown that controlling the average particle size below 0.5μm is the key to the stable suspension of graphite in lubricating oil, and it is also a condition for exerting lubricating performance. The graphite particles are too large to enter between the friction pairs, and cannot isolate and hinder the contact between the two friction surfaces, thereby affecting the lubrication performance. However, it is obvious that if the graphite particles are too small, the graphite layered crystal structure will be severely damaged, the friction reduction mechanism of graphite sheet slip will also be lost, and the graphite lubrication effect will be poor. Therefore, the appropriate graphite particle size is the key to graphite's lubricating effect.

The structure of graphite

The structure of graphite is one of the factors that affect the lubricating effect of graphite. Different graphite structures determine different types of graphite. There is no report comparing the lubricating effects of expanded graphite, fluorinated graphite, graphite intercalation compound and flake nano-graphite. It can be seen that under the appropriate graphite particle size conditions, different graphite types have their own optimal lubricating environment, which is difficult to compare. For example, expanded graphite has a strong absorption capacity and enrichment effect, which can be mixed with extreme pressure additives to achieve the best effect; when the F/C ratio of fluorinated graphite reaches 1.0, the wear resistance life reaches the best value; and Temperature determines the degree of deintercalation of graphite intercalation compounds; some scholars have pointed out that as the ratio of graphite diameter to thickness increases, the specific wear of the lubricated material decreases significantly. It can be seen that the diameter-to-thickness ratio affects the lubricating effect of flake nano-graphite.

External environment

The particle size and structure of graphite are the internal factors that determine the lubricating effect of graphite, and the external environment is the external cause of the lubricating effect of graphite. As early as the 1940s, Robert proposed that humidity is an important factor affecting the lubricating effect of graphite. Water vapor and other small molecules can be adsorbed on the edge of graphite crystals and invade along the dissociation surface (sandwich), thereby reducing the surface energy of the graphite layer. Make it easier for graphite to be adsorbed on the friction surface and form a film, thereby improving the lubrication effect. Bowden et al. It is also proposed that the friction coefficient of graphite under vacuum conditions is significantly increased. Once air is introduced, the friction coefficient drops rapidly. Therefore, improving the environmental medium of graphite-based lubricating materials is also the key to obtaining more effective graphite lubricity. Graphite and graphite derivatives are widely used in lubricating fields such as lubricant additives due to their good lubrication advantages. However, it is worth noting that the preparation process of ultra-fine high-purity graphite still requires technological breakthroughs. Graphite nanoization and industrial production of high-purity sulfur-free and chlorine-free graphite will be the future development trend of graphite; at the same time, with the development of technology, the development of new graphite-derived materials such as hollow nanometers will also provide a material basis for graphite to provide excellent lubricants. 

The price of graphite lubricant

The price of graphite lubricants will vary randomly with the production cost, transportation cost, international situation and the supply and demand situation of the graphite lubricant market. Tanki New Materials Co.,Ltd helps all industries and chemical wholesalers find high-quality, low-cost nanomaterials and chemicals by providing a full set of customized services. If you are looking for graphite lubricant, please feel free to send an inquiry to get the latest price of graphite lubricant.

Supplier of graphite lubricants

As a global graphite lubricant supplier, Tanki New Materials Co., Ltd has extensive experience in the performance, application and cost-effective manufacturing of advanced and engineered materials. The company has successfully developed a series of powder materials (the best oil additives for nano-diamond, lithium stearate, nano-copper and nano-oil additives), high-purity targets, functional ceramics and structural devices, and provides OEM services.

Physical and Chemical Data of Graphite

Properties of Graphite