What is solid lubricant?
Solid lubricant is a sort of material that reduces the friction coefficient and wear by preventing direct contact of friction components below ordinary use or excessive load. In high-quality instances wherein liquid lubricants, which include oil and grease, can not be used, solid lubricants have an excellent application market. Besides, the strong lubricant is also an additive cloth for high-overall performance anti-chunk and anti-wear coatings. It is regularly combined with grease and lubricating oil inside the shape of powder debris to play a sliding function. This kind of special strong lubricant will slip while the friction pair slides exceptionally Fill out hard surfaces. Consequently, under excessive working conditions, solid lubricant affords sufficient boundary lubrication situations, thereby lowering the friction coefficient and lowering put on. Normally speakme, stable lubricants have a better advantage than liquid oils under high vacuum situations underneath 10-2 Pa and close to atmospheric stress above 104 Pa, and low temperatures underneath zero℃and high temperatures above 177℃.
There are 5 essential forms of solid lubricants: carbon-based substances, transition metal disulfides (such as mos2 and ws2), polymers (such as ptfe lubricant), tender metal, and ceramic high-temperature lubricating materials. Amongst them, carbon-primarily based materials and transition metal disulfides belong to the everyday layered shape strong lubricant.
(1) Carbon-primarily based lubricating cloth
Graphite is a standard carbon-based totally lubricating cloth with excessive-temperature resistance and corrosion resistance and is thought for its dependable lubrication traits. Graphite has a layered stable with a hexagonal lattice. The atoms in the carbon base plane are bonded collectively via sturdy covalent bonds, at the same time as the base planes are mixed by susceptible Van der Waals forces, ensuing in a broken mechanical dating among the plane. The presence of water vapor and oxygen in the environment can promote the shear movement among graphite crystal layers. While the base floor is worn, those active edges are neutralized (passivated) by using adsorbing water or other vapors. Graphite also can maintain low friction. This is actual for different carbon-based, totally stable lubricants. Carbon-primarily based lubricants additionally consist of diverse styles of DLC coatings and low-friction carbon coatings (NFC).
2) Transition steel organization disulfide (TMD) lubricating substances
In the TMD circle of relatives, MoS2 and WS2 are widely used for their reliable lubrication performance. The number one mechanism for accomplishing low shear resistance at the interface is a base floor-oriented parallel to the sliding route and a transfer film fashioned at the friction couple. MoS2 and WS2 coatings do now not oxidize or react with water vapor in a dry gas or ultra-excessive vacuum, thereby retaining their reliable internal lubrication. However, in humid air, friction oxides, which include MoO3 and WO3, can be fashioned because of the dangling or unsaturated bonds on the brink of the bottom floor reacting with water vapor or oxygen inside the surroundings. At this time, the sliding friction coefficient is highly excessive (0.15 ~ zero.2), and the damage life is also concise.
(3) PTFE lubricant:
Polymer solid lubricant is generally deposited inside the shape of a coating (film) on the surface of a substrate (such as polymer-based totally engine bearing cover). The molecular shape of those substances includes long chains parallel to every difference, and the bond energy between molecules weak can also slip under low shear strain. PTFE is regular for such stable lubricants. Not like another stable lubricant, PTFE does now not have a layered shape, but PTFE macro molecules effortlessly slide, similar to a layered structure. The minimal static and dynamic coefficient of friction of PTFE can be reduced to 0.04. The PTFE-covered steel may be used below harsh temperature, strain, and medium, and can gain a prolonged safety length. Polymer-primarily based nanocomposites, together with PTFE / nano Al2O3, also show remarkable friction performance below distinct takes a look at situations.
(4) gentle metallic lubricating substances
Because of low shear energy and high plasticity, some tender metals additionally have lubricating houses inclusive of lead, tin, bismuth, indium, zinc, cadmium, and valuable metals inclusive of gold and silver. As an instance, Zn and Sn have been utilized in sliding bearings; at the same time as precious metals, which include gold and silver, have started within the aerospace enterprise. In each day’s life, tender metals are extensively used as strong lubricants in engine bearing substances.
Gentle metals used as strong lubricant materials normally have a face-focused cubic lattice, so their crystals are all isotropic. Consequently, those tender metals do now not have an excessive bearing ability, and the external load can best be borne via the substrate. Another benefit of face-focused cubic crystals is that there may be no low-temperature brittleness, and the lubricating homes will not be lost in low-temperature environments.
(5) excessive temperature resistant lubricating substances
Certain oxides, consisting of B2O3, MoO2, MoO3, ZnO, Re2O7, TiO2, V2O5, and PbO, and so forth., have decrease melting points, soften at high temperatures, and have higher houses.