WO2024086035A1

WO2024086035A1 - Lubricating coating and coating compositions for forming same

Info

Publication number: WO2024086035A1
Application number: PCT/US2023/034716
Authority: WO
Inventors: Benedict Yorke Johnson
Original assignee: Corning Incorporated
Priority date: 2022-10-19
Filing date: 2023-10-09
Publication date: 2024-04-25

Abstract

A lubricating coating includes a cured product of a coating composition. The coating composition is a reaction product of a precursor coating composition. The precursor coating composition includes a polysiloxane precursor, an acid, a ceramic filler, a solvent, and lubricating particles.

Description

LUBRICATING COATING AND COATING COMPOSITIONS FOR FORMING

SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63/417,362 filed October 19, 2022, the content of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Mechanical failures in machine components, such as engines, gears, bearings, piston, and cylinder liners are mainly caused due to inefficient lubrication. Approximately one-third of the total energy loss is reported to be caused by friction and wear every year. Furthermore, over 40% of the energy generated by consuming mined mineral is wasted to overcome friction, and about 2.7% of CO2 emission worldwide is attributed to friction and wear. Therefore, efficient strategies for decreasing friction and wear loss and saving energy are needed.

[0003] Solid lubricants are critically important for safe and smooth operations of numerous tribological systems. More recently, solid lubricants have become highly attractive substitutes for petroleum-based oils, as they are environmentally friendly and less toxic. Their uses are expected to further increase in coming years, mainly because the operating conditions of future tribological systems are becoming more and more demanding and because liquid and grease-type lubricants are undesirable due to environmental concerns. [0004] Various extrusion dies are coated with titanium carbonitride (TiCN)-based wear resistant coatings via chemical vapor deposition (CVD) to serve two necessary purposes: (1) significantly extend the use-life of the dies, and (2) bring the dies to their final operating dimensions in terms of slot width and feed hole diameter. Production facilities typically observe high die pressure when indexing new or freshly recoated high cell density, ultrathin slot dies for making heavy duty substrates. The initial high die pressure can cause the twin screw machine extruder (TSM) to shut down due to over pressure condition. This then requires feed rate to be reduced to manage the system and die pressure in an acceptable range. The high start-up pressure, a so-called pressure spike, can take up to several hours to decay to a steady value. As the process becomes stable, the feed rate is incrementally increased until the full feed rate is achieved; however, reaching the full feed rate in some instances can take several hours, and during this period, the quality of the ware being produced is compromised due to the instability of the process. Until the pressure reaches a steady state, the extruded parts exhibit defects which cannot be shipped to customers and must be discarded or recycled for reuse.

[0005] Due to the highly abrasive nature of the ceramic batches, extrusion of the pastes causes mechanical wear of the hard coating. Hence, the coating degrades during the extrusion process and the dies become unusable after several production cycles. Thus, the coating needs to be replaced frequently if the dimensional accuracy of the extrudates is to be maintained. To reuse the expensive die, the coating is entirely removed and recoated.

SUMMARY OF THE INVENTION

[0006] In various aspects, the present invention provides a precursor coating composition for forming a lubricating coating. The precursor coating composition includes a first component including a polysiloxane precursor, a ceramic filler, and lubricating particles. The precursor coating composition includes a solvent. The precursor coating composition also includes an acid.

[0007] In various aspects, the present invention provides a precursor coating composition for forming a lubricating coating. The precursor coating composition includes a first component. The first component includes a polysiloxane precursor including an alkoxysilane. The polysiloxane precursor is 50 wt% to 97 wt% of the first component of the precursor coating composition. The first component includes a ceramic filler including zirconium oxide (ZrCh), titania (TiCh), silica carbide (SiC), ceria (CeCh), magnesium oxide (MgO), zinc oxide (ZnO), copper oxide (CuO), silica (SiCh), alumina (AI2O3), or a combination thereof. The ceramic filler is 0.1 wt% to 40 wt% of the first component of the precursor coating composition. The first component also includes lubricating particles including tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof. The lubricating particles are 0.01 wt% to 40 wt% of the first component of the precursor coating composition. The precursor coating composition includes an acid that is 0.05 wt% to 5 wt% of the precursor coating composition. The precursor coating composition also includes a solvent including a (Ci-C5)alcohol, wherein the solvent is 5 wt% to 95 wt% of the precursor coating composition. [0008] In various aspects, the present invention provides a coating composition for forming a lubricating coating. The coating composition includes a reaction product of the precursor coating composition of the present invention.

[0009] In various aspects, the present invention provides a coating composition for forming a lubricating coating. The coating composition includes a polysiloxane, lubricating particles, and a solvent.

[0010] In various aspects, the present invention provides a coating composition for forming a lubricating coating. The coating composition includes a first component. The first component includes a polysiloxane that is 50 wt% to 99.9 wt% of the first component of the coating composition. The first component includes lubricating particles including tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof. The lubricating particles are 0.01 wt% to 40 wt% of the first component of the coating composition. The coating composition also includes a solvent including a (Ci-C5)alcohol. The solvent is 5 wt% to 95 wt% of the coating composition.

[0011] In various aspects, the present invention provides a lubricating coating that includes a cured product of the coating composition of the present invention.

[0012] In various aspects, the present invention provides a lubricating coating that includes a cured product of a coating composition. The coating composition is a reaction product of a precursor coating composition. The precursor coating composition includes a polysiloxane precursor, an acid, a ceramic filler, a solvent, and lubricating particles.

[0013] In various aspects, the present invention provides a lubricating coating that includes a cured product of a coating composition. The coating composition is a reaction product of a precursor coating composition. The precursor coating composition includes a first component. The first component includes a polysiloxane precursor including an alkoxysilane. The polysiloxane precursor is 50 wt% to 97 wt% of the first component of the precursor coating composition. The first component includes a ceramic filler including zirconium oxide (ZrCh), titania (TiCh), silica carbide (SiC), ceria (CeCh), magnesium oxide (MgO), zinc oxide (ZnO), copper oxide (CuO), silica (SiCh), alumina (AI2O3), or a combination thereof. The ceramic filler is 0.1 wt% to 40 wt% of the first component of the precursor coating composition. The first component also includes lubricating particles including tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof. The lubricating particles are 0.01 wt% to 40 wt% of the first component of the precursor coating composition. The precursor coating composition includes an acid that is 0.05 wt% to 5 wt% of the precursor coating composition. The precursor coating composition also includes a solvent including a (Ci-C5)alcohol. The solvent is 5 wt% to 95 wt% of the precursor coating composition. The precursor coating composition is a ball-milled precursor coating composition and/or the coating composition is a ball-milled coating composition. [0014] Various aspects of the present invention provide a method of forming the precursor coating composition of the present invention and/or the coating composition of the present invention. The method includes forming a mixture. The mixture includes lubricating particles, solvent, ceramic filler, and polysiloxane precursor. The method includes adding the acid to the mixture, to form the precursor coating composition.

[0015] Various aspects of the present invention provide a method of forming a lubricating coating on a substrate. The method includes forming a mixture. The mixture includes lubricating particles, a solvent, a ceramic filler, and a polysiloxane precursor. The method includes adding an acid to the mixture. The method includes allowing the acid and the polysiloxane precursor to react to form a coating composition including a polysiloxane, the lubricating particles, and the solvent. The method includes applying the coating composition to the substrate. The method includes drying the coating composition on the substrate. The method also includes curing the coating composition on the substrate, to form the lubricating coating on the substrate.

[0016] Various aspects of the present invention provide a substrate including the lubricating coating of the present invention.

[0017] Various aspects of the present invention provide an extrusion die including the lubricating coating of the present invention.

[0018] Various aspects of the present invention provide a method of using the extrusion die of the present invention that includes a lubricating coating. The method includes extruding an extrudable composition through the extrusion die.

[0019] Although conventional polytetrafluoroethylene (PTFE)-based solid coatings offer good lubrication, these coatings have at least two major disadvantages for use on dies. First, PTFE-based coatings have poor mechanical strength which make them susceptible to abrasive wear. Second, PTFE-based coatings are extremely difficult to strip from a die surface at the end of its useful operational lifetime.

[0020] Various aspects of the lubricating coating, coating compositions for making the same, and substrates such as dies that include the lubricating coating, have various advantages over conventional lubricating coatings (e.g., PTFE-based solid coatings), compositions for forming the same, and substrates including the same. For example, in various aspects of the present invention, the lubricating coating of the present invention can provide equivalent or superior mechanical strength as compared to PTFE-based solid coatings. In various aspects of the present invention, the lubricating coating of the present invention can be easier to remove or strip by chemical methods than PTFE-based solid coatings, due to less use of or no use of relatively unreactive fluorinated materials in the coating.

[0021] In various aspects, the lubricating coating of the present invention can provide greater wear-resistance, such as on an extrusion die, as compared to other lubricating coatings, such as compared to PTFE-based solid coatings.

[0022] In various aspects, the lubricating coating of the present invention on an extrusion die surface can provide lower friction than other coated extrusion dies, including during use of new or freshly recoated dies. Avoiding pressure spikes during startup can avoid lost product during startup due to flow instabilities, avoid lost production time during startup, and avoid aborted runs during startup. In various aspects, the lubricating coating of the present invention can provide equivalent or better lubrication, such as on extrusion dies, as compared to PTFE-based solid coatings.

[0023] In various aspects, extrusion dies coated with the lubricating coating of the present invention can experience a longer production lifetime overall. The lubricating coating can protect the underlying surface of the extrusion die, decreasing or eliminating wear thereon. By protecting the underlying surface of the extrusion die, replacement of hard protecting coatings on the die that lie underneath the lubricating coating can be reduced in frequency or avoided entirely.

[0024] In various aspects, the lubricating coating of the present invention can have a surface that is hydrophobic and oleophilic. The hydrophobic and oleophilic surface can facilitate migration of oil to the die-batch interface which can enhance the formation of slippage and low friction at the interface. The slippage promotion can enable significant reduction of oil used in oil-containing batches, which can reduce or eliminate the occurrence of oil-induced fissures and the corresponding unsafe work environment that results from kilnfiring extruded parts that develop oil-induced fissures.

[0025] In various aspects, the lubricating coating of the present invention can have boundary layer properties to reduce or minimize friction between extrusion batch material and the die wall, which can lead to reduced pressure during extrusion. The reduced extrusion pressures consequently will reduce the wear on the hard coating on the die; therefore, the lubricating coating of the present invention can extend the use life of an extrusion die.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Reference will now be made in detail to certain aspects of the disclosed subject matter. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended to limit the claims to the disclosed subject matter.

[0027] Throughout this document, values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “about 0.1% to about 5%” or “about 0.1 % to 5%” should be interpreted to include not just about 0.1% to about 5%, but also the individual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “about X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “about X, Y, or about Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.

[0028] In this document, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” or “at least one of A or B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.

[0029] In the methods described herein, the acts can be carried out in a specific order as recited herein. Alternatively, in any aspect(s) disclosed herein, specific acts may be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited. Furthermore, specified acts can be carried out concurrently unless explicit claim language recites that they be carried out separately or the plain meaning of the claims would require it. For example, a claimed act of doing X and a claimed act of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process. [0030] The term “about” as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1 % of a stated value or of a stated limit of a range, and includes the exact stated value or range.

[0031] The term “substantially” as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%. The term “substantially free of’ as used herein can mean having none or having a trivial amount of, such that the amount of material present does not affect the material properties of the composition including the material, such that about 0 wt% to about 5 wt% of the composition is the material, or about 0 wt% to about 1 wt%, or about 5 wt% or less, or less than, equal to, or greater than about 4.5 wt%, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.01, or about 0.001 wt% or less, or about 0 wt%.

[0032] As used herein, the term “polymer” refers to a molecule having at least one repeating unit and can include copolymers.

[0033] The term “alkyl” as used herein refers to straight chain and branched alkyl groups and cycloalkyl groups having from 1 to 40 carbon atoms, 1 to about 20 carbon atoms, 1 to 12 carbons or, in some embodiments, from 1 to 8 carbon atoms. Examples of straight chain alkyl groups include those with from 1 to 8 carbon atoms such as methyl, ethyl, n- propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, and n-octyl groups. Examples of branched alkyl groups include, but are not limited to, isopropyl, iso-butyl, sec-butyl, t-butyl, neopentyl, isopentyl, and 2,2-dimethylpropyl groups. As used herein, the term “alkyl” encompasses n- alkyl, isoalkyl, and anteisoalkyl groups as well as other branched chain forms of alkyl.

Precursor coating composition.

[0034] Various aspects of the present invention provide a precursor coating composition for forming a lubricating coating. The precursor coating composition can include a first component. The first component can include a polysiloxane precursor, a ceramic filler, and lubricating particles. The precursor coating composition can also include a solvent. The precursor coating composition can also include an acid.

[0035] The polysiloxane precursor of the first component of the precursor coating composition can include any suitable precursor material for forming a polysiloxane. The polysiloxane precursor can include an alkoxysilane, such as an alkyltrialkoxysilane, a dialkyldialkoxysilane, a tetraalkoxysilane, or a combination thereof. The polysiloxane precursor can include an alkyltrialkoxysilane, a tetraalkoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, methyltrimethyoxysilane (MTMS), tetraethoxysilane (TEOS), or a combination thereof. The polysiloxane precursor can include methyltrimethyoxysilane (MTMS), tetraethoxysilane (TEOS), or a combination thereof. The polysiloxane precursor can be any suitable proportion of the first component, such as 50 wt% to 99.9 wt%, 80 wt% to 97 wt%, or equal to or less than 99.9 wt% and greater than or equal to 50 wt%, 55, 60, 65, 70, 75, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 wt%.

[0036] The ceramic filler of the first component of the precursor coating composition can include any suitable ceramic filler, such as zirconium oxide (ZrCE), titania (TiCE), silica carbide (SiC), ceria (CeCE), magnesium oxide (MgO), zinc oxide (ZnO), copper oxide (CuO), silica (SiCE), alumina (AECE), or a combination thereof. The ceramic filler can include silica, alumina, or a combination thereof. The ceramic filler can be any suitable proportion of the first component, such as 0.01 wt% to 40 wt%, 2 wt% to 15 wt%, or less than or equal to 40 wt% and greater than or equal to 0.01 wt%, 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, or 38 wt%.

[0037] The lubricating particles of the first component of the precursor coating composition can include any suitable lubricating particles, such as tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof. The lubricating particles can include graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof. The lubricating particles can be any suitable proportion of the first component, such as 0.01 wt% to 40 wt%, 2 wt% to 10 wt%, or less than or equal to 40 wt% and greater than or equal to 0.01 wt%, 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, or 38 wt%. The lubricating particles in the first component of the precursor coating composition can have any suitable average particle size, such as a number average particle size of 0.01 micron to 500 microns, 50 nm to 500 nm, or less than or equal to 500 microns and greater than or equal to 10 nm, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 250, 300, 400, 500, 600, 800 nm, 1 micron, 2, 4, 6, 8, 10, 15, 20, 50, 100, 200, 350, or 450 microns. The particle size of the lubricating particles in the first component of the precursor coating composition be achieved by any suitable technique, such as by reducing particle size. An example of a process that can be used to reduce particle size is ball milling. For example, the precursor coating composition can be a ball-milled composition, such that the entire precursor coating composition or one or more components thereof are ball milled prior to and/or during the reaction of the acid with the polysiloxane precursor to form the polysiloxane. In various aspects, the lubricating particles can have any suitable number average particle size prior to particle size reduction, such as 100 nm to 500 microns, or 500 nm to 100 microns. The lubricating particles are homogeneously distributed in the precursor coating composition, the coating composition, and the lubricating coating.

[0038] The precursor coating composition can be substantially free of fluoropolymers, titanium (e.g., elemental titanium), titanium compounds, titanium salts, organic polymers, carbon nanotubes, or a combination thereof; for example, any one or more of these materials can be 0 wt% to 1 wt% of the precursor coating composition, or 0 wt% to 0.1 wt%, or 0 wt% to 0.001 wt%, or 0 wt%.

[0039] The precursor coating composition can include a solvent. The solvent can be any suitable solvent, such as an organic solvent. The organic solvent can be an alcohol, such as a (Ci-C5)alcohol, such as ethanol or methanol. The solvent, and the precursor coating composition, can be substantially free of water; for example, water can be 0 wt% to 1 wt% of the precursor coating composition, or 0 wt% to 0.1 wt%, or 0 wt% to 0.001 wt%. The solvent can be any suitable proportion of the precursor coating composition. The solvent can be substantially removed later during drying of the coating composition formed from the precursor coating composition. The solvent can be 5 wt% to 95 wt% of the precursor coating composition, 10 wt% to 80 wt%, or less than or equal to 95 wt% and greater than or equal to 5 wt%, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 wt%.

[0040] The precursor coating composition can include an acid. The acid can be any suitable acid. The acid can be a mineral acid, an organic acid, or a combination thereof. The acid can include citric acid. The acid can be any suitable proportion of the precursor coating composition, such as 0.01 wt% to 10 wt%, 0.05 wt% to 5 wt%, or less than or equal to 10 wt% and greater than or equal to 0.01 wt%, 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, or 9 wt%.

[0041] The precursor coating composition can include any suitable weight ratio of the polysiloxane precursor to the lubricating particles, such as 5:1 to 80:1, or 10:1 to 45:1, or less than or equal to 80:1 and greater than or equal to 5:1, 6:1, 8: 1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55: 1, 60:1, 65:1, 70:1, or 75:1.

[0042] The precursor coating composition can include any suitable weight ratio of the ceramic additive to the lubricating particles, such as 0. 1 :1 to 10:1, or 0.5:1 to 4: 1, or less than or equal to 10: 1 and greater than or equal to 0.1 :1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1. [0043] The precursor coating composition can include any suitable weight ratio of the polysiloxane precursor and the ceramic additive to the lubricating particles, such as 1 : 1 to 80:1, or 5:1 to 45:1, or less than or equal to 80:1 and greater than or equal to 1 :1, 2:1, 3:1, 4:1, 5:1, 6:1, 8:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65: 1, 70:1, or 75:1.

[0044] The precursor coating composition can be subjected to a particle size reduction process. For example, the entire precursor coating composition can be subjected to the particle size reduction process, or one or more components of the precursor coating composition can be subjected to the particle size reduction process. The first component of the precursor coating composition, or one or more components thereof, can be subjected to the size reduction process. The first component and the solvent can be subjected to the particle size reduction process. The first component, the solvent, and the acid can be subjected to the particle size reduction process. The particle size reduction process can be any suitable process for reducing particle size, such as grinding, milling, or a combination thereof. The particle size reduction process can be ball-milling. The precursor coating composition can be a ball-milled precursor coating composition, such that at least the first component and optionally the acid and/or solvent are included during the ball-milling.

Coating composition.

[0045] Various aspects of the present invention provide a coating composition for forming a lubricating coating. The coating composition includes a reaction product of the precursor coating composition of the present invention. For example, the coating composition includes a reaction produce of a precursor coating composition that includes an acid, a solvent, and a first component, wherein the first component includes a polysiloxane precursor, a ceramic filler, and lubricating particles. The coating composition can include a polysiloxane, lubricating particles, and solvent. The coating composition can be cured to form a lubricating coating. The solvent can be substantially removed (dried) from the coating composition prior to or during curing of the coating composition to form a lubricating coating. The coating composition can be a sol-gel. The polysiloxane can form a matrix in the coating composition, wherein the lubricating particles are homogeneously distributed in the polysiloxane matrix.

[0046] In various aspects, the coating composition can be characterized as including the solvent and a first component, wherein the first component includes the polysiloxane and the lubricating particles. The polysiloxane can be 50 wt% to 99.9 wt% of the first component of the coating composition, or less than or equal to 99.9 wt% and greater than or equal to 50 wt%, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99 wt%. The lubricating particles can be 0.01 wt% to 40 wt% of the first component of the coating composition, or less than or equal to 40 wt% and greater than or equal to 0.01 wt%, 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, or 38 wt%. The solvent can be any suitable proportion of the coating composition, such as 5 wt% to 95 wt% of the coating composition, or less than or equal to 95 wt% and greater than or equal to 5 wt%, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 85, or 95 wt%.

Lubricating coating.

[0047] Various aspects of the present invention provide a lubricating coating. The lubricating coating includes a cured product of the coating composition of the present invention.

[0048] The lubricating coating can include a cured product of a coating composition that includes a polysiloxane and lubricating particles. The coating composition can optionally include a solvent that is removed during the during, or the coating composition can be dried prior to the curing.

[0049] The lubricating coating can include a cured product of a coating composition. The coating composition can be a reaction product of a precursor coating composition including a polysiloxane precursor, an acid, a ceramic filler, a solvent, and lubricating particles.

[0050] In various aspects, the lubricating particles in the lubricating coating can include the polysiloxane in pores and/or crevices of the lubricating particles that are otherwise inaccessible to the polysiloxane without being formed therein. Such structure can result from forming the polysiloxane polymer from an intimate mixture of the lubricating particles and the polysiloxane precursor. Such structures are absent from lubricating coatings wherein the polysiloxane polymer is formed prior to addition of the lubricating particles thereto.

Method of forming precursor coating composition or coating composition.

[0051] Various aspects of the present invention provide a method of forming the precursor coating composition of the present invention and/or the coating composition of the present invention. The method can include forming a mixture including the lubricating particles, solvent, ceramic filler, and the polysiloxane precursor of the precursor coating composition. The method can include adding the acid of the precursor coating composition to the mixture, to form the precursor coating composition. The method can include allowing the polysiloxane precursor and the acid to react, to form the coating composition of the present invention. The polysiloxane precursor and the acid can react to form the polysiloxane of the coating composition.

[0052] The method can further include performing a size reduction process on the mixture that includes the solvent, ceramic filler, the polysiloxane precursor, and the acid, or the size reduction process can be performed on one or more components thereof. The size reduction process can include ball-milling. The method can include ball-milling the first component of the precursor coating composition or one or more components thereof. The method can include ball-milling the first component of the precursor coating composition with the solvent and/or the acid added thereto. The size reduction process of the mixture can provide the precursor coating composition (e.g., a size-reduced precursor coating composition, such as a ball-milled precursor coating composition). The size reduction or ball-milling can be performed before or after the addition of acid to the mixture. The ballmilling can be conducted for any suitable period of time, such as 0.5 h to 10 h, or less than or equal to 10 h and greater than or equal to 0.5 h, 1, 2, 3, 4, 6, or 8 h.

[0053] In various aspects, the method of forming the precursor coating composition of the present invention and/or the coating composition of the present invention is a one-pot method.

Method of forming lubricating coating.

[0054] Various aspects of the present invention provide a method of forming a lubricating coating. The method can include forming, or obtaining or providing, the precursor coating composition of the present invention, then allowing the precursor coating to react to form the coating composition. The method can include applying the coating composition to a substrate, and drying the coating composition on the substrate. The method can include curing the coating composition, to form the lubricating coating on the substrate. [0055] In various aspects, the method of forming a lubricating coating on a substrate can include forming a mixture that includes lubricating particles, a solvent, a ceramic filler, and a polysiloxane precursor. The method can include adding an acid to the mixture. The method can include allowing the acid and the polysiloxane precursor to react to form a coating composition including a polysiloxane, the lubricating particles, and the solvent. The method can include applying the coating composition to the substrate. The method can include drying the coating composition on the substrate. The method can also include curing the coating composition on the substrate, to form the lubricating coating on the substrate. In various aspects, the method includes ball-milling the mixture after the addition of the acid and the polysiloxane precursor thereto.

[0056] The substrate can be any suitable substrate. For example, the substrate can be an extrusion die. The coating can be applied to the coating in any suitable way that produces a coating on the desired portions of the surface at a desired thickness. For example, the method can include dipping the substrate into the coating composition to apply the coating composition to the substrate.

[0057] The drying of the coating composition on the substrate can include heating.

The drying can include heating at 40 °C to 100 °C for 1 min. to 24 h, or at 60 °C to 90 °C for 30 min. to 2 h, or less than or equal to 100 °C and greater than or equal to 40 °C, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95 °C for less than or equal to 24 h and greater than or equal to 1 min, 2, 4, 6, 8, 10, 15, 20, 30, 40, 50 min, 1 h, 2, 4, 6, 8, 10, 15, or 20 h.

[0058] The curing of the coating composition can include heating, such as heating at 100 °C to 300 °C for 1 min. to 24 h, or heating at 150 °C to 250 °C for 30 min. to 2 h, or less than or equal to 300 °C and greater than or equal to 100 °C, 120, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 280, or 290 °C.

Substrate including lubricating coating.

[0059] In various aspects, the present invention provides a substrate including the lubricating coating of the present invention. The substrate can be any suitable substrate. For example, the substrate can be an extrusion die, such as an extrusion die for extrusion of ceramic compositions.

Method of using an extrusion die including lubricating coating.

[0060] In various aspects, the present invention provides a method of using an extrusion die, wherein the extrusion die includes the lubricating coating of the present invention. The method can include extruding an extrudable composition, such as a ceramic composition, through the extrusion die.

Examples [0061] Various aspects of the present invention can be better understood by reference to the following Examples which are offered by way of illustration. The present invention is not limited to the Examples given herein.

[0062] The dynamic coefficient of friction, a measure of lubricity of (COF) of the solgel derived lubricious coatings of the invention was measured and compared to that of current PTFE coating. The following parameters were used: counter material: granite; sliding distance: 25 mm; applied load: 3000 g; and sliding speed: 10 mm/min.

[0063] Without intending to limit the invention in any manner, the present invention will be more fully understood from the detailed description presented below:

Example 1. Boron nitride with MTMS, TEOS, and colloidal silica.

[0064] In Example 1 , two different sol-gel precursors were used: tetraethyl orthosilicate (TEOS) and methyltrimethoxy silane (MTMS). Boron nitride and colloidal silica were used respectively as a solid lubricant and a ceramic filler. A mixture was prepared by combining 18.41 parts ethanol with 1.5 parts boron nitride powder, then 4.41 parts colloidal silica (LUDOX TMA, 34 wt%) was added to the mixture, and then 20.43 parts MTMS and 41.66 parts TEOS were added to the mixture. Citric acid (0. 1 parts) was then added to the mixture. The mixture was stirred at room temperature for 3 hours and then ball- milled for 3 hours. After ball-milling, the solution was ready for application to the substrate. [0065] The substrate used was a TiCN -coated 422 SS coupon. The sol-gel coating was formed on the coupon as follows: The as-received coupon was cleaned with acetone in an ultrasonic bath for 10 minutes. It was then soaked in isopropyl alcohol in an ultrasonic bath for 10 minutes and rinsed in deionized water. Subsequently, the coupon was dried at 110 °C for 30 minutes. Then, the sol-gel solution was applied to the clean coupon by dipping in the coating solution for 20 seconds followed by drying in a convection oven in air at 80 °C for 1 hour. After drying, the sol-gel derived coating was cured at 200 °C for 1 hour. The composition of the coating is presented in Table 1. The lubricity of the coating as characterized by dynamic COF is presented in Table 4, which can be seen to be close to that of the current PTFE coating. [0066] Table 1. Composition of coating prepared in Example 1.

Example 2. Boron nitride with MTMS, colloidal silica, and alumina.

[0067] In Example 2, the sol-gel precursor used was MTMS. Boron nitride was used as a solid lubricant. Colloidal silica and alumina powder were used as ceramic fillers. The sol-gel coating solution was prepared in the same as in Example 1. The solution was prepared by mixing 57.84 parts ethanol and 1.75 parts boron nitride powder, then adding 10.29 parts colloidal silica (LUDOX TMA, 34 wt%) and 1.75 parts alumina powder, and then adding 35.14 parts MTMS. An amount of 1.02 parts citric acid was then added to the mixture. The mixture was stirred at room temperature for 3 hours and then ball-milled for 3 hours. After ball-milling, the solution was ready to be applied to the substrate.

[0068] The coating application and thermal treatment were performed in the same manner as Example 1. The composition of the coating is shown in Table 2. The dynamic COF of the coating is shown in Table 4.

[0069] Table 2. Composition of coating prepared in Example 2.

Example 3. Boron nitride and molybdenum disulfide with MTMS and colloidal silica.

[0070] In Example 3, the sol-gel precursor used was MTMS. Boron nitride (BN) and molybdenum disulfide (M0S2) were used as solid lubricants. Colloidal silica was used as ceramic filler. The coating solution was prepared by mixing 42.48 parts ethanol, 1.75 parts boron nitride powder, and 0.65 parts M0S2. To the mixture was added 10.29 parts colloidal silica (LUDOX TMA, 34 wt%), and then 26.36 parts MTMS were added. An amount of 0.78 parts citric acid was then added to the mixture. The mixture was stirred at room temperature for 3 hours and then ball-milled for 3 hours. After ball-milling, the solution was ready to be applied to the substrate. [0071] The coating application and thermal treatment were performed in the same manner as in Example 1. The composition of the coating is presented in Table 3. The dynamic COF of the coating is presented in Table 4. The PTFE coating was a PTFE dispersion incorporated with colloidal silica and WS2 lubricating particles which was applied to the same substrate used for the inventive compositions by using dip coating followed by heat treatment.

[0072] Table 3. Composition of coating prepared in Example 3.

[0073] Table 4. Coefficient of friction values for the sol-gel derived lubricious coatings of Examples 1 -3 and compared to that of the current PTFE coating.

[0074] The terms and expressions that have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the aspects of the present invention. Thus, it should be understood that although the present invention has been specifically disclosed by specific aspects and optional features, modification and variation of the concepts herein disclosed may be resorted to by those of ordinary skill in the art, and that such modifications and variations are considered to be within the scope of aspects of the present invention.

Exemplary Aspects.

[0075] The following exemplary aspects are provided, the numbering of which is not to be construed as designating levels of importance:

[0076] Aspect 1 provides a precursor coating composition for forming a lubricating coating, the precursor coating composition comprising: a first component comprising a polysiloxane precursor, a ceramic filler, and lubricating particles; a solvent; and an acid.

[0077] Aspect 2 provides the precursor coating composition of Aspect 1, wherein the polysiloxane precursor is 50 wt% to 99.9 wt% of the first component of the precursor coating composition.

[0078] Aspect 3 provides the precursor coating composition of any one of Aspects 1-

2, wherein the polysiloxane precursor is 80 wt% to 97 wt% of the first component of the precursor coating composition.

[0079] Aspect 4 provides the precursor coating composition of any one of Aspects 1-

3, wherein the polysiloxane precursor comprises an alkoxysilane.

[0080] Aspect 5 provides the precursor coating composition of any one of Aspects 1-

4, wherein the polysiloxane precursor comprises an alkyltrialkoxysilane, a tetraalkoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, methyltrimethyoxysilane (MTMS), tetraethoxysilane (TEOS), or a combination thereof.

[0081] Aspect 6 provides the precursor coating composition of any one of Aspects 1-

5, wherein the polysiloxane precursor comprises methyltrimethyoxysilane (MTMS), tetraethoxysilane (TEOS), or a combination thereof.

[0082] Aspect 7 provides the precursor coating composition of any one of Aspects 1-

6, wherein the ceramic filler is 0.01 wt% to 40 wt% of the first component of the precursor coating composition.

[0083] Aspect 8 provides the precursor coating composition of any one of Aspects 1-

7, wherein the ceramic filler is 2 wt% to 15 wt% of the first component of the precursor coating composition.

[0084] Aspect 9 provides the precursor coating composition of any one of Aspects 1-

8, wherein the ceramic filler comprises zirconium oxide (ZrCE), titania (TiCh), silica carbide (SiC), ceria (CeCE), magnesium oxide (MgO), zinc oxide (ZnO), copper oxide (CuO), silica (SiCE), alumina (AI2O3), or a combination thereof. [0085] Aspect 10 provides the precursor coating composition of any one of Aspects 1 -9, wherein the ceramic filler comprises silica, alumina, or a combination thereof.

[0086] Aspect 11 provides the precursor coating composition of any one of Aspects 1-10, wherein the lubricating particles are 0.01 wt% to 40 wt% of the first component of the precursor coating composition.

[0087] Aspect 12 provides the precursor coating composition of any one of Aspects 1-11, wherein the lubricating particles are 2 wt% to 10 wt% of the first component of the precursor coating composition.

[0088] Aspect 13 provides the precursor coating composition of any one of Aspects 1-12, wherein the lubricating particles comprise tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof.

[0089] Aspect 14 provides the precursor coating composition of any one of Aspects 1-13, wherein the lubricating particles comprise graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof.

[0090] Aspect 15 provides the precursor coating composition of any one of Aspects 1-14, wherein the lubricating particles have a number average particle size of 0.01 micron to 500 microns.

[0091] Aspect 16 provides the precursor coating composition of any one of Aspects 1-15, wherein the lubricating particles have a particle size of 50 nm to 500 nm.

[0092] Aspect 17 provides the precursor coating composition of any one of Aspects 1-16, wherein the precursor coating composition is substantially free of fluoropolymers, titanium, titanium compounds, organic polymers, carbon nanotubes, or a combination thereof.

[0093] Aspect 18 provides the precursor coating composition of any one of Aspects 1-17, wherein the solvent is 5 wt% to 95 wt% of the precursor coating composition.

[0094] Aspect 19 provides the precursor coating composition of any one of Aspects 1-18, wherein the solvent is 10 wt% to 80 wt% of the precursor coating composition.

[0095] Aspect 20 provides the precursor coating composition of any one of Aspects 1-19, wherein the solvent comprises an organic solvent.

[0096] Aspect 21 provides the precursor coating composition of any one of Aspects 1 -20, wherein the solvent comprises alcohol.

[0097] Aspect 22 provides the precursor coating composition of any one of Aspects 1-21, wherein the solvent comprises ethanol. [0098] Aspect 23 provides the precursor coating composition of any one of Aspects 1 -22, wherein the precursor coating composition is substantially free of water.

[0099] Aspect 24 provides the precursor coating composition of any one of Aspects 1-23, wherein the acid is 0.01 wt% to 10 wt% of the precursor coating composition.

[0100] Aspect 25 provides the precursor coating composition of any one of Aspects 1-24, wherein the acid is 0.05 wt% to 5 wt% of the precursor coating composition.

[0101] Aspect 26 provides the precursor coating composition of any one of Aspects 1-25, wherein the acid comprises an organic acid, a mineral acid, or a combination thereof.

[0102] Aspect 27 provides the precursor coating composition of any one of Aspects 1 -26, wherein the acid comprises citric acid.

[0103] Aspect 28 provides the precursor coating composition of any one of Aspects 1 -27, comprising a weight ratio of the polysiloxane precursor to the lubricating particles of 5:1 to 80:1.

[0104] Aspect 29 provides the precursor coating composition of any one of Aspects 1-28, comprising a weight ratio of the polysiloxane precursor to the lubricating particles of 10:1 to 45:1.

[0105] Aspect 30 provides the precursor coating composition of any one of Aspects 1-29, comprising a weight ratio of the ceramic additive to the lubricating particles of 0. 1 :1 to 10:1.

[0106] Aspect 31 provides the precursor coating composition of any one of Aspects 1-30, comprising a weight ratio of the ceramic additive to the lubricating particles of 0.5:1 to 4:1.

[0107] Aspect 32 provides the precursor coating composition of any one of Aspects 1-31, comprising a weight ratio of the polysiloxane precursor and the ceramic additive to the lubricating particles of 1 : 1 to 80: 1.

[0108] Aspect 33 provides the precursor coating composition of any one of Aspects 1-32, comprising a weight ratio of the polysiloxane precursor and the ceramic additive to the lubricating particles of 5:1 to 45: 1.

[0109] Aspect 34 provides the precursor coating composition of any one of Aspects 1-33, wherein the precursor coating composition is a ball-milled composition.

[0110] Aspect 35 provides a precursor coating composition for forming a lubricating coating, the precursor coating composition comprising: a first component comprising a polysiloxane precursor comprising an alkoxysilane, wherein the polysiloxane precursor is 50 wt% to 97 wt% of the first component of the precursor coating composition, a ceramic filler comprising zirconium oxide (ZrCh), titania (TiCh), silica carbide (SiC), ceria (CcCh), magnesium oxide (MgO), zinc oxide (ZnO), copper oxide (CuO), silica (SiCh), alumina (AI2O3), or a combination thereof, wherein the ceramic filler is 0.1 wt% to 40 wt% of the first component of the precursor coating composition, and lubricating particles comprising tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof, wherein the lubricating particles are 0.01 wt% to 40 wt% of the first component of the precursor coating composition; an acid that is 0.05 wt% to 5 wt% of the precursor coating composition; and a solvent comprising a (Ci-C5)alcohol, wherein the solvent is 5 wt% to 95 wt% of the precursor coating composition.

[0111] Aspect 36 provides a coating composition for forming a lubricating coating, the coating composition comprising a reaction product of the precursor coating composition of any one of Aspects 1-35.

[0112] Aspect 37 provides a coating composition for forming a lubricating coating, the coating composition comprising: a polysiloxane; lubricating particles; and a solvent.

[0113] Aspect 38 provides a coating composition for forming a lubricating coating, the coating composition comprising: a first component comprising a polysiloxane that is 50 wt% to 99.9 wt% of the first component of the coating composition, and lubricating particles comprising tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof, wherein the lubricating particles are 0.01 wt% to 40 wt% of the first component of the coating composition; and a solvent comprising a (Ci-C5)alcohol, wherein the solvent is 5 wt% to 95 wt% of the coating composition. [0114] Aspect 39 provides a lubricating coating comprising a cured product of the coating composition of any one of Aspects 36-38.

[0115] Aspect 40 provides the lubricating coating of Aspect 39, wherein the lubricating particles in the lubricating coating comprise the polysiloxane in pores and/or crevices that are inaccessible to the polysiloxane without being formed therein.

[0116] Aspect 41 provides a lubricating coating comprising: a cured product of a coating composition, wherein the coating composition is a reaction product of a precursor coating composition comprising a polysiloxane precursor, an acid, a ceramic filler, a solvent, and lubricating particles.

[0117] Aspect 42 provides a lubricating coating comprising: a cured product of a coating composition, wherein the coating composition is a reaction product of a precursor coating composition comprising a first component comprising a polysiloxane precursor comprising an alkoxysilane, wherein the polysiloxane precursor is 50 wt% to 97 wt% of the first component of the precursor coating composition, a ceramic filler comprising zirconium oxide (ZrCh), titania (TiCh), silica carbide (SiC), ceria (CeCh), magnesium oxide (MgO), zinc oxide (ZnO), copper oxide (CuO), silica (SiCh), alumina (AI2O3), or a combination thereof, wherein the ceramic filler is 0.1 wt% to 40 wt% of the first component of the precursor coating composition, and lubricating particles comprising tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof, wherein the lubricating particles are 0.01 wt% to 40 wt% of the first component of the precursor coating composition; an acid that is 0.05 wt% to 5 wt% of the precursor coating composition; and a solvent comprising a (Ci-C5)alcohol, wherein the solvent is 5 wt% to 95 wt% of the precursor coating composition; wherein the precursor coating composition and/or the coating composition are ball- milled. [0118] Aspect 43 provides a method of forming the precursor coating composition of any one of Aspects 1-35 and/or the coating composition of any one of Aspects 36-38, the method comprising: forming a mixture comprising the lubricating particles, the solvent, the ceramic filler, and the polysiloxane precursor; adding the acid to the mixture, to form the precursor coating composition.

[0119] Aspect 44 provides the method of claim 43, further comprising allowing the polysiloxane precursor and the acid to react, to form the coating composition of any one of Aspects 36-38.

[0120] Aspect 45 provides the method of any one of Aspects 43-44, further comprising ball-milling the mixture after the addition of the acid thereto, to form the precursor coating composition of Aspects 1-35.

[0121] Aspect 46 provides the method of Aspect 45, wherein the ball-milling is conducted for 0.5 h to 10 h.

[0122] Aspect 47 provides the method of any one of Aspects 43-46, further comprising ball-milling the mixture before the addition of the acid thereto.

[0123] Aspect 48 provides the method of any one of Aspects 43-47, wherein the method is a one -pot method.

[0124] Aspect 49 provides a method of forming a lubricating coating on a substrate, the method comprising: forming a mixture comprising lubricating particles, a solvent, a ceramic filler, and a polysiloxane precursor; adding an acid to the mixture; allowing the acid and the polysiloxane precursor to react to form a coating composition comprising a polysiloxane, the lubricating particles, and the solvent; applying the coating composition to the substrate; drying the coating composition on the substrate; and curing the coating composition on the substrate, to form the lubricating coating on the substrate.

[0125] Aspect 50 provides the method of Aspect 49, further comprising ball-milling the mixture after the addition of the acid and the polysiloxane precursor thereto.

[0126] Aspect 51 provides the method of any one of Aspects 49-50, wherein the substrate comprises an extrusion die.

[0127] Aspect 52 provides the method of any one of Aspects 49-51 , wherein applying the coating composition to the substrate comprises dipping the substrate into the coating composition.

[0128] Aspect 53 provides the method of any one of Aspects 49-52, wherein the drying comprises heating.

[0129] Aspect 54 provides the method of any one of Aspects 49-53, wherein the drying comprises heating at 40 °C to 100 °C for 1 min. to 24 h.

[0130] Aspect 55 provides the method of any one of Aspects 49-54, wherein the drying comprises heating at 60 °C to 90 °C for 30 min. to 2 h.

[0131] Aspect 56 provides the method of any one of Aspects 49-55, wherein the curing comprises heating.

[0132] Aspect 57 provides the method of any one of Aspects 49-56, wherein the curing comprises heating at 100 °C to 300 °C for 1 min. to 24 h.

[0133] Aspect 58 provides the method of any one of Aspects 49-57, wherein the curing comprises heating at 150 °C to 250 °C for 30 min. to 2 h.

[0134] Aspect 59 provides a substrate comprising the lubricating coating of any one of Aspects 39-42.

[0135] Aspect 60 provides an extrusion die comprising the lubricating coating of any one of Aspects 39-42.

[0136] Aspect 61 provides a method of using the extrusion die of Aspect 60, the method comprising: extruding an extrudable composition through the extrusion die.

[0137] Aspect 62 provides the precursor coating composition, coating composition lubricating coating, method, substrate, or extrusion die of any one or any combination of Aspects 1-61 optionally configured such that all elements or options recited are available to use or select from.

Claims

CLAIMS What is claimed is:

1. A lubricating coating comprising: a cured product of a coating composition, wherein the coating composition is a reaction product of a precursor coating composition comprising a first component comprising a polysiloxane precursor, a ceramic filler, and lubricating particles; a solvent; and an acid.

2. The lubricating coating of claim 1, wherein the polysiloxane precursor is 80 wt% to 97 wt% of the first component of the precursor coating composition.

3. The lubricating coating of any one of claims 1-2, wherein the polysiloxane precursor comprises methyltrimethyoxysilane (MTMS), tetraethoxysilane (TEOS), or a combination thereof.

4. The lubricating coating of any one of claims 1-3, wherein the ceramic filler is 2 wt% to 15 wt% of the first component of the precursor coating composition.

5. The lubricating coating of any one of claims 1-4, wherein the ceramic filler comprises silica, alumina, or a combination thereof.

6. The lubricating coating of any one of claims 1-5, wherein the lubricating particles are 2 wt% to 10 wt% of the first component of the precursor coating composition.

7. The lubricating coating of any one of claims 1-6, wherein the lubricating particles comprise graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof.

8. The lubricating coating of any one of claims 1-7, wherein the lubricating particles have a number average particle size of 50 nm to 500 nm.

9. The lubricating coating of any one of claims 1-8, wherein the precursor coating composition is substantially free of water.

10. The lubricating coating of any one of claims 1-9, wherein the acid comprises citric acid.

11. The lubricating coating of any one of claims 1-10, wherein the precursor coating composition is a ball-milled composition.

12. A lubricating coating comprising: a cured product of a coating composition, wherein the coating composition is a reaction product of a precursor coating composition comprising a first component comprising a polysiloxane precursor comprising an alkoxysilane, wherein the polysiloxane precursor is 50 wt% to 97 wt% of the first component of the precursor coating composition, a ceramic filler comprising zirconium oxide (ZrCh), titania (TiCh), silica carbide (SiC), ceria (CeCh), magnesium oxide (MgO), zinc oxide (ZnO), copper oxide (CuO), silica (SiCh), alumina (AI2O3), or a combination thereof, wherein the ceramic filler is 0.1 wt% to 40 wt% of the first component of the precursor coating composition, and lubricating particles comprising tungsten disulfide, graphene, graphene oxide, talc, calcium fluoride, cerium fluoride, graphite, boron nitride (BN), molybdenum disulfide (M0S2), or a combination thereof, wherein the lubricating particles are 0.01 wt% to 40 wt% of the first component of the precursor coating composition; an acid that is 0.05 wt% to 5 wt% of the precursor coating composition; and a solvent comprising a (Ci-C5)alcohol, wherein the solvent is 5 wt% to 95 wt% of the precursor coating composition; wherein the precursor coating composition and/or the coating composition are ball- milled.

13. A method of forming a lubricating coating on a substrate, the method comprising: forming a mixture comprising lubricating particles, a solvent, a ceramic filler, and a polysiloxane precursor; adding an acid to the mixture; allowing the acid and the polysiloxane precursor to react to form a coating composition comprising a polysiloxane, the lubricating particles, and the solvent; applying the coating composition to the substrate; drying the coating composition on the substrate; and curing the coating composition on the substrate, to form the lubricating coating on the substrate.

14. The method of claim 13, further comprising ball-milling the mixture after the addition of the acid thereto.

15. The method of any one of claims 13-14, wherein the substrate comprises an extrusion die.

16. The method of any one of claims 13-15, wherein the drying comprises heating at 60 °C to 90 °C for 30 min. to 2 h.

17. The method of any one of claims 13-16, wherein the curing comprises heating at 150 °C to 250 °C for 30 min. to 2 h.

18. A substrate comprising the lubricating coating of any one of claims 1-12.

19. An extrusion die comprising the lubricating coating of any one of claims 1-12.

20. A method of using the extrusion die of claim 19, the method comprising: extruding an extrudable composition through the extrusion die.