DESC:FIELD OF INVENTION

[001] The present invention relates to lubricant coatings on metallic components. In particular, the present invention relates to solid base lubricant coatings having corrosion-resistance. More particularly, the present invention relates to solid base lubricant coatings, which improves wear-resistance of metallic components, e.g. tractor bell-cranks to meet precise field-requirements thereof. The present invention also relates to a method for applying solid base lubricant coatings on metallic components which require high wear resistance only in the functional areas thereof.

BACKGROUND OF THE INVENTION

[002] Metallic components used in farm-equipment, e.g. tractors have to bear varying degree of loads and should have appropriate wear-resistance to these loads. For example, BELL CRANK is a typical tractor component, which should have sufficient wear-resistance at the surface on inside diameter or bore thereof, because it supports the shaft passing there through during rotation thereof. This shaft rotation induces frictional forces on bell crank bore, which tend to wear-off the inner diameter surface.

PRIOR ART

[003] In the functional areas of the metallic component which require localized hardening, induction hardening is generally employed for imparting wear-resistance to such functional areas, because it is not possible to carry out induction hardening on the surface of the bore or inner diameter.

[004] The conventionally employed surface hardening process is SURSULF process, which is a salt bath nitriding or soft nitriding process carried out on the entire surface of the component. It is a heat treatment process quite similar to nitriding and normally carried out between 540°C and 570°C.
DISADVANTAGES WITH THE PRIOR ART

[005] The disadvantages with the existing Sursulf process briefly discussed above and used for increasing the wear-resistance in metallic components such as bell crank are as given below:

• Complete bell crank surface should be hardened during Sursulf process to harden the functional surface on the internal diameter to cover just 5% area thereof.

• Normally, the entire bell crank is surface hardened, which causes additional 95% hardening, a Non-value adding (NVA) activity.

• Sursulf process requires heating at about 5600C for 3 hours and thus involves high costs, e.g. about INR 80 per bell crank.

• Sursulf is a high-temperature process, requiring special set-up therefor.

[006] Therefore, there is an existing need for developing an alternative hardening process to improve the wear resistance only at the functional area of the components, such as bell crank to be hardened.

PRIOR ART

[007] US3497376A discloses a method for applying a solid lubricant to a metal substrate by mechanical means to apply a base coat of a lubricant-binder composition made up of a mixture of binder particles and solid lubricant particles, sintering the applied base coat and then applying a top coat of lubricant-binder composition by electrostatic means to said base coat, the particles applied in said top coat being at least in part smaller in size than said base coat particles, and thereafter sintering said top coat, said binder particles being of vitreous material comprising at least one of the materials selected from the group of lead oxide, silicon dioxide, lithium oxide, sodium oxide, potassium oxide, titanium dioxide, lead trioxide, boron trioxide, zinc dioxide, cadmium oxide, sodium silica fluoride, aluminum trioxide, cobalt trioxide, nickel oxide, calcium oxide, lithium nitrate, sodium carbonate, and the boron compound having the formula K2B4O7; and said lubricant particles comprising at least one of the materials selected from the group consisting of tungsten disulfide, molybdenum disulfide, boron nitride, iron oxide, silver sulfate, ferrous chloride, lead oxide, ferrous sulfide, silver, graphite, mica, lead sulfide, and calcium nitrate. Here, solid film types of lubricants are applied to the metal and other substrates and to surfaces which require a reduction of friction and abrasive wear.

[008] US 7998572 B2 discloses a machine component, comprising a substrate; and a coating on at least a portion of the substrate, the coating including: a base material; nanoparticles of a lubricant material; and a non-metallic shell surrounding the nanoparticles of the lubricant material. These nanoparticles have a composite structure and made of a solid lubricant material. The shell being composed of a material different than the lubricant material to impart the desirable properties to the self-lubricating coating. The self-lubricating coating is used to reduce the friction and/or wear between any moving parts. The self-lubricating coating includes nanoparticles of a first material to enhance the lubricating properties of this coating.

[009] GB1602603A discloses a solid lubricant coating for tractor parts machining set up. It includes a composition for coating a metal-working tool, comprising by weight: (a) molybdenum disulfide, graphite or other solid lubricant in an amount of 5 to 60 parts, in an aqueous solution of: (b) an aluminum phosphate binder, in an amount of 1 to 5 parts calculated as aluminum hydroxide, (c) ortho-phosphoric acid, in an amount of 3 to 25 parts calculated as the 88 to 93% acid, (d) optionally a chromate or dichromate incorporated as such or as chromium trioxide, in an amount of up to 5 parts calculated as chromium trioxide.

[010] Accordingly, none of the prior arts disclose or teach about a low-cost, low-temperature solution for quick application of a solid lubricant only in the functional area of a metallic component, such as bell crank used in tractors.

OBJECTS OF THE INVENTION

[011] Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

[012] An object of the present invention is to provide a solid base lubricant coating to substantially improve wear-resistance of metallic components.

[013] Another object of the present invention is to provide solid base lubricant coating in functional area of metallic components e.g. bell cranks.

[014] Still another object of the present invention is to provide a low-cost solid base lubricant coating for local application in metallic component portions exposed to high wear.

[015] A yet another object of the present invention is to provide a solid base lubricant coating locally applied by using simple tools and baked at low temperatures.

[016] A further object of the present invention is to provide a process for locally applying in the functional area of the metallic components.

[017] A still further object of the present invention is to provide a low-temperature and low-cost, quicker coating process for the metallic components.

[018] A yet further object of the present invention is to provide a process for applying solid base lubricant coating to the metallic components, which does not require special set-up.

[019] These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.
STATEMENT OF THE INVENTION

[020] In accordance with the present invention a solid base lubricant coating formulation and a method of application thereof on the functional areas of metallic component/s like tractor’s bell crank, particularly internal diameter or bore thereof subjected to high frictional stresses is provided, wherein the solid base lubricant coating formulation is applied on the metallic component/s in a controlled environment to improve wear resistance and corrosion resistance thereof. The solid base lubricant formulation is made by dispersing an inorganic binder (B) graphite in molybdenum disulphide (MoS2) graphite or polytetrafluoroethylene (PTFE) lubricating solids to obtain a solid base lubricant formulation (SL). Accordingly, this formulation is obtained by preparing a mixture of diluting agents by mixing a thinner with a solvent Xylene in 70:30 ratio by weight diluting the solid base lubricant (SL) formulation with the mixture of diluting agents in a 70:30 ratio by weight. Subsequently, the targeted functional surface of bell crank is cleaned by a degreasing solution like Xylene. The degreased bell crank is pre-heated in an oven and maintained at 600C for 10 minutes therein to obtain good coating adhesion thereon subsequently. The pre-heated bell crank is removed from the oven and a coating of the diluted solid base lubricant (SL) formulation is applied only on bore or internal diameter thereof to obtain a predfined thickness of the anti-friction coating in the bore thereof. Now, the coated bell crank is baked in the oven by maintaining it at 2000C for 30 minutes. Finally, the coated and baked bell crank is removed from the oven and allowed to cool to room temperature and the dry film thickness (DFT) thereof is measured. In case, the dry film coating thickness is still lower than the required DFT, then the coating process is repeated, and a double coating or multiple coating is carried out in the same manner until obtaining the targeted DFT.

SUMMARY OF INVENTION

[021] In accordance with an embodiment of the present invention, there is provided a solid base lubricant coating for metallic components for improving the wear resistance and corrosion resistance thereof, said solid base lubricant coating comprising a solid base lubricant (SL) formulation made of an anti-friction coating solution and a thinner in a predetermined ratio and in a controlled environment, to be applied as a paint-like solid base coating on the functional surfaces of the metallic components.

[022] In Typically, the solid base lubricant formulation (SL) contains molybdenum disulphide (MoS2) graphite or polytetrafluoroethylene (PTFE) lubricating solids dispersed in an inorganic binder (B) graphite.

[023] In Typically, the formulation (SL) comprises:

• a diluted anti-friction coating diluted with a mixture of diluting agents;

• the mixture of diluting agents includes a thinner with a solvent Xylene in 70:30 ratio by weight;

wherein the anti-friction coating is diluted with the mixture of of diluting agents in a 70:30 ratio by weight to obtain a predefined anti-friction coating thickness of 10 to 30 µm ± 5 µm.

[024] In Typically, the formulation is applied on the bore or internal diameter or bore of metallic components after degreasing and subsequent pre-heating thereof in a controlled environment of a predetermined temperature for a predefined duration.

[025] In Typically, the formulation is applied on the functional surface areas of bell crank bore or internal diameter exposed to high wear, the formulation ratio predefined based on the field-specific surface hardening requirements thereof.

[026] In In accordance with an embodiment of the present invention, there is also provided a method for making wear resistance metallic component/s by applying the solid base lubricant coating formulation in a controlled environment to improve wear resistance and corrosion resistance thereof, the method comprising the steps of:

• dispersing an inorganic binder (B) graphite in molybdenum disulphide (MoS2) graphite or polytetrafluoroethylene (PTFE) lubricating solids to obtain a solid base lubricant formulation (SL);

• preparing mixture of diluting agents by mixing a thinner with a solvent Xylene in 70:30 ratio by weight;

• diluting the solid base lubricant (SL) formulation with the mixture of diluting agents in a 70:30 ratio by weight;

• cleaning the targeted functional surfaces of the component/s to be coated with the solid base lubricant coating by means of a degreasing solution like Xylene;

• pre-heating the degreased component/s in an oven and maintaining at 600C for 10 minutes to obtain good coating adhesion thereon subsequently;

• removing the pre-heated component/s from the oven and applying a coating of the diluted solid base lubricant (SL) formulation only on the surface thereof requiring a predfined thickness of the anti-friction coating;

• baking the coated component/s by keeping again keeping in the oven at 2000C for 30 minutes; and

• removing the coated and baked component/s from the oven and allowing cooling thereof to room temperature.

[027] In Typically, the component is bell crank of an off-road vehicle like a tractor and the functional surface to be coated with the solid base lubricant (SL) formulation is internal diameter or bore thereof coated with the anti-coating film.

[028] In Typically, the anti-friction coating is measured for the dry film thickness (DFT) thereof by means of a measuring gauge, such as Elcometer.

[029] In Typically, the dry film thickness (DFT) the anti-friction coating is in a range of 10 to 30 µm ± 5 µm.

[030] In Typically, the method as claimed in claim 6 is repeated for coating the component again by applying the solid base lubricant coating formulation to obtain a double coating to achieve the predefined dry film thickness (DFT) thereof.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[031] The present invention will be briefly described with reference to the accompanying drawings, wherein:

[032] Figure 1 shows a schematic arrangement of a bell crank used in tractors.

[033] Figure 2a shows perspective top view of bell crank shown in Fig. 1.

[034] Figure 2b perspective bottom view of bell crank shown in Fig. 1.

[035] Figure 3 shows cross-sectional view of a solid-lubricant anti-friction coating carried on the bell cranks of tractors.

[036] Figure 4 shows a flow chart of process flow of the method according to the present invention for applying solid base lubricant coatings on metallic components requiring high wear resistance only in functional areas thereof.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[037] In the following, the solid base lubricant coating for locally improving the wear-resistance of the metallic components of tractors, e.g. bell-cranks and configured in accordance with the present invention is described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

[038] Figure 1 shows a schematic arrangement of bell crank used in tractors. It includes a sleeve 12 fitted on a spool 14 resting on an actuating draft control (DC) link 16 which is connected substantially at the middle portion thereof to a draft control (DC) feedback rod 18 fitted to a draft control (DC) plunger 20. A top link spindle 22 fitted with a 3-lip seal 24 and 2-lip seal 26 each and carrying the bell crank 30 at the top thereof passes through the draft control (DC) plunger 20 and is supported on a spring 28. A lift arm 32 is also shown. One end of bell crank 30 moves towards right (in this figure) on a side loading 34 on the shaft due to the tractor’s application requirement, while the other end of the bell crank is applied with, e.g. 1000 kg load 36 at 1 Hz frequency.

[039] Figure 2a shows perspective top view of bell crank shown in Fig. 1.

[040] Figure 2b perspective bottom view of bell crank shown in Fig. 1.

[041] Figure 3 shows the cross-sectional view of a solid-lubricant anti-friction coating formulation prepared according to the present invention, consisting of a solid base lubricant SL and a binder B in a predetermined proportion applied on the rough surface 38 of the component, like a bell crank 30 of Fig. 1. However, before applying this lubricant on the component, the surface to be coated is prepared by cleaning it by degreasing with a solvent, like xylene or toluene and then pre-heated preferably at 60° for about 10 minutes and then this solid base lubricant formulation is applied on it in a warm condition thereof. This coating produces a smooth sliding surface 40 thereon. Here, the film thickness ft is between 10 to 30 µm with a tolerance of ± 5 µm. The solid base lubricant anti-friction and anti-corrosion coating prepared in accordance with the present invention preferably consist of a bonded, dry-film solid lubricant SL containing molybdenum disulfide (MoS2), graphite or PTFE lubricating solids dispersed in an inorganic binder B. It provides a superior lubrication even in harsh operating conditions and extreme environmental conditions.

[042] Figure 4 shows a flow chart of process flow of the method according to the present invention for applying solid base lubricant coatings on metallic components such as bell crank 30, which require substantially high wear resistance only in functional areas thereof. The coating process is as under:

• Step A: Component/s to be coated with solid base lubricant coating are cleaned with Xylene as a degreasing solution.

• Step B: keeping the component/s in a pre-heating oven maintained at 600C for 10 minutes to obtain good coating adhesion thereon.

• Step C: Removing the component/s from pre-heating oven and applying one coat of diluted anti-friction coating (70% Molykote PA 744 + 30% diluted thiiner mixture) only on the surface thereof requiring anti-friction coating, e.g. bell crank internal diameter.

• Step D: Baking the coated component/s by keeping it in the oven at 2000C for 30 minutes.

• Step E: Removing the coated and baked component/s from the oven and allowing to cool to room temperature. Inspect the component/s such as bell crank/s for internal diameter/bore thereof.

[043] In case, the required coating thickness is not obtained, the above coating process can be repeated to achieve the targeted coating thickness.

[044] The container of the solvent Molykote PA 744 to be used in this process should be stirred before use and the lid thereof to be closed to avoid solvent losses. Further, after preparing the anti-coating solution and before start-up production thereof, coat the panel using above standard operating procedure (SOP) and check the dry film thickness (DFT) of this coating by a measuring gauge, such as Elcometer.

[045] As safety measure, after cleaning or degreasing of the component/s, coating substrate or surface should not be touched with bare hands. Moreover, always use safety goggles and plastic hand gloves and mask while handling coating materials and use cotton hand gloves while handling hot component/s.

[046] A precise engineered formulation of such solid base lubricant coating can be configured with these or other lubricating solids, based on the lubrication requirements of the component like bell crank 30 to offer customized solutions therefor in order to fulfil typical tractor application and also depending on the observed wear pattern of the coating. Further, products can be selected with right formulation and type of coating method depending on the service requirements of the relevant component.

[047] After conducting a series of trials and experimentations, an optimum combination of lubricant and thinner in a specific ratio is arrived at. The thinner also contains 2 parts. In the pre-coating preparation stage, the selction of ratio of lubricant and thinner in the coating (make Dow Corning, e.g. PA744 + Thinner), the selection of temperature at which this coating is to be applied as well as the heating duation thereof led to the desired result with minimum use of resources like expensive lubricant and thinner, thereby making this process very economical. This process can be adopted in the shop-floor by smoothly integrating it to other processes with minimum training to the exsting operator. Such solid coatings are economical (i.e. they cost just about INR 50 per bell crank) and can be applied simply by means of a brush and then baked to a substantially lower temperature of 1800C for just 10 minutes and still offer a much longer shelf-life than the conventional bell cranks.

EXPERIMENTS

[048] An exemplary composition was formulated by mixing two parts thereof as under:

• Molykote PA 744 anti-friction coating, and
• Thinner, a mixture of Molykote 7415 thinner 70% with Xylene 30%.

This diluted thinner mixture is used for dilution of the exemplary coating material Molykote PA 744 anti-friction coating in the following ratio:

• Molykote PA 744 anti-friction coating, 70%, and
• Above diluted thinner mixture 30%.

WORKING OF THE INVENTION

[049] The working of the present invention is discussed below:

• Solid base lubricant anti-friction coatings include solid lubricant particles dispersed in carefully selected blends of resin and solvents.

• The volume concentration of lubricants and selection of raw materials are important factors for obtaining the desired lubricating and corrosion-protection properties.

• The component to be coated can be pre-cleaned with a special cleaner, e.g. xylene. On applying these coatings to a metallic component, these paint-like solutions bond with the coated surface to provide a smooth, dry and clean lubricating film.

• This lubricating film effectively covers the complete surface roughness to optimize a metal-to-metal, metal-to-plastic or plastic-to-plastic friction even under extreme loads and working conditions.

[050] The process of applying this solid base lubricant coating on the relevant component is as follows:

• Cleaning the component, i.e. degreasing by means of Xylene.

• Applying solid lubricant on the component.

• Baking at about 2000C for up to 30 min, preferably at 1800C for 10 minutes.
[051] In addition, the component can be pre-heated at 600C for 10 minutes to improve the adherence of the solid base anti-friction coating on the component to be coated.

[052] A double coating can also be deployed (wet on wet) with intermittent heating at 600C for 5 minutes for obtaining the required coating thickness, if not achieved in a single coating thereof.

[053] For ensuring the consistency of solid lubricating coating, the coating thickness is measured in terms of weight difference by using a highly accurate digital weighing balance (with a least count of 0.001 gm). Normally, the coating thickness can be measured directly by a coating thickness meter, which is suitable for measuring coating thickness on flat surfaces of the subtrate.

[054] However, for measuring the coating on curved surface, such as inner surface, e.g. internal diameter (IDs), which is addressed by the present invention, it is quite difficult to measure the coating thickness of the inner surfaces like IDs by using such coating thickness meter and this measurement may not be accuarate enough. Therefore, the present invention uses an indirect method of measurement of coating thickness by weighing the components before and after coating. The difference in weight of the components before and after applying this coating accurately indicates the thickness of the coating.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

[055] The solid-lubricant anti-friction coating configured in accordance with the present invention has the following technical and economic advantages:

• Offers a dry, clean lubrication unaffected by dust, dirt and moisture.

• Provides a lifetime lubrication without aging, evaporation or oxidation.

• Facilitates rust prevention even without surface treatments like galvanizing.

• Provides non-flammable, non-staining protection on metals and plastics.

• Makes a controlled film thickness for exact load-bearing capabilities.

• Provides a fully effective lubrication even after a prolonged non-use of the component.

• Dry film thickness can be adjusted by applying multiple coatings.

[056] The exemplary embodiment described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention. Therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiment.

[057] It is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

[058] Therefore, while the embodiment herein has been described in terms of a preferred embodiment, the skilled person can easily make innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies, assemblies and in terms of the size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

[059] Many of the fastening, connection, processes and other means and components utilized in this invention are widely known and used in the field of the invention described, and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art and they will not therefore be discussed in significant detail.

[060] The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

[061] Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

[062] In the claims and the description, the terms “containing” and “having” are used as linguistically neutral terminologies for the corresponding terms “comprising”.

[063] Also, any reference herein to the terms ‘left’ or ‘right, ‘up’ or ‘down, or ‘top’ or ‘bottom’ are used as a matter of mere convenience and are determined by standing at the rear of the machine facing in its normal direction of travel. ,CLAIMS:We claim:

1. A solid base lubricant coating for metallic components for improving the wear resistance and corrosion resistance thereof, said solid base lubricant coating comprising a solid base lubricant (SL) formulation made of an anti-friction coating solution and a thinner in a predetermined ratio and in a controlled environment, to be applied as a paint-like solid base coating on the functional surfaces of said metallic components.

2. Solid base lubricant coating as claimed in claim 1, wherein said solid base lubricant formulation (SL) contains molybdenum disulphide (MoS2) graphite or polytetrafluoroethylene (PTFE) lubricating solids dispersed in an inorganic binder (B) graphite.

3. Solid base lubricant coating as claimed in claim 1, wherein said formulation (SL) comprises:

• a diluted anti-friction coating diluted with a mixture of diluting agents;

• said mixture of diluting agents includes a thinner with a solvent Xylene in 70:30 ratio by weight;

wherein said anti-friction coating is diluted with said mixture of of diluting agents in a 70:30 ratio by weight to obtain a predefined anti-friction coating thickness of 10 to 30 µm ± 5 µm.

4. Solid base lubricant coating as claimed in claim 1, wherein said formulation is applied on the bore or internal diameter or bore of metallic components after degreasing and subsequent pre-heating thereof in a controlled environment of a predetermined temperature for a predefined duration.

5. Solid base lubricant coating as claimed in claim 1, wherein said formulation is applied on the functional surface areas of bell crank bore or internal diameter exposed to high wear, said formulation ratio predefined based on the field-specific surface hardening requirements thereof.

6. A method of application of metallic component/s with the solid base lubricant coating formulation as claimed in claim 1 in a controlled environment to improve wear resistance and corrosion resistance thereof, said method comprising the steps of:

• dispersing an inorganic binder (B) graphite in molybdenum disulphide (MoS2) graphite or polytetrafluoroethylene (PTFE) lubricating solids to obtain a solid base lubricant formulation (SL);

• preparing mixture of diluting agents by mixing a thinner with a solvent Xylene in 70:30 ratio by weight;

• diluting said solid base lubricant (SL) formulation with said mixture of diluting agents in a 70:30 ratio by weight;

• cleaning the targeted functional surfaces of said component/s to be coated with said solid base lubricant coating by means of a degreasing solution like Xylene;

• pre-heating said degreased component/s in an oven and maintaining at 600C for 10 minutes to obtain good coating adhesion thereon subsequently;

• removing said pre-heated component/s from the oven and applying a coating of said diluted solid base lubricant (SL) formulation only on the surface thereof requiring a predfined thickness of said anti-friction coating;

• baking said coated component/s by keeping again keeping in the oven at 2000C for 30 minutes; and

• removing said coated and baked component/s from the oven and allowing cooling thereof to room temperature.

7. Method as claimed in claim 6, wherein said component is bell crank of an off-road vehicle like a tractor and said functional surface to be coated with said solid base lubricant (SL) formulation is internal diameter or bore thereof coated with said anti-coating film.

8. Method as claimed in claim 7, wherein said anti-friction coating is measured for the dry film thickness (DFT) thereof by means of a measuring gauge, such as Elcometer.

9. Method as claimed in claim 8, wherein the dry film thickness (DFT) said anti-friction coating is in a range of 10 to 30 µm ± 5 µm.

10. Method as claimed in claim 9, wherein said method as claimed in claim 6 is repeated for coating said component again by applying said solid base lubricant coating formulation to obtain a double coating to achieve the predefined dry film thickness (DFT) thereof.

Digitally Signed.

Dated: this 21st day of March 2018.

(SANJAY KESHARWANI)
REGN. No. IN/PA-2043
APPLICANT’S PATENT AGENT