Impregnation liquid, treatment method using the impregnation liquid, and parts obtained thereby

Abstract

An impregnation liquid comprising 20 to 50% by mass of diacetone alcohol, 20 to 50% by mass of glycerol trioleate, 10 to 40% by mass of castor oil, 3 to 5% by mass of acetone, and 0 to 1.5% by mass of at least one sulfonate. A surface treatment method for an iron part, comprising an impregnation step with the impregnation liquid, and a treated part obtained thereby.

Description

[Technical Field]

[0001] The present invention relates to an impregnation liquid and a method for treating the surface of a steel part, which comprises an impregnation step with the impregnation liquid. [Background technology]

[0002] Many parts, depending on their intended use, require corrosion resistance and wear resistance, sometimes throughout the entire part, while also seeking improved friction and anti-scaling properties.

[0003] For this purpose, they are subjected to, for example, nitriding, oxidation and impregnation treatments, as described, for example, in WO 2016 / 102813, which complete the corrosion protection of the parts and sometimes improve other properties, such as the coefficient of friction.

[0004] In the treatments used on brake components (e.g. brake caliper pistons, which are iron components, usually made of steel, such as XC10 or 1.0335, forged and locally machined), it has become clear that some impregnation products cause incompatibility between the treated components and some brake fluids, especially the DOT4 type, which is frequently used as brake fluid.

[0005] Furthermore, it has been found that some products used on parts so treated have a tendency to swell seals, for example seals made from EPDM (ethylene propylene diene monomer).

[0006] Since the treated components come into contact with brake fluid, it is also desirable that the treatment avoid the creation of two different phases in the brake fluid. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016 / 102813 Summary of the Invention [Problem to be solved by the invention]

[0008] The purpose of the present application is to at least partially remedy the aforementioned drawbacks and to provide further advantages. [Means for solving the problem]

[0009] For this purpose, in a first aspect of the invention, an impregnation liquid is proposed comprising: - 20% to 50% by weight of diacetone alcohol (4-hydroxy-4-methylpentan-2-one, CH 12 O2), - 20% to 50% by weight of glycerol trioleate (C 57 H 104 O6), - 10% to 40% by mass of castor oil (ricinolein (the main component of castor oil): C 57 H 104 O9), - acetone (C3H6O) in a proportion of 3% to 5% by weight, and - at least one sulfonate (R-SO3 - (ion), R1-SO2-O-R2 (ester) The total amount is 100%.

[0010] As used herein, percentages refer to mass percentages and are also expressed as "wt.%."

[0011] Such impregnation liquids are based on oily liquids that are kept fluid by the presence of solvents, in particular here diacetone alcohol and acetone.

[0012] Sulfonates, for example, are thickeners involved in the formulation of high performance greases and contribute to corrosion resistance.

[0013] To facilitate compatibility with brake fluids, the impregnation fluid is completely free of any aqueous phase (i.e., does not contain water (H2O)), since aqueous phases are generally incompatible with brake fluids, particularly DOT4 types.

[0014] Such impregnation liquids are miscible with, for example, brake fluids, which limits the risk of different phases forming.

[0015] Such fluids are even more compatible with EPDM, a material frequently used to manufacture seals for brake pistons.

[0016] For example, the proportion of diacetone alcohol is at least 30% by weight and / or not more than 40% by weight.

[0017] For example, the proportion of glycerol trioleate is at least 30% by weight and / or not more than 40% by weight.

[0018] For example, the proportion of castor oil is at least 20% by weight and / or not more than 30% by weight.

[0019] For example, the proportion of acetone is at least 3.5% by weight and / or not more than 4.5% by weight.

[0020] For example, the proportion of the at least one sulfonate is at least 0.01% by weight.

[0021] For example, the proportion of the at least one sulfonate is between 1% and 1.5% by weight.

[0022] For example, the at least one sulfonate includes at least one sulfonate selected from calcium sulfonate, barium sulfonate, magnesium sulfonate, aluminum sulfonate, and sodium sulfonate, and preferably includes calcium sulfonate.

[0023] The present invention also relates to a method for treating the surface of ferrous parts to provide high wear and corrosion resistance.

[0024] For this purpose, a method for the surface treatment of iron parts is also proposed, which comprises an impregnation step with the aforementioned impregnation liquid.

[0025] Such a method more particularly relates to, for example, at least partially machined steel parts.

[0026] Such a method also relates to other ferrous parts, which may not be cast but are preferably machined.

[0027] The part is, for example, a part made from steel with a low carbon content.

[0028] Here, low carbon steel refers to steel with a carbon content between 0.05% and 0.8%, or between 0.05% and 0.2%, by mass, relative to the mass of iron.

[0029] The component is, for example, in particular a brake piston.

[0030] For example, the impregnation liquid is used at ambient temperature, i.e., a temperature of, for example, 10°C to 45°C, or, for example, at least 15°C and / or 30°C or less.

[0031] The impregnation liquid is applied by dipping or spraying. DETAILED DESCRIPTION OF THE INVENTION

[0032] Thus, in one example embodiment, the step of impregnating with the impregnating liquid includes a step of immersing the component in the impregnating liquid.

[0033] The impregnation liquid then constitutes the impregnation bath.

[0034] Immersion is typically performed on multi-component loads, for example, immediately after a nitriding step and possibly after an oxidation step as described below.

[0035] The soaking step lasts, for example, 10 to 15 minutes.

[0036] However, the immersion step may be very short, for example lasting up to a few seconds, for example 1 second, especially if complete filling of the pores in the surface of the part is not required.

[0037] Alternatively, the immersion step may last for a few minutes or even for several hours, for example 1 hour, especially if complete filling of the pores is desired.

[0038] According to an interesting option, the method may include the step of stirring the bath.

[0039] For example, the agitation may be mechanical or ultrasonic.

[0040] In another example embodiment, the impregnating step includes spraying the impregnating liquid onto at least a portion of the component.

[0041] The spraying process may last, for example, a few seconds, for example, from 1 to 60 seconds.

[0042] Impregnation by spraying is carried out, for example, when the treatment method comprises individual treatment substeps, ie in the case of treatments which are usually carried out part by part, for example polishing treatments.

[0043] In this case, spraying is carried out after the treatment substep, and the parts can, for example, be transferred automatically from the treatment substep to the impregnation step by spraying.

[0044] The impregnation process, which is here for example the final processing step, has been specially developed for the specific application of the method to brake pistons, to be compatible with the brake system, i.e. in particular with the brake fluid and seals.

[0045] In one embodiment, the method may include a drying step after the impregnation step, where the drying is natural and / or thermally accelerated drying (oven drying).

[0046] The treated parts may be subjected to other surface treatments before the impregnation step in order to improve certain properties of the material, or to complement the protection of the part against certain attacks, or to improve the adhesion of the impregnated layer.

[0047] Thus, in one embodiment, the method includes a nitriding or nitrocarburizing process (hereinafter simply referred to as the "nitriding process") configured to form a composite layer.

[0048] Such a step may be carried out, for example, before the impregnation step.

[0049] Such a nitriding process (also called "nitrocarburizing") consists, for example, in enriching the material of the component with nitrogen and carbon, which process provides very high layer uniformity and excellent reproducibility.

[0050] For example, the nitriding process is configured to form a composite layer having a thickness of at least 8 micrometers (μm), for example, between 8 μm and 30 μm, alternatively between 10 μm and 30 μm, alternatively between 15 μm and 30 μm, and preferably approximately 20 μm.

[0051] For example, the nitriding step may be configured to form a composite layer formed by nitrides, for example iron nitride in the ε and / or γ' phases.

[0052] This nitriding can be obtained by different methods, such as nitriding in an ionic liquid medium (salt bath), plasma nitriding or gas nitriding.

[0053] In one embodiment, the nitriding / nitrocarburizing process is carried out at a temperature of 500°C to 650°C, alternatively 550°C to 650°C, alternatively 550°C to 635°C, more preferably 580°C to 630°C, preferably around 590°C (i.e., between 585°C and 595°C).

[0054] In one embodiment, the nitriding / nitrocarburizing process is carried out for 45 to 200 minutes.

[0055] For example, the nitriding / nitrocarburizing treatment is carried out at a temperature of 590° C. for 60 to 200 minutes.

[0056] For example, the nitriding / nitrocarburizing treatment is carried out at a temperature of 630° C. for 30 to 150 minutes.

[0057] In one embodiment, the nitriding step comprises immersing the component in a nitriding or nitrocarburizing bath (hereinafter referred to as a nitriding bath for simplicity).

[0058] The nitriding bath here refers to an ionic liquid medium.

[0059] For example, the part is immersed in the nitriding bath for at least 45 minutes, such as 45 to 200 minutes, preferably 90 to 150 minutes.

[0060] For example, the nitriding bath contains cyanate (CNO - ) and carbonate (CO3 2- ) is included.

[0061] For example, the nitriding bath may contain 14% to 90% by weight, or alternatively 20% to 80% by weight, of an alkali cyanate.

[0062] Here, the alkali compound refers to a sodium, potassium, or lithium compound.

[0063] For example, a nitriding bath may contain, in mass percentages: - Between 0% and 5% by mass of lithium ions (Li +), - Between 5% and 25% by mass of sodium ions (Na + ), - Between 15% and 50% by mass of potassium ions (K + ), - Between 10% and 50% by mass of carbonate ions (CO3 2- ), and - Between 10% and 50% by weight of cyanate ions (CNO - ) Includes.

[0064] An interesting option is a bath containing between 10% and 40% by weight of chloride ions.

[0065] In one embodiment, the nitriding or nitrocarburizing process is carried out in an ionic medium forming a plasma under reduced pressure, i.e., at a pressure between 10 Pa and 1000 Pa, and at a temperature of approximately 350°C to 600°C, in an atmosphere containing at least nitrogen (N2) and hydrogen (H2).

[0066] According to another example embodiment, the nitriding step is carried out in a gaseous medium.

[0067] It involves, for example, immersing the part in a nitriding (or nitrocarburizing) gas.

[0068] For example, the nitriding gas includes ammonia (NH3).

[0069] In one embodiment, the nitriding gas in which the part is immersed has a temperature between approximately 500°C and 630°C.

[0070] According to an interesting implementation option, prior to the nitriding step, the method further comprises a step of degreasing the part.

[0071] According to an interesting implementation option, prior to the nitriding step, the method further comprises a step of preheating the part.

[0072] According to an interesting implementation option, after the salt bath nitriding step, the method further comprises a step of cleaning the part.

[0073] In one embodiment, the method includes an oxidation step configured to produce an oxide layer.

[0074] Such a step may be carried out, for example, before the impregnation step.

[0075] Such a step is carried out, for example, after a nitriding / nitrocarburizing step.

[0076] For example, the oxidation step, also called post-oxidation, can be carried out in a liquid medium, ie, by immersing the part in a bath called an oxidation bath.

[0077] In one embodiment, the part is immersed in the oxidation bath for 10 to 90 minutes, for example, at least 10 minutes and / or up to 20 minutes.

[0078] For example, the oxidation bath is an ionic liquid medium containing: sodium nitrate (NaNO3), in particular between 10% and 40% by weight, - between 5% and 30% by weight of at least one carbonate, for example lithium, potassium, or sodium carbonate, and - Sodium hydroxide (NaOH) between 20% and 45% by weight.

[0079] The temperature of such a bath is maintained, for example, between 400°C and 500°C, typically around 450°C.

[0080] According to one example, the oxidizing bath is a water bath containing alkali hydroxides, alkali nitrates, and alkali nitrates (ie, of sodium, potassium, lithium).

[0081] Such baths are typically maintained at a temperature of from 110°C to 130°C.

[0082] According to another example, the oxidation step is carried out in a gaseous medium consisting mainly of water vapor.

[0083] For example, the oxidation step in a gaseous medium is carried out at a temperature between approximately 450°C and 550°C.

[0084] For example, the oxidation step in a gaseous medium is carried out for approximately 30 to 120 minutes.

[0085] For example, the oxidation step may be configured to produce an oxide layer approximately between 0.1 μm and 3 μm thick.

[0086] According to an interesting implementation option, after the oxidation step in the oxidation bath, the method further comprises a step of cleaning the part.

[0087] In some cases, the method also includes polishing the surface of the component.

[0088] For example, the polishing process is configured to produce a roughness suited to the requirements, in particular a roughness Ra between 0.05 and 0.40 and a roughness Rz between 1.5 and 3.0.

[0089] Ra and Rz refer to roughness parameters commonly used in industry. Roughness parameters are defined, for example, in ISO 21920-2:2021. In particular, Ra is the arithmetic mean of the profile heights, and Rz is the mean of the total differences.

[0090] A corresponding measuring tool is the roughness meter, which directly provides the parameters according to the aforementioned standards.

[0091] For example, the polishing process includes what is also called a "centerless" polishing process.

[0092] "Centerless" grinding refers to a specific grinding on the cylindrical portion of the part.

[0093] The polishing is often done by means of a belt or wheel.

[0094] The choice of abrasive wheel, rotation and / or pressure parameters is chosen on a case-by-case basis.

[0095] For example, in the case of parts made of low carbon steel, polishing is advantageously carried out using a compressed non-woven abrasive wheel, for example made of a polymer.

[0096] The diameter of the wheel is, for example, from 200 mm to 500 mm.

[0097] For example, the pressure of the wheel on the part is between 0.5 bar and 2 bar (1 bar = 10 5 Pa).

[0098] For example, the rotation frequency of a wheel is between 20 Hz and 50 Hz.

[0099] In one embodiment, the impregnation step is combined with the polishing step.

[0100] For example, polishing may be done part by part on a processing line, and the parts move from polishing to the impregnation step on line, especially if the impregnation is done by spraying. All could be automated, for example.

[0101] In one embodiment, the polishing step includes a brushing step.

[0102] In another example embodiment, the polishing step is performed between the nitrocarburizing step and the impregnation step, or between the oxidation step and the impregnation step.

[0103] According to another aspect, a processed part is also proposed which is obtainable by a method including all or part of the steps described above.

[0104] For example, such a treatment component includes at least a ferrous component, for example made of steel, forming a substrate.

[0105] For example, the ferrous part is at least partially machined.

[0106] The steel parts are made from, for example, low carbon steel.

[0107] Here, low carbon steel refers to steel with a carbon content between 0.05% and 0.8%, or between 0.05% and 0.2%, by mass, relative to the mass of iron.

[0108] For example, the processing component is a brake piston.

[0109] For example, the processing component may include an impregnated layer that forms a surface of the processing component.

[0110] For example, the impregnated layer has a fatty appearance.

[0111] For example, the impregnation layer comprises glycerol trioleate and / or castor oil, and optionally at least one sulfonate selected from calcium, barium, sodium, aluminum or magnesium sulfonates.

[0112] Glycerol trioleate has a tendency to leave a greasy film on the surface of the part, thus giving the part an oily appearance.

[0113] Sulfonates, although present in small amounts, may be present on the surface and contribute to imparting anti-corrosion and anti-oxidation properties to the treated parts.

[0114] For example, the processing component includes a diffusion layer.

[0115] The diffusion layer may for example extend to a depth of at least 50 μm or more, for example from 50 μm to 500 μm.

[0116] The diffusion layer extends from the initial surface of the ferrous part, for example, which forms the substrate.

[0117] For example, the diffusion layer includes nitrogen.

[0118] For example, the processing component may include a composite layer.

[0119] For example, the composite layer is formed on the surface of the substrate, i.e., at least partially covering the diffusion layer.

[0120] For example, the composite layer may include nitrides, such as iron nitride in the ε and / or γ' phases.

[0121] For example, the composite layer has a thickness of at least 8 μm, for example between 8 μm and 30 μm, alternatively 10 μm and 30 μm, alternatively 15 μm and 30 μm, and preferably around 20 μm.

[0122] For example, the treatment portion may include an oxide layer.

[0123] The oxide layer includes, for example, iron oxide (Fe3O4).

[0124] For example, an oxide layer is formed on the composite layer.

[0125] For example, the oxide layer has a thickness between 0.1 μm and 3 μm.

[0126] Thus, in one example embodiment, the treatment component includes, in the following order: a base ferrous part forming a substrate, a diffusion layer, a composite layer, an oxide layer, and an impregnation layer. [Example]

[0127] To verify the corrosion resistance of parts treated according to the present invention, two parts were treated: a cold-forged 1.0335 steel brake piston and a machined XC10 piston.

[0128] After degreasing, the parts were washed and dried before undergoing the nitriding treatment.

[0129] The nitriding treatment was carried out in a molten salt bath containing the following ions (in mass percentages): 2.8wt.% to 4.2wt.% lithium ion (Li + ), 16wt.% to 19wt.% sodium ions (Na + ), 20wt.% to 23wt.% potassium ions (K + ), 38wt.% to 43wt.% carbonate ions (CO3 2- ), 12 wt.% to 17 wt.% cyanate ions (CNO - )

[0130] The bath temperature is maintained at substantially 590°C (±5°C) and the duration of the nitriding step is 120 minutes.

[0131] The parts were then immersed in an oxidizing salt bath containing, in particular, between 35% and 40% by weight of sodium nitrate (NaNO3), between 15% and 20% by weight of carbonates (lithium, potassium, sodium), and between 40% and 45% by weight of sodium hydroxide (NaOH) at a temperature of 450°C for 15 minutes.

[0132] After washing and drying, the parts were subjected to approximately 1 second of polishing by passing between an abrasive wheel and a rubber wheel, the abrasive wheel rotating due to the movement of the rubber wheel and therefore not fixed in the centre.

[0133] The polishing wheel is, for example, a compressed nonwoven polishing wheel (for example, sold under the name Norton 7 SF), the pressure is 0.8 bar to 1.4 bar, and the rotation frequency of the polishing wheel is between 30 Hz and 50 Hz.

[0134] The parts were then impregnated by spraying with a liquid containing 35% by weight diacetone alcohol, 35% by weight glycerol trioleate, 25% by weight castor oil, 4.2% by weight acetone, and 0.8% by weight calcium sulfonate.

[0135] These parts were then subjected to a salt spray corrosion test with the following results: - For forged parts: Edges: Resistance to salt spray for up to 120 hours confirmed. · Smooth surface: Resistance to salt spray was confirmed for at least 240 hours. - For machined parts: Edges: Resistance to salt spray for up to 240 hours confirmed. · Smooth surface: Resistance to salt spray has been confirmed for at least 300 hours.

[0136] For the two types of parts mentioned above, this resistance was found to be very satisfactory.

[0137] The compatibility of the impregnation liquid with the EPDM seal was confirmed by immersing such a seal in the impregnation liquid for 24 hours.

[0138] No swelling of the seal was observed.

Claims

1. An impregnation liquid, diacetone alcohol in a proportion of 20% to 50% by weight, 20% to 50% by weight of glycerol trioleate, Castor oil in a proportion of 10% to 40% by weight, acetone in a proportion of 3% to 5% by weight, and containing at least one sulfonate in a proportion of 0% to 1.5% by weight, The total amount of the impregnation liquid is 100%.

2. 2. The liquid according to claim 1, wherein the proportion of diacetone alcohol is 30% by mass or more and / or 40% by mass or less.

3. The liquid according to claim 1 or 2, wherein the proportion of glycerol trioleate is 30% by mass or more and / or 40% by mass or less.

4. The liquid according to claim 1 , wherein the proportion of castor oil is at least 20% by mass or more and / or 30% by mass or less.

5. The liquid according to claim 1 , wherein the proportion of acetone is 3.5% by mass or more and / or 4.5% by mass or less.

6. 6. Fluid according to any one of claims 1 to 5, wherein the proportion of said at least one sulfonate is between 1% and 1.5% by weight.

7. 7. The fluid of claim 1, wherein the at least one sulfonate comprises at least one sulfonate selected from calcium sulfonate, barium sulfonate, magnesium sulfonate, aluminum sulfonate, and sodium sulfonate.

8. 8. The fluid of claim 7, wherein the at least one sulfonate comprises calcium sulfonate.

9. A method for surface treatment of an iron part, comprising an impregnation step using the impregnation liquid according to any one of claims 1 to 8.

10. 10. The method of claim 9, wherein the impregnation liquid has a temperature of from 10° C. to 45° C.

11. 11. The method according to claim 9 or 10, wherein the step of impregnating with the impregnating liquid comprises immersing the part in the impregnating liquid.

12. 11. The method of claim 9 or 10, wherein the impregnating step comprises spraying the impregnating liquid onto at least a portion of the component.

13. 13. The method according to any one of claims 9 to 12, wherein the method comprises a nitriding step to form a composite layer, the nitriding step being carried out before the impregnation step.

14. 14. The method according to any one of claims 9 to 13, wherein the method comprises an oxidation step designed to produce an oxide layer, the oxidation step being carried out before the impregnation step.

15. A processed component obtainable by the method according to any one of claims 9 to 14.

16. 16. A treatment component according to claim 15, wherein the treatment component forms a brake piston and the treatment component comprises an impregnation layer forming a surface of the treatment component, the impregnation layer comprising glycerol trioleate and / or castor oil, and / or at least one sulfonate selected from calcium, barium, sodium, aluminum or magnesium sulfonate.

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