Procedure for producing at least a bearing part with a layer and bearing part

Abstract

The invention starts from a procedure for producing at least a bearing part (10), which comprises a layer at least after a final step of the procedure. It is proposed that the layer is produced at least by immersing (14) and / or moving at least a steel region (16) of a component (18) in an oxalic acid solution.

Description

[0001] 1 202400198

[0002] Procedure for producing at least a bearing part with a layer and bearing part

[0003] The invention concerns a procedure for producing at least a bearing part with a layer and a bearing part. It reveals an advantageous layer alternative to black oxide.

[0004] Tribological Black Oxide (in the following the abbreviation “TBO” is used for Tribological Black Oxide) is known to have numerous advantages for rolling bearings. TBO is the best-selling layer in bearing industry and in its history worldwide. Black oxide is a conversion layer consisting of iron oxides, thus containing iron from the workpiece, and oxygen from the reaction chemicals. The oxygen content of TBO is relatively high and the layer comprises mainly Fe3O4. Raceways of many rolling bearings have TBO as a surface layer. In this situation TBO reduces the risk for various damage mechanisms as well as supports reduced friction and prolonged bearing life. The following advantages are known for the case, in which a raceway of a rolling bearing has TBO as a surface layer:

[0005] - Improved surfaces running-in behavior

[0006] - Low-kappa safety (protection during deficient lubrication)

[0007] - Protection against smearing

[0008] - Protection against fretting

[0009] - Reduced friction in operation

[0010] - Sliding wear reduction

[0011] - Adhesive wear reduction

[0012] - Improved lubricant adhesion

[0013] - Corrosion protection

[0014] - Protection against Extreme Pressure additives

[0015] - Protection against spalling

[0016] - Protection against micropitting

[0017] - Protection against surface cracks

[0018] - Barrier against hydrogen intrusion

[0019] During the production of TBO at least two baths with 135-150°C each are necessary. TBO parts need pre- and post- treatments and an immersion duration of typically at least 20 minutes per bath with a batch throughput time in the range of two hours. Moreover, it should be mentioned that the 2 202400198 required chemicals for TBO production and the plant hardware for a constant and dependable process induce relevant costs.

[0020] The TBO production process has limitations for very large bearing rings. The necessity of high- temperature heating brings variation into the process as massive parts require longer time to reach correct reaction temperature, or will never reach correct surface temperature during a realistic production setup. It has been tried to solve these issues via electrolytical black oxidation, which reduces energy consumption but adds the necessity for electrical workpiece contact and imposes the natural drawbacks of galvanic approaches. In addition, to produce a TBO layer being safe for a bearing raceway and not just to produce a general black oxide layer, certain hardware and software enhancements are necessary at the production plant, so that worldwide production of TBO requires a certain outlay, which can be hard to manage in certain regions of the world.

[0021] In the Japanese publication Kiyoshi Nomura and Yusuke Ujihira, Analysis of oxalate coating on steels, Journal of Materials Science June 1983, oxalate coatings of steel were analyzed.

[0022] Oxalic acid treatment is also known from chemical vibrofinishing (CVF) processes. A batch of for example 500 kg cylindrical rollers is added into a CVF vibrofinishing machine filled with slightly abrasive chips of relatively low aggressivity. Wetting the chips with an oxalic acid solution produces oxalates on the roller surfaces and these soften the surface to a degree that the chips can remove this etching layer. While machining of hardened steel would require chips with higher abrasion and would deliver a higher roughness result, the acid support can shorten the manufacturing time and at the same time accept less abrasive chips to receive a higher degree of surface polishing. The oxalic acid process and a similar phosphoric acid process or a citric acid process are thus used in vibrofinishing either for time reduction, or for better surface quality, or for both. In CVF a produced layer is only used in combination with mechanical surface refinement methods and is always removed to receive the final workpiece.

[0023] Oxalic acid is occasionally used for iron corrosion removal in restoration of objects as it dissolves rust and does not harm the substrate, and it is sometimes used as (electrolytic) laboratory etching fluid in visualisation of steel and stainless steel microstructures. For restoration rust removal, the typical concentration is 7-10%. As laboratory etching fluid, 10% is standard. 3 202400198

[0024] Oxalic acid C2H2O4 (or alternatively written as H2C2O4) is a cheap and very common organic / carbon acid, to be more precise a so-called carboxylic acid, and is widely present in certain vegetables and nature. It is used for wood refurbishment, metal restoration, stainless steel or zinc post-treatments, and for many other purposes. It can be purchased as a powder at low cost (typically as dihydrate) and can be dissolved in water to form oxalic acid fluid. Watery oxalic acid, for example 5% concentration, reacts with iron and forms oxalates FeC2O4 already at room temperature. The conjugate base is oxalate C2O4(2')which acts chelating for metal cations. The chelate effect provides enhanced affinity of the chelating ligand for the metal ion compared to its monodentate ligand counterpart, contributing to layer stability. A 25 kg bag oxalic acid powder (>99.6% purity) is typically below 4 € / kg, and the price for higher volumes is even much lower. The substance is available worldwide with no known shortage. Oxalic acid can be entered into most neutralising factory waste water treatments without additional equipment.

[0025] Oxalic acid is not a common substance for industrial steel etching. Dominant substances are for example sulfuric acid, hydrochloric acid, nital acid, or dry acid.

[0026] The problem of the invention is in particular to provide a bearing part with a layer which is advantageous for a use as bearing raceway surface in an efficient way. The problem is solved according to the invention by the features of claim 1, by the features of claim 7 and by the features of claim 8, while advantageous embodiments of the invention are presented in the subclaims.

[0027] The invention proceeds from a procedure for producing at least a bearing part, which comprises a layer at least after a final step of the procedure.

[0028] It is proposed that the layer is produced at least by immersing and / or moving at least a steel region of a component in an oxalic acid solution. Through this a layer can be efficiently provided, which is advantageous for a use as bearing raceway surface. In particular, the oxygen content of a surface range of the steel part can be raised, which implies advantages of TBO as a surface of a bearing raceway.

[0029] Moreover, it is suggested that before the immersing and / or moving at least the steel region is immersed and / or moved at least in a phosphoric acid solution and / or is brought in contact with at 4 202400198 least one oxidation promoter. Through this a layer can be efficiently provided, which has further increased advantages for a use on bearing raceways. In particular, a coefficient of sliding friction between the layer and steel is smaller than the coefficient of sliding friction between steel and steel. Especially cold welding during operation can be avoided. In particular, damages on a raceway can be prevented when a rolling element receives load and starts a rotation around its axis with initial sliding during acceleration. Especially better corrosion protection than the one which is given by TBO can be achieved.

[0030] With advantage the oxalic acid solution has an oxalic acid concentration between 3 % and 20 % and / or a pH value of the oxalic acid solution is below 2. An oxalic acid solution has a concentration of XY %, if XY % of the mass of the oxalic acid solution consists of oxalic acid and (100-XY) % of the mass of the oxalic acid solution consists of water, wherein XY can be a number between 0 and 100. Thereby a uniform layer quality can be reached in a reasonable reaction time and in a reasonable temperature range.

[0031] Furthermore, it is proposed that a duration, during which the steel region is immersed and / or moved in the oxalic acid solution, is between one minute and thirty minutes. Through this a relatively constant layer thickness together with a relatively quick process duration can be achieved.

[0032] Advantageously a temperature of the oxalic acid solution is between 20°C and 80°C, when the steel region is immersed and / or moved in the oxalic acid solution. Thereby low energy consumption can be reached.

[0033] Moreover, it is suggested that the phosphoric acid solution has a phosphoric acid concentration between 3 % and 30 %. Through this an effect of the oxalic acid solution towards a high oxygen content of the layer, which is connected with TBO like advantages for the use of the layer on a raceway of a bearing, together with a gentle behavior of the phosphoric acid solution towards the steel region can be achieved.

[0034] In particular, during the procedure a water-insoluble and oil-insoluble compound is formed based on Fe2+, which gets part of the layer.

[0035] Furthermore, a bearing part produced through a procedure as described is proposed. Thereby a bearing part with a layer which is advantageous for a use as a bearing raceway surface can be 5 202400198 provided in an efficient way. In particular, a high oxygen content of the layer can be achieved, which is connected to the mentioned advantages of TBO.

[0036] Moreover, a bearing part, in particular produced through a procedure as described, comprising a layer, which comprises iron oxalate or a derivative compound of iron oxalate, is suggested. A derivative compound of iron oxalate is in particular a compound, which can be produced from iron oxalate through at least one chemical reaction. Through this a bearing part with a layer can be efficiently provided, which is advantageous for a use as bearing raceway surface. In particular, a high oxygen content of the layer can be achieved, which is connected to the mentioned advantages of TBO.

[0037] The bearing part is finished, finally machined and ready-made.

[0038] In particular, the bearing part can be a component of a finished, finally machined and ready-made bearing.

[0039] In particular, the layer can be insoluble in water.

[0040] With advantage the layer comprises carbon and oxygen in a mass ratio carbon: oxygen, which is between 0.3 and 0.5. Through this the layer can be produced in a simple way.

[0041] Advantageously the layer has an oxygen content of twenty to fifty percent by weight. Thereby advantages of TBO mentioned above can be achieved. Advantageously phosphoric acid solution pre-treatment is used in order to increase the oxygen content of the layer of the bearing part after the final procedure step.

[0042] Further advantages can be seen in the following description of the drawings. An example of an embodiment of the invention is shown in the drawings. The drawings, the description and the claims contain numerous features in combination. The skilled person will expediently also consider the features individually and combine them to form useful further combinations.

[0043] Fig. 1 shows a section through a part of a bearing part according to an embodiment of the invention,

[0044] Fig. 2 shows process chart of a procedure for producing a bearing part according to the invention, and

[0045] Fig. 3 shows a component at a start of the procedure. 6 202400198

[0046] Figure 1 shows a section through a part of a bearing part 10 according to an embodiment of the invention. The bearing part can for example be a bearing ring or a rolling element. The bearing part comprises in particular after a final step of a procedure for producing the bearing part a layer 12 with carbon and oxygen in a mass ratio carbon: oxygen, which is between 0.3 and 0.5. Moreover, the layer 12 has an oxygen content of twenty to fifty percent by weight. The layer comprises a surface of a raceway of the bearing part 10.

[0047] In the following the procedure for producing the bearing part 10 is described. Preferably the whole procedure takes place at temperatures below 200°C. In a first step, a solvent or preferably alkaline cleaning with or without ultrasonics of a component 18 is performed. The component 18 is a steel region 16. It is preferably hardened. The component 18 has approximately a form of the bearing part, which is supposed to be produced. In a second step, water rinsing is performed with the component 18. In a third step, the component and therefore the steel region is immersed 20 and / or moved in a phosphoric acid solution (figure 2). The phosphoric acid solution has a phosphoric acid concentration between 3% and 30 %, typically 10 %. A temperature of the phosphoric acid solution can be between 20°C and 80°C, and is typically 40-60°C. An immersion duration of the component can be between 1 min and 30 min, typically below 10 min, preferred around 3-8 min (“min” stands for minutes). In the third step a coating is created, which comprises a surface area of the component. Iron phosphate is at least a part of the coating. The iron phosphate does not remain detectable in the final layer after step five. As an alternative to the phosphoric acid solution oxidation promoters can be used such that iron oxides are formed. In a fourth step, water rinsing is performed with the component 18. In a fifth step, the component is immersed 14 and / or moved in an oxalic acid solution. The oxalic acid solution has an oxalic acid concentration between 3% and 20 %, typically 5 %. Its pH value is below 2, typically around 1. The temperature of the oxalic acid solution can be between 20°C and 80°C, typically 40-60°C, preferred 50°C. The duration of the immersion and / or movement of the component in the oxalic acid solution can be between 1 min and 30 min, typically below 15 min, preferred 6-10 min. In a sixth step, water rinsing is performed with the component. In a seventh step, the component is exposed to soda neutralization, which is an immersion in sodium carbonate solution. In an eighth step water rinsing is performed with the component. In a ninth step, water is removed from the 7 202400198 component. The steps are carried out one after the other according to their numbering. The layer 12 is a surface reaction layer.

[0048] For step five it has been found that a variation of the acid concentration is much less effective in adjusting the process time of step five than a variation in temperature. A limitation in permitted process time of step five at the same time limits a time slot in step five of potential hydrogen ingression into the steel region to avoid hydrogen embrittlement.

[0049] After the ninth step the component is identical with the bearing part 10 plus, in some cases, a small excess deposit, which can be wiped off with cloth or which can remain. The original surface of the component with its manufacturing marks before the first step is completely retained. No pittings or etching damages or pores are visible. The excess deposit can also be removed by letting the component through a corn dryer vibrofinish machine or a nutshell vibrofinish machine. The corn or nutshell is sufficient to polish the surface to a semi-gloss dark grey result that looks and feels smooth. Beforehand the corn can be treated with a mild polishing agent. Instead of using a vibrofinish machine a dewatering with fluid washing can be used.

[0050] After a potentially present excess deposit is removed, the layer is clean and free from preservative residues and organic contaminations. Then the layer is either mainly an iron oxalate or mainly a derivative compound thereof, showing the main elements Fe, C, O in an EDS (“EDS” stands for Energy Dispersive X-ray Spectroscopy) scan, and with a ratio C:O of roughly 0.375 or at least between 0.3 and 0.5.

[0051] If the third step is included and a part of the steel region 16, which is covered by the layer 12, is examined with a scanning electron microscope, no cracks, no pores and no pittings were found. It should also be noted that the used oxalic acid solution does not attack the steel region 16.

[0052] While it is a common observation that acid treatments can be dangerous to the microstructure of steel and harmful for rolling bearing raceways, this does not occur with the chosen process. A prolonged immersion in oxalic acid solution will still not harm the surface but slow down its reaction and start to produce wipeable deposits. While the TBO process for bearings, although alkaline, must be kept at ultimate time and temperature exactness to avoid surface damages of the workpiece, there is no such risk and precision requirement at the use of the described oxalic acid process. 8 202400198

[0053] Each single one of the steps one to four and six to nine are optional.

[0054] The procedure may contain additional incipient, intermediate or concluding steps such as cleaning, degreasing, water rinsing, neutralisation, drying or dewatering, and preservation. Here “intermediate” means between two of the mentioned steps.

[0055] If only step five is performed, the layer of the bearing part has an oxygen content of 8-12 % by weight. If all of the steps one to nine are executed, the layer has an oxygen content of 20-50%, typically 25-35 %, wherein measuring results depend on an EDS beam intrusion depth.

[0056] The oxalic acid solution and / or the phosphoric acid solution may contain additional additives such as oxidizing agents, accelerators, surface tension reducers, reactive agents, and inhibitors.

[0057] A characteristic of the produced surface reaction layer is that neither cross-sectional cut nor surface scan with EDS at a magnification of 5000 reveal any microstructural damages to a substrate, which consists of a part of the steel region 16, such as cracks, pits, etching voids or grain losses.

[0058] As a tenth step, which is also optional and which would be the last step, the component may undergo a thermal treatment. The thermal treatment may remove the carbon content from the layer and may partially or in total change it from an iron oxalate-based layer to an iron oxide layer.

[0059] All of the described steps are electroless. The layer stays on the bearing part and is not removed. It is a conversion layer.

[0060] In iron oxalate each Fe2+bonds to an oxalate anion complex, which is (C2O4)2' . This chelator is a multi-binding (in this case bidentate) anionic ligand which connects to the central iron ion at two bridges instead of only one binding bridge. This stable structure makes dissociation unlikely. The conversion layer has relatively good chemical stability.

[0061] To make sure that the layer is insoluble, some rules have been obeyed. Below a pH value of 1.23 the oxalic acid is in the form H2C2O4. At higher pH, it can be HCvCE^and at pH above 4 it can be CvC2' / A layer production shall thus safeguard that the oxalic acid solution remains around pH 1. It is of big difference if the reaction forms an oxalate compound or an oxalate complex. The complexes are water soluble, and there are numerous possible 9 202400198 unwanted outcomes like Fe2(C2O4)3, Fe(C2O4)(+), Fe(C2O4)2('), Fe(C2O4)3(3')which are based on Fe(III) and remain soluble. The desired outcome is instead a compound with the structure FeC2O4*2H2O based on Fe(II). The low-pH oxalic acid has a reducing capability to turn Fe(III) to Fe(II) so that the risk of soluble results is reduced as long as the solution is controlled and fresh and no such inhibitors or other additives are chosen and added, that would reduce the acidity of the solution. Lab tests have proven that the resulting layer formation is dependably controlled, and the layer is fully insoluble, and completely stable against prolonged mechanical rubbing with dry or wet cloth. Following the above rules, none of the extensive lab tests has produced a soluble layer, all were instead stable and insoluble.

[0062] It has been tested for step five if modifying the pH value within logical limits by further diluting the acid changes the reaction. At 5% oxalic acid in demineralised water, the pH is so low that measurement devices may even indicate 0. In the range of 4.5% it is around pH 0.9, still below 1. Diluting down to 4% delivers a pH slightly above 1, but with the same outcome. The theoretical background was that a pH «1 might have primary focus on etching and iron dissolution instead of forming a conversion layer and could hinder the correct outcome, while pH around 1 might better support layer formation. This was not observed.

[0063] If step three is not included, an iron oxalate conversion coating is formed which contains oxygen and is softer than the original steel surface, allowing for running-in smoothening. Oxalate layers are also known to have good oil retaining capability. If all the described steps are included, the layer 12 contains carbon and oxygen in a mass ratio carbon: oxygen, which is between 0.35 and 0.36.

[0064] During step three sugar and / or saccharide and / or cyclodextrins can be used as an additive to the solution. This additive has the effect of an inhibitor. Again it should be mentioned that a short duration of step three limits hydrogen ingress into the steel region. Step three greatly supports step five towards a high oxygen content.

[0065] As already mentioned in step three as an alternative to phosphoric acid solution oxidation promoters can be used such that Fe2C>3 -based brown oxidation (corrosion) is produced. This can for example be done in the following way in step three: The component is treated in oxalic acid solution to form a grey layer, then it is flushed in water and immersed in sodium hydroxide 10 202400198 solution for a second. Then the component is flushed in water and then corroded at ambient air within approximately 30 seconds. After this step four is not performed. In step five the oxalic acid now finds a surface with availability of more accessible iron and intensifies its reaction compared to an initial etching. The resulting layer can be of increased intensity.

[0066] Furthermore, to support the function of the uniform oxalate formation, a surface tension reducer and an inhibitor should be added to the acidic treatment solution in step five and / or in step three. Surface tension reduction allows the acid to better attack the surface independent of surface scratches and narrow roughness profiles. In addition, small hydrogen bubbles that form during acidic treatment shall not rest on the metal surface but shall rise. Surface tension adjustment and removal of hydrogen bubbles can be made by various additives. Here tensides as additive works fine. Preferred tenside is sodium lauryl sulfate. It is further possible to additionally use petroleum sulfonates or other sulfonates as supporting additives in step three and / or step five.

[0067] For step three and / or step five the use of an additional inhibitor suppresses local attack to get a more homogenous etching, and again countless variants are available. There seems to be no literature and no experience background to determine which inhibitor works for oxalic acid. Among the simplest inhibitors are butindiol (e.g., for sulfuric acid) or urotropin (e.g., for hydrochloric acid) or hexamethylentetramin. The reactivity of urotropine can be unwanted in some acidic constellations. It has thus been decided to add 2-Butin-l,4-diol, CAS 110-65-6. Under all safety precautions, it has been verified that Butindiol can be added both to oxalic acid as well as to phosphoric acid without unwanted side reactions. Thiourea can also be chosen. As it has been found that oxalic acid hardly attacks the steel, and that phosphoric acid can be used at reduced concentration with little harm, the use of an inhibitor, which would be typical for most etching treatments, is not mandatory in this case.

[0068] The fourth step can comprise also a treatment of the component with hydrogen peroxide. For example the component can be immersed for several minutes in 5 % hydrogen peroxide. After this step five gives a more uniform and intense result.

[0069] In step three the phosphoric acid solution may contain alcohol, for example 5 %, as surface tension reducer and / or Butindiol as inhibitor.

[0070] The fully produced layer 12 can additionally be treated with mineral oil for the purpose of preservation. Afterwards the bearing part can be wrapped in VCI paper. 11 202400198

[0071] The bearing part is finished, finally machined and ready-made.

[0072] In particular, the bearing part can be a component of a finished, finally machined and ready-made bearing.

[0073] By holding the bearing part at a borderline acceptable temperature around 190-200°C or 300°C, it is possible to form CO and CO2 gas evaporating from the layer, leaving a FeO iron-oxidic structure. When a heating to 300°C is done, the component must have been subject to an appropriate hardening process in order to not get destroyed. FeO is not stable and equally the starting point of black oxide formation. For instable FeO, the reaction is 4 FeO -> FesO4 + Fe, which means that the received FeO will automatically continue to recombine to black oxide. It is thus a possibility to transform the oxalate layer to a black oxide or iron oxide layer. At sufficient temperature and duration, the oxygen surplus combines with the included carbon and evaporates as CO (50%) and CO2 (50%). Due to the very low weight and volume of the layer, the evaporation volumes are extremely low and neither dangerous nor otherwise recognisable. They do not enter the CO2 balance. It is recommended to perform this “burning” of the contained carbon at air atmosphere or oxygen-enriched atmosphere to make sure that sufficient oxygen remains available for the iron oxide.

[0074] It is only optional to transform the oxalate layer to TBO via thermal treatment. The layer 12 itself, if produced in the oxygen-enhanced state as described, has excellent properties as a bearing coating and can be used without further transformation.

[0075] Compared with TBO the layer 12 can be produced in a much more efficient way. The processing time is only 25 % or less compared to TBO and the used temperatures are also much lower, which means that the energy consumption is lower. Moreover, the layer 12 can be produced in a simple way and worldwide. Compared to TBO the costs and effort to produce the layer 12 are massively reduced.

[0076] During the production of the layer 12 the component temperature is preferably below 200°C. If no thermal transformation is done, the temperature can even be below 60 °C.

[0077] If all the described steps are executed, the following conclusion can be made:

[0078] The costs of the needed chemicals, the energy consumption, the plant investment, and the production duration are much lower than in the case of TBO production. 12 202400198

[0079] On a reference sample with TBO, an oxygen content of 23 % by weight was found on the surface. In contrast, an identical reference sample with the layer 12 had an oxygen content on the surface of 36 % by weight. While a TBO coating is always about 0.7-1.2 micrometers thick, the layer 12 can be produced in the range of 0.7-3.0 micrometers and has a target thickness above 1 micrometer, for example 2 micrometers. The layer 12 has an almost identical oxygen content on the surface compared to a TBO coating. The layer 12 therefore binds at least as much oxygen to the surface as a tribological black oxide coating, and even significantly more, taking into account the greater target thickness.

[0080] The layer 12 shows a uniform and gapless coverage of the workpiece surface in terms of structure and thickness. The measured element distribution is uniform everywhere. Under very high magnification in the scanning electron microscope, a surprising microcrystalline structure is revealed, which is reminiscent of manganese phosphate in its structural shape, albeit with much smaller crystals under a much higher magnification factor. This structure explains why some of the roughness and surface topography parameters are 10 times higher in the surface scan than in a tribological black oxide layer. A detrimental effect could not be deduced from this.

[0081] On the contrary, an alternating sliding test with oiled surfaces in rolling bearing quality showed a coefficient of friction of around 0.1, which was consistently slightly lower over a sliding distance of 25 meters than with reference bodies made of uncoated steel. As expected, a similar sliding test in a dry state showed a coefficient of friction with steel-steel contact that repeatedly shot up to 1.0 and whose mean value rose with increasing test duration because the ground surfaces were increasingly damaged by cold welding and micro-damage. The same test setup with the layer 12 without lubrication provided coefficients of friction between 0.6-0.8 without any noticeable deterioration. Cold welding and surface damage in the absence of lubrication could therefore be reliably prevented by the layer 12.

[0082] Cross-sections through workpieces with the layer 12 revealed that, as expected, the layer 12 does not cause any substrate damage in its manufacture. Neither pitting nor cracks or preliminary stages of surface damage were found under the layer 12.

[0083] A scratch test with a Rockwell C tip and a force slowly increasing to 50 N during the scratching movement was used to determine the manner in which the layer 12 fails. There are no delaminations or flaking. The layer 12 wears according to its moderate hardness by smoothing 13 202400198 and by abrasive wear increasing with pressure, but even at the end of the test the scratch mark is still not free of particles of the layer 12. A black oxide coating gives up somewhat more quickly, which may be due to its lower intermeshing.

[0084] If step five is performed and step three is omitted, the layer 12 is lower in oxygen content than with the inclusion of step three and the layer 12 cannot compete with TBO as a bearing raceway surface.

[0085] 14 202400198

[0086] List of reference numerals:

Claims

15 202400198Claims:

1. Procedure for producing at least a bearing part (10), which comprises a layer at least after a final step of the procedure, characterized in that the layer is produced at least by immersing (14) and / or moving at least a steel region (16) of a component (18) in an oxalic acid solution.

2. Procedure according to claim 1, characterized in that before the immersing (14) and / or moving at least the steel region (16) is immersed (20) and / or moved at least in a phosphoric acid solution and / or is brought in contact with at least one oxidation promoter.

3. Procedure according to claim 1 or claim 2, characterized in that the oxalic acid solution has an oxalic acid concentration between 3 % and 20 % and / or a pH value of the oxalic acid solution is below 2.

4. Procedure according to at least one of the preceding claims, characterized in that a duration, during which the steel region is immersed (14) and / or moved in the oxalic acid solution, is between one minute and thirty minutes.

5. Procedure according to at least one of the preceding claims, characterized in that a temperature of the oxalic acid solution is between 20°C and 80°C, when the steel region (16) is immersed (14) and / or moved in the oxalic acid solution.

6. Procedure according to at least one of the preceding claims, characterized in that the phosphoric acid solution has a phosphoric acid concentration between 3 % and 30 %.

7. Bearing part produced through a procedure according to at least one of the preceding claims.16 2024001988. Bearing part (10), characterized in that the bearing part comprises a layer (12), which comprises iron oxalate or a derivative compound of iron oxalate.

9. Bearing part according to claim 8, characterized in that the layer (12) has an oxygen content of twenty to fifty percent by weight.

10. Bearing with a bearing part according to at least one of the claims 8 or 9.

Images