Component with black oxide layer and method for manufacturing the same

Abstract

The invention discloses a component (1) having a black oxide layer (10), wherein a metal additive element (4) is incorporated into the structure of the black oxide layer (10). In addition, a method for manufacturing such a component (1) is disclosed, the method comprising the steps of depositing the metal additive element (4) on the component (1) and immersing the component (1) with the deposited metal additive element (4) in a black oxide solution (6), wherein the metal additive element (4) is incorporated into the structure of the black oxide layer (10).

Description

Technical Field

[0001] The invention relates to a component having a black oxide layer and a method for producing the component. Background Art

[0002] It is known to perform a blackening treatment on components in order to protect them from various damages caused by sliding movements on the surface. In this process, the iron on the surface of the component is immersed in one or more oxidising baths. This produces a conversion layer that is firmly bonded to the substrate, which does not have a substantial effect on the dimensions of the component.

[0003] The wear resistance of this black oxide is sometimes too low to be used in very wear-intensive applications, so that after test runs or running-in, the black oxide is already chipped or worn away, whereas in other more favorable applications it can be stable for many years. Observed erosion of the layer is usually associated with sliding motion distribution. If the layer is in sliding contact with the counterface, it can be removed after a very short time, since it has a lower hardness than the usually hardened steel in the counterface. Summary of the invention

[0004] It is therefore an object of the present invention to provide a component having enhanced wear resistance.

[0005] This object is achieved by the assembly of the present application and the method of producing the assembly of the present application.

[0006] Often, depositing additional substances has a favorable effect on the coating. Until now, it has been known to produce a black oxide layer on a component and then apply another layer with various additional elements (e.g. tungsten compounds or even polymers) on the black oxide layer to enhance the black oxide layer or provide further properties through this layer. However, this has the disadvantage that the additional element represents a separate layer which cannot improve the properties of the black oxide layer itself, such as wear resistance.

[0007] However, the inventors have now found that the properties of the black oxide layer can be improved by alloying the black oxide layer. Through this alloying, the properties of the layer produced during the blackening process can be adjusted (especially improved).

[0008] Therefore, a component with a black oxide layer is proposed. Components that are not bearing components can be, in particular, components that are subject to sliding movements, such as guide rods, piston rods, steering components, linear guides and slides. Bolts on blackening guns can also be subject to sliding wear.

[0009] In order to provide an anti-black oxide layer, a metal additive element is incorporated into the structure of the black oxide layer. The metal additive element is not provided as a separate layer providing its own properties, but is directly embedded in the black oxide layer, i.e. incorporated into the structure of the black oxide layer. In this way, they adjust the properties of the black oxide layer, rather than adding further properties of the additional element.

[0010] The alloyed black oxide layer is provided on areas of the component that are not in rolling contact. This area may, for example, be subject to sliding movements, as is the case with piston rods etc.

[0011] By manufacturing the alloyed black oxide layer, the metal additive element is incorporated substantially over the radial extension of the black oxide layer or at least over a significant portion of the radial layer extension. Compared to previous manufacturing processes, in which the additive element was only present in the radial boundary regions of the black oxide layer, i.e. in the black oxide layer or in open cavities and pores on its surface, the metal additive element provided here is present in the radial extension of the black oxide layer, i.e. within the layer structure, and not just on top of the layer. In this way, the metal additive element contributes to improving the properties of the black oxide layer over its radial extension.

[0012] In rolling bearings, the black oxide layer must intentionally lose about 50% of its oxidation depth during the running-in process, while the remaining 50% usually protects the surface in a stable and long-term manner as a residual layer. Therefore, it is only necessary to achieve a change in the layer properties to an oxidation depth of more than 50% in order to change the properties of the remaining layer after running-in. A change in the layer properties over the full oxidation depth of the black oxide layer is desirable and ideal, but is not absolutely necessary for improving the stability of the layer.

[0013] According to one embodiment, the percentage of the metal additive element of the black oxide layer is set between 0.1 and 1%, in particular between 0.3 and 0.7% (mass percentage). Due to the low percentage of the metal additive element, it can be achieved that these elements do not change the overall properties of the black oxide layer due to their own properties as a material, but adjust the properties of the actual black oxide layer. The mass percentage used is similar to the various percentages of alloying elements in steel, although low concentrations are far below 1%, but significant changes in properties are achieved.

[0014] On the one hand, the low concentration of additive elements allows a resource-saving coating process without high chemical inputs, high losses and high costs. On the other hand, maintenance and analysis of black oxide are also simple.

[0015] If the additional element is deposited as "islands" in the layer, in order to significantly change the overall properties of the layer through the specific properties of the additional element, several mass percentages of the additional element must be introduced into the layer. Such large island structures may disturb the uniformity of the layer, endanger the internal stability and require a high material input of the additional element during the coating process.

[0016] Therefore, if one wants to place an additional element in the layer rather than on it, the ideal situation is that the additional element is distributed in the layer by structural connections (such as lattice structure) or distributed in the layer by chemical reaction, and there are no island-like separated agglomerates. This is achieved by the assembly described in this article. At the same time, the metal additive element is added to the basic structure of the layer, making it possible to achieve relevant performance improvements even at very low concentrations.

[0017] According to another embodiment, the metallic additive element is incorporated into the black oxide layer in a percentage that increases radially outwards.

[0018] Blackening is achieved by immersing the component in one or more black oxide tanks. During immersion, the iron or iron oxides contained in and on the component material (such as steel) are continuously dissolved and continuous redeposition and reorganization occur. Compared to two-layer painting, in which the second layer is applied on top of the first layer of constant static, in the double tank blackening process, the second tank will also change the depth of the first oxidation that has been deposited again. The oxide layer becomes more dense and stable, and the percentage of free FeO decreases in favor of Fe3O4. The deeper the layer area, the slower the transformation occurs until a static state is reached and usually the final desired oxidation state is reached.

[0019] For example, metallic additive elements applied to the component by means of a pre-dip solution are not only embedded in the black layer, but also undergo a dissolution reaction, which means that they can be partially lost back into the black oxide bath during the restructuring of the area in which they are embedded.

[0020] If during the layer formation, in particular between the blackening baths, the component is immersed again in a suspension containing the metal additive element, the concentration of the metal additive element increases again from the layer surface and the metal additive element diffuses into the black oxide layer which is being further converted. This leads to a concentration gradient, because the deeper the layer area, the more difficult it is to "refill" it with the metal additive element. The end result is a black oxide with a measurable concentration gradient. The deepest areas of the layer have a lower content of the metal additive element, which increases towards the surface. However, the metal additive element is not located at the surface, but in the blackened layer, mainly in the upper area, with a concentration gradient towards the inside.

[0021] This is different from conventional blackened surfaces, where the additive elements simply remain on the surface, at most are pressed into the surface during operation, or are deposited in the outwardly open pores of the black oxide layer. In contrast, the metallic additive elements in the components presented here are clearly incorporated into the microstructure of the black oxide layer, with the maximum concentration being near the black oxide layer surface, but not above it.

[0022] According to another embodiment, the metal additive element is configured to adjust the properties of the black oxide layer. As mentioned above, the properties of the additional element are not used directly, but the metal additive element is used to adjust (especially improve) the existing properties of the black oxide layer.

[0023] The tests showed that neither the color, scanning electron microscopy surface structure or porosity of the layer alloyed with metallic additive elements showed relevant differences from conventional black oxide layers. In terms of the determination accuracy, the corrosion protection and friction were also exactly the same. In rolling contact, there were no significant differences in the wear tracks. However, in sliding tests, there were reproducible and significant differences between the components described here and those with conventional black oxide layers.

[0024] It has been shown that for all loads in the test rig used as the basis, the wear track of the components described here is significantly reduced:

[0025] - At 0.9 GPa, from 0.85 μm to 0.50 μm (-41%)

[0026] - At 1.1 GPa, from 1.50 μm to 0.85 μm (-43%)

[0027] - At 1.4 GPa, from 2.15 μm to 1.20 μm (-44%)

[0028] Studies conducted through nanoindentation testing have shown that the alloyed black oxide layer described in this article has the following improvements compared to conventional black oxide layers:

[0029] -The alloying black hardness of the smooth polished surface increases to 227%.

[0030] -The alloying black hardness of the ground rough surface increased to 192%.

[0031] -The elastic modulus of the smooth polished surface increases to 220%.

[0032] -The elastic modulus of the rough ground surface increased by 229%.

[0033] In summary, the black oxide layer described herein (alloyed with the metal additive element) can achieve twice the hardness, twice the elastic modulus, and half the sliding wear compared to a conventional black oxide layer. However, as previously mentioned, the metal additive element does not provide a separate layer, but rather doubles the relatively low hardness and resistance of a "soft" black oxide layer that tends to wear quickly under sliding conditions. In the process, none of the other desired properties are compromised.

[0034] Alloyed black oxide layers show improved properties, especially in the presence of sliding motion distribution. Since many components (such as guide rods or piston rods), depending on their design and application, have more or less sliding motion distribution, the improvement of wear resistance in sliding motion is relevant for these components.

[0035] According to another embodiment, the metallic additive element may contain titanium. In particular, the metallic additive element comprises a metal oxide, in particular titanium oxide or titanium iron oxide.

[0036] Black oxides include Fe3O4 (magnetite), whose crystal structure has cubic symmetry. When selecting metal additive elements, special attention should be paid to adding or generating compounds that are as similar as possible to magnetite, especially compounds based on iron oxide. The compound should have approximately the same hardness and properties, but should not have a cubic lattice structure, but have, for example, a trigonal lattice structure. If the additional element has similar properties, but a different lattice structure, the combination of different lattice structures can lead to new and inevitably slightly distorted arrangements. Perturbations in the lattice structure and available sliding planes can significantly change the hardness and elastic modulus of the entire layer. The actual structure of the blackening, which is simply described as Fe3O4, is an approximate description of the larger structure of Fe11O16, and can therefore be effectively strained by adding very small percentages of other related lattice structures, especially at Fe defects. Similar effects can be measured from the combination of Fe3O4 with excess Fe2O3.

[0037] For example, ilmenite (FeTiO3) can be used as an additive in the layered structure, which has all the desired properties. It is black, like ordinary black oxides. It has a Mohs hardness similar to that of magnetite. It is also an iron oxide. It has a trigonal structure, so it is possible to strain and harden the cubic structured layers in the lattice. It contains a very good detectable element Ti, which provides information about the ilmenite content of the layer. Since ilmenite uses only one iron atom in its structure, it cannot hinder the parallel Fe3O4 formation in all conceivable concentrations. The excess oxygen generated by the nitrite in the black oxide tank is always available to meet the needs of ilmenite formation.

[0038] The presence of other mixed oxides is conceivable. In addition to ilmenite (FeTiO3), FeTiO4 (iron II titanate) and FeTiO5 may also be present in the black oxide layer. Thus, in addition to the three iron oxides FeO, Fe2O3 and Fe3O4, in the presence of an excess of oxygen, three groups of iron-titanium oxides, namely FeTiO3, FeTiO4 and FeTiO5, may also be present.

[0039] Preferably, mixed oxides can be combined with mixed oxides. If the oxygen ratio in the black oxide bath is not precisely maintained, this will produce closely related iron-titanium oxides, rather than allowing the reaction to drift in other unintended directions. Each iron-titanium oxide can structurally distort the magnetite of the black oxide layer.

[0040] Various titanium compounds can be used for pre-dipping. None of these substances are soluble in water, which is why a suspension is prepared for the metal additive elements in the dipping tank by air injection, as is common, for example, for activation before phosphating (with some other solids). Analogously to such activation, at least one pre-dipping tank containing an aqueous suspension is kept in the coating plant, in which the workpieces are dipped before the first blackening step and possibly repeated as a short break during blackening.

[0041] Titanium dioxide is a very cost-effective and non-toxic titanium compound with high availability in the global market. It is also inert and does not cause any undesired side reactions. When used in suspensions, there is no danger associated with inhalation. Suitable particle sizes are specified for the preparation of suspensions, in particular KA 100 (0.25-0.35 mm).

[0042] Titanium dioxide optionally has the structures of rutile, anatase and brookite, which are not equivalent in application. In industry, pigments are usually defined by color strength and whiteness. Preferably, rutile can be used for suspension, which has the highest color strength at the same time and is the most widely used structure in business. Therefore, for the pre-impregnation process, it is preferred to define a raw material with a color strength of at least 1280. Other raw material properties specified for successful application can be, for example, oil number (preferably a maximum of 25g / 100g), sieve residue 45 (preferably <0.015%) and purity content (preferably>98%).

[0043] Titanium dioxide can be preferably used as a metal additive element due to its influence on the oxidation behavior of iron. Titanium dioxide (TiO2) favorably modifies the ionic diffusion of oxygen anions O with iron and iron oxide. Here, the external Fe cation diffusion is replaced by the internal O anion diffusion. This means that the addition of TiO2 not only increases the diffusion rate of oxygen anions in the substrate and the black oxide layer and supports the formation of the layer, but exchanges the main ion transfer mechanism of iron oxidation in favor of a more efficient variant.

[0044] It has been established that the incorporation of titanium compounds into the black oxide layer follows a natural mass ratio. The black oxide layer typically contains about 0.4-0.7% titanium. If the pre-dip suspension is operated with a significantly increased titanium dioxide concentration, for example at double the concentration, the same results can still be achieved. This is because the incorporation of titanium mixed oxides into the structural Fe11O16 matrix follows a certain ratio, just as a chemical reaction can only handle a certain ratio of reaction partners. This fact allows for a particularly simple and stable tank management of the pre-dip suspension, since it can be operated as a chemical feedstock in excess concentration and the same results can always be achieved despite different concentrations.

[0045] Although the nominal ideal concentration of titanium dioxide in the pre-impregnation suspension is set at 10 g / L, a tolerance range of 5-20 g / L can be set for equivalent functionality with no change in results.

[0046] The temperature of the pre-immersion suspension also does not lead to a change in the results. Both room temperature and heated elevated temperatures produce the same accumulation of sticky particles with the same intensity and similar stickiness. In order to ensure the stability of the pre-immersion process, in addition to the continuous and sufficient injection of air through the nozzle tube at the bottom of the container to achieve intensive circulation and maintain a stable suspension in suspension, attention should be paid to the use of deionized or other demineralized water for tank preparation, as well as sufficient residence time of the workpiece in the suspension. For the first accumulation of sticky particles on the surface of the billet, an immersion residence time of 2 to 5 minutes is usually required. In the case of an already existing black oxide layer, the surface energy and structure are changed, and the intermediate immersion process can be shorter. The possibility of a shorter intermediate immersion process avoids the associated drop in the core temperature of the workpiece, which would prolong the entire process.

[0047] According to another aspect, a method of manufacturing a component as described above is proposed. The method comprises the steps of depositing a metallic additive element on the component and immersing the component with the deposited metallic additive element in a black oxide solution, wherein the metallic additive element is incorporated into the structure of the black oxide layer and preferably over an approximately complete radial extent of the black oxide layer.

[0048] In particular, the metal additive element may be deposited by immersion in the pre-dip solution. If titanium dioxide powder is used as the metal additive element, it may be present in the pre-dip solution in the form of a suspension having a particle size of 0.25-0.35 mm. It has been found that about 10 g / L is sufficient. Higher concentrations are possible but not necessary.

[0049] By means of this simple and cost-effective pre-dip solution, alloyed black oxide can be reliably produced, despite very low contents of alloying components (i.e. metal additive elemental components), but its capabilities in several properties are doubled as mentioned above. This leads to the fact that, using this alloyed black oxide layer, in applications with increased sliding motion distribution, the black oxide layer is not lost prematurely.

[0050] According to another embodiment, the steps of depositing the metallic additive element and immersing in the black oxidizing solution are repeated, wherein the immersion in the black oxidizing solution is always a step after deposition. In addition, the assembly may first be degreased and rinsed (in several steps) before depositing the metallic additive element.

[0051] An exemplary process with multiple pre-dip or intermediate dips and a black oxidation process may proceed as follows:

[0052] - Degrease, clean and rinse the material surface and, if necessary, use further activation aids.

[0053] - Pre-impregnated in a titanium dioxide suspension that can be maintained at room and elevated temperatures,

[0054] - Transfer to the first black oxidation tank,

[0055] - optionally interrupting the first blackening process (e.g. after 10 minutes), re-quenching and intermediate immersion in the same titanium dioxide suspension, immediate lifting and further blackening,

[0056] -After the first blackening is completed, quench in the coldest possible water,

[0057] - Pre-dip in another titanium dioxide suspension, which can be kept at room temperature and elevated temperature. This can be a second pre-dip tank so as not to interfere with the equipment,

[0058] - Transfer to the second black oxidation tank,

[0059] - optionally interrupting the second blackening process (e.g. after 10 minutes), re-quenching and intermediate immersion in the same titanium dioxide suspension, immediately lifting out and further blackening,

[0060] -After the second blackening is completed, quench in the coldest possible water,

[0061] -Finally, various hot and cold rinsing baths are given, followed by treatment with dehydrating fluids and antiseptic oils.

[0062] If desired, the process can be expanded to include a third pre-dip tank and a third black oxide tank and a third quench rinse.

[0063] Compared to black oxide systems for double tank blackening for tribology, alloyed blackening requires only two additional containers and, apart from air injection, does not require any special mandatory equipment, especially no heaters or cooling systems, no protective hoods, and no particularly high-quality materials. The activation of these additional containers can be optionally switched on or off in the sequence program for individual workpiece types without any changeover or modification between alloyed and unalloyed blackening batches.

[0064] The above-mentioned pre-dip tank can have a titanium dioxide-water suspension, whose TiO2 is kept in suspension under continuous air injection. When the component is immersed here, the component surface is inoculated with titanium dioxide. The component is then moved directly into the first black oxide tank without rinsing. There, the layer reaction takes place immediately using the titanium dioxide present. As is known from the inoculation in phosphating, this inoculation will not separate from the surface when lifted directly, while avoiding the intermediate rinsing step. Excess titanium dioxide (which can be dissolved when immersed in the black oxide tank) enters the black oxide tank sludge without causing harm. It has been found that titanium dioxide cannot be kept in suspension in a boiling black oxide tank, but will precipitate immediately. It can then be disposed of together with the black oxide tank sludge.

[0065] Therefore, the black oxide bath does not contaminate or degrade in any way and can be used for normal blackening at any time without producing a layer containing any Ti. The advantage is that the same black oxide bath can be used for different blackening processes, with or without metal additive elements from a previous pre-impregnation step. Depending on the product and other requirements, the same equipment can alternately produce black oxide layers for non-alloyed tribology or black oxide layers for alloyed tribology, without these processes interfering with each other.

[0066] As described herein, in tribological black oxides, the total blackening time is distributed over several blackening steps. For particularly long blackening times in a black oxide bath, the process is usually interrupted by an intermediate quench in a water bath to saturate the elements with an affinity for oxygen and reactivate the surface. Therefore, as described above, each black oxide bath and each blackening step can be preceded by a separate pre-dip in a titanium dioxide suspension or other pre-dip solution containing metallic additive elements. This does not complicate or delay the coating process. Such intermediate immersions lead to a re-enrichment on the component surface to compensate for the loss of titanium dioxide and restore the native Ti content of the layer to about 0.5%.

[0067] Features relating to the method also apply to the component and vice versa.

[0068] Further advantages and advantageous embodiments are given in the description, the drawings and the claims.In particular, the combinations of features given in the description and the drawings are purely exemplary, so that these features can also be presented alone or in different combinations.

[0069] In the following, the present invention will be described in more detail with reference to the exemplary embodiments shown in the accompanying drawings. The exemplary embodiments and combinations shown in the exemplary embodiments are purely exemplary and are not intended to limit the scope of protection of the present invention. This is only limited by the attached claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] It shows:

[0071] Figure 1 is a schematic sequence of methods for manufacturing an assembly. DETAILED DESCRIPTION

[0072] In the following, identical or functionally similar elements are marked with the same reference numerals.

[0073] Figure 1 A possible schematic sequence of a method for producing a component 1 with a black oxide layer 10 is shown. The component 1 is here exemplified in the form of a ring or a cylinder, but any other shape can also provide such a black oxide layer 10.

[0074] The component 1 is first immersed in a pre-dip solution 2 containing metal additive elements. For example, these metal additive elements can be titanium dioxide, which is present in a titanium dioxide suspension in the pre-dip solution 2. By immersing the component 1 in the pre-dip solution 2, the metal additive elements are deposited on the surface of the component 1, as shown here by the beads 4.

[0075] The component 1 is then transferred to a black oxide bath 6. In this bath, the component surface is converted into a black oxide layer 8. As a result, the iron and iron oxides contained in the component 1 material are dissolved and continuously redeposited and reorganized. The metal additive elements 4 that have been deposited on the component 1 are thus incorporated into the black oxide layer 8. In particular, the metal additive elements are embedded in the structure of the black oxide layer 8.

[0076] The pre-immersion and blackening in the pre-immersion solution 2 and the black oxidation tank 6 can be repeated as many times as needed, preferably two to three times. In addition, the component 1 can be quenched after each black oxidation tank 6.

[0077] After the black oxidation process is completed, a component 1 with a homogeneously alloyed black oxide layer 10 is obtained. The metallic additive element 4 is embedded in this layer over the entire radial extent and cannot be identified as a separate element. Only a possible excess of the additional element can be seen as a local concentration peak, but it does not have a negative impact on the function. The metallic additive element 4 serves in particular to adjust the properties of the black oxide layer 8 and does not affect its own properties.

[0078] The alloyed black oxide layer 10 can be used in particular to improve the performance of the black oxide layer in terms of wear resistance and degree of wear.

[0079] Reference numerals list

[0080] 1 Components

[0081] 2 Pre-soaking solution

[0082] 4 Metal additive elements

[0083] 6 Black Oxidation Solution

[0084] 8 Black oxide layer

[0085] 10 Alloyed black oxide layer

Claims

1. A component (1) having a black oxide layer (10), characterized in that The black oxide layer (10) is alloyed with a metal additive element (4), so that the metal additive element (4) is not located on the surface of the black oxide layer (10) but is located in the black oxide layer (10), and the metal additive element (4) includes FeTiO3.

2. The component according to claim 1, wherein the percentage of the metal additive element (4) of the black oxide layer (10) is between 0.1% and 1%.

3. The component according to claim 1 or 2, wherein the black oxide layer (10) is alloyed with the metallic additive element (4) in a percentage that increases radially outwards.

4. The component according to claim 1 or 2, wherein the metal additive element (4) is configured to adjust the properties of the black oxide layer (10).

5. The component according to claim 1 or 2, wherein the black oxide layer (10) is arranged on areas of the component (1) without rolling contact.

6. The component according to claim 1, wherein the percentage of the metal additive element (4) of the black oxide layer (10) is between 0.3% and 0.7%.

7. A method of manufacturing an assembly (1) according to any one of the preceding claims, the method comprising the following steps: depositing a metallic additive element (4) on the component (1), and The component (1) containing the deposited metal additive element (4) is immersed in a black oxide solution (6), wherein the black oxide layer (10) is alloyed with the metal additive element (4) so ​​that the metal additive element (4) is not located on the surface of the black oxide layer (10), but is located in the black oxide layer (10), and wherein the metal additive element (4) includes FeTiO3.

8. The method according to claim 7, wherein the deposition of the metallic additive element (4) is performed by immersion in a pre-impregnation solution (2).

9. The method according to claim 7 or 8, wherein the steps of depositing the metallic additive element (4) and immersing in the black oxidizing solution (6) are repeated, wherein the deposition is followed by immersing in the black oxidizing solution (6).

Images