WO2024051897A1

WO2024051897A1 - Main body comprising a coating system

Info

Publication number: WO2024051897A1
Application number: PCT/DE2023/100671
Authority: WO
Inventors: Tobias Phillip Utsch; Dominik DOBRZANSKI
Original assignee: HPL Technologies GmbH
Priority date: 2022-09-11
Filing date: 2023-09-11
Publication date: 2024-03-14

Abstract

The invention relates to a main body (1) comprising a coating system (2), the coating system (2) comprising at least one layer (3, 4) having a matrix alloy (5), at least one of the layers (3, 4) comprising at least the following elements in wt.% of the matrix alloy (5): iron; from 10 wt.% to 26 wt.% chromium; from 0.3 wt.% to 5 wt.% carbon; and from 0.5 wt.% to 15 wt.% the sum of niobium, titanium and vanadium, wherein the coating system (2), in at least one of the layers (4) having the matrix alloy (5), also comprises separately added carbide particles (6) in a proportion of at least 20 vol.% to 70 vol.% of the entire layer (4). The proposed main body comprising a coating system makes it possible to achieve an outstandingly corrosion-resistant and wear-resistant surface, especially for the friction surface of a brake disc.

Description

Base body with a coating system

The invention relates to a base body with a coating system, a powder material mixture with such a base body for a coating system of a base body, and a method with such a powder material mixture for coating a base body.

In industry, for example the automotive industry, balancing the quality criteria of components with a high level of cost awareness is a constant challenge. Sustainability issues are also becoming increasingly relevant in this equation. This problem becomes particularly evident in the area of brake discs or other coated parts that are exposed to high stress.

Brake discs are known in the prior art, for example, as inexpensive components made of gray cast iron. However, a problem with cast brake discs is that they tend to corrode and do not have sufficient abrasion resistance, which contributes to increased particulate matter pollution. For example, the braking process of uncoated cast brake discs causes around 15% of a vehicle's total fine dust emissions. These negative properties can be reduced by coating the brake disc base body. Laser coating processes have generally prevailed over paint coatings because, for example, a functional layer can be created that achieves higher abrasion resistance, improved corrosion protection and a reduction in fine dust emissions.

A method known in the art for coating base bodies, for example brake discs, is flame spraying. Here, a welding filler material made of wire or powder is introduced into a nozzle. When a powdery welding filler material is supplied, the powder material used is conveyed uniformly from a powder container and guided by a conveying gas stream through the burner nozzle to the burner flame. This will ensures that melted or partially melted particles adhere to the surface to be coated, accelerated by the burning flame. Flame spraying is a comparatively simple and inexpensive process, but the resulting coatings can have a relatively high porosity, there is no melt metallurgical connection to the base body and gas consumption is high.

An alternative is laser deposition welding [LA], in which, for example, lower porosity can be achieved with reduced gas consumption. LA is a welding process that uses laser radiation to melt the welding filler material used, supplied in powder form or wire form. When a powdery welding filler material is supplied, this powder material is guided to a processing point using carrier gas under a protective gas atmosphere. The processing point is aligned with the base body surface. A laser beam is focused on the processing point and melts the substrate and the powder material passing through the processing point. Powder particles of the powder material that have not been melted are completely melted in the melt pool. The powder nozzle is moved over the surface using movable axes and creates weld beads. A coating is created which essentially (i.e. completely within technical tolerance apart from a transition area, the so-called mixing zone) consists of the powder material. This means that, for example, the composition of the powder material can be drawn directly from material tests on the finished coating. Underneath the coating is the mixing zone, which consists of additional material and substrate material. The melted powder material collects above the mixing zone and forms the coating system.

A person skilled in the art will immediately recognize that a melt-metallurgical composite is formed regardless of the layer thickness and/or number of layers, thereby resulting in a technical improvement to, for example, thermally sprayed layers. The melt metallurgical bond leads to a mixing between the coating and the substrate. However, because the mixing zone in LA is minimal compared to other welding processes be inferred accordingly from the coating to the coating material.

High-speed laser deposition welding [HVLA: High-Velocity Laser Application] emerged from the LA. In order to achieve higher feed speeds than with LA, with HVLA the welding filler material, provided as a powder, is melted or melted using laser energy before it arrives on the substrate, i.e. above the substrate surface. This is achieved by crossing the powder streams to be melted in a so-called powder focus one or several millimeters above the substrate surface. It should be noted that the HVLA is preferably carried out with the welding device in the earth's gravity field above the substrate. However, this may differ in some applications. Above means at least only at a distance from the substrate surface. The powder focus is superimposed with a laser beam so that powder particles pass through the laser beam and shade it. As a result, not all of the energy from the laser reaches the surface of the substrate. The ratio of the total laser power [LI] to the laser power reaching the substrate is usually calculated by those skilled in the art as the transmittance. By adjusting various process parameters and the resulting transmittance, a coating as a melt-metallurgical composite can be achieved using HVLA.

A special HVLA process (referred to there as extreme high-speed laser deposition welding [EHLA]) is described, for example, in Schopphoven et. al (“Experimental and model-theoretical investigations into extreme high-speed laser deposition welding”, dissertation at the Fraunhofer Institute for Laser Technology ILT, 2019, published online on the university library website), and DE 102011 100 456 A1.

The documents WO 2021/007 209 A1 and WO 2021/126 518 A1 disclose coatings. The expensive carbide formers titanium and niobium and sometimes also chromium are used in large quantities. Proceeding from this, the present invention is based on the object of at least partially overcoming the disadvantages known from the prior art. The features according to the invention result from the independent claims, to which advantageous embodiments are shown in the dependent claims. The features of the claims can be combined in any technically sensible manner, for which the explanations from the following description and features from the figures, which include additional embodiments of the invention, can also be consulted.

The invention relates to a base body with a coating system, the coating system comprising at least one layer with a matrix alloy, at least one of the layers comprising at least the following elements in weight percent of the matrix alloy:

Iron; and from 10% to 26% by weight chromium; and from 0.3 wt% to 5 wt% carbon; and the sum of niobium, titanium and vanadium 0.5% by weight to 15% by weight, the coating system further comprising separately added carbide particles in at least one of the layers with the matrix alloy in a proportion of the total in question Location of at least 20% by volume to 70% by volume.

Ordinal numbers used in the preceding and following descriptions, unless explicitly stated to the contrary, only serve to clearly distinguish them and do not reflect the order or ranking of the designated components. An ordinal number greater than one does not mean that another such component must necessarily be present.

It should first be understood that all quantities with regard to the powder material used or the powder material mixture, as well as the coating system according to the present invention, are in the quantities mentioned in percent by weight [% by weight] based on a total weight of the corresponding powder material or the matrix. Alloy of the coating system should be understood. It should also be understood that iron serves as the base material of the powder material in the coating system and is preferably included in a balanced form.

It should be expressly pointed out that the weight percent does not refer to the finished coating system with the separately added carbide particles. In comparison to a (for example glass fiber) reinforced plastic, the separately added carbide particles correspond to the reinforcing material, while the matrix alloy forms the matrix in which the separately added carbide particles are embedded. The carbide particles are classified as so-called hard material particles.

Furthermore, it should be noted that the separately added carbide particles are not only formed during the welding process using the so-called carbide formers, but rather as carbide particles (for example elementary pure and / or in a chemical composite), for example as titanium carbide [TiC], tungsten carbide [WC], vanadium carbide [VC], chromium carbide [Cr _x C _y ] or others can be added to the coating system. The mass of the carbide particles varies greatly, for example titanium carbides are much lighter than tungsten carbides. These are therefore given in percent by volume [% by volume] with reference to the respective layer or to the entire coating system. In a preferred embodiment, the mixing zone is free of separately added carbide particles, so no separately added carbide particles are contained there.

Percentages used in the preceding and following description are to be understood as percent by weight of the specified matrix alloy of a relevant layer, unless another definition (for example volume percent [vol.-%]) is explicitly stated.

The alloy of the coating system itself that can be formed using the matrix alloy of the welding material shown here (i.e. without the separately added carbide particles) already has excellent wear resistance and/or abrasion resistance. For this purpose, carbide formers (especially niobium, titanium and/or vanadium) are present in the coating system Carbides, and sometimes borides, are largely responsible. At the same time, with this welding material it is possible to form the coating system by applying the welding material directly to the base body during deposition welding. The known standard so far is that an intermediary primer (a so-called adhesive layer, binding layer or buffer layer) must first be provided. With a single welding material or a single layer on the base body, shorter process times, lower susceptibility to errors, thinner layer thicknesses and possibly a smaller number of layers, i.e. less frequently repeated applications, can be achieved to produce the (single) layer of the coating system.

It should be noted that, as used here, a layer means an area of material with the same chemical composition or an application (possibly multiple layers) of chemically identical welding filler material. In the latter case, the areas of the respective mixing zones with adjacent material are ignored, for example a layer is defined up to the middle of a respective mixing zone.

Furthermore, it should be noted that a layer is formed one order in one pass from the beginning to the end, for example in the case of a friction surface of a brake disc from radially inside to outside or vice versa. Interruptions in the order between the beginning and the end due to the process or a result to be achieved are not significant. In another definition, a single layer is an application that is applied to a surface that is cold from a welding point of view and cools to a new surface (without further input of welding energy). In one embodiment, a single layer is not necessarily formed to cover a surface. In one embodiment, a single layer is not necessarily formed by a single welding device.

What is achieved is a coating system in the form of a corrosion-resistant, naturally hard alloy, whereby the properties of corrosion protection and wear protection are combined. By using different carbide formers with different precipitation kinetics and thus Different distributions also lead to good resistance to wear particles (e.g. dirt or released carbide particles between the brake disc and brake pad) of different sizes.

It is therefore proposed here that carbide particles and, if necessary, other hard material particles are added to the coating system (preferably as a component of the powder material). It was found that these hard material particles do not take part in the welding process and are therefore not melted. It should be noted that if the grain size is very small, hard material particles will melt or even evaporate. However, this proportion is negligible. For example, such hard material particles of a desired grain size are only melted on the surface or heated only in the deposition welding process.

In a supplementary embodiment, hard material particles are additionally added depending on the position of a plurality of layers (forming the coating system). In this case, there is a different amount of or exclusively in at least one of the layers in different layers. Preferably, the lowest layer (i.e. closest to the base body) or a plurality of (adjacent) lowest layers including the very lowest layer is free of separately added carbide particles, preferably free of hard material particles, i.e. no carbide particles or hard material particles are embedded. Alternatively or additionally, the top (i.e. outside) layer or a plurality of (preferably adjacent) top layers, preferably including the very top layer, is preferably free of separately added carbide particles, preferably free of hard material particles, i.e. no carbide particles or hard material particles embedded.

In one embodiment, the carbide particles make up a proportion of the entire relevant layer of at least 20% by volume [twenty percent by volume] to 70% by volume, preferably from at least 35% by volume to 70% by volume or 20 % by volume to 60% by volume, particularly preferably from 40% by volume to 50% by volume, added separately. In a preferred embodiment, the separately added carbide particles are larger than 1 m [one micrometer], particularly preferably greater than 1.5 pm [fifteen tenths of a micrometer],

According to one embodiment, the volume percent is measured according to the amount of welding filler material added. In one embodiment, the volume percent is measured according to the microscopically detectable number and its volume fraction in a micrograph of a coating system formed, with preference being given to separately added carbide particles only those having a grain size greater than 1 pm, particularly preferably greater than 1.5 pm, exhibit. Metallographic analyzes known from the prior art are used here. In particular, after preparation and etching under the light microscope, the number of carbide particles, and preferably the surface area, can be determined directly by visual inspection, if necessary with computer-aided image recognition. The area percentage corresponds to the volume percent.

In one embodiment, the volume percents are measured after a (preferably microscopic) examination of an external surface of a finished coating system. The area proportion is equated to the volume proportion, at least when the layer forming the outer surface is provided with separately added carbide particles. If the layer forming the outer surface is free of separately added carbide particles, the protruding carbide particles and elevations in the otherwise smooth outer surface are counted and multiplied by an area factor, the area factor being multiplied, for example, by the square of the mean grain diameter with TT/2 [half the circle number]. The area factor is alternatively a different mathematical-statistical approximation of the area or volume of an average carbide particle. In one embodiment, the manufacturer's information is used as the mean grain diameter. In one embodiment, individual carbide particles are released from the coating system and they themselves and/or the remaining hole or holes that have already formed as a result of use (by releasing particles) are measured for their diameter and/or their respective area. Of the diameters or areas of the random The agent is formed using selected carbide particles and/or holes. The calculated product corresponds to the volume fraction. This method for determining the volume percent can be used regardless of the type of layer forming the outer surface.

It should be noted that in one embodiment, the material of the coating system described here or the matrix alloy in the welding filler material is provided as an alloy of the welding material, for example as a wire or powder, whereby the powder material does not necessarily have to have the described composition in every powder particle, if necessary even varies greatly if different base materials are put together to form a powder mixture or are put together in-situ. In one embodiment, the desired separate carbide particles (and possibly further hard material particles) are added to the welding filler material, which, however, are not added to the welding material as particles that do not take part in the welding process, but are referred to as separately added particles.

Powder material or powder material mixture as used conceptually herein preferably refers to the welding material with which the coating system of the base body is produced. It should be understood that the welding material is preferably kept for deposition welding as a powder material for powder deposition welding.

Balanced as used conceptually herein preferably means that the amount of iron is adjusted accordingly (filling up to 100%) in order to achieve the specified weight percent of other components, so that the main component of a coating system proposed herein is an iron-based alloy.

This coating system represents a cost-effective coating system for a base body compared to a coating known from the prior art. This is achieved primarily through the use of niobium, titanium and/or vanadium, and preferably by avoiding relatively expensive ones Components, and a very small amount of them compared to previously known coatings.

The present inventors have surprisingly found that the coating system proposed here additionally has properties that are advantageous for their use and is not excessively prone to cracking and/or pore formation, has a generally high corrosion resistance and good bonding of the weld layers, as well as a hardness that is advantageous for their use having.

In a preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises: iron; and preferably from 0.5 to 15.0% by weight vanadium; and preferably at most 4.0% by weight niobium; and further preferably at most 0.35% by weight titanium; and further preferably at most 0.3% by weight nickel; and more preferably from 0.3 to 3.0 wt% carbon; and more preferably from 10 wt% to 26 wt% chromium; and more preferably from 1.0 to 10% by weight of manganese; and more preferably from 0.05 to 1.0% by weight of molybdenum; and more preferably from 0.25 to 1.25% by weight of silicon; and more preferably at most 0.75% by weight tungsten; and more preferably at most 0.15% by weight phosphorus; and more preferably at most 0.25% by weight sulfur; and more preferably from 0.01 to 0.5% by weight nitrogen; and more preferably 0.01 to 0.09% by weight of oxygen.

The present inventors have surprisingly found that the coating system proposed herein can be produced with vanadium. Vanadium [V] is a relatively inexpensive component compared to tungsten [W], niobium [Nb] and/or titanium [Ti]. Vanadium, titanium and/or niobium serve primarily as so-called carbide formers in the coating system.

With the use of vanadium, more expensive components such as niobium and titanium can be used in significantly smaller quantities. The welding material preferably contains no niobium and no titanium, at least not beyond usual impurities.

It was surprisingly found that the property profile of corresponding alloys can be precisely adjusted through the coordinated addition of monocarbide formers such as vanadium. Through fine distribution (finely dispersed precipitation of primary vanadium carbide), in conjunction with grain refinement effects, the crack length of the weld layers, which are often heavily cracked, can be shortened. Impacting wear and tear no longer leads to immediate breakouts. This results in advantages in the event of abrasive and impact wear. Another advantage is the extremely high hardness and high melting point of vanadium carbide, which is in the range of titanium carbide and above tungsten carbide. Vanadium carbide has a hardness of 2950 HVo,oi [two thousand nine hundred and fifty hardness Vickers], with 0.102 kp [one hundred and two thousandths of a kilopond] test force and a standard loading time of 10 s [ten seconds] to 15 s and a melting point of 2830 ° C [two thousand eight hundred and thirty degrees Celsius].

The resulting mixed carbides of type (Cr, Fe) 7C3 have a hardness of 1700 HV10 [one thousand seven hundred hardness Vickers] to 2100 HV10. From a content of around 0.6%, boron leads to a hardening of the (Cr, Fe) 7C3 carbides. The most important hard materials besides Cr7C3 are the chromium carbides Cr3C2 and Cr23C6. The Cr7C3 carbides and Cr23C6 carbides, which have a needle-shaped to plate-shaped structure, have proven particularly useful under abrasion wear.

In addition, the addition of manganese [Mn] and silicon [Si] (in addition to a typically significant improvement in welding properties as a result of the high oxygen affinity and thus deoxidation) to increase the wear resistance of the applied coating system.

In particular, an increased hardness of the coating system can be achieved through a higher proportion of vanadium. However, too high a proportion of vanadium can cause the grid to become too tense.

It should be noted that the comparisons listed herein are made to a composition with less or more of the respective element in the coating system. It is at least true that a less or more of this element is present due to a corresponding more or less of the iron [Fe] as a base. Alternatively or additionally, more or less of another of the elements mentioned is present in a considerable quantity within the scope of the quantities mentioned. This is explicitly stated in some examples, provided that the respective element can be used as a substitute. However, it is also within the skill of the art, at least based on the explanations given herein, to use a suitable alloy within the scope of the invention proposed here, in which the elements are present in a combination that are not listed here as an explicit example.

The more vanadium is used, the more additional carbide formers can be dispensed with, such as niobium and titanium, but also molybdenum. It should be noted that it is not necessary to replace the other carbides in the same amount because vanadium carbide occurs in a very finely divided form and is one of the very high-quality carbides due to its high hardness and high melting point.

Such a coating system preferably comprises at least 0.75% by weight, more preferably at least 1.0% by weight, more preferably at least 1.6% by weight, more preferably at least 2.5% by weight, and more preferably at least 5.0% by weight vanadium.

At the same time, a relatively low proportion of vanadium is advantageous because it reduces the tendency to crack. Too little vanadium can However, it can be disadvantageous because a sufficiently high hardness may not be achieved.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises at most 15% by weight, preferably at most 12.5% by weight, more preferably at most 12% by weight and more preferably at most 10% by weight. % vanadium.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises: preferably from 0.5 to 15.0% by weight, more preferably from 0.75 to 15.0% by weight, more preferably from 1.0 to 15.0% by weight, more preferably from 1.6 to 15.0% by weight, more preferably from 2.5 to 15.0% by weight, more preferably from 5.0 to 15.0% by weight, more preferably from 0.5 to 12.5% by weight, more preferably from 0.75 to 12.5% by weight, more preferably from 1.0 to 12.5% by weight. -%, more preferably from 1.6 to 12.5% by weight, more preferably from 2.5 to 12.5% by weight, more preferably from 5.0 to 12.5% by weight, more preferred from 0.5 to 12.0% by weight, more preferably from 0.75 to 12.0% by weight, more preferably from 1.0 to 12.0% by weight, more preferably from 1.6 to 12.0% by weight, more preferably from 2.5 to 12.0% by weight and more preferably from 5.0 to 12.0% by weight, preferably from 0.5 to 10.0% by weight , more preferably from 0.75 to 10.0% by weight, more preferably from 1.0 to 10.0% by weight, more preferably from 1.6 to 10.0% by weight, more preferably from 2 .5 to 10.0% by weight and more preferably from 5.0 to 10.0% by weight of vanadium.

In an advantageous embodiment, the coating system comprises a proportion of niobium. A proportion of niobium is present in the coating system as a carbide former.

At the same time, a relatively low proportion of niobium is advantageous in order to keep the costs of the coating system low.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further comprises at most 4.0% by weight of niobium. In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises: preferably at most 3.5% by weight, more preferably at most 3.0% by weight, more preferably at most 2.0% by weight , more preferably at most 1.0% by weight, more preferably at most 0.75% by weight, more preferably at most 0.5% by weight, more preferably at most 0.25% by weight, more preferably at most 0, 1% by weight and more preferably at most 0.01% by weight of niobium.

In an advantageous embodiment, the coating system comprises a proportion of titanium.

A proportion of titanium is present in the coating system as a carbide former and/or corrosion protection element. At the same time, a relatively low proportion of titanium is advantageous in order to keep the costs of the coating system low.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further comprises at most 0.4% by weight of titanium.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises: preferably at most 0.35% by weight, more preferably at most 0.25% by weight, more preferably at most 0.1% by weight. % and more preferably at most 0.01% by weight of titanium.

In an advantageous embodiment, the coating system comprises a proportion of nickel.

Nickel [Ni] in the coating system serves in particular to provide increased corrosion protection. A higher proportion of nickel also improves weldability. At the same time, a relatively low proportion of nickel is advantageous in order to reduce the proportion of substances that are harmful to health to a minimum can, or also in order to comply with more modern standards, such as the so-called REACH regulation.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further comprises at most 0.5% by weight of nickel, preferably at most 0.3% by weight, further at most 0.2% by weight, more preferably at most 0.1% by weight and more preferably at most 0.01% by weight of nickel.

In an advantageous embodiment, the coating system comprises a proportion of carbon [C].

Carbon in the coating system serves in particular as a so-called carbide former. A higher proportion of carbon can be detrimental to weldability. At the same time, the hardness can be advantageously increased through a higher proportion of carbon. At the same time, a relatively low proportion of carbon is advantageous in order to improve weldability. A relatively low proportion of carbon also advantageously reduces the formation of cracks.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system preferably further comprises at least 0.3% by weight of carbon.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system preferably further comprises at least 0.5% by weight, more preferably at least 0.75% by weight, more preferably at least 1.0% by weight and more preferably at least 1.5% by weight of carbon.

Such a high proportion of carbon is beneficial for austenite formation. It should be noted that a high proportion of the carbon in the powder material reacts during deposition welding and does not arrive in the alloy of the coating system, for example with atmospheric oxygen that has penetrated into it. For example, in the alloy of the coating system with the The aforementioned amount in the welding material achieves a proportion of carbon in percent by weight of 0.5% to 1.5%.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 4.5% by weight, more preferably at most 3.0% by weight, more preferably at most 2.5% by weight. and more preferably at most 2.0% by weight of carbon.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises: more preferably from 0.3 to 5% by weight, more preferably from 0.5 to 5% by weight, more preferably from 0, 75 to 5% by weight, more preferably from 1.0 to 5% by weight, more preferably from 1.5 to 5% by weight, more preferably from 0.3 to 4.5% by weight, further preferably from 0.5 to 4.5% by weight, more preferably from 0.75 to 4.5% by weight, more preferably from 1.0 to 4.5% by weight, more preferably from 1.5 to 4.5% by weight, more preferably from 0.3 to 3.0% by weight, more preferably from 0.5 to 3.0% by weight, more preferably from 0.75 to 3.0% by weight .-%, more preferably from 1.0 to 3.0% by weight, more preferably from 1.5 to 3.0% by weight, more preferably from 0.3 to 2.5% by weight, further preferably from 0.5 to 2.5% by weight, more preferably from 0.75 to 2.5% by weight, more preferably from 1.0 to 2.5% by weight, more preferably from 1.5 to 2.5% by weight, more preferably from 0.3 to 2.0% by weight, more preferably from 0.5 to 2.0% by weight, more preferably from 0.75 to 2.0% by weight .-%, more preferably from 1.0 to 2.0% by weight and more preferably from 1.5 to 2.0% by weight of carbon.

In an advantageous embodiment, the coating system comprises a proportion of chromium.

Chromium is an important component for corrosion resistance, especially in water-containing solutions, such as (salt-added) rainwater. In combination with molybdenum it is particularly effective against pitting corrosion. The lower the proportion, the cheaper the welding material is. However, too little chromium can impair corrosion resistance immensely. Chromium in the coating system prevents this, especially in the case of one (low) exposure to oxygen effectively leads to the formation of iron oxide - especially when processing under a protective gas atmosphere. A proportion of chromium in the coating system advantageously serves to increase corrosion protection and as a carbide former. In addition, chromium in the proposed welding material represents a component for the formation of hard phases.

A higher proportion of chromium increases the corrosion resistance of the coating system in particular.

In a further preferred embodiment of the base body with the coating system, the chromium is present freely in the matrix. This is particularly advantageous in order to be able to guarantee corrosion protection. Bound chromium in the form of chromium carbides may not contribute to corrosion protection. The person skilled in the art will recognize that vanadium is used as a sacrifice (sufficiently high) in the coating system proposed here, so that carbon is advantageously bound to vanadium and not to chromium.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at least 10% by weight, more preferably at least 12.5% by weight, more preferably at least 13% by weight and more preferably at least 15.0% by weight chromium.

A proportion of at least 12.0% by weight of chromium in the coating system is particularly preferred.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 25% by weight, more preferably at most 20% by weight of chromium.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises from 10% by weight to 25% by weight, more preferably from 12.5% by weight to 25% by weight, more preferably from 13% by weight to 25% by weight, more preferably from 15.0% by weight to 25% by weight, more preferably from 10% by weight to 20% by weight .-%, more preferably from 12.5% by weight to 20% by weight, more preferably from 13% by weight to 20% by weight, more preferably from 15.0% by weight to 20% by weight. -% chrome.

In an advantageous embodiment, the coating system comprises a proportion of manganese.

Manganese [Mn] in the coating system is used in particular to improve weldability, strength and wear resistance, as well as to optimize hardenability. A pronounced balance of manganese is advantageous in order to avoid higher proportions of brittle phases. The carbon together with the manganese supports the formation of austenite (face-centered cubic lattice structure of an iron alloy) and thus the desired toughness of the coating system. The proportion of manganese is also an effective work hardening agent.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at least 1.0% by weight, more preferably at least 1.25% by weight and more preferably at least 1.4% by weight , manganese.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 10% by weight, more preferably at most 7.5% by weight and more preferably at most 6.5% by weight of manganese.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises from 1.0 to 10% by weight, more preferably from 1.25 to 10% by weight, more preferably from 1.4 to 10% by weight, more preferably from 1.0 to 7.5% by weight, more preferably from 1.25 to 6.5% by weight, more preferably from 1.4 to 6.5% by weight % and more preferably from 1.4 to 6.5% by weight, manganese.

In an advantageous embodiment, the coating system comprises a proportion of molybdenum. Molybdenum [Mo] in the coating system is particularly advantageous for improving weldability and fine grain formation. In addition to the properties described above, molybdenum has the property of providing corrosion resistance to non-oxidizing solutions, such as hydrochloric acid, which also occur in the environment in non-negligible quantities. Molybdenum is also another carbide former. A higher proportion of molybdenum increases the corrosion resistance in particular.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at least 0.05% by weight, more preferably at least 0.1% by weight and more preferably at least 0.25% by weight Molybdenum.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 1.0% by weight, more preferably at most 0.75% by weight and more preferably at most 0.6% by weight. Molybdenum.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises from 0.05 to 1.0% by weight, more preferably from 0.1 to 1.0% by weight, more preferably from 0.25 to 1.0% by weight, more preferably from 0.05 to 0.75% by weight, more preferably from 0.1 to 0.75% by weight, more preferably from 0.25 to 0.75% by weight, more preferably from 0.05 to 0.6% by weight, more preferably from 0.1 to 0.6% by weight and more preferably from 0.25 to 0.6% by weight. -% molybdenum.

In an advantageous embodiment, the coating system comprises a proportion of silicon.

A higher proportion of silicon [Si] in particular advantageously increases the wear resistance and strength of the coating system.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at least 0.1% by weight of silicon. In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at least 0.25% by weight, more preferably at least 0.3% by weight, and more preferably at least 0.5% by weight. % silicon.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 1.25% by weight, more preferably at most 1.0% by weight and more preferably at most 0.7% by weight. Silicon.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises from 0.25 to 1.25% by weight, more preferably from 0.3 to 1.25% by weight, more preferably from 0.5 to 1.25% by weight, more preferably from 0.25 to 1.0% by weight, more preferably from 0.3 to 1.0% by weight, more preferably from 0.5 to 1.0% by weight, more preferably from 0.25 to 0.7% by weight, more preferably from 0.3 to 0.7% by weight, and more preferably from 0.5 to 0.7% by weight .-% silicon.

In an advantageous embodiment, the coating system comprises a proportion of tungsten.

Even in very small amounts, tungsten [W] is advantageous as a carbide former (for example for a highly friction-resistant and/or highly heat-resistant surface). However, it is particularly advantageous in small quantities as a mixed crystal solidifier and for the high-temperature resistance of the coating system.

Tungsten carbides have proven to be an effective hard material additive in the state of the art, especially in so-called dual-layer systems. They significantly increase the hardness of a welded layer. The disadvantage is that they make the welding process more difficult because an even distribution of the carbides in the melt must be ensured. In addition, melting of the carbides should be prevented in order to utilize the technological advantage of the carbides and reduce the risk of the matrix becoming brittle. In addition, their high price is a problem for economic viability. A higher proportion of tungsten in particular advantageously increases the high-temperature strength of the coating system. Tungsten also serves advantageously as a carbide former. However, a high proportion of tungsten can be uneconomical due to high material costs.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 0.75% by weight, more preferably at most 0.6% by weight, more preferably at most 0.5% by weight , more preferably at most 0.25% by weight, more preferably at most 0.05% by weight, and more preferably at most 0.01% by weight of tungsten.

In an advantageous embodiment, the coating system comprises a proportion of phosphorus.

A relatively low proportion of phosphorus [P] is advantageous because phosphorus is a disadvantage as a steel pest.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 0.15% by weight, more preferably at most 0.1% by weight, more preferably at most 0.05% by weight , and more preferably at most 0.25% by weight of phosphorus.

In one embodiment, the coating system comprises a proportion of sulfur.

A relatively low proportion of sulfur [S] is advantageous. The expert will recognize that sulfur is bound by manganese.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 0.25% by weight, more preferably at most 0.1% by weight and more preferably at most 0.01% by weight , sulfur. In one embodiment, the coating system comprises a proportion of nitrogen.

In the state of the art, nitrogen-alloyed steels are increasingly being used. However, the expert will generally consider nitrogen to be a steel pest and will keep the proportion of nitrogen [N] as low as possible. Nitrogen can be used as an alloying component.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 0.5% by weight, more preferably at most 0.25% by weight, and more preferably at most 0.1% by weight. % nitrogen.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at least 0.01% by weight, more preferably at least 0.02% by weight and more preferably at least 0.05% by weight Nitrogen.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises from 0.01 to 0.5% by weight, more preferably from 0.02 to 0.5% by weight, more preferably from 0.05 to 0.5% by weight, more preferably from 0.01 to 0.25% by weight, more preferably from 0.02 to 0.25% by weight, more preferably from 0.05 to 0.25% by weight, more preferably from 0.01 to 0.1% by weight, more preferably from 0.02 to 0.1% by weight, more preferably from 0.05 to 0.1% by weight. -% nitrogen.

In one embodiment, the coating system comprises a proportion of oxygen.

A relatively low proportion of (elemental) oxygen [O] is advantageous because this can lead to embrittlement and other negative properties. It is worth mentioning that some of the other alloy components described can also have a deoxidizing effect. The person skilled in the art will recognize that oxygen should advantageously be avoided, and other alloy components can also be designed to counteract oxygen contamination.

In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises 0.01 to 0.09% by weight of oxygen.

It should be understood that the coating system according to the present invention can be suitable for coating any base body that requires wear protection and corrosion protection. In the context of the present invention, the term base body preferably refers to a component that requires wear protection and corrosion protection.

The present inventors have further surprisingly found that the coating system proposed here can be used in the form of a single-layer coating system, i.e. can be applied directly to the base body. This significantly simplifies the process for producing coated base bodies and therefore makes it more cost-effective.

It is further proposed in an advantageous embodiment of the base body that the coating system is designed as a single layer.

The single-layer coating system as used conceptually herein preferably refers to a coating system which is applied as a layer to the surface of the base body to be coated, with no primer being used.

This does not mean (as already explained above) that such a layer is or has been necessarily welded on in a single pass. It is known to those skilled in the art that the presence of a single-layer coating can be determined using a cross-sectional image. Metallographic analyzes known from the prior art are used here. In particular, after preparation and etching under the light microscope, the number of layers can be determined directly by visual inspection. It should be understood that in comparison to coating systems described in the prior art, the single-layer coating consists of the actual functional layer, which is usually referred to as a friction layer when used in a brake disc and similar applications, and is not applied to a primer.

The expert knows that materials differ in their suitability for welding. One criterion is the carbon content of the material. In general, the higher the carbon content, the harder a material is to weld. In order to weld a layer from or onto a material that is difficult to weld, it is already recommended in the prior art to first weld on a primer. Such a binding layer made of a material that can be easily welded is placed between the substrate (surface of the base body to be coated) and the weld seam that actually forms or enables the desired properties of the newly formed outer surface. The material of the binding layer is selected so that it achieves both a melt metallurgical bond to the substrate and can also create a bond to the layer above.

It is further proposed in an advantageous embodiment of the base body that the coating system is designed in multiple layers, with at least a first layer being formed without separately added carbide particles, and with at least one layer arranged higher up, preferably a penultimate and/or last layer the matrix alloy is formed with the separately added carbide particles. wherein preferably the at least one first layer, and optionally a last layer, is formed from the matrix alloy, wherein more preferably the matrix alloys of the first layer and the layer with the separately added carbide particles, particularly preferably all layers, are identical .

In this embodiment, no primer is preferably provided or such a primer (at the bottom) is provided from a first layer the above description. This (at least one) first layer is preferably formed with a matrix alloy according to the description here, particularly preferably without separately added carbide particles. The matrix alloy of this at least one first layer and the further layer containing carbide particles is not necessarily identical. For example, in the at least one, preferably all, first layer applied directly to the surface of the base body to be coated, the proportion of chromium [Cr], carbide formers or other elements that tend to become brittle is lower than in the layer containing carbide particles.

In one embodiment, for example, a first layer as a primer (multi-layer or single-layer) consisting of at least one layer of the matrix alloy, then a second layer (multi-layer or single-layer) consisting of at least one layer with separately added carbide particles with the (chemical identical or different) matrix alloy, and finally a third layer as an outer surface (for example friction surface of a brake disc) consisting of at least one layer of the matrix alloy (chemically identical or different to the first layer and / or second layer) free of separate added carbide particles are formed. Alternatively, the first layer and/or third layer is omitted, i.e. only a first layer and a second layer or only a second layer and a third layer or only a second layer is formed, preferably in each case without a primer.

It is further proposed in an advantageous embodiment of the base body that at least the layer with the matrix alloy and the separately added carbide particles of the coating system is applied by means of high-speed laser deposition welding, preferably with an area rate of at least 500 cm ² /min to a reference - Layer thickness of 100 pm.

The coating system is provided by means of a method for coating a base body with a coating system according to the preceding description and/or a powder material mixture according to the following description, by means of deposition welding, for example LA and/or HVLA an area rate of at least 500 cm ² /min [five hundred square centimeters per minute],

It should be understood that an area rate of at least 500 cm ² /min, preferably at least 850 cm ² /min, makes the coating process particularly economical. An area rate is preferably normalized herein to a layer height of 100 pm [one hundred micrometers]. This means that if a lower layer height is desired, a higher area rate is achieved, for example, by increasing the feed rate while the process parameters are otherwise the same. In embodiments in which the coating system is designed as a single-layer coating system, a significant increase in economic efficiency can be achieved compared to a two-layer system with similar area rates, because the production of two-layer coatings known in the prior art is due to the correspondingly larger number of layers and / or a necessary Converting the device for a different powder material takes longer. However, it should be understood that the coating system proposed here is not limited to being designed as a single-layer coating.

It is further proposed in an advantageous embodiment of the base body that the coating system has a hardness of 300 HVo.oi to 1100 HVo.oi.

In one embodiment, the coating system preferably has a hardness of at least 350 HVo.oi, more preferably at least 400 HVo.oi, more preferably at least 450 HVo.oi and more preferably at least 500 HVo.oi. In one embodiment, the coating system preferably has a hardness of at most 700 HVo.oi, and more preferably at most 600 HVo.oi.

A higher hardness advantageously achieves improved wear resistance of the coating. At the same time, too much hardness can promote undesirable crack formation. It should be noted that in one embodiment the values given relate to the pure welding material, i.e. the matrix alloy without separately added carbide particles of the stated hardness having. In one embodiment, high values, for example the 1100 HVo.oi, are determined statistically averaged, with the hardness measured on a carbide particle and the hardness measured on the matrix alloy being calculated weighted according to the area fraction and/or the volume percent.

It is further proposed in an advantageous embodiment of the base body that a proportion of separately added carbide particles comprises at least 35% by volume, preferably at least 40% by volume, more preferably at least 50% by volume. wherein preferably the separately added carbide particles are selected from titanium carbides and/or tungsten carbides, with particularly preferably the separately added carbide particles being exclusively titanium carbides.

The lower the volume fraction of separately added carbide particles, the more cost-effective the coating system is. The more separate carbide particles are added, the better the wear resistance of a friction surface. It also shows that the braking behavior, i.e. response (the so-called sharpness of the braking), is improved with the increasing number of separately added carbide particles.

Titanium carbides are particularly cost-effective. Tungsten carbides are suitable for higher temperatures, for example for a coating system on a brake disc for a sports car braking system.

It is further proposed in an advantageous embodiment of the base body that the base body is a gray cast iron base body and/or a brake disc.

The person skilled in the art will immediately recognize that such a base body can benefit from the coating system, which is exposed to increased wear, friction or other mechanical stress. The coating system is particularly advantageous for base bodies that serve as braking devices, for example brake discs. Brake discs are particularly high Exposed to wear and corrosion. The coating system proposed here counteracts wear and corrosion in a particularly advantageous manner and protects the base body. Furthermore, the coating system advantageously achieves a base body which also achieves a particularly advantageous reduction in fine dust, such as that required in ELIRO7.

It is further proposed in an advantageous embodiment of the base body that the carbide particles have a grain size window of 6 pm to 120 pm, preferably comprising at least one, particularly preferably exclusively one, of the following separate grain size windows:

- 3pm to 45pm; and

- 45pm to 90pm, preferably until 106pm.

The grain size window specified here is a trade-off between the required layer thickness or total thickness of the coating system and a good solidification effect. If the grain size window is too large, statistically some carbide particles can no longer be integrated well into the matrix alloy and will detach from the matrix alloy under load. This in turn can lead to opposite results, for example when used as a friction surface of a brake disc, if such dissolved carbide particles eat into a brake pad and thus lead to the formation of grooves in the friction surface of the brake disc. If the grain size window is too small, the desired wear resistance results will not be achieved.

However, it was also found that the volume fraction of the separately added carbide particles can be reduced as the grain size increases. This means that cost advantages can also be achieved in applications other than brake discs.

It was also found that with a large grain size window, the advantages of high hardness and good braking behavior (compare above) that are particularly relevant for a friction surface can be achieved very well at the same time. According to a further aspect, a powder material mixture is proposed for a coating system of a base body according to an embodiment according to the above description, wherein the powder material mixture contains the elements of the matrix alloy and the carbide particles to be added separately.

The powder material mixture proposed here makes it possible to create the coating system proposed above. At the same time, it is particularly simple and therefore cost-effective for the powder material mixture to already contain the carbide particles to be added separately, so that they do not have to be added separately.

According to a further aspect, a method for coating a base body according to an embodiment according to the above description and / or a powder material mixture according to an embodiment according to the above description is proposed, wherein at least one, preferably all, of the layers by means of deposition welding, preferably laser deposition welding, particularly preferably high-speed - Laser deposition welding is applied, preferably with an area rate of at least 500 cm ² /min to a reference layer thickness of 100 pm.

Reference is made to the previous description of the coating system at least with regard to the coating process. It should be noted that laser deposition welding requires less energy, but at the same time the energy intensity of, for example, high-velocity flame spraying [HVOF] can reach similar values and is therefore suitable for producing a coating system, for example using the powder material mixture described above. The advantages of laser deposition welding, especially high-speed laser deposition welding [HVLA], is the quality and lower achievable layer thickness of the coating system, so that not only less energy is required for the respective welding process, but also less material and possibly can also be achieved in a shorter time and thus also requires less energy. However, the respective advantages depend heavily on the application at hand.

The invention described above is explained in detail below against the relevant technical background with reference to the associated drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, although it should be noted that the drawings are not true to size and are not suitable for defining size relationships. It is presented in

Fig. 1: a coating device with a base body;

Fig. 2: a section of a schematic micrograph of a coated base body;

Fig. 3: a micrograph of an embodiment according to Example No. 3;

Fig. 4: Example No. H according to Table 1;

Fig. 5: Example No. W according to Table 1;

Fig. 6: a coating system on a brake disc;

Fig. 7: an alternative coating system on a brake disc;

Fig. 8: an enlargement of the micrograph from Fig. 3;

Fig. 9: a hardness measurement according to Vickers;

Fig. 10: first brake discs before and after a corrosion resistance test;

Fig. 11: second brake discs before and after a corrosion resistance test; and

Fig. 12: a micrograph through the right brake disc according to Fig. 11.

In Fig. 1, a coating device 10 with a base body 1, for example a brake disc 7, is shown in a schematic view. The coating device 10 shown here includes (here two) storage containers 15 for the welding material, for example for a powder mixed from two powder components. The powder is, for example, partly metallic and partly an additive, for example hard material particles, which are used, for example, in a friction coating of a brake disc 7. A supply line 16 is connected to the storage container 15 and opens into one Feed device 12, here an annular gap nozzle. Here it is optionally shown that a flow measurement 17 is arranged at a bypass line 18 and thus the flow in the supply line 16 (extrapolated from the data of the bypass line 18) can be detected by means of the flow measurement 17. The feed device 12 (here annular gap nozzle) is aligned in such a way that the (here powdery) welding material can be fed into a focus and the focus can be moved in a defined manner by means of a feed actuator 13 (here indicated only schematically for a single feed direction in the image plane from right to left). . The coating device 10 further comprises a welding device 11, here for example a laser for LA, preferably for HVLA. The welding device 11 is set up in such a way that the welding material (here by the laser) is melted or melted in the focus, so that the welding material (preferably in a melt pool) in the region (as shown) below the focus in the surface 21 of the base body to be coated 1 hits and thus (after curing) a coating is formed on the workpiece.

In Fig. 2, a section of a micrograph of a coated base body 1, for example a brake disc 7, is shown schematically. A coating system 2 is formed with several (purely optionally two) layers 3,4. The lowest (first) layer 3 is formed solely from the matrix alloy 5. The upper or outer (second) layer 4 is formed from a matrix alloy 5 and separately added carbide particles 6, which are shown here in different grain sizes as a representation of the grain size window 8. The second layer 4 is preferably produced directly from a premixed powder material mixture 9 as a welding filler material.

Production of embodiments

The powder material is used in an HVLA process using a device, as shown schematically in FIG. 1, and applied as a coating to a gray cast iron base body. The hard material particles used, which improve wear protection, should be replaced by naturally hard materials. The iron-based alloy is intended to replace the tungsten carbide used in the prior art as a hard material. For the PS, if present, a matrix alloy is used, for example, as described above. It should be noted that the powder material mentioned here can be applied directly to the surface of the gray cast iron base body to be coated or to a previously applied PS (also referred to as HS). It is irrelevant whether the respective layer is formed in a single pass or in several passes (i.e. in multiple layers). If the process is carried out appropriately, the weld layers and therefore their number can no longer be identified in a layer with a single powder material. The number of layers in a layer is determined for a required minimum thickness and/or for a guaranteed coverage due to the track width of the weld beads, which are laterally rounded due to the process.

To carry out various comparative experiments, (executive) examples 1 to 9 of the present coating were created and analyzed for their chemical composition. The results of the chemical analysis are shown in Table 1.

Table 1 - Chemical analysis of welding material applied as a coating to a base body in percent by weight

In Table 1, embodiments No. 1 to No. 9 of the present invention and No. W and No. H are shown as demarcations and not belonging to the invention, which were examined for their composition by chemical analysis. Table 1 shows the composition by element and in percent by weight. Iron (Fe) is present in a balanced (bal) amount.

Production of embodiments according to the two-layer model

In a two-layer model, coatings according to the present invention are applied to the PS (also referred to as HS) as a functional layer (in this case designed as a friction layer), which comprise a high proportion of titanium carbides. The PS here is an AISI 316 steel. The friction layer is the coating proposed herein, namely in this example according to Example No. 2 above (see Table 1). Table 2 below shows various examples (No. 10 to No. 13) and compares them with regard to their properties when used with a gray cast iron brake disc. Table 2 describes the layers and shows the carbide content and the grain size of the carbides in the carbide content. The carbide content in Table 2 refers to those carbides that are added during the welding process (using HVLA) in addition to the powder material, which is applied as a friction layer. It should be understood that this does not refer to the carbides as present in the powder material or formed during the welding process as described above. It should be noted that these additional carbides entered the powder focus and are therefore entered directly into the liquid material. The carbides themselves, provided they have the specified grain size, are not melted because the respective intrinsic melting temperature is significantly above the process temperatures. The carbides are available as powder material with the specified grain size or grain size window.

Table 2 - List of examples of coatings containing carbides

PS in Table 2 stands for buffer layer, which is formed from the AISI 316 steel specified below. In Table 2, RS stands for the functional layer, i.e. here the friction layer, which is mixed with the respective carbide, i.e. 50% by weight in the respective layer or (in example no. 10 and no. 11)

60% by weight. The carbides are TiC [titanium carbide]. Alternatively, WC [tungsten carbide] is used as a partial or partial replacement. The grain size windows can be viewed approximately as a Gaussian distribution, in which a negligible amount of the powder is smaller than the minimum value and larger than the maximum value of the grain size window. The grain size windows are usually achieved by manufacturers through sieving. Example product from manufacturers such as Durum Wear Protection GmbH, HC Starck Tungsten GmbH, Gesellschaft für Wolfram Industries mbH or Höganäs Germany GmbH. The PS is formed from a material commonly referred to as austenitic stainless steel. It is the alloy 1.4404, also known as 316L or AISI 316, which has very good corrosion resistance due to its high chromium content and high molybdenum content in conjunction with a low carbon content. The annealed strength is approximately 600 MPa [six hundred mega-pascals] for large diameters, but can be increased by cold working for small sections. The friction layer is referred to as RS_1, which consists of stainless steel, here more precisely the alloy 1.4016 or 430L. The friction layer, which is made of the same material as the PS, is designated as RS_2 (in examples No. 11 and No. 12). The values are given according to DIN EN 10095:2018, Appendix D.

The friction layer (in Example No. 13) is designated as RS_3, which is formed from the material from Example No. 2 (see Table 1).

Experimental results

A performance test was carried out for exemplary embodiments No. 10, No. 11, No. 12 and No. 13 according to Table 2 according to the two-layer model. The performance test was carried out in accordance with the so-called WLTP standard. WLTP [English: Worldwide harmonized Light vehicles Test Procedure] is an international driving cycle standard of the EU, valid from September 1, 2017, in the current version valid on the registration date. The result will be positive for embodiments according to the present invention.

Table 3 - Overview of the performance of the examples shown in Table 2

Table 3 shows the results of the performance test. The symbol O stands for average performance, symbol - for poor performance, symbol -- for very poor performance and symbol + for good to very good performance.

Evaluation criteria for the performance of the brake disc are the abrasion in the form of a profile height variance over the radius of the brake disc, i.e. the distance between the highest and lowest points on the surface of the brake disc. A profile height variance of less than 3 pm [three micrometers] is considered good, and 7 pm is considered poor. An average coefficient of friction of 0.48 [forty-eight hundredths] is rated as very good, with a pressure of 20 bar [twenty bar], 30 bar and 40 bar on a piston with a diameter of 57 mm [fifty-seven millimeters] on a brake disc with 330 mm [three hundred and thirty millimeters] has been abandoned. An average coefficient of friction of less than 0.45 is rated as poor.

The evaluation criteria for the performance of the brake pads is whether grains have eaten into the brake disc, which lead to the formation of grooves in the surface of the brake disc, and whether grooves have formed on the brake pads themselves. This is done after a visual inspection. For comparison, a condition of a brake pad that is rated as poor in this context is shown in FIG. 6 (Example No. 12). A condition of a brake pad rated as very good in this context is shown in Fig. 7 (Example No. 13).

3 shows a micrograph of an embodiment according to Example No. 3 according to Table 1 above of the coating proposed herein, in which the following parameters were achieved:

Process parameters:

• Beam intensity: about 1300 W/mm ² [one thousand three hundred watts per square millimeter]

• Energy density: 1.3 J/mm ³ [thirteen tenths of a joule per cubic millimeter]

• Powder mass density: 0.2 mg/mm ³ mg/mm ³ [one hundred and twelve tenths of a milligram per cubic millimeter]

• High-quality coating without layer defects (bonding, pores, cracks)

• Hardness about 400 to 440 HVo.oi

• Cr content > 12% by weight

4 and 5 show an embodiment of the coating, which is made from a powder material. 4 shows the result of Example No. H according to Table 1, an increased hard phase due to an increased chromium content compared to the coating from FIG. or chipping. Due to the increased hard phase, the layer hardness increases to > 450 HVo,oi.

Fig. 5 shows an embodiment of the coating according to Example No. W according to Table 1, which is made from a powder material. As a result, Fig. 5 shows a reduced hard phase with a high-quality coating result. Due to the reduced hard phase, the hardness is around 350 HVo.oi.

Fig. 6 shows photographs of brake disc 7 and brake pad (each on a brake pad) in a brake system. The two rows of illustrations in Fig. 6 and Fig. 7 show the result on the inside (bottom row) and outside (top row), with the right image showing the brake disc 7 and the left image showing the side of the brake disc shown on the right 7 associated brake pads.

The photographs show the braking system after one driving cycle. Such a driving cycle test can be carried out in accordance with the above-mentioned WLTP [Worldwide harmonized Light vehicles Test Procedure, valid from September 1, 2017]. The result will be positive for embodiments according to the present invention.

In particular, a driving cycle test can be carried out over 7 days. When using a coating according to Example 12 and Examples 3 according to Table 2, essentially the following results can be achieved:

Fig. 7 shows the result on the inside and outside when using a coating according to Example No. 13. The suitability of the coating according to Example No. 13 is significantly improved compared to the coating according to Example 12 (see circled and arrow-caused damage in Fig. 4a ). The comparisons after visual evaluation of the coatings tested in Example 12 and Example 13 clearly show that the coating according to Example 13 is superior to the examples shown in the prior art in all tested parameters.

In Fig. 8 is an enlargement of the micrograph from Fig. 3 with the same material combination and with respect to a display of the length of 100 pm shown. The cross-sectional sample was analyzed using energy dispersive X-ray spectroscopy EDX [according to DIN ISO 22309 as of November 2015]. The measurement took place in the axial direction of the brake disc 7, from top to bottom to the base body 1 (compare the middle illustration). An almost defect-free coating and a melt metallurgical bond were found within the coated surface 21, and an inhomogeneity was also found using EDX analysis. The spectroscopic analysis is shown on the right and illustrates the transition from base body 1 to the coating.

9 shows a hardness measurement according to Vickers [according to EN ISO 6507-1:2018] on a cross section of a brake disc 7 with a coated surface 21 according to FIG. 3 with respect to a display of the length of 30 pm in a scanning electron microscope representation. A section of the polished cross section is shown at the bottom left. The indentations of the Vickers test specimen can be seen in a cross shape on the cross sections at the bottom left and right. The hardness test here ran axially through the coating and orthogonally, approximately in the middle within the coating. The test parameters here were 10 ponds of indentation force with a 15 second increase in force and a hold time of 20 seconds.

The Vickers hardness determined over the horizontal series of measurements is shown at the top left of the illustration. The Vickers hardness is almost constant along the horizontal with a value of 400 HVo,oi.

In Fig. 10 and Fig. 11, two brake discs 7 are shown from both sides before and after a corrosion resistance test [according to the draft of ISO/DIS 9227:2021], with the outside shown at the top and the inside shown at the bottom. On the left in Fig. 10 a brake disc 7 is shown with a coating which is not based on the invention (two-layer structure, with PS [buffer layer] and RS [friction layer] made of AISI 316). The pot of the brake disc 7 is free of a coating.

It can be clearly seen here that the pot is subject to significantly more corrosion than the contact surface of the brake disc 7. 11 shows a brake disc 7 with a coating based on the invention, namely in a single-layer structure without PS [buffer layer] and with RS [friction layer] (i.e. applied directly to the base body 1) according to Example No. 3 in Table 1 . Analogous to the left brake disc 7, the pot here is also free of a coating, so that it is also subject to similar or the same corrosion as the left brake disc 7. Both contact surfaces of the brake discs 7 only show little to no corrosion in this view.

12 shows a microscopic close-up of a microscopic image through the right brake disc 7 according to FIG. 11. Here it is clearly visible that the coating only has surface rust 19 at its upper end (see upper arrow), but this has not spread into the coating or only to a very small extent.

At the left end shown in the illustration, the edge area of the brake disc 7, it is not coated and has underlying corrosion there, so that the base body 1 has been attacked (see lower arrow). However, this undercorrosion is within an acceptable target range, which is below the standards at the time of the corrosion resistance test, and within the requirements required by the market.

With the base body with coating system proposed here, an excellent corrosion-resistant and wear-resistant surface can be achieved, especially for the friction surface of a brake disc. Reference character list

Base body Coating system first layer second layer Matrix alloy Carbide particles Brake disc Grain size window Powder material mixture Coating device Welding device Feed device Feed actuator Brake medium Storage container Supply line Flow measurement Bypass line Surface rust Welding beam Surface to be coated

Claims

Claims Base body (1) with a coating system (2), which

Coating system

(2) comprising at least one layer (3,4) with a matrix alloy (5), at least one of the layers (3,4) comprising at least the following elements in % by weight of the matrix alloy (5). :

Iron; and from 10% to 26% by weight chromium; and from 0,

3% by weight to 5% by weight carbon; and the sum of niobium, titanium and vanadium 0.5% by weight to 15% by weight, the coating system (2) further containing separately added carbide in at least one of the layers (4) with the matrix alloy (5). Particles (6) comprise a proportion of the entire relevant layer (4) of at least

20% by volume to 70% by volume. Base body (1) according to claim 1, wherein the coating system (2) is designed in one layer. Base body (1) according to claim 1, wherein the coating system (2) is designed in multiple layers, with at least a first layer (3) being formed without separately added carbide particles (6), and at least one arranged higher up, preferably a penultimate and /or last layer (4) is formed from the matrix alloy (5) with the separately added carbide particles (6). wherein preferably the at least one first layer (3), and optionally a last layer (3), is formed from the matrix alloy (5), further preferably the matrix alloys (5) of the first layer (3) and the layer (4) are identical to the separately added carbide particles (6), particularly preferably all layers (3, 4). Base body (1) according to one of the preceding claims, wherein at least the layer (3,

4) with the matrix alloy (5) and separately added carbide particles (6) of the coating system (2) are applied by means of high-speed laser deposition welding, preferably with an area rate of at least 500 cm ² /min to a reference layer thickness of 100 pm.

5. Base body (1) according to one of the preceding claims, wherein the coating system (2) has a hardness of 300 HVo.oi to 1100 HVo.oi.

6. Base body (1) according to one of the preceding claims, wherein a proportion of separately added carbide particles (6) comprises at least 35% by volume, preferably at least 40% by volume, more preferably at least 50% by volume. wherein preferably the separately added carbide particles (6) are selected from titanium carbides and/or tungsten carbides, with particularly preferably the separately added carbide particles (6) being exclusively titanium carbides.

7. Base body (1) according to one of the preceding claims, wherein the base body (1) is a gray cast iron base body and / or a brake disc (7).

8. Base body (1) according to one of the preceding claims, wherein the carbide particles (6) has a grain size window (8) of 6 pm to 120 pm, preferably at least one, particularly preferably exclusively one, of the following separate grain size windows (8) includes:

- 3pm to 45pm; and

- 45pm to 90pm, preferably until 106pm.

9. Powder material mixture (9) for a coating system (2) of a base body (1) according to one of the preceding claims, wherein the powder material mixture (9) contains the elements of the matrix alloy (5) and the carbide particles (6) to be added separately are. Method for coating a base body (1) according to one of claims 1 to claim 8 and / or a powder material mixture (9) according to claim 9, wherein at least one, preferably all, of the layers (3, 4) by means of deposition welding, preferably laser deposition welding, particularly preferred High-speed laser deposition welding is applied, preferably with an area rate of at least 500 cm ² /min to a reference layer thickness of 100 pm.