WO2020043712A1

WO2020043712A1 - Component of a brake for a vehicle

Info

Publication number: WO2020043712A1
Application number: PCT/EP2019/072817
Authority: WO
Inventors: Reiner Becker; Wilfried Strauss
Original assignee: Fritz Winter Eisengiesserei Gmbh & Co. Kg
Priority date: 2018-08-27
Filing date: 2019-08-27
Publication date: 2020-03-05
Also published as: DE102018120897A1; EP3844320A1

Abstract

The invention relates to a component of a brake for a vehicle, comprising a metal main body having a surface (5a, 5b) that is provided with a coating (B) for increasing the wear resistance thereof, said coating comprising an intermediate layer (Z) deposited on the main body (2), and a cover layer (D) deposited on the intermediate layer (Z), wherein the intermediate layer (Z) has a higher toughness than the cover layer (D), which in turn has a higher hardness than the intermediate layer (Z). The aim of the invention is to simplify the production of such a component and to optimize the wear resistance thereof. This aim is achieved, according to the invention, in that the intermediate layer (Z) is formed of an Ni or Cr alloy each having an Ni or Cr content of more than 50 wt%, and optionally, in order to improve the wear resistance, having hard material particles embedded in the intermediate layer, and in that the cover layer (D) is formed from a high-grade steel matrix having hard material particles embedded therein, wherein the thermal conductivity of the main body (2) is 1.5 to 3 times greater than the thermal conductivity of the intermediate layer (Z), the thermal conductivity of the cover layer (D) is 2 to 4.5 times greater than the thermal conductivity of the main body (2), and the thickness ratio Vd - Dd/Dz formed from the thickness Dz of the intermediate layer (Z) and the thickness Dd of the cover layer (D) is Vd ≥ 1.5.

Description

Component of a brake for a vehicle

The invention relates to a component of a brake for a vehicle. The component has a base body with a surface which is provided with a coating to increase its wear resistance. This

Coating is made of a layer lying on the base body

Intermediate layer and one lying on the intermediate layer

Cover layer composed. To be a good one

Wear resistance and, on the other hand, to ensure a good connection to the base body, the intermediate layer has a higher toughness than the cover layer on the one hand and the hardness on the other hand has a higher hardness than the intermediate layer.

A component of this type designed as an internally ventilated brake disc is known from DE 10 2008 053 637 B4. The friction surface formed on the friction ring of the brake disc, which is loaded during a braking process by a brake lining pressed against it, is coated with a two-layer coating in this brake disc, in which one

Intermediate layer is applied directly to the friction surface of the base body of the brake disc and for connecting the outer cover layer of the coating lying thereon and for thermal dissipation of the entered in the outer layer during a braking operation

Serves thermal energy. The intermediate layer consists of one

Zinc and / or nickel based alloy, whereas the top layer is a carbide layer or a metal matrix composite layer. The thickness of the coating is based on the geometric relationships of the internally ventilated Disc tuned by the thickness of the coating above the cooling channels of the brake disc is greater than above the knobs or webs delimiting the cooling channels.

DE 10 2005 008 569 A1 also describes a brake disc, on the friction surface of which there is also a layer consisting of two layers

Coating has been applied. The layers are made

Coating powder produced. The coating powders are composed in such a way that they form a matrix based on nickel or nickel-cobalt, in which hard material particles such as WC or TΪO ₂ are embedded in order to set the required hardness. The respective coating powder is applied by high-speed flame spraying to the surfaces of the brake disc to be coated, first a thin intermediate layer and then a thicker cover layer being sprayed on. This is followed by a heat treatment in which the previously sprayed-on layers are melted in order to bring about their material connection to the base body of the brake disc, which is made of gray cast iron material. The toughness and hardness of the layers are matched to one another in such a way that the connection of the cover layer is ensured by the intermediate layer.

From US 5,407,035 A it is also known to coat a coating on a friction surface of a brake disc in at least two layers

to design that an intermediate layer lying on the base body of the brake disk achieves a connection of the cover layer lying on it, the thickness of the intermediate layer being significantly smaller than the thickness of the cover layer.

Against the background of the state of the art, the task has arisen of an easy to manufacture one for optimizing it

To create wear resistance with a coated component for a vehicle brake, in which not only an optimal effect of the Coating, but also an optimal adhesion of the coating on the base body is guaranteed over a long period of use.

The invention has solved this problem by a component which has at least the features specified in claim 1.

Advantageous embodiments of the invention are in the dependent

Claims indicated and are explained in detail below as the general inventive concept.

Accordingly, a component according to the invention in accordance with the prior art explained at the outset has a base body which has a surface which, in order to increase its wear resistance, is provided with a coating which comprises an intermediate layer resting on the base body and a cover layer resting on the intermediate layer, wherein the intermediate layer has a higher toughness than the top layer, which in turn has a higher hardness than that

Intermediate layer.

According to the invention is now

- The intermediate layer made of a Ni or Cr alloy with a Ni or Cr content of at least 50 wt .-% and - optionally - in the

Intermediate layer to increase wear resistance

embedded hard material particles,

- The cover layer made of a stainless steel matrix with embedded

Hard material particles formed,

- The thermal conductivity of the base body by 1.5 to 3 times greater than the thermal conductivity of the intermediate layer, and - The thermal conductivity of the cover layer by 2 to 4.5 times greater than the thermal conductivity of the base body, wherein

- For that from the thickness Dz of the intermediate layer and the thickness Dd

Vd = Dd / Dz thickness ratio Vd> 1, 5.

Advantageous embodiments of the invention are specified in the dependent claims and, like the general inventive concept, are explained in detail below.

The invention is based on the knowledge that it is

Ensuring high resilience and even under high ones

Long durability loads on the respective component

It is not only necessary for the coating applied according to the invention that the intermediate layer has sufficient toughness in order to

Operation to compensate for stresses occurring in the coating, but that it is also necessary to reduce the thermal conductivity of

The top layer, intermediate layer and base body are thus one on top of the other

to coordinate that the removal of the heat from the respective layer is so effective in accordance with the hardness of the respective layer and the base body that the tensions, which in use are caused in particular in the cover layer itself and between the cover layer and the intermediate layer by frictional heat, a braking process occurs, are kept at a level which is sufficiently far below the stress level at which there are cracks in the cover layer or the cover layer peels off from the intermediate layer.

The intermediate layer fulfills several functions. So it serves

on the one hand to compensate for unevenness and depressions, such as pores or breakouts, on the surface of the surface covered with the coating respective component are present. If the component consists of a

Cast material, the depressions are usually the result of graphite inclusions exposed there on the surface to be coated.

On the other hand, the intermediate layer absorbs and compensates for temperature-related tensions. For this purpose, according to the knowledge of the invention, it must have a significantly lower heat transfer value than the cover layer, which, due to its high hardness, is particularly susceptible to the development of temperature-induced stress and cracks induced thereby.

At the same time, the basic body must also be adequate

Have thermal conductivity so that the heat generated during braking can be absorbed and transported away quickly enough.

For the ratio Ug / Uz of the heat transfer value Ug of the base body to the heat transfer value Uz of the intermediate layer, Ug / Uz = 1, 5 - 3 applies according to the invention

The coating according to the invention then results when

Ug / Zu = 1, 6 - 2.8.

According to the invention, Ud / Ug = 2 - 4.5 applies to the ratio Ud / Ug of the heat transfer value Ud of the cover layer to the heat transfer value Ug of the base body. There are particularly good ones here

Performance characteristics if Ug / Uz = 2.1 - 4.1 applies.

Accordingly, the ratio Ud / Uz of the thermal transmittance Ud of the cover layer to the thermal transmittance Uz is one

Coating according to the invention at Ud / Uz = 3-13.5, preferably Ud / Uz = 3.36-11.5. Practical heat transfer values Ug of the base body are 48 - 52 W / (m ^» K).

Practical heat transfer values Uz of the intermediate layer are 19 - 28 W / (m * K).

Practical heat transfer values Ud of the top layer are 19 - 28 W / (m * K).

In order to meet the requirements according to the invention with regard to their toughness, hardness and thermal conductivity, the intermediate layer consists of a Ni or Cr alloy with a Ni or Cr content of more than 50% by weight in each case.

In the event that the intermediate layer is formed from a Ni alloy, a suitable alloy specification provides that the intermediate layer consists of (in% by weight) 18-25% Cr, 2-5% Mo, 24-29% Fe, 9 - 11% Nb,

Remaining nickel and production-related inevitable impurities. By increasing the Cr content by 8-12% by weight at the expense of the Ni content, the adhesion of the Ni intermediate layer to the

Base body and the top layer are optimized so that the

Intermediate layer is particularly well able to compensate for the thermal expansion and possible changes in position of the cover layer during a braking operation.

In the event that the intermediate layer is formed from a Cr alloy, a suitable alloy specification provides that the intermediate layer consists of (in% by weight) 3 - 5% Mo, 24 - 29% Fe, 6 - 10% Nb, 2 - 4% Ta, remainder chrome and production-related inevitable impurities. An increase in the Cr content to values of 52-60 wt optimal adhesion of the intermediate layer to the base body and to the cover layer can be guaranteed.

The intermediate layer provided according to the invention is optimally suitable for compensating for the expansion of the cover layer which is associated with its heating during a braking operation if the coefficient of thermal expansion of the intermediate layer is 11.7-16.2 [10 ⁶ / K].

In order to increase the wear resistance of the coating provided according to the invention, hard material particles, which can be oxides, carbides or nitrides, can optionally be embedded in the intermediate layer. Examples of the hard materials in question are:

Tungsten carbide, chrome carbide or silicon carbide.

The cover layer of a component according to the invention comprises a

Stainless steel matrix in which hard materials are embedded. On the one hand, the stainless steel matrix ensures that the hard materials are held securely and that they develop their hardness-increasing effect over a long service life. At the same time, the stainless steel matrix provides effective corrosion protection and a sufficiently high thermal conductivity of the cover layer that meets the requirements of the invention.

According to the invention, the matrix of the cover layer is formed by a stainless steel. These stainless steels include, in particular, the stainless, austenitic steels. Suitable for this are, for example, stainless steels that are standardized under the material number 1.4404 or in accordance with the US standards AISI / ASTM in the number series 340 - 430L.

The hard material particles embedded in the matrix of the cover layer

ensure the necessary hardness and the associated Wear resistance of the top layer. Hard material particles suitable for this purpose are in particular metal-like, covalent or ionic carbides.

The hard materials that are present according to the invention in the cover layer and optionally in the intermediate layer include here in particular

Tungsten carbide, chrome carbide or silicon carbide.

An optimum ratio of matrix material to hard material particles with regard to the use properties of the cover layer is obtained if the volume fraction of the hard material particles embedded in the steel matrix of the cover layer is 20-70% by volume of the total volume of the cover layer. For the ratio Vk / Ve from the volume Vk that is taken up by the hard materials to the volume Ve that by the matrix material

Vk / Ve = 2/8 - 7/3. Even higher hard material contents would deteriorate the strength and the heat transfer values of the top layer. The required hardness would not be achieved with lower hard material contents.

The hard material particles embedded according to the invention in the stainless steel matrix of the cover layer develop their optimum effect with an average grain size of 3-5 pm. Hard material particles of this size are securely held in the stainless steel matrix of the cover layer over a sufficiently long period of use. Accordingly, the optional in the

The hard material particles provided between the layer have a size lying in this area.

The hardness of the cover layer of a coating according to the invention determined in accordance with DIN EN ISO 6507-1 is typically 950-1050 HV.

The notched impact work of the Ni or Cr material of the intermediate layer, determined in the impact test according to DIN EN ISO 148-1 and used as a measure for assessing its toughness, should be at least 250 joules, the upper limit for the impact energy in practice is 450 joules.

The thickness of the coating provided according to the invention is

typically 130-250 pm, the thickness of the intermediate layer being 60-100 pm and the thickness of the cover layer 70-150 pm. The thickness Dz of the intermediate layer and the thickness Dd of the cover layer are selected such that Vd> 1.5, in particular> 3, applies to the thickness ratio Vd = Dd / Dz

Coordination of the thicknesses of the intermediate layer and cover layer according to the invention ensures, on the one hand, that there is sufficient hard, wear-resistant material in the area of the cover layer for a sufficiently long service life. On the other hand, the thickness of the intermediate layer is chosen so that it

Compensate for unevenness on the coated surface of the base body and its balancing function between the movements and changes in shape required to avoid thermal stresses

Cover layer is exposed to a strong warming, such as occurs during a braking operation.

The invention shows a particularly good effect in the event that

Component coated according to the invention is a friction ring of a brake disc and the surface covered with the coating is on the friction ring

existing friction surface against which a during braking

Actuator with a brake pad acts. The

Friction ring represent a separately manufactured component of the brake disc, which in a special assembly step with the respective support part of the

Brake disc is connected as it is built in so-called "

Brake discs "or in the case of brake discs, in which the supporting part in a separate step on the friction ring or the friction ring in

is cast onto the support part in a separate working step. Likewise, the friction ring can of course be part of one piece, in particular Casting, manufactured brake disc, are integrally connected to each other in the supporting part and friction ring.

The material from which the base body of the component according to the invention is made is typically a metallic cast material that enables the base body to be cast. These include in particular iron ore

Cast aluminum materials whose thermal conductivity corresponds particularly well to the requirements of the invention and which are particularly suitable for the production of friction rings.

The application of the coating provided according to the invention to the respective surface can in principle be carried out with any thermal

Application processes such as build-up welding, spray welding or plasma welding can be carried out. The techniques required for this are basically known from the prior art.

Methods for high-speed laser cladding have proven to be particularly advantageous for the application of the coating. An example of such a method is that in DE 10 2011 100 456 B4

Described laser deposition welding process, in which a weld pool with at least one molten filler material is irradiated onto a surface to be coated by means of a beam radiating onto the weld pool

Laser beam is generated by melting powder of the filler material by means of the laser beam, the filler material being melted by the laser beam at a distance from the weld pool and the

Melting bath is fed in completely molten form. The melt pool and a focus of the laser beam are shifted parallel to each other relative to the surface to be coated at a speed of at least 20 m / min and the powder density is set so that a laser power of the laser beam in the melt pool is less than 60% of the laser power before the laser beam comes into contact with the powder. By the use of such methods can result in a particularly intensive connection of the intermediate layer to the base body and the cover layer

so that there is a risk of delamination of the cover layer from the

Intermediate layer or the coating as a whole is particularly minimized by the base body. The performance of the known

Laser cladding processes can be optimized by adapting the area covered by the laser beam device used in each case to the coating area. So with the

Coating the friction surfaces of friction rings for brake discs

Laser beam devices proven, in which the diameter of the

Laser head is up to 40 mm, which is a correspondingly large one

Area irradiated by the laser beam and over this area itself

extending melt pool is generated. Optimal adhesion of the

Coating on the respective surface of the base body can be done

This ensures that, before the coating is applied, the surface to be coated is processed in such a way that there is an "average roughness depth Rz" of 12.5 - 25 pm determined in accordance with DIN EN ISO 4287.

As an aid to monitoring the state of wear, the

Intermediate layer and the cover layer have different colors, so that when the color of the intermediate layer appears, it is clear that the cover layer has been used up.

The invention is explained in more detail below using an exemplary embodiment / using exemplary embodiments.

The single figure shows a brake disc 1 for a motor vehicle in one

Section along its axis of rotation X-X.

The brake disc 1 which is a component in the sense of the invention has a base body 2 which is designed and constructed in a conventional manner a cast iron material known for this purpose is cast with the DIN-EN designation EN-JL1040. The heat transfer value Ug of the base body is 45 - 50 W / (m * K).

The brake disc 1 has a cup-shaped support part 3 and a friction ring 4 cast thereon, which is shown here as consisting of solid material, but also in a conventional manner as

internally vented friction ring 4 can be formed.

The friction ring 4 also has, in the usual way, an annular ring on its end faces, which are oriented normal to the axis of rotation X-X

Friction surface 5a, 5b.

In the case of the base body 2 provided for the coating, friction surfaces 5a, 5b after the casting of the base body 2 have been prepared by machining in a manner known per se so that they have an average roughness depth Rz of 20 pm on their upper side.

A coating B, which consists of an intermediate layer Z and a cover layer D, is applied to the friction surfaces 5a, 5b of the base body 2 processed in this way.

The intermediate layer Z has been produced from a commercially available powdered Ni base material, which consists of (in% by weight) 19% Cr, 18% Fe, 3.0% Mo, 5% Nb + Ta, rest Ni and unavoidable

Contamination existed. His impact energy was 350 joules. In the exemplary embodiment described here, no hard material particles have been embedded in the intermediate layer Z.

The thickness Dz of the intermediate layer Z was 70-90 gm. To apply the intermediate layer Z, the brake disk has been positioned in a horizontal position in a tensioning device (not shown here), which is also shown here by means of a tensioning device (not shown here)

Rotary drive about the axis of rotation X-X of the brake disc 1 was driven to rotate. Subsequently, the intermediate layer Z is

Laser order shots have been generated. For this purpose, a laser beam device (not shown here) (laser head diameter = 5 mm) has been positioned in a starting position on the inner diameter of the friction ring 4 and the

Brake disc has been rotated at 60 revolutions per minute. Starting from the starting position, the laser was then moved radially at a speed of 10 m / min in the direction of the outer circumference of the friction ring. The laser was ignited when moving off and switched off when the outer diameter was reached. With the start of laser radiation, the powdery Ni material of the intermediate layer Z is in accordance with the procedure described in DE 10 2011 100 456 B4

Laser beam has been given each swept area. The average temperature in the area melted by the laser beam was 600 - 800 ° C.

The intermediate layer Z thus produced on the friction surfaces 5a, 5b has a heat transfer value Uz of 24 W / (m ^« K).

The intermediate layer Z compensates for any unevenness on the friction surfaces 5a, 5b and closes the pores 6, so that after the application of the intermediate layer Z on its side facing away from the base body 2 there was a flat surface optimally suitable for the application of the cover layer D. .

After the intermediate layer Z, the cover layer D has been applied to the intermediate layer Z. This is based on how to apply the

Intermediate layer Z rotatably clamped brake disc 1 is a powder that consists of a mixture of 50 vol .-% from one under the Material number 1.4404 according to the StahlEisen list of standardized stainless steel and 50 vol.% Tungsten carbide particles with an average grain size of 4 pm. This powder has in turn been applied to the intermediate layer Z in accordance with the procedure described in DE 10 2011 100 456 B4.

The cover layer D produced in this way had a thickness Dd of 110 pm and a heat transfer value of 180 W / (nvK) with a hardness of 1005 HV.

REFERENCES

1 brake disc

2 basic bodies

3 pot-shaped support part

4 friction ring

5a, 5b friction surfaces

6 pores on the friction surfaces 5a, 5b

B coating

D top layer

Dz thickness of the intermediate layer Z

X-X axis of rotation of the brake disc 1

Z intermediate layer

Claims

PATENT CLAIMS

1. Component of a brake for a vehicle, with a metallic

Base body which has a surface (5a, 5b) which is provided with a coating (B) to increase its wear resistance, which has an intermediate layer (Z) resting on the base body (2) and a cover layer (Z) resting on the intermediate layer (Z) D), the intermediate layer (Z) having a higher toughness than the cover layer (D), which in turn has a higher hardness than the intermediate layer (Z), characterized in that

that the intermediate layer (Z) made of a Ni or Cr alloy with a Ni or Cr content of more than 50% by weight and optionally embedded in the intermediate layer to increase wear resistance,

- That the top layer (D) from a stainless steel matrix with it

embedded hard material particles is formed,

- That the thermal conductivity of the base body (2) is 1.5 to 3 times greater than the thermal conductivity of the intermediate layer (Z)

- That the thermal conductivity of the cover layer (D) is 2 to 4.5 times greater than the thermal conductivity of the base body (2) and

- That for the thickness ratio Vd = Dd / Dz formed from the thickness Dz of the intermediate layer (Z) and the thickness Dd of the cover layer (D) applies Vd> 1.5.

2. Component according to claim 1, characterized in that the thermal conductivity of the base body (2) is 1.6 to 2.8 times greater than the thermal conductivity of the intermediate layer (Z).

3. Component according to one of the preceding claims, characterized

characterized in that the thermal conductivity of the cover layer (D) is 2.1 to 4.1 times greater than the thermal conductivity of the base body (2).

4. Component according to one of the preceding claims, characterized

characterized in that the thermal conductivity of the base body (2) 48 - 52 W / (m ^» K), the thermal conductivity of the intermediate layer (Z)

19-29 W / (m * K) and the thermal conductivity of the top layer (D)

122-190 W / (m ^« K).

5. Component according to one of the preceding claims, characterized

characterized in that the thermal expansion coefficient of the intermediate layer (Z) is 11.7-16.2 [10 ⁶ / K].

6. Component according to one of the preceding claims, characterized

characterized in that it is a friction ring (4) of a brake disc (1) and the surface covered with the coating (B) is one on the

Friction ring existing friction surface (5a, 5b), against which at one

Braking an actuator with a brake pad acts.

7. characterized in that the volume fraction of the hard material particles embedded in the steel matrix of the cover layer (D) in the total volume of the cover layer (D) is 20-70% by volume.

8. Component according to one of the preceding claims, characterized

characterized in that the hard material particles embedded in the stainless steel matrix of the cover layer (D) have an average grain size of

3 - 5 pm.

9. Component according to one of the preceding claims, characterized

characterized that the in the stainless steel matrix of the

Cover layer (D) embedded hard material particles consist of metal-like, covalent or ionic carbides.

10. Component according to one of the preceding claims, characterized

characterized in that the hard material particles contained in the cover layer (D) or optionally in the intermediate layer consist of one or more hard materials from the following group:

"Tungsten carbide, chromium carbide, silicon carbide"

11. Component according to one of the preceding claims, characterized

characterized that for the ratio VKA / E, that of the embedded in the stainless steel matrix of the top layer (D)

The volume VK of the hard material particles and the volume VE of the stainless steel matrix itself is formed:

2/8 <VK / VE <7/3.

12. Component according to one of the preceding claims, characterized

characterized in that the intermediate layer (Z) or, in the case of the optional incorporation of hard material particles, the matrix of the

Intermediate layer (Z) is formed from a Ni alloy, which consists of (in

Wt .-%) 18-25% Cr, 2-5% Mo, 24-29% Fe, 9-11% Nb, rest of nickel and production-related unavoidable impurities.

13. Component according to one of claims 1 -10, characterized

characterized in that the intermediate layer (Z) is formed from a Cr alloy which consists of (in% by weight) 3 - 5% Mo, 24 - 29% Fe, 6 - 10% Nb, 2 - 4% Ta, the rest Chromium and production-related inevitable impurities.

14. Component according to one of the preceding claims, characterized

characterized in that the stainless steel matrix of the top layer (D) consists of a stainless steel with the material number 1.4404 or one of the stainless steels, which are standardized in the US standards AISI / ASTM under the numbers 340 - 430L.

15. Component according to one of the preceding claims, characterized

characterized in that the intermediate layer (Z) has a different color than the cover layer (D).