DE102009044876A1 - Use of functional elements with diamond coating on intermediate layers on steel substrates as functional elements with protective coating against cavitation erosion - Google Patents

Abstract

The invention relates to the use of a multilayer functional element (1) with a surface coating, wherein the functional element (1) consists of a steel substrate (1a) and the surface coating consists of a layer element at least partially covering the substrate (1a), the layer element at least an intermediate layer (1b) connected to the substrate and finally comprising a diamond layer (1c) bonded to the outermost one of the intermediate layers, as a protective coating against cavitation erosion.

Description

Technical area

The invention relates to a use of a multilayer functional element with a surface coating, wherein the functional element consists of a steel substrate and with a multi-layer covering the substrate. The multilayer has at least one chemically bonded to the steel substrate intermediate layer z. Example of titanium boron nitride (TiBN) or chromium carbides (Cr ₃ C ₂ , Cr ₂₃ C ₆ ) and then on with the outermost of the intermediate layers and chemically bonded diamond layer.

State of the art

Ultrasound - especially power ultrasound - coupled via ultrasound radiating surfaces in liquids, may u. a. be used to apply to these objects located objects with ultrasound and ultrasound-induced transient cavitation and thus to edit their surfaces -. B. to clean, deburr, roughen or deliberately damage or even disintegrate.

Corresponding cleaning systems generally consist of trough-like formations, either surface areas (bottom, side walls) of the trough-like formations or special partial surfaces of the troughs (welded therein or by means of sealing frame screwed therein vibration plates) directly attached to their outer surfaces active ultrasonic transducer or suspended therein immersion vibrators active Have ultrasound transducer. The ultrasonic transducers convert high-frequency electrical or magnetic alternating fields into mechanical oscillations, which are coupled into the liquid via the functional elements, that is to say the surface areas and special sub-areas of the trough-like formation or the immersion oscillator, as an ultrasound radiating surface.

In the case of systems with very high input ultrasonic intensity over small ultrasound radiating surfaces -. B. for disintegration of objects in the liquid - the mechanical vibrations of the ultrasonic transducers are transformed before their emission by means of a horn to larger vibration amplitudes of the functional element with (compared to the ultrasonic transducer) smaller ultrasound radiating surface and radiated from the smaller end face of the horn into the liquid. The most replaceable tail of the horn with the functional element of the ultrasound radiating end face is referred to as a sonotrode. In all three cases - area or partial area of a trough-like design, immersion oscillator and sonotrode - the ultrasonic vibrations are coupled into the liquid and emitted by the ultrasound radiating surface of the functional element.

Disadvantages of the prior art

The term transient cavitation is understood to mean a formation and a chaotic implosion of bubble-like transient cavities in liquids. The transient bubbles also contain liquid vapor and gases dissolved in the surrounding liquid.

The ultrasound above certain ultrasound intensities (thresholds of the ultrasound intensity for transient ultrasound-induced cavitation) bubbles collapse chaotically by the action of the external and the positive sound pressure half-wave - it comes to implosions. The resulting local shock waves and / or liquid microjets lead to damage in the vicinity, d. H. few bubble radii away from the imploding bubble, located surfaces of objects. There is a cavitation erosion of the object surfaces.

For cavitation erosion of object surfaces, it also comes through transient bubbles generated by rapid periodic movements of objects in liquids caused alternating pressures, such. B. on ship propellers or pump parts.

Even ultrasound-induced cavitation erosion is produced on the surfaces of the functional elements themselves radiating into the liquid. This cavitation erosion causes there wear of the functional elements. These are usually a material removal that accelerates with continuous ultrasound operation above the intensity threshold. This leads to the fact that the functional elements are to be exchanged after a corresponding period of use.

In order to counteract the wear caused by cavitation erosion, various approaches are known from the prior art. Coatings and materials with improved cavitation erosion resistance are available: special stainless steels, for example duplex steels or high-strength materials, for example TiAlV alloys. Hard chromium and other coatings on steels could delay but not prevent cavitation erosion.

The problem of previous known coatings is that their adhesion to the substrate under the conditions of ultrasonic operation with transient cavitation in the liquid is not sufficient.

This results in microscopic cracks and, as a result, spalling of the coatings, which in turn provide attack surfaces for the further destruction of the coatings due to cavitation erosion. If microscopically fine cracks and small spalling occur, the accelerating material removal due to cavitation erosion can no longer be prevented.

An approach from the prior art ( DE 40 41 365 A1 ) ( FR 2 670 690 A1 ) provides for the surface of the substrate facing the liquid to be provided with a diamond layer. Even a diamond layer proves to be vulnerable if it does not adhere sufficiently to the substrate. How out K. Kellermann, JC Bareiss, SM Rosiwal and RF Singer: Advanced Engineering Materials, page 657, 10 (2008) and JC Bareiss, G. Hackl, N. Popovska, SM Rosiwal, RF Singer: Surface and Coatings Technology, page 718, 201 (2006) Known and summarized below, can be applied without intermediate layers with certain properties no adherent diamond layers on steel substrates and the material of the steel substrates for cooling on temperature ranges, as they are required for a chemically bonded to the intermediate layer, an expansive γ → undergo α-phase transformation. Therefore, the design idea according to DE 40 41 365 A1 and FR 2 670 690 A1 with diamond layer applied to unspecified steel substrates without matched intermediate layer has hitherto been unsuccessful.

Out K. Kellermann, JC Bareiss, SM Rosiwal and RF Singer: Advanced Engineering Materials, page 657, 10 (2008) is the connection of a steel substrate on at high temperatures applied to the substrate and partially diffused chromium carbide intermediate layers (Cr ₃ C ₂ , Cr ₂₃ C ₆ ) with a CVD-like coating applied diamond layer known. The abbreviation CVD stands for Chemical Vapor Deposition and refers to the deposition of a solid, amorphous, polycrystalline or monocrystalline layer on a substrate from the gas phase.

Under the title "Well Adherent Diamond Coatings on Steel Substrates", it is shown that in a defined temperature range above the α → γ phase transformation of the steel substrate, diamond can be deposited on steel with good adhesion in a CVD process mediated by said intermediate layer. The increase in volume of the steel in the back transformation γ → α during cooling at least partially compensates for the lower thermal contraction of the diamond during cooling, and thus the chemical adhesion produced at high temperatures by covalent bonding between diamond and chromium carbide interlayers is maintained. With this choice of temperature for the CVD-like diamond coating, stable diamond layer thicknesses in the single-digit μm range were applied. With this method, the covalent chemical bonds between the chromium carbides and diamond formed during CVD coating on the one hand and the anchoring of the intermediate chromium carbide layer with the chromium diffused into the steel substrate on the other hand can be used for the adhesion of the diamond layer. The diamond layer itself provides the desired, well-adhering and very hard surface.

In JC Bareiss, G. Hackl, N. Popovska, SM Rosiwal, RF Singer: Surface and Coatings Technology, page 718, 201 (2006) For example, the deposition of a diamond layer on a titanium boron nitride (TiBN) interlayer on steel substrates is shown by CVD on the example of 41Cr4 in the temperature range described above, again above the α → γ phase transformation. The combination with a TiBN interlayer of small layer thickness of about 6 .mu.m and a subsequent CVD-deposited diamond layer of 3.5 .mu.m causes an excellent adhering diamond layer, which has much better mechanical properties, in particular a high hardness compared to the prior art for ultrasound radiating surfaces ,

Here, too, the covalent chemical bonds between the boron nitride and diamond produced at temperatures above the α → γ phase transformation between the boron nitride and diamond during cooling remain, since the increase in volume of the steel during the back transformation γ → α during cooling results in the lower thermal contraction of the Diamants compared to the steel substrate is at least partially compensated for cooling. On the other hand, by the diffusion of B and N into the substrate, the TiBN layer is also firmly anchored to the steel substrate via covalent chemical bonds with the compounds FeB, Fe ₂ B, Fe ₄ N formed there.

In addition to the particular adhesion of the diamond layers thus applied by means of chromium carbide or titanium boron nitride intermediate layers, the intermediate layers in both cases also fulfill the function of a diffusion barrier against the outdiffusion of iron from and carbon into the steel substrate, both of which are otherwise known to be poor in iron-catalyzed formation promote adhering graphite layers on the steel substrate surface. Although a diamond layer can be deposited thereon, it does not sufficiently adhere to the steel substrate with the intermediate graphite layer.

Furthermore, both intermediate layers have thermal expansion coefficients between those z. Martensitic steel substrates (~ 12 × 10 ^-6 K ^-1 ) and that of diamond ((1-5) × 10 ^-6 K ^-1 ) between space and CVD process temperature.

The development of the above-described multiple layers has always been carried out with the aim of providing mechanically abrasion-resistant steel surfaces with low friction exclusively for tools for mechanical surface treatment. Therefore, the use of such a multi-layer on the material processing, namely contact tool, workpiece is limited.

Object of the invention

Therefore, the object of the invention is to provide functional elements with a surface that at least with sufficiently good design of the coating no erosion by particular ultrasound-induced cavitation erosion experiences and at the same time mechanically, statically and dynamically as particular ultrasound radiating surface in liquids is sufficiently resilient.

Solution of the task

According to the invention the object is achieved by the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

Advantages of the invention

The solution is therefore to provide a multi-layered functional element with a surface coating and apply the functional element comprises a steel substrate and on the steel substrate at least one applied by means of CVD or similar methods, with him chemically bonded intermediate layer and another layer with the intermediate layer is also chemically connected, is provided - namely a diamond layer. With this multilayer functional element, cavitation erosion, for example, an ultrasound-induced cavitation can be reduced or even avoided. This has a significant advantage that the functional elements have as ultrasound radiating surfaces having this structure of the multilayer, a much longer service life and, associated with a longer service life.

The use of such a functional element is diverse. A particular advantageous application of the invention is the functional element or objects that this multilayer, namely a steel substrate with an intermediate layer z. Example of titanium boron nitride or chromium carbides and a diamond layer applied thereto in the areas where cavitation erosions arise.

The use of such a functional element on the basis of a substrate with a corresponding intermediate layer and a further layer facing the liquid, namely a diamond layer, undergoes little or no removal, for example by ultrasound-induced cavitation erosion. At the same time, this multiple layer on a substrate is mechanically, statically and dynamically sufficiently loadable for power-noise applications with transient cavitation in liquids, including in aqueous solutions.

In a particular embodiment, the substrate material is a weldable, non-rusting martensitic carbonaceous chromium steel with γ → α-phase transformation on cooling from the temperature range of the diamond coating. For surface areas (bottom, side surfaces) or partial surfaces of trough-like formations (therein welded or by means of sealing frame screwed therein vibration plates) may be provided for this purpose, a corresponding steel sheet. For example, the steel substrate material may be a chrome steel sheet of material no. 1.4116 or the designation DIN EN X50 CrMoV15 be.

Essential for the desired property, in particular in order to counteract ultrasound-induced cavitation erosion, is the adhesion of the diamond layer, at least indirectly with respect to the substrate. Serve once the application of the intermediate layer by means of CVD method and the application of the diamond layer by CVD or CVD-like method by the formation of covalent chemical bonds with this type of coating allowed to be diffused into the steel substrate and anchored there products of CVD (Cr ₃ C ₂ , Cr ₂₃ C ₆ or FeB, Fe ₂ B, Fe ₄ N).

In addition, additional measures were taken to improve the adhesion of the intermediate layers on the steel substrate and the diamond layer on the intermediate layer (roughening of the steel surface prior to the application of the intermediate layer, ultrasonically assisted injection of diamond crystallites into the TiBN intermediate layer before the diamond coating).

In order to enable the use of the steel substrate, in particular for vibrating plates in ultrasonic cleaning pans, it is intended to use stainless weldable chrome steel sheet.

Swing plates require a sealing frame, with which they can be screwed with trough-like designs. Therefore, it is necessary to weld the frame, which is provided with screw holes, to the steel substrate to enable its fluid-tight connection with a cleaning trough.

Further uses envisage using the steel substrate as a so-called sonotrode with a multiple coating covering at least the ultrasound radiating surface and made of a combination of a titanium boron nitride or chromium carbide intermediate layer with a diamond layer applied thereon. The horn is designed as a steel substrate. The front side is the ultrasound radiating surface of the multiple coating.

Further advantageous embodiments will become apparent from the following description of an embodiment, the drawings and the claims.

drawings

Show it:

1 a schematic side view of a part of a functional element together with an ultrasonic transducer and a part of the schematically indicated liquid;

2 an enlarged view of the embodiment of the functional element according to 1 and according to 3 consisting of the substrate, the intermediate and diamond layers;

3 a schematic view of an ultrasonic horn whose immersed in the liquid to be sonicated, often replaceable shaped part is also referred to as a sonotrode, with the substrate, the intermediate and the diamond layer according to the 1 and 2 ,

Description of an embodiment

In 1 and 3 is a functional element 1 shown. The functional element 1 is used to that of an ultrasonic transducer 2 that is directly related to the functional element 1 connected, generated sound in one on the ultrasonic transducer 2 opposite side of the functional element 1 existing liquid 4 couple. The coupled sound (represented schematically in the form of sound propagation lines 5 ) spreads within the fluid 4 out. Above certain ultrasound intensities (thresholds of ultrasound intensity for transient ultrasound-induced cavitation) is present in the fluid 4 , also generates transient cavitation near the sound-radiating surface (represented by bubbles 6 ), which is responsible for the cavitation erosion at this surface on the liquid 4 facing side is responsible.

At the in 3 illustrated embodiment is the functional element 1 at the front of a horn 3 or a sonotrode arranged. The usually replaceable horn is with the ultrasonic transducer 2 coupled. The coupled sound spreads, as in 1 already described.

In 2 is an enlarged view of the inventive design of the functional element 1 shown. The functional element 1 consists of the steel substrate 1a and at least two layers, namely an intermediate layer 1b and another layer, namely a diamond layer 1c ,

In the embodiment shown here, the substrate 1a a stainless martensitic chromium steel with γ → α phase transformation on cooling from the temperature range of the diamond coating, which is preferably weldable.

This illustrated functional element 1 with ultrasonic transducers 2 is inserted into a framed recess on the bottom or side walls of a tub and bolted to it using gaskets. For this purpose, the functional element 1 also on his part an enclosed frame. To provide such a framework, it is necessary that substrate 1a is weldable, so that accordingly a frame with threaded holes can be tightly fixed.

On the side facing the liquid is the diamond layer 1c intended. This diamond layer 1c is a very hard layer that is in direct contact with the liquid 4 stands. It is itself of such high strength and adheres so well that the shockwaves and micro-liquid jets of the micro-implosions, which are the bubbles 6 For example, in ultrasound-induced transient cavitation bring about, no damage to this layer 1c so cause neither cracks nor their replacement. This is partly due to the fact that this layer 1c a chemical and mechanical connection with the intermediate layer 1b enters, with the intermediate layer 1b Titanium boron nitride (TiBN).

This layer 1b by CVD deposition on the substrate 1a is producible, is also a thermal stress balancing link between the substrate 1a and the diamond layer 1c and thus avoids damage by the different thermal expansion coefficients (Cracks, spalling) of steel substrate 1a and diamond layer 1c arise.

Preferably, the substrate is made 1a of chromium steel sheet, for example a substance with the active substance number: 1.4116 ( DIN EN X50 CrMoV15 ). However, it is also conceivable that other carbonaceous martensitic chromium steels with γ → α phase transformation when cooled from the temperature range of the diamond coating can be used. The steel types differ in terms of their weldability.

According to the invention, a multi-layer functional element has thus been provided which is suitable for coupling power ultrasound into a liquid and which has the properties with correctly applied coatings of resisting cavitation erosion and, at the same time, the conditions on the supporting substrate of such functional elements as already disclosed in US Pat State of the art are known (weldable and mountable to the corresponding trough-like configurations), met.

LIST OF REFERENCE NUMBERS

1

Functional element with surface coating

1a

substratum

1b

interlayer

1c

diamond layer

2

ultrasound transducer

3

horn

4

liquid

5

Sound propagation lines

6

vesicle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4041365 A1 [0012]
• FR 2670690 A1 [0012]

Cited non-patent literature

• K. Kellermann, JC Bareiss, SM Rosiwal and RF Singer: Advanced Engineering Materials, page 657, 10 (2008) [0012]
• JC Bareiss, G. Hackl, N. Popovska, SM Rosiwal, RF Singer: Surface and Coatings Technology, page 718, 201 (2006) [0012]
• K. Kellermann, JC Bareiss, SM Rosiwal and RF Singer: Advanced Engineering Materials, page 657, 10 (2008) [0013]
• JC Bareiss, G. Hackl, N. Popovska, SM Rosiwal, RF Singer: Surface and Coatings Technology, page 718, 201 (2006) [0015]
• DIN EN X50 CrMoV15 [0025]
• DIN EN X50 CrMoV15 [0043]

Claims (9)

Use of a multilayer functional element ( 1 ) with a surface coating, wherein the functional element ( 1 ) of a steel substrate ( 1a ) and the surface coating of at least a part of the substrate ( 1a ), wherein the layer element comprises at least one intermediate layer ( 1b ) and finally a diamond layer bonded to the outermost of the intermediate layers ( 1c ) as a protective coating against cavitation erosion. Use of the functional element ( 1 ) with the surface coating according to claim 1 as an ultrasound radiating surface. Use of the functional element ( 1 ) according to claim 1 or claim 2, characterized in that the intermediate layer ( 1b ) consists of titanium boron nitride. Use of the functional element according to one of claims 1 to 3, characterized in that the diamond layer ( 1c ) on the liquid ( 4 ) side facing, wherein the coupling of the ultrasound of the diamond layer ( 1c ) facing away from the substrate into the liquid. Use of the functional element according to at least one of the preceding claims, characterized in that the functional element ( 1 ) Is part of a sonotrode, wherein the surface coating is arranged on the ultrasound radiating end face of the sonotrode. Use of the functional element according to claim 1, characterized in that the substrate ( 1a ) consists of steel. Use of the functional element according to claim 6, characterized in that the substrate ( 1a ) consists of a steel with γ → α-phase transformation on cooling from the temperature range of the diamond coating. Use of the functional element according to claim 6, characterized in that the substrate ( 1a ) consists of martensitic chromium steel with γ → α phase transformation on cooling from the temperature range of the diamond coating. Use of a functional element ( 1 ) according to claim 6 for a submersible.

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