Method for selective deposition of diamond coatings

Abstract

The present invention relates to a method for producing a selectively diamond-coated substrate, the selectively diamond-coated substrate comprising a substrate (1) having a surface comprising a cemented carbide material, the substrate (1) having regions (10) of the substrate surface selected to be coated and regions (20) of the substrate surface not selected to be coated, and one or more diamond coatings (30) deposited on the regions (10) of the substrate surface selected to be coated, the method comprising the steps of: a first masking step, prior to carrying out one or more chemical pretreatment steps, in which the regions (20) of the substrate surface not selected to be coated but which may be chemically attacked during the one or more chemical pretreatment steps are masked with a latex coating covering these regions (20) to avoid any chemical attack of the substrate material in these regions (20). a mask removal step, which is performed after one or more chemical pretreatment steps and before one or more coating steps, in which the latex mask (50) is completely removed; and a second masking step, which is performed before one or more coating steps, in which the latex mask (50) is removed and regions (20) of the substrate surface that are not selected to be coated but that may be coated with one or more diamond coatings (30) during the one or more coating steps are covered with one or more masking covers (60) to prevent deposition of any diamond coatings (30) on these regions.

Description

[Technical Field]

[0001] The present invention relates to a method for obtaining selective deposition of a diamond coating on a substrate, the method comprising a masking step, in which areas of the substrate surface that are not selected to be coated but that may be chemically eroded during the performance of one or more chemical pretreatment steps are masked by applying a latex mask so that the latex mask covers areas of the substrate material that need not be affected by any chemical erosion.

[0002] A latex mask in the context of the present invention is in particular a mask of a material that contains or consists of rubber.

[0003] In the context of the present invention, a latex mask is a mask of material resulting from the coagulation of latex into rubber.

[0004] In the context of the present invention, for example, natural latex (including natural rubber) can be used to manufacture latex masks, however, the present invention is not limited to the use of natural latex.

[0005] In general, the term "latex" can be used to refer to a dispersion containing natural rubber, or even to refer directly to natural rubber (in German, the term used to refer to "natural rubber" is "Naturkautschuk" or simply "Kautschuk").

[0006] In German-speaking countries, the term "Silikone" is sometimes used to refer to "latex". [Background technology]

[0007] Technical field and state of the art To deposit a diamond coating on a cemented carbide (also known as tungsten carbide) substrate, the substrate surface to be coated is typically chemically pretreated by removing the Co binder (cobalt binder) from a WC-Co composite (composite with or primarily composed of tungsten carbide and cobalt), as described, for example, by Karner et al. in U.S. Patent No. 6,096,377. After this step to ensure growth and sufficient adhesion of the diamond coating during the coating deposition process, the chemically pretreated substrate is seeded, i.e., nucleated, with diamond powder by frictional contact, for example, in an ultrasonic bath containing a diamond powder suspension, as described, for example, by Karner et al. in U.S. Patent No. 6,096,377.

[0008] Specifically, the method described in U.S. Pat. No. 6,096,377 relates to a process for coating a substrate of sintered metal carbide (i.e., sintered tungsten carbide metal with a Co binder) with a diamond film, which can be achieved as follows:

[0009] -Co etching, -Tungsten carbide etching, -Diamond powder nucleation, -Diamond coating, or -Tungsten carbide etching, -Diamond powder nucleation, -Co etching, -Diamond coating, or -Tungsten carbide etching -Co etching -Diamond powder nucleation -Diamond coating US Patent No. 6,096,377 further proposes the use of suitable chemical systems to achieve selective tungsten carbide etching and selective Co etching, respectively. Such suitable chemical systems are described, for example, in DE 19 522 372 A1.

[0010] In particular, for depositing a diamond coating on a cemented carbide substrate, such as a cemented carbide tool, the surface of the substrate to be coated is usually chemically pretreated to remove at least the Co binder from the cemented carbide material (hereinafter also referred to as a WC-Co composite material). The cemented carbide substrate is usually immersed in an appropriate acid and alkaline solution to carry out the above chemical pretreatment step, and then immersed or exposed to a diamond powder suspension in an ultrasonic bath to carry out the seeding step.

[0011] Shortcomings of the state of the art For carrying out such types of pretreatment and seeding steps, and subsequently for carrying out the deposition of the diamond coating, there are significant challenges when the substrate to be coated exhibits a complex geometric shape and only some areas of the substrate surface (hereinafter also referred to as selected areas or selected portions) are to be pretreated and subsequently coated.

[0012] In such cases, the surface of the substrate to be coated should not be completely coated, but rather selectively coated, which cannot be achieved in a simple manner by the standard or conventional pretreatment steps, seeding steps and coating methods described above.

[0013] In the context of this specification, the term "selective coating" is used to refer to those cases where the surface of the substrate is only partially coated, in other words, only some selected areas (or some selected "portions") of the surface of the substrate are selected to be pre-treated and coated with the diamond coating. Summary of the Invention [Problem to be solved by the invention]

[0014] Object of the invention The object of the present invention is to at least partially avoid or overcome the above-mentioned drawbacks, to provide a method for depositing diamond coatings that is ecologically and economically advantageous, and to provide a method that allows for the deposition of diamond coatings on selected substrate surfaces without compromising the coating quality and without damaging the substrate surfaces that are not to be coated. [Means for solving the problem]

[0015] Description of the invention The object of the present invention is achieved by providing a method for obtaining a selectively diamond coated substrate as described below and as set out in claim 1. Further features and details of the invention can be derived from the respective dependent claims, the description and the drawings.

[0016] The present invention provides a method for producing a selectively diamond coated substrate, the selectively diamond coated substrate comprising: a substrate having a surface comprising a cemented carbide material, the substrate having areas of the substrate surface selected to be coated and areas of the substrate surface not selected to be coated; one or more diamond coatings deposited on areas of the substrate surface selected to be coated; The method comprises the steps of: one or more chemical pretreatment steps in which the -Co binder is removed from the cemented carbide material contained on the substrate surface; and one or more coating steps in which one or more diamond coatings are deposited on the areas of the substrate surface selected to be coated; The method comprises the steps of: a first masking step, carried out before carrying out one or more chemical pretreatment steps, in which areas of the substrate surface that are not selected to be covered but that may be chemically attacked during the carrying out of one or more chemical pretreatment steps are masked by applying a latex mask covering these areas in order to avoid any chemical attack of the substrate material in these areas; a mask removal step, carried out after one or more chemical pretreatment steps and before one or more coating steps, in which the latex mask is completely removed; - a second masking step carried out before carrying out the one or more coating steps, in which the latex mask is removed and areas of the substrate surface that are not selected to be coated but that may be coated with one or more diamond coatings during the carrying out of the one or more coating steps are covered with one or more masking covers to avoid deposition of any diamond coating on these areas.

[0017] The masking cover can be made of any material suitable for carrying out the diamond coating process, for example, by using chemical vapor deposition (CVD) technology or plasma enhanced chemical vapor deposition (PA_CVD) technology, which means any material that does not adversely affect the coating process and coating quality.

[0018] Preferably, the one or more masking covers are made of copper and / or stainless steel, or made of a material that mainly comprises copper and / or stainless steel.

[0019] In other words, the present invention provides a method for achieving selective area chemical pretreatment and selective area diamond deposition on substrates having complex geometries (hereinafter also referred to as complex geometry parts) where areas that should not be coated with chemical pretreatment and diamond are protected.

[0020] The inventors were surprised at the very good results obtained by using the method of the present invention.

[0021] The inventors believe that masking areas of the substrate surface with a latex mask according to the present invention is very suitable and effective for avoiding unwanted chemical pre-treatment of these areas, because the latex mask is non-porous, watertight, does not react with the chemical solutions used to carry out the above-mentioned chemical pre-treatments, and can be easily removed (simply by hand (fingers)) after any chemical pre-treatment has been carried out. Typical chemical solutions used in this context are, for example, those mentioned by Lee et al. in the patent application US Pat. No. 5,700,518 or by Haubner et al. in the article "Murakami and H2SO4 / H2O2 Pretreatment of WC-Co Hard Metal Substrates to Increase the Adhesion of CVD Diamond Coatings" published in: Journal de Physique IV Colloque, 1995, 05 (C5), pp. C5-753-C5-760.ff10.1051 / jphyscol:1995589ff.ffjpa00253951.

[0022] Diamond coatings do not adhere very well to areas that have not been chemically pretreated, and therefore although it may be possible to carry out the deposition of the diamond coating without masking these areas during the diamond coating process, the inventors recommend covering the areas that have not been chemically pretreated with a copper cover before carrying out the diamond coating step or steps, as this contributes greatly to achieving better quality in terms of good differentiation between diamond-coated and non-diamond-coated areas.

[0023] The advantage of using latex to make the latex mask used as the masking material during chemical pretreatment and copper as the masking material during diamond coating is that these materials exhibit excellent masking effects without affecting the chemical pretreatment and diamond deposition processes, respectively, which the inventors believe is due to the inertness of each of these materials during each respective process.

[0024] The method of the present invention is suitable for any of a variety of cemented carbide substrates that can be coated with a diamond coating for a variety of applications (e.g., parts or components or tools made of cemented carbide or with a diamond-coated surface made of or comprising cemented carbide).

[0025] The substrate may comprise a mounting portion that is not coated with a diamond coating and a non-mounting portion that is coated with a diamond coating, and the mounting portion may be configured to be mountable on a substrate holder, the substrate holder being suitable for holding the substrate in a coating process, in particular a chemical vapor deposition and / or plasma-assisted chemical vapor deposition process.

[0026] The cemented carbide material contains a Co binder (cobalt binder), and in particular, the surface of the cemented carbide material contains the Co binder.

[0027] It is further contemplated that the latex mask may be applied using natural latex, which has the advantage that it is degradable by a wide range of bacteria, resulting in a lower ecological impact.

[0028] The natural latex may be of the pre-vulcanized liquid natural latex type having a solids content between 50% and 80% by weight. Liquid natural latex is easily processable. Pre-vulcanized latex further simplifies handling, as it typically does not require a aging period. Solids contents between 50% and 80% by weight have been found to result in high-quality, non-porous coatings that are easy to deposit and remove.

[0029] Advantageously, within the scope of the present invention, it can be provided that the natural latex is ammonia-free or contains a low ammonia fraction between 0.0% and 3% by weight, which offers the advantage of less serious contamination compared to higher ammonia fractions.

[0030] It is further conceivable that the ammonia fraction is between 0.0% and 1% by weight. A very low ammonia fraction between 0.0% and 1% by weight offers the advantage of a very low ecological impact while still ensuring the stability of the latex.

[0031] One or more masking covers (60) may be provided that are made of copper and / or stainless steel, or that are made primarily of a material that includes copper and / or stainless steel. Both materials offer the advantage that a diamond coating deposited on such a masking cover will spontaneously peel off during cooling after the coating process due to the difference between the expansion coefficients of the respective materials. In this way, masks that include or are made of copper and / or stainless steel do not adversely affect the coating process and the quality of the diamond coating.

[0032] Advantageously, within the scope of the present invention, it may be provided that the substrate is a tool, in particular a hob cutter or a drilling tool, and comprises a mounting part formed as an area of ​​the substrate surface that is not selected to be coated and that is adapted to be mountable on a substrate holder for holding the substrate during one or more coating steps, and a dynamic part, in particular teeth and / or drills, formed as an area of ​​the substrate surface that is selected to be coated, the dynamic part being suitable for providing the functionality of the tool, in particular cutting and / or drilling.

[0033] Further means for improving the present invention can be obtained from the following description of some embodiments of the present invention, which are illustrated diagrammatically in the drawings. All features and / or advantages arising from the claims, the specification or the drawings, including structural details, spatial arrangements and process steps, may be essential to the present invention both individually and in various combinations. It should be noted that the drawings are for illustrative purposes only and are not intended to limit the present invention in any way. [Brief explanation of the drawings]

[0034] [Figure 1] Figure 1: Schematic diagram of a hob 1 as a substrate with selected areas 10 of the substrate surface selected to be coated with a diamond coating, the selected areas including the teeth of the hob, and non-selected areas 20 of the substrate surface not selected to be coated with a diamond coating (in this case the non-selected areas are the so-called mounting parts of the hob). [Figure 2] 2: A schematic diagram of the hob 1 shown in FIG. 1 with a latex mask 50 according to the invention covering one of the two non-selected areas 20 shown in FIG. 1 that should be protected from chemical attack during chemical pretreatment. [Figure 3] 3: A schematic diagram of the hob 1 shown in FIG. 1 after removing the latex mask 50 shown in FIG. 2, in which two copper covers 60 according to the present invention cover the two non-selected areas 20 shown in FIG. 1 that should be prevented from being covered with diamond coating during the coating process. [Figure 4]4: A schematic diagram of the hob 1 shown in FIG. 1 after carrying out the coating process according to the present invention and after removing the cooper cover 60 shown in FIG. 3, the selectively coated hob 1 showing the selected areas 10 shown in FIG. 1 coated with the diamond coating 30 and the non-selected areas 20 that have not been subjected to any chemical pretreatment and that remain without a diamond coating deposited thereon (i.e., showing the selected areas 10 coated with the diamond coating 30 and the non-selected areas 20 that remain uncoated). DETAILED DESCRIPTION OF THE INVENTION

[0035] Example of a procedure for producing selectively coated tools using the method according to the present invention [Example]

[0036] Example 1 of the present invention: As a showcase of the method of the present invention, a chemical pretreatment process and subsequent coating process for depositing a diamond coating on selected areas of a double-sided mounted hob cutter (such a double-sided mounted hob cutter is shown diagrammatically in FIG. 1) was carried out as follows.

[0037] a) One of the two mounting parts 20 of the hob cutter 1, in this case the mounting part that will be subjected to the chemical pretreatment together with the part including the teeth 10, was covered (masked) with a latex mask made of natural latex, in some cases by applying the natural latex to the above-mentioned mounting part 20 using a paint brush, and in other cases by immersing the above-mentioned part 20 in a natural latex pad after a drying process of 24 hours under normal ambient conditions (air atmosphere).

[0038] b) The above step a) was repeated at least three times. The resulting latex mask 50 (schematically shown in Figure 2) exhibited a smooth, uniformly colored, and hole-free surface (visual appearance).

[0039] c) The part of the hob cutter including the teeth (selected area 10) as well as the mounting part masked with a latex mask was immersed in an acidic solution commonly used to perform a chemical pretreatment to remove the Co binder from the cemented carbide material contained in the selected area of ​​the substrate surface to be subsequently coated.

[0040] d) The latex mask was easily removed by hand from each mounting portion of the hob cutter. e) The part of the hob cutter including the teeth (selected areas 10) as well as the mounting part from which the latex mask has been removed is immersed in a diamond seeding bath in order to seed the selected areas 10 of the substrate surface already chemically pretreated as described in step c) and later coated with a diamond coating.

[0041] f) After the seeding step e), the hob cutter 1 was attached to the substrate holder so that both mounting parts were covered with the Cooper cover, and the substrate holder was placed inside a CVD (chemical vapor deposition) coating chamber for carrying out the diamond coating process.

[0042] 7. A diamond coating was deposited on the hob cutter while the mounting portion 20 was covered with a copper cover 60 as shown in FIG.

[0043] The diamond coating deposited on the copper cover during the coating process spontaneously peels off during cooling after the coating process due to the difference in the expansion coefficients of diamond (the coating material) and copper (the cover material). Thus, the use of the copper cover during the diamond coating process does not adversely affect the coating process or the quality of the diamond coating.

[0044] The hob cutter was then selectively coated in accordance with the present invention so that only selected areas 10 were coated and the coating process and coating quality were not compromised. [Example]

[0045] Example 2 of the present invention: A selectively coated drilling tool was fabricated using a procedure similar to that described above in Inventive Example 1.

[0046] In this case, the upper part of the functional area of ​​the drilling tool is a non-selected area, which should not be chemically pre-treated or coated with a diamond coating in order to avoid any influence on the stability of the upper drilling tool surface and also to avoid any influence on the geometry of the upper drilling tool surface, in particular to avoid any undesirable reduction in the mechanical stability, in particular the impact strength, of the upper part of the drilling tool (including the drill bit).

[0047] As a result, to extend the life of the drilling tool, only those portions of the drilling tool that will define the final drilling tool diameter should be coated with a diamond coating.

[0048] Therefore, in this example, a latex mask was applied over the drill bit of the drilling tool prior to any chemical pretreatment process to remove the Co binder from the cemented carbide material that formed the selected areas to be coated.

[0049] Similarly, after the chemical pretreatment process was performed, the latex mask was mechanically removed. The drilling tools are placed in copper sleeves to cover the respective shafts of the drills, and the drill bits are in each case covered with respective copper covers to avoid undesired deposition of diamond coating on the shafts of the drilling tools or on the drill bits during the coating process.

[0050] To apply the latex masks of the present invention, the inventors recommend using natural latex, such as a pre-vulcanized liquid natural latex with a solids content of between 50% and 80% by weight (wt% = weight percent) and no or a low ammonia content, preferably between 0.0% and 3% by weight, more preferably between 0.0% and 1% by weight. For example, to apply the latex masks described above, some of the examples of the present invention used a pre-vulcanized liquid natural latex with a solids content of 60% by weight and an ammonia content of 0.3% by weight. The above description, examples, and drawings are intended to aid in a better understanding of the present invention and should not be construed as limiting the present invention.

[0051] The above description of the embodiments explains the invention only in the context of examples. It will be understood that the individual features of the embodiments can be freely combined with one another, as far as is technically reasonable, without departing from the scope of the invention. [Explanation of symbols]

[0052] Reference sign 1. Base material, tool, hob cutter 10 Selected Area, Teeth 20 Non-selected area, implementation part 30 Diamond Coating 50 latex mask 60 Masking cover, copper cover

Claims

1. 1. A method for producing a selectively diamond coated substrate, the selectively diamond coated substrate comprising: a substrate (1) having a surface comprising a cemented carbide material, with areas of the substrate surface (10) selected to be coated and areas of the substrate surface (20) not selected to be coated; one or more diamond coatings (30) deposited on the areas (10) of the substrate surface selected to be coated, The method comprises the steps of: one or more chemical pretreatment steps in which the -Co binder is removed from the cemented carbide material contained on the substrate surface; and one or more coating steps in which one or more diamond coatings (30) are deposited on the areas (10) of the substrate surface selected to be coated, The method comprises the steps of: a first masking step, carried out before carrying out said one or more chemical pretreatment steps, in which said areas (20) of the substrate surface that have not been selected to be covered but that may be chemically attacked during the carrying out of said one or more chemical pretreatment steps are masked by applying a latex mask (50) covering these areas (20) in order to avoid any chemical attack of the substrate material in these areas (20); a mask removal step, carried out after carrying out said one or more chemical pretreatment steps and before carrying out said one or more coating steps, in which said latex mask (50) is completely removed; - a second masking step carried out before carrying out said one or more coating steps, in which said latex mask (50) is removed and said areas (20) of the substrate surface that are not selected to be coated but that may be coated with one or more diamond coatings (30) during the carrying out of said one or more coating steps are covered with one or more masking covers (60) to avoid deposition of any diamond coatings (30) on these areas.

2. 2. The method of claim 1, wherein the latex mask (50) is applied by using natural latex.

3. 3. The method according to claim 2, characterized in that the natural latex is of the pre-vulcanized liquid natural latex type having a solids content between 50% and 80% by weight.

4. 4. The method according to claim 3, characterized in that the natural latex is ammonia-free or contains a low ammonia fraction between 0.0% and 3% by weight.

5. 5. The method according to claim 4, characterized in that the ammonia fraction is between 0.0% and 1% by weight.

6. 6. The method according to any one of claims 1 to 5, characterized in that the one or more masking covers (60) are made of copper and / or stainless steel or made of a material that mainly contains copper and / or stainless steel.

7. The substrate (1) is a tool (1), in particular a hob cutter (1) or a drilling tool (1), a mounting portion (20) formed as a region (20) of the substrate surface that is not selected to be coated and that is adapted to be mountable on a substrate holder for holding the substrate during the one or more coating steps; a dynamic part (10) in which, in particular, teeth (10) and / or drills (10) are formed as areas (10) of the substrate surface selected to be coated, said dynamic part (10) being suitable for providing the functionality of the tool (1), in particular cutting and / or drilling; The method according to any one of claims 1 to 6, characterized in that it comprises:

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