METHOD FOR SELECTIVE DEPOSITION OF DIAMOND COATINGS

Abstract

A method for producing a selective diamond-coated substrate, wherein the diamond-coated substrate includes: a substrate having surfaces including cemented carbide material, areas selected to be coated, and areas not selected to be coated; and one or more diamond coatings on the areas selected to be coated, the method including following steps in order: a first masking step, wherein the areas not selected to be coated but could be chemically attacked during a chemical pre-treatment step, are masked by applying a latex-mask covering these areas; one or more chemical pre-treatment steps; a mask-removing step, wherein the latex-mask is removed; a second masking step, wherein the areas of the substrate surfaces from which the latex-mask was removed and not selected to be coated but could be coated with one or more diamond coatings during one or more coating steps, are covered with one or more masking-covers; and one or more coating steps.

Claims

1. A method for producing a selective diamond-coated substrate, wherein the selective diamond-coated substrate comprises: a substrate (1) having surfaces comprising cemented carbide material and having areas of the substrate surfaces selected to be coated (10) and areas of the substrate surfaces that are not selected to be coated (20), and one or more diamond coatings (30) deposited on the areas of the substrate surfaces selected to be coated (10), the method includes following steps: one or more chemical pre-treatment steps, in which Co binder is removed from the cemented carbide material comprised in the substrate surfaces, and one or more coating steps, in which one or more diamond coatings (30) are deposited on the areas of the substrate surfaces selected to be coated (10), characterized in that, the method further includes following steps: a first masking step, conducted before conducting the one or more chemical pre-treatment steps, wherein in the first masking step the areas of the substrate surfaces that are not selected to be coated (20) but could be chemically attacked during conduction of the one or more chemical pre-treatments steps, are masked by applying a latex-mask (50) covering these areas (20) for avoiding any chemical attacks of the substrate material in these areas (20), mask-removing step, conducted after conducting the one or more chemical pre-treatments steps and before conducting the one or more coating steps, in which the latex-mask (50) is completely removed, a second masking step conducted before conducting the one or more coating steps, wherein in the second masking step the areas of the substrate surfaces, from which the latex-mask (50) was removed and are not selected to be coated (20) but could be coated with one or more diamond coatings (30) during conduction of the one or more coating steps, are covered with one or more masking-covers (60) for avoiding deposition of any diamond coatings (30) on these areas.

2. Method according to claim 1, characterized in that the latex-mask (50) is applied by using natural latex.

3. Method according to claim 2, characterized in that the natural latex is of the type: liquid natural latex, pre-vulcanized, having a solid fraction between 50 wt. % and 80 wt. %.

4. Method according to claim 3, characterized in that the natural latex is free of ammoniac or comprises a low ammoniac fraction between 0.0 wt. % and 3 wt. %.

5. Method according to claim 4, characterized in that the ammoniac fraction is between 0.0 wt. % and 1 wt. %.

6. Method according to claim 1, characterized in that the one or more masking-covers (60) are made of copper and/or stainless steel; or are made of a material mainly comprising copper and/or stainless steel.

7. Method according to claim 1, characterized in that the substrate (1) is a tool (1), comprising: a mounting part (20), the mounting part (20) being formed as an area of the substrate surfaces that are not selected to be coated (20) and suited to be mountable on a substrate holder for holding the substrate during the one or more coating steps; an active part (10) formed as an area of the substrate surfaces selected to be coated (10), wherein the active part (10) is configured to provide a functionality of the tool (1).

8. Method according to claim 7 wherein the substrate is configured to be a hob cutter or a drilling tool, the active part is configured as teeth and/or a drill, and the active part is configured for cutting and/or drilling.

Description

[0053] Further measures improving the invention result from the following description of some embodiments of the invention, which are shown schematically in the figures. All features and/or advantages arising from the claims, the description or the drawings, including constructional details, spatial arrangements and process steps, may be essential to the invention both individually and in a wide variety of combinations. It should be noted that the figures are descriptive only and are not intended to limit the invention in any way.

[0054] FIG. 1: Schematic representation of a hob 1 as substrate, with selected areas 10 of the substrate surfaces that are selected to be coated with a diamond coating, the selected areas comprising the teeth of the hob, and non-selected areas 20 of the substrate surfaces that are 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).

[0055] FIG. 2: Schematic representation of the hob 1 shown in FIG. 1, with a latex-mask 50 according to the present invention, covering one of the two non-selected areas 20 shown in FIG. 1, which is to be protected from any chemical attacks during conduction of a chemical pre-treatment.

[0056] FIG. 3: Schematic representation of the hob 1 shown in FIG. 1, after removing the latex-mask 50 shown in FIG. 2, with two cooper covers 60 according to the present invention, covering the two non-selected areas 20 shown in FIG. 1, which are to be protected from being coated with a diamond coating during coating step.

[0057] FIG. 4: Schematic representation of the hob 1 shown in FIG. 1, after conducting the coating step according to the present invention and after removing the cooper covers 60 shown in FIG. 3, the selective-coated hob 1 showing the selected area 10 shown in FIG. 1 coated with a diamond coating 30 and the non-selected areas 20 remaining without any effect of any chemical pre-treatment and also without any diamond coating deposited on them (i.e. showing selected areas 10 coated with diamond coating 30 and non-selected areas 20 remaining uncoated).

EXAMPLES OF A PROCEDURE FOR PRODUCING A SELECTIVE-COATED TOOL BY USING A METHOD ACCORDING TO THE PRESENT INVENTION

Inventive Example 1

[0058] As a showcase of the inventive method, a chemical pre-treatment process and afterwards a coating process for deposition of a diamond coating on selected areas of hob cutters with two-sides mounting parts (a such hob cutter with two-sides mounting parts is shown schematically in FIG. 1) was conducted as following: [0059] a). One of the two mounting parts 20 of the hob cutters 1, in this case exactly the mounting part that would be exposed to chemical pre-treatment together with the part comprising the teeth 10, was covered (masked) with a latex-mask consisting of natural latex, in some cases by applying natural latex on the above referred mounting part 20, by using a paintbrush, and in other cases by immersion of the above referred part 20 in a natural latex bad, following a drying process under normal ambient conditions (air atmosphere) for 24 hours. [0060] b). The above described step a). was repeated at least three times. The obtained latex-mask 50 (as schematically shown in FIG. 2) exhibited a smooth, uniform colored and pore free surface (visual appearance). [0061] c). The part of the hob cutters comprising the teeth (selected area 10) as well the mounting part masked with latex-mask were submerged in an acid solution commonly used for conducting a chemical pre-treatment for removing Co binder from the cemented carbide material comprised in the selected areas of the substrate surfaces that afterwards should be coated. [0062] d). The latex-masks were removed from the respective mounting parts of the hob cutters in an easy manner by hand. [0063] e). The part of the hob cutters comprising the teeth (selected area 10) as well the mounting part, from which the latex-masks were removed, were submerged in a diamond seeding bath for seeding the selected areas 10 of the substrate surfaces that were already chemical pre-treated as described in step c). and will be afterwards coated with a diamond coating. [0064] f). The hob cutters 1 after seeding step e). were mounted in a substrate holder in such a manner that both mounting parts were covered with cooper covers and the substrate holder was positioned inside of a CVD (chemical vapor deposition) coating chamber for conducting a diamond coating process. [0065] 7. The diamond coating was deposited on the hob cutters, while the mounting parts 20 were covered with the cooper covers 60 as shown in FIG. 3.

[0066] Stripping of the diamond coating deposited on the cooper covers during coating process occurs spontaneously during cooling after coating process because of the difference between the coefficients of expansion of the respective materials: diamond (coating material) and copper (covers material). In this manner, the use of cooper covers during diamond coating process does not affect in any negative manner the coating process and also not the diamond coating quality.

[0067] The hob cutters were then selective-coated according to the present invention in such a manner that only the selected areas 10 were coated and the coating process and coating quality were not jeopardized.

Inventive Example 2

[0068] A similar procedure as described above in the inventive example 1, was used for producing selective-coated drilling tools.

[0069] In this case, the upper part of the function area of the drilling tools was the non-selected area, which should neither chemical pre-treated nor coated with a diamond coating, in order to avoid any influences on the stability of the upper drilling tools surface and also to avoid any influences on the geometry of the upper drilling tool surface, in particular for avoiding any undesirable reduction of the mechanical stability, in particular of the impact strength in the upper part of the drilling tools (including the drill bit).

[0070] Consequently, only the part of the drilling tools considered defining the final drilling tools diameter should be coated with a diamond coating, in order to increase the lifetime of the drilling tools.

[0071] Therefore, in this example the latex-mask was applied covering the drill bits of the drilling tools before conducting any chemical pre-treatment process for removing Co binder from the cemented carbide material forming the selected areas to be coated.

[0072] In similar manner, the latex-masks were mechanically removed after conducting the chemical pre-treatment processes.

[0073] The drilling tools were placed in cooper sleeves for covering the respective shafts of the drills and the drill bits were covered with respective cooper covers, in both cases for avoiding undesirable deposition of a diamond coating on the shafts or on the drill bits of the drilling tools during coating process.

[0074] For applying a latex-mask according to the present invention, the inventors recommend to use preferably natural latex for example of the type: liquid natural latex, pre-vulcanized, having a solid fraction (of natural rubber) between 50 wt. % and 80 wt. % (wt. %=in weight percentage), free of ammoniac or with low ammoniac fraction, preferably a fraction of ammoniac between 0.0 wt. % and 3 wt. %, more preferably between 0.0 wt. % and 1 wt. %. For example, in some of the inventive examples liquid natural latex, pre-vulcanized, having a solid fraction of 60 wt. % and ammoniac fraction of 0.3 wt. % was used for applying the latex-mask as mentioned above. The above-mentioned description, examples and figures are intended to be used to help to better understand the present invention and do not should be understand as a limitation of the present invention.

[0075] The foregoing explanation of the embodiments describes the present invention exclusively in the context of examples. Of course, individual features of the embodiments can be freely combined with each other, provided that this is technically reasonable, without leaving the scope of the present invention.

REFERENCE SIGNS

[0076] 1 Substrate, Tool, Hob cutter [0077] 10 Selected Area, Teeth [0078] 20 Non-selected Area, Mounting Part [0079] 30 Diamond Coating [0080] 50 Latex Mask [0081] 60 Masking-cover, Copper Cover