JPH07299752A - Production of wear resisting molding close to final shape - Google Patents

Abstract

PURPOSE: To simply manufacture a wear-resistant molding close to the final shape by preparing a molding having a surface selected to provide it with wear resistance, coating the surface by a specific component, and then sintering the molding for a predetermined period of time under high temperature and high pressure conditions. CONSTITUTION: When a wear-resistant molding, for example, a rotary cutting tool is manufactured, an end mill 10 having a plurality of end cutting edges 12 and a spiral cutting edge 14 defining a groove 16 is first prepared and is attached to a shank to perform preliminary molding. Next, the whole end mill 10 is coated using diamond powders or CBN(cubic boron nitride) powders by electric migration coating or the like. At this time, coating is applied to each edge 12, 14 only, and the groove 16 which is not coated is masked. Then, the coated end mill 10 is sintered. At this time, sintering temperature is set to 1250 deg.C to 1500 deg.C, and sintering pressure is set to at least 40 kilobars.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a near-final-shape cutting tool or molded article having one or more wear-resistant surfaces or a method for producing the same, and more particularly, to consolidated polycrystalline cubic nitriding. Abrasion resistant tool or molded article having a selected abrasion resistant surface formed of boron or polycrystalline diamond, or a method of manufacturing the same.

[0002]

BACKGROUND OF THE INVENTION Coated articles are known in which electrophoretic coating (EPD) has been used to form thin films of cubic boron nitride, diamond, and diamond-like materials. US Patent No. 51280
No. 06 discloses such a process. Also, US Pat. No. 3,932,231 discloses a method of coating the surface of a cemented carbide article with titanium carbide by EPD, then removing the organic binder from the coating layer and heating the coated article in a hot, reduced pressure atmosphere. ing. Also, US Pat. No. 3,762,882 discloses an end mill, drill, which discloses a method of electrodeposition of diamond particles on a metal surface by simultaneously electroplating a metal on a metal substrate and electrophoretic coating a diamond layer.
It is desired to incorporate polycrystalline diamond or polycrystalline cubic boron nitride into the cutting surface of a rotary cutting tool such as a reamer. U.S. Pat. No. 4,991,467 discloses a twist drill having a diamond cutting tip made by compacting diamond powder in a transverse channel formed at the end of a drill blank. The polycrystalline diamond material is then sintered under high pressure to compact the diamond powder. A portion of the drill blank channel is then mechanically removed to expose the diamond cutting edge.

US Pat. No. 5,273,557 teaches that preformed polycrystalline diamond or polycrystalline cubic boron nitride is brazed to the transverse channels and then a drill blank is machined to expose the diamond or cubic boron nitride cutting surface. It discloses a similar process to allow. U.S. Pat. No. 5,031,484, like U.S. Pat. No. 4,991,467, makes an end mill having polycrystalline diamond filled in a spiral groove that can later become a helical cutting surface when the end mill groove is machined into an end mill blank. Discloses the process. US Patent No. 50
70748 is a continuation-in-part application of US Pat. No. 5,031,484, which discloses a method of making such an end mill. U.S. Pat. No. 5,226,760 discloses a similar method of making an end mill by compressing diamond into the spiral groove cuts in the end mill blank and then machining the groove in the end mill blank to expose the diamond cutting edge. Disclosure. U.S. Pat. No. 5,272,940 discloses a similar method of making an end mill, but filling the helical groove with a plurality of polycrystalline diamond or cubic boron nitride segments,
Braze to spiral groove before machining end groove.

The above-described method of making a grooved rotary cutting tool is very costly, in that the cutting tool blank first machined a spiral groove into it, and then the groove was made of diamond or cubic boron nitride powder. Filling,
This is because the diamond or cubic boron nitride must then be consolidated and bonded to the rotary cutting tool blank. Then braze the blank to the shank,
Finally, the groove is machined into a cutting tool blank to expose the diamond or cubic boron nitride cutting edge and then finished to dimensional tolerances.

[0005]

Means and Solutions for Solving the Problems The present invention is
The present invention relates to a method of manufacturing a rotary cutting tool having a cutting edge of polycrystalline diamond or polycrystalline cubic boron nitride and having a cutting edge close to a final dimension, and a method of manufacturing various molded articles having a wear resistant surface having a final dimension. These rotary cutting tools and wear resistant moldings are first coated on a given surface or rotary cutting tool edge with a composition comprising diamond powder or cubic boron nitride powder. This coating is a spray,
It can be performed by dipping or electrophoretic coating. Also,
The parts of the tool or the part that should not be subjected to the wear resistant coating (ie the grooves of the rotary cutting tool) can be masked before the coating process. The coating is applied directly to a pre-finished carbon steel or tungsten carbide rotary cutting tool (ie a rotary cutting tool having a shank and a groove but not finishing the cutting edge), whereby
The extra machining process required to machine a flute in such a rotary cutting tool after forming diamond or cubic boron nitride cutting edges in the spiral groove in the cutting tool blank. Omit it. Then, the coated cutting tool is sintered under high pressure to consolidate,
Crystallize and bond a diamond or cubic boron nitride coating layer to the underlying substrate. High pressure sintering provides the required high strength and abrasion resistance required for material removal operations such as drilling, milling, tapping and the like. This results in a near final shape cutting tool or other wear resistant surface molding that requires very little post-processing of the cutting edge coated polycrystalline diamond or polycrystalline cubic boron nitride.

The method of the present invention uses polycrystalline diamond (P
CD) or polycrystalline cubic boron nitride (PCBN) to expose the cutting edge, eliminating the need to machine a groove into the blank of a torsion drill or end mill. Rather, the rotary cutting tool produced by the method of the present invention is
Starting from a commercially available end mill, such as an end mill having a plurality of end cutting edges 12 and a spiral cutting edge 14 defining a groove 16 as shown in FIG. The body of the end mill 10 is attached to the shank 18 and preformed in the usual manner.

In producing an end mill having a finish shape coated with polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN), specifically, a machined end cutting edge 12 and a machined spiral cutting edge 14 are prepared.
It is preferred to start with a preformed end mill that includes all components except for. In this aspect, the base end mill "blank" for producing the PCD or PCBN coated cutting tool can be produced relatively inexpensively in that the finishing step of the end mill "blank" can be omitted. More importantly, the pre-finishing edge that is going to form the cutting edge is rounded, and PCD or PCBN
The coatings that define the cutting edges may be less prone to cracking, unless the coatings have sharp corners that can be prone to cracking and damage.
This is clearly shown in FIG. 3, where the prefinished end mill spiral cutting edge 14 is slightly rounded, which is different from machining sharp edges such as finished rotary cutting tools.

FIG. 2 shows a commonly available end mill similar to the end mill shown in FIG. 1 having a body entirely coated with a composition of diamond powder or CBN powder according to the method of the present invention. It will be appreciated that any commonly practiced coating method can be used to coat the end mill 10 of the present invention. Specifically, the end mill can be dip coated or spray coated. The inventors have found that the preferred method is electrophoretic coating (EPD), because diamond powder or CBN powder coatings provide the best conditioning when applied by EPD.

Whether the diamond powder or CBN powder is applied onto the substrate by spray coating, dip coating or electrophoretic coating, only the substrate or area where an abrasion resistant coating is actually needed is applied. It is economically wise to coat. Therefore, it is preferable to mask surfaces or areas not intended for wear resistance before coating. This is shown in FIG. 4, where the end mill groove 16 is masked prior to applying the diamond, CBN, etc. coating,
As a result, the coating has the desired wear resistance of the end mill, namely the end cutting edge 12 and the spiral cutting edge 14.
Applies only to.

The liquid composition of EPD applied to the end mill constitutes a suspension of abrasive particles (diamond, CBN, tungsten carbide, etc.) in a pure state or in a combination of an organic binder and a sintering aid. Organic binders are essentially low temperature (room temperature) adhesives that act to adhere the abrasive particles to the end mill surface. The sintering aid is cobalt, nickel, cobalt aluminide, nickel aluminide, cobalt-nickel aluminide, hexagonal boron nitride, titanium aluminide, titanium carbide, titanium carbonitride, aluminum-silicon alloy, etc., and should be contained in the liquid medium. The sintering aid functions to help sinter the composition on the end mill substrate, as described in detail below. The composition may also include an organic binder that acts as an adhesive to hold the particulate material together in a pre-sintered state. We used about 30% by weight of CBN in ethyl alcohol in the EPD process.
It has been found that a composition containing the is suitable for coating high purity CBN.

[0011]

The individual steps of the method of the invention are illustrated in the process flow chart of FIG. Preparing an EPD solution composition,
After cleaning the substrate (end mill, etc.), the unfinished end mill as shown in FIG. 1 is coated with a thin coating of diamond or CBN solution as shown in FIG. The preferred method of applying the coating to the end mill is EPD. In EPD, a suspension composition of abrasive particles (diamond, CBN, etc.) with or without a sintering aid (nickel aluminide, cobalt aluminide, etc.) in an organic liquid medium (eg, ethyl alcohol) is prepared. This suspension composition is used in conventional rotary or vibrating mills for the purpose of imparting a net surface charge to the abrasive particles (diamond, CBN, etc.) and / or sintering aid (if present). First mix thoroughly in. Alternatively, the pH of the suspension composition can be adjusted to impart a net surface charge to the abrasive particles. In this composition, the size of the abrasive particles (diamond, CBN, etc.) is about 0.5-5 microns. The prepared suspension composition is placed in a vessel that is continuously stirred to keep charged particles in the suspension.

An end mill is placed in the suspension composition in a container and fitted with an EPD electrode on which particles of charged diamond, CBN, etc. from the suspension are to be deposited. A direct current is applied to the end mill for a time sufficient for electrophoretic coating to produce a composition coating of the appropriate thickness on the end mill (the particle suspension composition container is the other electrode).

The following examples show preferred suspension compositions and EPD criteria. Example 1-No sintering aid-Weight of bottle = 31.28 g-Weight of bottle + ethyl alcohol = 134.2 g-Weight of bottle + ethyl alcohol + CBN = 143.
Grinding media = 10 balls Grinding time = 1 hour Grinding conditions = Voltage: 500 Volts, Time: 60 seconds This EPD composition of Example 1 deposited a CBN layer on an end mill about 2 mm thick. become. The coating layer of EPD is then dried at room temperature, then 0.
5g of polyvinylproporan (PVP, polyvinylpropo
lane) was impregnated with the binder solution. The PVP binder was then dried during preparation for subsequent processing steps.

Example 2-With sintering aid-Bottle weight = 31.28 g-Bottle + ethyl alcohol weight = 135 g-Bottle + ethyl alcohol + CBN (10 g) + Ni
-Al sintering aid (1.0 g) = 146 g-Crushing medium = 10 balls-Crushing time = 1 hour-Deposition conditions = voltage: 500 V, time: 60 seconds The EPD of this solution was deposited on the end mill. The resulting CBN layer has a thickness of about 1.5 mm. The deposited layer was again dried at room temperature and then 0.5 g PV in ethyl alcohol.
Impregnated with a binder solution of P binder, then PVP
The binder was dried during preparation for subsequent processing steps.

The preferred method of coating the end mill or other desired wear resistant surface is EPD. It will be appreciated here that the coating of diamond powder or CBN powder can also be applied by dip coating or spray coating to a given object surface to be wear resistant. In dip coating, the alcohol content in the solution composition will be significantly less than the above% indicated in EPD. Similarly, if the abrasive particle solution is spray coated onto a particular article, the alcohol content in the solution composition will be about half way between the EPD method and the dip coating method.

Regardless of the rotary cutting tool or the method of coating the surface to be wear-resistant, this coating step is followed by a so-called pre-encapsulation step and the coated end mill is coated with niobium, titanium, molybdenum, zirconium, tantalum, Place in a heat resistant container such as hafnium. This process is shown in FIG. Then, in a heat resistant metal container, to keep the coating layer in place on the end mill after the binder solution is removed by heating,
Non-reactive inert material, such as aluminum oxide powder,
Fill with hexagonal boron nitride or the like.

The next step, referred to as the organic binder burn-off step, heats the coated article in an open refractory metal container (ie, atmospheric pressure) at about 600 ° C. for about 6 hours. As mentioned above, this step burns off any remaining organic binder solution in the coating layer and burns with diamond or CBN particles in the layer bound to the underlying cutting tool or other molded substrate. Leave only the aid. After this binder burnout step, the coated article is allowed to cool in a refractory metal container in preparation for the next process step.

In preparation for the next process step, the lid of the metal container is sealed and the coated end mill or other article is encapsulated to prevent the coating from contacting oxygen or other contaminants. The sealed refractory metal container is then placed in a high pressure, high temperature hot press for sintering the coated diamond or CBN layer under high pressure on a rotary cutting tool or other intended substrate surface. This high-pressure sintering is a method for producing diamond powder, CBN powder, etc. with PC having extremely strong chemical bonds at grain boundaries.
Change to D, PCBN. We have found that high pressure sintering of diamond or CBN coating layers on rotating tools such as end mills is performed at temperatures of about 1250 ° C-1500 ° C and pressures of 40-80 kbar for about 30 minutes to 1 hour. I find that I can bring it by doing. This is also shown schematically in FIG. 6, where the refractory metal container is surrounded by pressure and heating elements and pressed to provide complete and uniform high pressure sintering of the coating on the article in the refractory container.・ Heating.

After high pressure sintering, the heat resistant metal container is allowed to cool to ambient temperature while maintaining high pressure. After the furnace has cooled, the high pressure of the refractory metal container is released and then the metal container is removed from the press. The metal container is then opened and the sintered article is removed from it. In most cases, heat-resistant metal cans and inert fillers will need to be scraped off the encapsulated PCD or PCBN coated articles (rotary cutting tools, wear resistant moldings, etc.) in order to open the coated article. is there. The coated article is then washed in the usual manner.

The final step is finishing of the cutting edge of the rotary cutting tool. In the case of a grooved end mill, a drill bit, etc., the end cutting edge 12 and the spiral cutting edge 14 are machined (ground) in order to obtain a cutting edge and an angle having a required diameter. In addition, the flat surface of the end face of the end mill and the outer diameter of the rotary cutting tool can be ground so as to match the tool diameters of these surfaces with the outer diameter. As a result, PC
A finishing end mill having a cutting edge such as D or PCBN can be obtained. This is shown in FIG.

For many of these other molded parts that only require wear resistant surfaces, a final finishing step may not be necessary. From the foregoing description, it will be appreciated that the present invention is suitable for all the objects and objects set forth herein, as well as other obvious advantages inherent in the apparatus. It will be appreciated that certain features and sub-combinations are beneficial and may be employed for other features and sub-combinations. These are considered and included in the scope of claims. Many embodiments of the invention are possible without departing from the scope of claims. Of course, the present invention is not intended to be limited to end mills, as all rotary cutting tools (drills, reamers, taps, etc.), all cutting tools (saw blades, scrapers, knives, etc.), wear resistant It is intended to include all other molded articles (skid pads, barrels, drawing dies, extrusion dies, nozzles, abrasive fluid pumps and valves, etc.) intended to The matter described in this specification or shown in the accompanying drawings is illustrative and should not be construed as limiting the meaning.

[Brief description of drawings]

FIG. 1 is a perspective view of a normal end mill before processing a final cutting surface.

FIG. 2 is a perspective view of an end mill having a coating of polycrystalline diamond or cubic boron nitride thereon.

3 is a cross-sectional view through line 3-3 of FIG.

FIG. 4 is a perspective view of an end mill coated with a masked groove before coating.

FIG. 5 is a view of the coated end mill in a niobium can before sintering.

FIG. 6 shows a sintering process under high pressure.

FIG. 7 is a flow chart of the steps of the method of the present invention.

FIG. 8 is a perspective view of a completed end mill with finish cutting edges.

9 is a cross-sectional view through line 7-7 in FIG.

[Explanation of symbols]

 10 ... End mill 12 ... End cutting edge 14 ... Spiral cutting edge 16 ... End mill groove

Claims (13)

[Claims] 1. A method of manufacturing an abrasion-resistant molded product having a shape close to the final shape, which comprises the steps of: -providing a molded product having a surface selected for abrasion resistance; -selecting the molded product. The coated surface is coated with a coating composition of cubic boron nitride or diamond powder, and the coated molded article is sintered under high temperature and high pressure conditions for a predetermined time. 2. The method according to claim 1, wherein the coating step is performed by electrophoretic coating. 3. The method of claim 1, wherein the coating step is dip coating. 4. The method according to claim 1, wherein the coating step is spray coating. 5. The method of claim 1, further comprising the step of finalizing selected surfaces of the molded article to desired dimensional tolerances. 6. The method of claim 1, wherein the selected surface of the shaped article is subjected to a predetermined amount of precoating with a dimension that is smaller than the dimensions of the final desired shaped article. 7. The temperature of the sintering step is 1250 ° C. to 15 ° C.
The method according to claim 1, which is 00 ° C. 8. A method according to claim 1, wherein the pressure of the sintering step is at least 40 kilobars. 9. The method of claim 1, further comprising the step of impregnating the coating composition with a binder solution prior to sintering. 10. The method of claim 1 further comprising the step of encapsulating the coated molding in a refractory metal container prior to sintering. 11. The refractory metal container contains at least one metal selected from the group consisting of titanium, zirconium, niobium, molybdenum, tantalum, and hafnium.
The method described in 0. 12. The coating composition comprises one or more components selected from the group consisting of nickel, cobalt, nickel aluminide, cobalt aluminide, nickel-cobalt aluminide, hexagonal boron nitride, titanium aluminide, and aluminum-silicon alloy. The method of claim 1, comprising: 13. An article having a surface coated according to the method of claim 1.