CH637611A5 - Tool component and process for making it - Google Patents

Description

The present invention relates to a tool part, such as a cutting tool, drilling tool and molding tool, in particular a tool insert made of abrasive particles, such as diamond and cubic boron nitride, for equipping cutting tools.

It has been found that a diamond body manufactured according to the teaching of US Pat. No. 3,745,623 and US Pat. No. 3,609,818 is only of limited use since it is damaged at temperatures above approximately 700 ° C. Similarly, it has been found that a cubic boron nitride body made according to the teachings of US Pat. No. 3,767,371 and US Pat. No. 3,743,489 is only of limited use since it also damages at temperatures above approximately 700 ° C. suffers. The use of such bodies is therefore not possible where (1) a hard solder is required to secure the body to a base, the melting point of which is close to or above the temperature at which the body is thermally damaged, or where (2) it is necessary to embed the body in a wear-resistant matrix with a high melting point, which is the case, for example, with a drill bit used for drilling rocks, the surface of which is usually fitted with cutting inserts.

The invention has for its object to provide a temperature-resistant tool part, in particular cutting insert.

This object is achieved by a tool part, with the characterizing of claim 1.

The tool part, which essentially consists of self-supporting abrasive particles and contains a network of interconnected disperse distributed pores, is produced by directly connecting a mass of abrasive particles to a self-bound body using a sintering aid material at high pressures and temperatures. The one formed under the influence of high pressures and temperatures

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637 611

Body contains self-bound, i.e. directly connected particles, and is interspersed with the sintering aid material, for example cobalt or cobalt alloys. The sintering aid material is then removed, for example by immersing the body in aqua regia. It has been found that by removing substantially all of the sintering aid material, an abrasive particle body is obtained which has a significantly improved resistance to thermal decomposition at high temperatures.

A further embodiment in the form of a laminated body, which can be produced in a manner similar to the first embodiment explained above, essentially consists of a layer of self-bonded abrasive particles and a base of preferably cemented carbide bonded to this layer.

The invention will now be explained in more detail with reference to the drawing, which shows a micrograph of an area of a ground surface of a diamond body produced according to the invention.

Although the grinding surface shown in the drawing relates to a diamond body, it can just as well be used to explain the alternative embodiments of the invention in which the abrasive particles consist of cubic boron nitride (CBN).

The body shown in the drawing contains diamond particles 11, which make up between 70 and 95 percent by volume of the body. Particles here mean a single crystallite or a fraction of a crystallite. At the interfaces 13, the self-binding of neighboring particles 11 can be seen, i.e. Diamond-diamond bond between adjacent particles 11. The diamond crystals 11 lying in the cut surface shown in the drawing are also bonded to adjacent diamond crystals (not visible) in the third dimension. The body is essentially uniformly penetrated by a metallic phase made of sintering auxiliary metal (not shown in the drawing). The metallic phase is believed to be encapsulated in sealed areas formed by adjacent diamond particles. The metallic phase comprises between approximately 0.05 and 3 percent by volume of the body. A network of interconnected empty pores 15 is dispersed over the entire body and is defined by the diamond particles 11 and the metallic phase (not shown). The pores 15 comprise between about 5 and 30 percent by volume of the body.

According to one embodiment, the body consists only of self-bound particles. According to another embodiment, the body is bound to a base (not shown), which preferably consists of carbon tungsten carbide cobalt cemented carbide.

The diamond particles 11 expediently have a particle size in the range from 1-1000 micrometers. For particles made of cubic boron nitride, a particle size in the range between 1-300 micrometers is expedient.

A preferred method for producing a tool part according to the invention comprises the following method steps:

a) A mass of diamond particles or CBN particles and a mass of a material which allows or favors the sintering together of the mass consisting of diamond particles or CBN particles is placed in a reaction vessel or a feed chamber,

b) the reaction vessel and its contents are simultaneously exposed to temperatures in the range from 1200-2000 ° C. and pressures of over 40 kb,

c) the heat supply to the reaction vessel is switched off,

d) the pressure on the reaction vessel is removed,

e) from the reaction vessel, the abrasive body formed by process steps a) to d) is removed, which consists of self-bonded, i.e. there are directly bonded particles and a metallic phase which is formed by the sintering aid material which has penetrated into the abrasive body, and f) the metallic phase which has penetrated into the body is essentially completely removed, so that the metallic phase remaining in the body is only 0.05 accounts for up to 3 percent by volume of the body.

The expression "at the same time" used in process step b) means that the action of high pressures and high temperatures takes place at the same time, but it is not necessary for the action of the high pressure and the high temperature to start or stop simultaneously, although this may also be possible.

The term “sintering aid material” used here denotes a material which acts as a catalyst for diamond and / or favors the sintering of CBN. It is not known how (catalytically or otherwise) the sintering aids promote or promote the self-binding of CBN (CBN-CBN binding).

Preferred embodiments of the process steps a) to e) mentioned above for producing a diamond body from diamond particles are explained in more detail in US Pat. No. 3,745,623 and US Pat. No. 3,609,818.

According to these patents, diamond bodies are produced under the action of high pressures and high temperatures, at which the hot, compressed diamond particles are infiltrated with a catalyst material which penetrates and penetrates the diamond particle mass axially or radially. During this penetration and infiltration process, a catalyzed sintering of the diamond particles takes place, which leads to an extensive diamond-diamond bond. The catalyst material used is one of the materials already described in US Pat. No. 2,947,609 and US Pat. No. 2,947,610, namely (1) a catalyst metal in elemental form from which the metals of group VIII of the periodic system, chromium, manganese and group comprising tantalum, (2) a mixture of one or more alloyable catalyst metals and one or more alloyable non-catalyst metals, (3) an alloy of at least two catalyst metals, or (4) an alloy of one or more catalyst metals and one or more non-catalyst metals. Cobalt is preferably used as a catalyst in elemental form or in the form of an alloy. The catalyst material forms a metallic phase in the abrasive body formed under the action of high pressures and high temperatures, as has already been mentioned in process step e).

Preferred embodiments of process steps a) to e) for producing a tool part from CBN particles are explained in US Pat. No. 3,767,371. According to Example 1 of US Pat. No. 3,767,371, CBN bodies are produced under high pressures and high temperatures by an infiltration process in which CBN particles are impregnated with a molten sintering aid material (cobalt metal) which is axially washed through the CBN particles. During this infiltration or flooding process, the CBN particles are sintered, which leads to extensive CBN-CBN binding. Other materials suitable as sintering aids for CBN are alloys made of aluminum and an alloy component made of nickel, cobalt, manganese, iron, vanadium

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and chromium group, as shown in U.S. Patent No. 3,743,489 at column 3, lines 6-20. However, cobalt and cobalt alloys are preferred. The sintering aid material forms the metallic phase mentioned in the explanation of process step e).

In one embodiment of the invention, in which process steps a) to e) are carried out in accordance with US Pat. No. 3,745,623, US Pat. No. 3,767,371 and US Pat. No. 3,743,489, a composite body is obtained by using an abrasive Particle layer (made of diamond or CBN) binds in situ on a sintered carbide base. The source of the auxiliary sintering material is preferably the material provided for forming the cemented sintered metal base (either in the form of a powder mixture or a preformed body). For further details regarding the document, reference is made to US Pat. No. 3,745,623, in particular column 5, line 58 to column 6, line 8, and column 8, line 57 to column 9, line 9.

In another embodiment of the invention, a body of essentially self-bonded abrasive particles is obtained. In this embodiment, process steps a) to e) are carried out in the same manner as explained above, only the material provided for forming the cemented carbide base for the abrasive particle layer in the form of a powder mixture or a preformed body preferably being omitted. In this case, the sintering aid material is added separately, for example in the manner described in US Pat. No. 3,609,818. Of course, after the metallic phase has been removed (process step f), a body can be fastened by brazing to a base made of cemented carbide or another material in order to create a body or insert for equipping a tool.

According to the invention, the metallic phase is removed from the body by acid treatment, extraction with liquid zinc, electrolytic removal or similar processes, so that a body of essentially 100% abrasive particles then remains in self-bound form. The remaining body contains essentially no or hardly any metallic phase. In the case of the known bodies with a metallic phase, the insufficient temperature resistance can theoretically be explained by the fact that the metallic phase catalyzes the conversion of the direct bonds between the abrasive particles and / or the direct bond between the particles breaks due to the thermal expansion of the metallic phase. It has been found that the body according to the invention, which is essentially free of a metallic phase, can withstand temperatures up to 1200-1300 ° C. without any noticeable thermal damage occurring.

The invention will now be explained in more detail using exemplary embodiments.

example 1

Disc-shaped diamond bodies were produced by (1) a 1.4 mm thick layer of fine diamond particles with a particle size of less than 8 micrometers and as a catalyst and as a base a disc with a thickness of 3.2 mm and a diameter of 8.8 mm made of cemented carbide (13% by weight Co, 87% by weight WC) were arranged within a zirconium container with a thickness of 0.05 mm, (2) several of these containers in a reaction vessel of the type shown in FIG. 1 of US Pat. No. 3 745 623 were stacked one on top of the other, (3) the reaction vessel feed was subjected to a pressure of approximately 65 kb and a temperature of approximately 1400 ° C for 15 minutes, (4) the temperature was slowly reduced first and then the pressure, and (5 ) the samples were ground after removal from the reaction vessel, resulting in bodies which had a 0.5 mm thick diamond layer which was bonded to a 2.7 mm thick cemented carbide layer. The sintered hard metal layer was then removed from each body by surface grinding.

As indicated in Table I, half of the samples were subjected to a leaching treatment in hot concentrated acids to remove the metallic phase and other other soluble non-diamond substances. Two different treatment methods were used to remove the infiltrated material. From a first group, comprising samples A-1 to A-4, samples A-3 and A-4 were only treated with a hot acid ice mixture of concentrated nitric acid and concentrated hydrofluoric acid in a ratio of 1: 1. In a second group, comprising samples B-1 to B-4, samples B-3 and B-4 were treated with hot aqua regia (concentrated hydrochloric acid and concentrated sulfuric acid in a ratio of 20 3: 1). It turned out that leaching was considerably faster when using aqua regia. Samples A-3 and A-4 were leached for 8 to 12 days, while samples B-3 and B-4 were leached for between 3 and 6 days. In both cases, the dimensions of the samples did not change during the acid treatment and no elimination of diamond was found. Since diamond is not dissolved by acids, the weight loss that occurs during acid treatment can be attributed to the removal of the metallic phase.

Before leaching, the proportion of metallic phase present in the samples was calculated to be approximately 8.1 percent by volume or 19.8 percent by weight (based on density measurements of the samples prior to leaching and 3s of the starting materials used to make them). After leaching, about 0.5% by volume or 0.2% by weight of metallic phase remains. The removal of up to 90% by weight of the metallic phases (sample B-4) also indicates that the metallic phase 40 is mainly located in a coherent pore network. Examination of a broken surface of a leached sample with a scanning electron microscope showed that the pore network runs over the entire diamond layer. The pores are distributed over the entire diamond layer and most of the pores have a diameter of less than one micrometer. This indicates that the acid has penetrated the entire diamond layer and has caused an essentially uniform removal of the metallic phase from the diamond layer.

As indicated in Table I, the flexural strength (fracture deflection) and the modulus of elasticity of the diamond layers were also measured. The strength test was carried out with a three-point loading device, in which two steel rollers were arranged on a support, 55 while a third steel roller was provided in the middle above the two steel rollers, parallel to the axis thereof. The samples were centered over the lower rollers and loaded until break. The elongation of the samples was measured parallel to the tensile stress using strain gauges that were connected to a strain gauge. Samples A-1 through A-4 were prepared for strength testing by finishing their surfaces with a diamond disc (diamond particles with a particle size of 177-250 microns). Samples 65 B-1 through B-4 were machined in preparation for strength testing on a lapping machine using diamond lapping powder with a particle size of 15 microns to give a better surface finish

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aim than was possible with samples A-1 to A-4 by grinding. It is believed that the better polished surfaces of the samples lapped with diamond powder give higher strength values because the surface is of higher quality, i.e. has fewer defects such as cracks or the like, at which stress concentration occurs under load. It can be assumed that the lower flexural strength values measured for the leached samples (A-3, A-4, B-3, B-4) are due to such surface defects.

Table I

Sample removal of bending strength modulus of elasticity metallic phase (kg / mm2) (E)

(% Weight loss) (x 103 kg / mm2)

A-l

0

111

-

A-2

0

101

-

A-3

16.1

73

-

A-4

16.2

87

-

B-l

0

129

89

B-2

0

143

92

B-3

17.0

88

78

B-4

17.9

81

80

In contrast to the bending strength values, the porosity has no influence on the measurement of the modulus of elasticity E (Table I), since the modulus of elasticity is a measure of the internal strength and stiffness of the material and does not depend on the formation of microcracks. After the infiltrated metallic phase has been removed from the samples, the modulus of elasticity is only reduced by approximately 12%. This difference is due to the porosity of the leached samples, since the following applies to the modulus of elasticity E:

_ M-C

E = —-—

in which E = modulus of elasticity M = moment

C = distance to the outer fiber I = moment of inertia of the surface and M • C do not change while I has decreased because the effective surface has decreased in proportion to the porosity. Therefore, if it is assumed that the pores have the shape of spheres and are randomly distributed, the following applies

_ MC I (l-x) '

in which x = the proportion of porosity, so that the modulus of elasticity must be greater than the measured value of E. For the leached samples B-3 and B-4, an elasticity module of 79 x 103 kg / mm2 was measured on average, so that, taking into account the porosity correction, the modulus of elasticity amounts to 85 x 103 kg / mm2, which is only 5% lower than the average value of 90 x 103 kg / mm2 measured on samples B1 and B-2.

The removal of the infiltrated metallic phase therefore has very little influence on the modulus of elasticity, from which it follows that the strength of the diamond layer is almost exclusively due to the diamond-diamond bond.

The modulus of elasticity of 90 x 103 kg / mm2 is only 10% lower than the average value of 100 x 103 kg /

mm2, which is calculated from the elastic constants of a diamond single crystal.

Example 2

A diamond body was produced in the same way as described in Example 1 for samples Al to A-4, except that instead of the diamond particles with a particle size of less than 8 micrometers, a diamond particle mixture of equal proportions of diamond particles with a particle size of 149 to 177 micrometers and diamond particles a particle size of 105 to 125 microns were used.

The composition of the body before leaching is calculated to be 89.1% by weight of diamond (96.5% by volume) and 11.9% by weight of metallic phase (4.5% by volume). After leaching, the body had a total weight that was 11.5% lower, so that only 0.15% by weight of the metallic phase (0.06% by volume) remained in the body.

Example 3

Four diamond bodies were produced in accordance with Example 1. The cemented carbide was ground from every body. In two bodies, the infiltrated metallic phase was leached out in hot acid mixtures

I HF: 1 HN03 and 3 HCl: 1 HNOs removed. All bodies were glued to a round tungsten carbide cemented carbide disc with a diameter of 0.89 cm using epoxy resin. The composite body thus formed was fastened to a tool holder of a lathe and tested for wear resistance during turning. A quartz sand was used as the filler-containing rubber rod. The following test conditions were applied: surface speed 107-168 m / min (the maximum range within a group subjected to the same heat treatment was 24 m / min), depth of cut 0.76 mm, cross feed 0.13 mm / per revolution, and test time 60 minutes. After testing, the samples were heat treated in a heating tube under a dry stream of argon gas. Treatment temperatures ranged from 700-1300 ° C with intervals of 100 ° C. The heat treatment time was 10 minutes at each treatment temperature. After each heat treatment, the samples were examined for damage with a scanning electron microscope and then except for those at 1000, 1100 and

1300 ° C treated samples subjected to the wear test. After both the upper and lower edges were used as cutting edges, the edges were reground.

The results of the wear test are from the table

II can be seen. The samples showed a fairly consistent behavior during the wear test. It was found that the samples heat-treated for the first time at 700 ° C. had a lower wear resistance than the samples that had not yet been heat-treated. Samples 3 and 4 that were not leached showed no changes in wear resistance until they failed between 800 and 900 C due to thermal damage. It turned out that the wear resistance is independent of the heat treatment until the diamond phase can no longer enclose the encapsulated metallic phase and crack formation occurs. This behavior also indicates the existence of two different phases, namely the bonded diamond phase, which ensures chip removal during the test, and the metallic phase, which is a remnant of the sintering process. Leached samples 1 and 2 withstood the heat treatment very well, even at 1200 C. At 1200 ° C

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there is a tendency for the sample to be slightly damaged, indicating that thermal re-conversion begins on the surface.

table

Heat treatment

Drained

Not drained

C.

Sample 1

Sample 2

Sample 3 Sample 4

untreated

150-200

120-150

150 100-120

700

150

120

120 100

800

120

100

120 100

900

120

100

radial cracks

1000

-

-

- -

1100

-

-

- -

1200

86-100

100-120

- -

1300

-

-

- -

The test results listed in Table II are the time per wear unit, whereby one wear unit corresponds to 0.25 mm. Tool wear was determined by measuring the width of the wear mark that was created on the cutting insert that was engaged with the workpiece. The data obtained are only important with regard to the relative behavior of the leached and unleached samples.

The leached samples gave on average a higher test value than the unleached samples. This may be due to the fact that the non-leached samples are thermally damaged during the wear test. The same damage effect can therefore occur both during the wear tests and during the heat treatments. Thus, when the tool tip engaged with the workpiece is heated to a high temperature, the cobalt phase expands more than the diamond phase, causing cracks to appear on the tool tip within the foremost particle layers. The damaged tool tip is weakened as a result and is therefore no longer as efficient. However, the leached samples are thermally stable up to a higher operating temperature and are therefore not thermally damaged when they are touched with the workpiece.

Examinations with a scanning electron microscope showed that unleached samples showed a different behavior compared to leached samples. In the case of samples that were not leached out, the metallic phase began to emerge from the surface between 700 and 800 ° C, as could be determined with a magnification of 2000 times. After the temperature was raised to 900 ° C., cracks running radially to the center of the sample were found from the rounded cutting edge. The leached samples, however, remained relatively unchanged up to approximately 1300 ° C. The diamond layers were still clean after heat treatment at 1200: C, however, photos taken after heat treatment at 1300: C with 20x magnification were blurred and blurred and photos taken with 100X magnification showed an etched surface with many biosslying crystals. This may be due to the thermal decomposition of the surface, but may also be due to slight oxygen residues in the argon atmosphere provided in the heat treatment furnace.

Example 4

Two diamond bodies (samples IV-1 and IV-2) were produced in accordance with Example 1, but the cemented carbide layer was not ground off. The sample IV-1 was cast with epoxy resin (Epon 826 with methyl anhydride at the nodes and benzyldimethylamine hardener) and the epoxy resin was cured. The surface of the diamond layer was then exposed by grinding the epoxy resin. Sample IV-1 was then held in a boiling mixture of 3 HCl: 1 HN03 for 37.15 hours. After removal from the acid mixture, the potting resin was removed from the cemented carbide layer. The visual inspection showed signs of a slight reaction between the acid mixture and the unexposed surfaces. However, the surface of the carbide layer did not appear to have been significantly affected by the acid. The surface of the diamond layer was then examined with a scanning electron microscope (up to 20 × magnification). The surface of the diamond layer was similar in appearance to the surface of the diamond layer of the leached samples of Example 1. Sample IV-1 was then subjected to X-ray analysis to compare the intensities of the constituents of the metallic phase with those of an unleached sample. The scanning and X-ray studies carried out with a scanning electron microscope showed that the acid had penetrated the diamond layer and had removed a substantial proportion of the metallic phase.

Samples IV-1 and IV-2 were then tested for wear resistance in the same manner as explained in Example 3. A wear value of 120-150 calculated in accordance with Example 3 was found for the leached sample IV-1, while a wear value of 100-120 was determined for the unleached sample IV-2. These test results, from which the superiority of the leached sample can be seen, agree with the results presented in Example 3 and therefore prove that an increase in the performance of the diamond body is achieved by removing the metallic phase in the area of the cutting edge.

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1 sheet of drawings

Claims (15)

637 611 1. Tool part, characterized by a) self-bonded particles of diamond or cubic boron nitride, which make up between 70 and 95 percent by volume of the tool part, and b) a network of interconnected empty pores, which make up between 5 and 30 percent by volume of the tool part and dispersed therein are distributed as well as between the particles and a metallic phase, the latter constituting between 0.05 and 3 percent by volume of the tool part and from (1) a catalyst metal in elementary form from which the metals of group VIII of the periodic system, chromium, manganese and Group comprising tantalum, (2) a mixture of one or more alloyable catalyst metals and one or more alloyable non-catalyst metals, (3) an alloy of at least two catalyst metals or (4) an alloy of one or more catalyst metals and one or more non-catalyst metals. 2. Tool part according to claim 1, characterized in that diamond particles are provided as particles. 2nd PATENT CLAIMS 3. Tool part according to claim 1 or 2, characterized in that the diamond particles have a particle size in the range from 1 to 1000 micrometers. 4. Tool part according to claim 1, characterized in that the particles consist of cubic boron nitride and the metallic phase penetrating the tool part essentially uniformly consists of cobalt, a cobalt alloy or an alloy of aluminum with nickel, manganese, iron, vanadium or chromium as the alloy metal . 5. Tool part according to claims 1 and 4, characterized in that the particles of cubic boron nitride have a particle size in the range between 1 to 300 micrometers. 6. Tool part according to claims 1 to 5, characterized in that the bending strength of the tool part is at least 35 kg / mm2. 7. Tool part according to claims 1 to 6, characterized in that the modulus of elasticity of the tool part is at least 50,000 kg / mm2. 8. Tool part according to claims 1 to 7, characterized in that the self-bonded particles are bound to a sintered hard metal base. 9. A method for producing a tool part according to claims 1 to 8, in which a) a mass of diamond particles or cubic boron nitride particles and a mass of sintering aid material for the respective particle mass is added to a reaction vessel, b) the reaction vessel and its contents are simultaneously exposed to temperatures in the range from 1200-2000 ° C. and pressures of over 40 kb, c) the supply of heat to the reaction vessel is switched off, and d) the abrasive body formed by the process steps a) -c) is removed from the reaction vessel, which consists of the directly bonded particles and the sintering aid material washed in between the particles, characterized in that the material washed into the body is substantially completely removed, so that the portion of this material remaining in the body is only 0.05 to 3 percent by volume of the body. 10. The method according to claim 9, characterized in that as particles diamond particles and as sintering aid (1) a catalyst metal in elemental form from the group VIII metals of the periodic system, chromium, manganese and tantalum, (2) a mixture of one or more alloyable catalyst metals and one or more alloyable non-catalyst metals, (3) an alloy of at least two catalyst metals or (4) an alloy of one or more catalyst metals and one or more non-catalyst metals. 11. The method according to claim 9, characterized in that particles of cubic boron nitride and cobalt as a sintering aid material, a cobalt alloy or an alloy of aluminum with an alloy metal consisting of nickel, manganese, iron, vanadium or chromium are used. 12. The method according to claims 9 to 11, characterized in that the metal is removed from the body by immersing the body in an acid. 13. The method according to claim 12, characterized in that the acid used is aqua regia, nitric acid, hydrochloric acid and / or hydrofluoric acid. 14. The method according to claims 9 to 11, characterized in that the metal is removed from the body by extraction with liquid zinc. 15. The method according to claims 9 to 11, characterized in that the metal is dissolved out of the body by means of electrolysis.