CH653055A5 - CEMENTED CARBIDE BODY. - Google Patents

Description

The present invention relates to the field of cemented carbide parts, having a binder material of cobalt, nickel, iron or their alloys, as well as to the manufacture of these parts. In particular, the invention relates to cutting grains having a surface coating of refractory hard oxide, nitride, boride or carbide.

In the past, different hard refractory coatings have been applied to the surface of the cemented carbide cutting grains to improve the wear resistance of the cutting edge and thus increase the life of the grain. Examples include US Patents 4,035,541, 3,564,683.3 616,506, 3,882,581.3 914,473, 3,736 107.3 967,035.3 955,038.3 836,392 and reissue patent 29,420. Unfortunately, these refractory coatings can reduce the hardness of cemented carbide grains to varying degrees. The degree of degradation depends at least in part on the structure and composition of the coating and the process used for its deposition, so while the refractory coatings have increased the wear resistance of the metal cutting grains, they have not helped reduce the brittleness of the cutting edge to breakage and crumbling, especially in interrupted cutting applications.

Up to now, efforts to improve the hardness or edge strength in coated cut grains have all revolved around the production of a cobalt-enriched layer extending inward from the substrate / coating interface. . It has been found that enrichment with cobalt of the surface layers of certain substrates with porosity C can be carried out during vacuum sintering cycles. These zones enriched in cobalt are characterized by a porosity A while the mass of the substrate has essentially a porosity C. There is generally a depletion in solid carbide solution at various depths and degrees in the regions enriched in cobalt. Cobalt enrichment is desirable in that, as is well known, increasing the cobalt content increases the hardness or impact resistance of cemented carbides. Unfortunately, the level of enrichment produced is difficult to control in substrates with porosity C. Typically, a coating of cobalt and carbon is formed on the surface of the substrate. This coating of cobalt and carbon is removed before the deposition of the refractory material on the substrate, in order to obtain an adhesive bond between the coating and the substrate. Sometimes the level of cobalt enrichment in the layers below the substrate surface is so high that it has an opposite effect on the sidewall resistance. The result is that, sometimes, the layer enriched with cobalt on the sides of the substrate is eliminated by crumbling, leaving the enrichment with cobalt only on the draft faces and the material to be

porosity C on the side. Compared with substrates with porosity of type A or B, substrates with porosity C are not chemically homogeneous. This may result in less control over the formation of the eta phase at the inter-face-coating / substrate (a hard and brittle phase affecting hardness), a reduction in the adhesion of the coating and an increase in the non-uniform coating growth.

By definition, the porosity observed in cemented carbides can be classified in one of the three categories recommended by the ASTM (American Society for Testing and Materials), as follows:

Type A for pore sizes less than 10 microns in diameter.

15 Type B for pore sizes between 10 and 40 microns in diameter.

Type C for irregular pores caused by the presence of carbon inclusions. These inclusions are removed from the sample during metallographic preparation, leaving the irregular pores mentioned above.

In addition to the classification above, a number from 1 to 10 can be assigned to the observed porosity to indicate the degree or frequency of the porosity. The method to be used for this can be found in Cemented Carbides by Dr. P. Schwarzkopf and Dr. R. Kieffer, published by The MacMil-lan Co., New York (1960) at Pages 116-120.

We can also classify cemented carbides according to their content by binding carbon and tungsten. The excess carbon tungsten-cobalt carbide alloys are characterized by a porosity C, which, as already mentioned, are actually inclusions of free carbon. Tungsten carbide-cobalt alloys which are low in carbon and in which the cobalt is saturated with tungsten are characterized by the presence of the eta phase, an MnC or Mf, C carbide, where 35 M represents cobalt and tungsten. Between the extremes of porosity C and the eta phase is a region of composition of intermediate binder alloys, which contain tungsten and carbon in solution at variable levels, but so that there is no carbon free, neither phase eta pre-40 feels. The level of tungsten present in tungsten-cobalt carbide alloys can also be characterized by the magnetic saturation of the binder alloy, since the magnetic saturation of the cobalt alloy is a function of its composition. The magnetic saturation of cobalt saturated with 45 carbon is given at 158 gauss-cmVg of cobalt and is indicative of the porosity of type C, while a magnetic saturation of 125 gauss-cm3 of cobalt is below indicates the presence of the phase eta.

The invention makes it possible, controllably and economically, to produce an enriched layer by bonding near the surface of a body of cemented carbides.

It therefore relates to a body of cemented carbide having a layer enriched by bonding near its surface and having through the whole body a porosity of types A to B. This 55 body comprises a first carbide, a high metal alloy and a solution solid of the first carbide with a second carbide.

The invention also makes it possible to combine the cemented carbide bodies mentioned above with a refractory coating of 60 so as to produce coated cutting grains having both a high wear resistance and a high hardness.

According to the invention, it has been found that a layer enriched in binder could be formed near the peripheral surface of a cemented carbide body using the following method. 65 The process consists in grinding and mixing a powder of a first carbide, a powder of binder and a powder of a chemical agent chosen from the group of metals, alloys, hydrides, nitrides and carbonitrides of the transition elements.

653,055

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of which the carbides have a free energy of formation more negative than that of the first carbide in the region of the melting point of the binder, then sintering or subsequently treating with heat a block of the mixed materials so as to at least partially transform the chemical agent in its carbide.

According to the present invention, this method can be used to produce an enriched layer by bonding near the peripheral surface of a cemented carbide body, preferably having, in practice, only a porosity of type A and B inside the body. Enrichment can also be obtained in cemented carbide bodies having carbon levels ranging from the eta phase to porosity C.

Preferably, the cemented carbide bodies according to the invention present under the layer enriched with binder, a layer partially depleted in binder.

Preferably, the first carbide is tungsten carbide. Preferably, the binding alloy can be cobalt, nickel, iron or their alloys, advantageously cobalt.

Preferably, the chemical agent is chosen from hydrides, nitrides and carbo-nitrides, elements from groups IVB and VB. This chemical agent is preferably added in small but effective amount, advantageously from 0.5 to 2% by weight of the powder. Very advantageously, the chemical agent is titanium nitride or titanium carbo-nitride.

It has been found that normally the layer enriched in binder is at least partially depleted in solid carbide solution. It has also been found that under this layer depleted in solid solution is a layer which is enriched in solid solution of carbides.

The cemented carbide bodies according to the invention may have, or cutting edge formed at the junction of a draft surface and a flank surface, a hard and dense refractory lining adhering to these faces. The layer enriched with binder can be removed from the side before affixing the coating.

The refractory lining preferably composed of one or more layers of oxide, carbide, nitride, boride or metallic carbo-nitride.

The invention will be better understood with reference to the appended drawing, in which:

Figure 1 is a schematic sectional view of a coated metal cutting grain, in one embodiment according to the present invention.

Figure 2 is a graphical representation of typical cobalt enrichment levels produced in a cemented carbide body, as a function of the depth below the draft surface.

Figure 3 is a graphical representation of the variation in relative concentrations of binder and solid carbide solution as a function of the depth below the draft surface. This figure corresponds to the sample of Example 12.

As indicated above, the process consists in thermally treating a block of cemented carbide containing an element whose corresponding carbide has a more negative formation energy than that of tungsten carbide, in a zone of high temperature, close to the melting point of the binder. For cut grain applications, this element or chemical agent can be chosen from the transition metals of groups IVB and BV, their alloys, nitrides, carbonitrides and hydrides. It has been found that the layer of material adjacent to the periphery of the body of cemented tungsten carbide can be appreciably enriched with binder and, generally, at least partially depleted in solid carbide solution, during sintering or annealing. a temperature above the melting point of the binder alloy, all of this by incorporating additions of nitrides into the powder charge,

hydrides and carbonitrides of groups IVB and VB.

During sintering, these additions of groups IVB and VB react with the carbon to form a carbide or a carbonitride. These carbides or carbonitrides can be present, partially or entirely, in solid solution with tungsten carbide and with any other carbide present. Typically, the level of nitrogen present in the final sintered carbide is reduced relative to the level of nitrogen added as nitride to carbonitride, since these additions are unstable at elevated temperatures above and below the point of melting of the binding alloy, which will lead to at least partial volatilization of the nitrogen out of the sample if the sintering athmosphere contains a nitrogen concentration lower than its equilibrium vapor pressure.

If the chemical agent is added as a metal, alloy or hydride, it will also be transformed into cubic carbide, typically into a solid solution with tungsten carbide and any other carbide present. The hydrogen from any added hydride is volatilized during sintering.

One can use, alone or in combination, tantalum titanium, niobium, hafnium metal, hydride, nitride and carbo-nitride to bring about a significant enrichment in cobalt during sintering or the subsequent heat treatment, tungsten alloys and cobalt carbide having a very variable carbon content. It has been found that additions up to approximately 15% by weight are usable. It is believed that zirconium and vanadium metal, nitride, carbonitride and hydride can also be used for this purpose. In alloys of porosity A and B and in carbon-deficient alloys containing the eta phase, carbon enrichment occurs without peripheral encapsulation of cobalt or carbon, thus eliminating the need to rid the surfaces of cemented carbide of excess cobalt and carbon before applying the refractory coating.

For carbide / tungsten cobalt-based alloys, additions of approximately 0.5 to 2% by weight are preferred, especially titanium in the form of titanium nitride or carbo-nitride. Since titanium nitride is not completely stable during vacuum sintering, causing at least partial volatilization of nitrogen, it is preferred to add one Vi mole of carbon per mole of leaving hydrogen, in order to maintain the carbon at the level necessary for the bonding alloy in tungsten poor in cobalt. It has been found that enrichment in cobalt by heat treatment of alloys based on tungsten carbide / cobalt occurs more easily when the alloy contains a tungsten binder poor in cobalt. Preferably, the cobalt-poor tungsten binder has a magnetic saturation of between 145 and 157 gauss-cm3 / g. The addition of titanium nitride, together with the necessary addition of carbon, in powder mixtures based on tungsten carbide / cobalt allows the formation of an alloy with cobalt binder having a magnetic saturation between 145 and 157 gauss-cm3 / f, an alloy which is usually difficult to obtain. Although a cobalt binder alloy having magnetic saturation is preferred as indicated above, it is also possible to enrich alloys containing tungsten binder alloys saturated with cobalt (less than 125 gauss-cm3 / g).

It has been noted that the presence of a layer enriched with cobalt of more than 6 microns results in a significant improvement in the solidity of the edge of the cut grains of cemented carbide coated and refractory. Although cobalt enrichments of up to 125 microns in depth can be obtained, for coated grain applications, a cobalt-enriched layer having a thickness of 12 to 50 microns is preferred. It is also preferred that the cobalt content of the cobalt-enriched layer on a

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cutting grain coated with refractory is between 150 and 300% average cobalt content, as measured on the surface by X-ray analysis (dispersive energy).

It is believed that binder enrichment must take place in all tungsten carbide / binder / cubic carbide alloys (for example tantalum, niobium, titanium, vanadium, hafnium, zirconium) which does not sinter into a continuous carbide skeleton. These alloys, containing at least 3% by weight of binder, must be enriched using the process described. However, for cut grain applications, a binder content of between 5 and 10% by weight of cobalt and a total cubic carbide content of 20% or less is preferred. Cobalt is the preferred binder, but other binders can be used in place of cobalt, such as nickel, iron and their alloys with each other, as well as with cobalt. Other binding alloys containing nickel or cobalt or iron can also be used.

The sintering and heat treatment temperatures used to obtain the binder enrichment are the typical liquid sintering temperatures. For cobalt-based alloys, these temperatures range from 1285 to 1540 ° C. Sintering cycles should be at least 15 minutes at these temperatures. Results can be optimized by controlling the cooling rates from processing temperatures to temperatures below the melting point of the binder alloy. These cooling rates can be between 25 and 85 ° C per hour, preferably between 40 and 70 ° C per hour. Advantageously, the heat treatment cycle for cutting grain substrates having a cobalt binder is from 1370 to 1500 ° C for 30 to 150 minutes, followed by cooling at the rate of 40 to 70 ° C per hour up to 1200 ° C. The pressures during the heat treatment can vary from 10 ~ 3 torr up to and including the high pressures typically used in hot isostatic pressing. The preferred pressures are between 0.1 and 0.15 torr. If additions of nitride or carbonitride are used, the vapor pressure of nitrogen in the sintering atmosphere is preferably below the equilibrium pressure, so as to allow volatilization of the nitrogen outside the substrate.

The initial enrichment occurs during sintering, but the subsequent grinding steps in the manufacturing processes of the metal cutting grains can remove the enriched areas. In these cases, a subsequent heat treatment can be used according to the above parameters, to develop a new enriched layer below the peripheral surfaces.

Substrates enriched with binder which are used in the coated cutting grains may exhibit enrichment by binding both on the draft surface and on the flanks. However, depending on the type of cutting grain desired, the enrichment by binding on the sides can be removed, without this being necessary in order to obtain optimum performance in all cases.

The substrates enriched in binder can be coated according to well-known refractory coating techniques. The refractory coating applied may have one or more layers comprising materials chosen from carbides, nitrides, borides and carbonitrides of groups IVB, VB, as well as aluminum oxide or oxynitride. However, it has been noted that it is possible to obtain both good solidity of the cutting edge and sidewall resistance by combining a substrate having a layer enriched with a binder according to the invention with an aluminum oxide coating on a layer. inner titanium carbide; or an inner layer of titanium carbide; or an inner layer of titanium carbide bonded to an intermediate layer of titanium carbonitride, which is bonded to an outer layer of titanium nitride or titanium nitride bonded to an inner layer of titanium carbide. A cemented carbide body having a layer enriched with a binder according to the invention is preferred, combined with a coating of titanium carbide / aluminum oxide. In this case, the coating has a thickness of 5 to 8 microns.

FIG. 1 represents an embodiment of a coated metal cutting grain 2. The cutting grain 2 consisting of a substrate or body 12 of cemented carbide having a layer 14 enriched with binder and a layer 16 depleted in binding above the mass 18 of the substrate 12, which has a chemistry substantially identical to the chemistry of the original powder mixture.

A layer 14 enriched with binder is present on the relief faces 4 of the cemented carbide body, but it has been eliminated from the sidewalls 6. Inward relative to the layer 14 enriched with binder is a zone 16 depleted in binder . This zone 16 depleted in binder develops, has it been noted, at the same time that the layer enriched in binder when the cemented carbide bodies are produced according to the process described.

Zone 16 depleted in binder is also enriched in solid carbide solution. The enriched layer 14 is partially depleted in solid carbide solution. Inside the zone 16 depleted by binding is the mass of the substrate 18.

A cutting edge 8 is formed at the junction of the relief faces 4 and the sides 6. The cutting edge 8 is shown here polished, and polishing is not necessary for all applications. It can be seen in FIG. 1 that the layer 14 enriched with binder extends as far as the zone of the cutting edge and, preferably, is adjacent to a part, or even to the entire polished edge 8. The zone 16 depleted in binder extends towards the sides 6 just below the cutting edge 8. A refractory lining 10 has been adhered, on the peripheral surface of the body 12 of cemented carbide.

The following examples illustrate the invention.

In these examples, the amounts and proportions are given in percentages by weight of metals added.

Example 1

A mixture containing 7000 grams of powder is ground, then it is thoroughly mixed for 16 hours with a paraffin, a Surfactant, a solvent, and tungsten carbide cycloids bonded to cobalt, in the proportions indicated below;

10.3% Ta (C)

5.85% Ti (C)

0.2% Nb (C)

8.5% Co

1.5% Ti (N) - 102.6 g WC + C to produce a binding alloy of 2% W-98% Co 2% paraffin (Sunoco 3420 from Sun Oil Co.)

2.5 1 solvent (perchlorethylene)

14 g Surfactant (Ethomeen S-15 from Armor Industriai chemical Co.)

Parts of square inserts having dimensions of 15.1 mm x 15.1 mm x 5.8 to 6.1 mm and a weight of 11.6 grams are compressed under a force of 8200 kg. The plates are then sintered under vacuum at 1496 ° C for 30 minutes, then cooled to room temperature in the oven. After sintering, the wafers weigh 11.25 grams and have dimensions of 13.26 mm x 13.26 mm x 4.95 mm. The plates are then brought to standard SNG433, as follows (this identification number is based on the standards of

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the American Standards Association, which have been widely adopted by the cutting tool industry. The international designation is: SNGN 12 04 12):

1. The upper and lower faces (draft faces) of the inserts are planed to a thickness of 4.75 mm.

2. The wafers are then heat treated at 1427 ° C for 60 minutes under a vacuum of 100 microns, then cooled at the rate of 56 ° C per hour to 1204 ° C, and finally cooled to the ambient conditions of the oven.

3. The periphery (flanks) is planed to produce a square of 12.70 mm side and the cutting edges are polished to a radius of 0.064 mm.

A coating of titanium carbide / titanium carbonitride / titanium nitride is then applied to the wafers using the vapor deposition techniques in the following order:

Table I

Coating Coating reactions

Type Temperature Pressure

1.

982-

-1025 ° C

H:

~ 1 atm. TiCU + CH4 TiC (s) + 4HC1

Tic

H:

2.

982-

O KJ

o o

~ 1 atm. TiCU + '/ iNz TiCN (s) + 4HC1

TiCN

3.

982-

u o

O IO O

~ 1 atm. TiCU + 2Hz + 'AN2 -

TiN

TiN (s) + 4HCI

In parallel with the preparation of the above platelets, platelets are prepared from the same mixture of starting powder, but without the titanium nitride and the carbon addition which accompanies it. The micro-structural data obtained for the coated wafers are indicated below (Table I).

Example 1 Example 1 without TiN with TiN

Porosity

Al

Al, B2

(mass, no

enriched)

Al (enriched)

Thickness of the enriched zone

Any

~ 22.9 microns cobalt

(area of

bare

only)

Thickness of the area

Any

~ 22.9 microns depleted in solid solution

(area of

bare

only)

Thickness of the Eta phase of

4.6 microns 3.3 microns substrate / TiC interface

Coating thickness

Tic

5.6 microns 5.0 microns

TiCN

2.3 microns 3.9 microns

TiN

1.0 microns 1.0 microns

Example 2

The procedure is as described in Example 1, with the same starting powders (with and without TiN and the addition of carbon which accompanies it). The plates are sintered at 1406 ° C for 30 minutes under a vacuum of 25 microns, then cooled to ambient oven temperatures. They are then polished (0.064 mm in radius) and subsequently coated with TiC / TiCN / TiC, in the vapor phase according to the techniques described in Table 1.

In this example, it should be noted that the cobalt-enriched layer is present both on the flanks and on the draft surfaces. The evaluation of the coated wafers gives the following result:

Example 2 Example 2 without TiN with TiN

Porosity

edges A-l enriched area A-2

center A-3 mass A-4

Thickness of the enriched zone

None up to 22.9

in cobalt microns

Thickness of the area

None partial and depleted in intermittent solid solution

up to 21

microns

Eta phase thickness of up to 5.9 3.3 microns TiC substrate interface

microns

Coating thickness

Tic

2.0 microns 1.3 microns

TiCN

1.7 microns 1.0 microns

TiN

8.8 microns 7.9 microns

Average hardness (mass) in

91.2 91.4

Rockwell "A"

Coercive force He

138 estreds 134 estreds

Example 3

A mixture comprising the materials indicated below is loaded into a cylindrical mill, with a surfactant, a fugitive binder, a solvent and 114 kg of cycloids.

85.15%

WC (2-2.5 microns: size of the

15,000 g

particle)

WC (4.5 microns: size of the

27.575 g

particle)

5.98%

TaC

2.990 g

2.60%

TiN

1,300 g

6.04%

Co

3.020 g

0.23%

C (Ravin 410 - a product of

115g

Industrial Carbon Corp.)

50,000 g

The powder is then brought to a total carbon percentage of 6.25% by weight. The mixture was ground for 90,261 revolutions to obtain an average particle size of 0.90 microns. The mixture is then sieved in the wet phase, dried and passed through a hammer mill. The blocks are formed by pressing, then sintered at 1454 ° C for 30 minutes, followed by cooling under ambient conditions of the oven.

This treatment produces a sintered block having an overall magnetic saturation (that is to say including the material enriched in binder) of 117 to 121 gauss-cm3 / g cobalt. By micro-strutural evaluation of the sintered block, it can be seen that the eta phase is present throughout the part, that the porosity is of type A-2 to B-3, that the thickness of the zone enriched in cobalt is approximately 26.9 microns and that the thickness of the area depleted in solid solution is approximately 31.4 microns.

Example 4

A cell of a mill measuring 190 mm in internal diameter and 194 mm in length is internally filled with a tungsten carbide / cobalt alloy. An additional 17.3 kg of 3.2 mm tungsten carbide / cobalt cycloids are added. These materials are ground and mixed together by rotating the mill cell around its cylindrical axis to

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at 85 rpm for 72 hours (367,200

turns).

Load composition

283g

(4.1%)

TaC

205g

(3.0%)

NbC

105g

(1.5%)

TiN

7.91g

(0.1%)

VS

381g

(5.5%)

Co

5946 g

(85.5%)

WC

105g

Sunoco 3420

14g

Ethomeen S-15

2500 ml

Perchlorethylene

The mixture was adjusted to have a binder alloy comprising 2% W for 98% Co. After grinding and mixing, sieving in the wet phase to remove the particles of too large size and the contaminating agents then drying at 93 ° C. under atmosphere of nitrogen and finally we mill in a hammer mill to break up the agglomerates, in a Fitzmill, Fitzpatrick Co. J-2 mill.

Using this powder, blocks are pressed and sintered at 1454 ° C for 30 minutes, followed by cooling to ambient conditions.

The upper and lower faces (that is to say the undercut faces of the wafer) are planed up to the final thickness, then the heat treatment is carried out at 1427 ° C. under a vacuum of 100 microns. After 60 minutes at this temperature, the plates are cooled at the rate of 56 ° C per hour to 1204 ° C, then to the ambient conditions of the oven. The peripheral surface (or flanks) is then planed to obtain a square of 12.70 mm on the side and the cutting edges are polished to a radius of 0.064 mm. The treatments lead to a substrate for wafers in which only the draft faces have a zone enriched in cobalt and depleted in solid solution, these same zones having been eliminated from the sides.

These wafers are then loaded into a reactor for coating with a thin layer of titanium carbide using the vapor deposition technique. The hot zone containing the wafers is first heated from room temperature to 900 ° C. During this heating period, hydrogen is admitted at the rate of 11.55 liters per minute. The pressure inside the reactor is maintained slightly under the atmospheric pressure. The hot zone is then brought from 900 ° C to 982 ° C. During this second temperature rise, the reactor pressure is maintained at 180 torr and a mixture of titanium tetrachloride and hydrogen is admitted into the reactor, and d pure hydrogen at a rate of 15 liters per minute and 33 liters per minute respectively, the mixture of titanium tetrachloride and hydrogen being obtained by passing hydrogen gas through a vaporizer containing titanium tetrachloride at a temperature of 47 ° C. Maintaining the temperature at 980 ° C., methane is also admitted into the reactor at the rate of 2.5 liters per minute, the pressure inside the reactor being reduced to 1 ^ 0 torr. Under these conditions, titanium tetrachloride reacts with metane in the presence of hydrogen to form titanium carbide on the hot surface of the wafers. These conditions are maintained for 75 minutes, after which the flow of titanium tetrachloride, hydrogen and methane is stopped. The reactor is then allowed to cool by admitting argon at the rate of 1.53 liters per minute, under a pressure slightly lower than atmospheric pressure. Examination of the microstructure of a final wafer reveals a zone enriched in cobalt extending inwards to a depth of 22.9 microns and a zone depleted in solid solution of cubic carbide extending towards inside up to 19.7 microns from draft surfaces. It is estimated that the porosity in the enriched zone and in the rest of the substrate is between A-1 and A-2.

Example 5

The following materials are mixed and ground together in two stages:

Stage I (489,600 laps)

141.6 g

(2.0%)

TaH

136.4g

(1.9%)

TiN

220.9 g

(3.1%)

NbC

134.3g

(1.9%)

TaC

422.6 g

(5.9%)

Co

31.2g

(0.4%)

VS

14g

Ethomeen S-15

1500 ml

Perchlorethylene

Stage II

(81,600 turns)

6098 g

(84.9%)

WC

140g

Sunoco 3420

1000 ml

Perchlorethylene

These values were adjusted to obtain an alloy binding at 2% W and 98% Co.

The test wafers are then manufactured and coated with TiC according to what was described in Example 4.

The evaluation of the micro-structure of the coated wafers reveals a porosity of type A-1, both in the material enriched with cobalt and in the mass proper. The cobalt-enriched zone and the zone depleted in solid solution extend inward from the draft surface to depths of approximately 32.1 and 36 microns respectively.

Example 6

A mill cell having an internal diameter of 190 mm is loaded with the following materials:

283g

(4.1%)

TaC

205g

(3.0%)

NbC

105g

(1.5%)

TiN

7.91g

(0.1%)

VS

381g

(5.5%)

Co

5946 g

(85.8%)

WC

140g

Sunoco 3420

14g

Ethomeen S-15

2500 ml

Perchlorethylene

Mixture intended to produce a binding alloy at 2% W and 98%

Co.

In addition, cycloids are added and the mixture is ground for four days. This is then dried in a Sigma mixer at 121 ° C under partial vacuum, after which it is sieved with Fitzmill through a 40 mesh sieve.

SNG433 wafers are then manufactured according to the technique described in Example 4. However, in this example, the wafers are coated by vapor deposition with a TiC / TiN coating. The coating process used is as follows:

1. TiC coating

The samples are kept in the coating reactor at an approximate temperature of 1026 to 1036 ° C under a vacuum of 125 torr. Hydrogen is admitted as carrier gas in a TiCU vaporizer at the rate of 44.73 liters per minute, the vaporizer being maintained under vacuum at a temperature of 33 to 35 ° C. TiCU vapors are

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entrained in the carrier gas H2 and admitted to the coating reactor. In this reactor, free hydrogen and free methane are also admitted at the rate of 19.88 and 3.98 liters per minute respectively. These conditions are now. bare for 100 minutes and produce a dense coating of TiC adhering to the surface of the substrate.

3. TiC coating

A mixture of H2 + TiCU and methane at a rate of 3.1 liters per minute is admitted to the reactor for 25 minutes at the rate of approximately 92 liters per minute. The TiCU vaporizer is maintained at approximately 0.4 atmospheres and 30 ° C.

2. TiN coating

The methane flow in the reactor is interrupted and N2 is admitted at the rate of 2.98 liters per minute. These conditions are maintained for 30 minutes and produce a dense coating of TiN adhering to the coating of TiC.

The evaluation of the coated wafers gives the following results:

Porosity

Thickness of the cobalt-enriched zone

Thickness of the depleted zone in solid solution Thickness of the eta phase Thickness of the TiC TiN coating

Average hardness of the mass in Rockwell "A"

Coercive force, He

A-l, mass

17.0 to 37.9 microns up to 32.7 microns up to 3.9 microns

3.9 microns 2.6 microns 92.0

98 estreds

Example 7

A mixture of materials is prepared using a two-stage milling cycle:

In step I, a mill cell having an internal diameter of 181 mm and a length of 194 mm is loaded with 17.3 kg of WC-Co 4.8 mm cycloids. The mill is rotated around its cylindrical axis at the rate of 85 revolutions per minute for 48 hours (244,800 revolutions).

140.8 g (2.0%) Ta

72.9 g (1.0%) Ti H

23.52 g (0.3%) C

458.0 g (0.3%) Co

30 g Ethomeen S-15

120 g Sunoco 3420

1000 ml Soltrol 130 (one solvent)

In stage II, 6314 grams (90.2%) WC and 1500 ml of Soltrol 130 are added and the mill is restarted for 16 hours (81 600 revolutions). The mixture was calculated to produce a binder alloy of 5% W and 95% Co. After mixing, sieving in the wet phase through a 400 mesh sieve, then drying under nitrogen at 93 ° C for 24 hours and sieving Fitzmill through a 40 mesh screen.

Test samples are pressed uniaxially under a total force of 16,400 kg to dimensions of 15.11 mm x 15.11 mm x 5.28 mm (8.6 grams / cm3).

These samples are then sintered at 468 ° C for 150 minutes under a vacuum of 1 micron. They are then cooled under the ambient conditions of the oven. Graphite flakes were used to separate the wafer from the graphite sintering trays.

The wafers as sintered are polished to a radius of 0.064 mm and then coated with a TiC / TiCN / TiN coating according to the following process:

1. The plates are placed in the reactor and the air is purged by a flow of hydrogen.

2. The wafers are heated to approximately 1038 ° C while maintaining the flow of hydrogen through the reactor. The pressure of the coating reactor is kept slightly higher than atmospheric pressure.

4. TiCN coating

The flow of H2 + TÌCI4, 10 is maintained for 13 minutes while the flow of methane is reduced by half. Finally, N2 is introduced into the reactor at the rate of 7.13 liters per minute.

5. TiCN coating

For 12 minutes, the methane flow is stopped and the hydrogen flow is doubled. When the TiN coating is finished, both the flow of H2 + TÌCI4 and N2 are interrupted, the heating elements of the reactor are cut and the latter is purged with free hydrogen until the temperature drops. -20 ture is dropped around 250 ° C. At 250 ° C, the reactor is purged with nitrogen.

It was then determined that the wafer substrates have a porosity A-1 to A-2 in the mass. A zone enriched in cobalt and a zone depleted in solid solution extend from the surfaces approximately 25 and 23 microns respectively. The unenriched interior has a hardness of 91.7 Rockwell "A". The coercive force Hc, of the substrate is measured at 186 estreds.

30

Example 8

260 kg of a powder mixture having carbon equilibrated with a C3 / C4 porosity are produced in the final substrate, using the following two-step process:

Stage I

The charge having the following composition is ground for 96 hours:

10 108 g

TaC (6.08% carbon)

7,321 g

NbC (11.28% carbon)

3,987 g

TiN

1,100 g

C (Molocco noir- a product of the Industrial

Carbon Corp.)

16 358 g

Co

500 g

Ethomeen S-15

364 kg

4.8 mm Naphta Co-WC cycloids

50 Stage II

The following mixture is added to this mixture:

221.75 kg WC (6.06% carbon)

5.0 kg Sunoco 3420 Naphta

55 and the milling is continued for 12 hours.

It is then sieved in the wet, dry phase and ground with Fitzmill.

Platelet samples are then pressed, then fried-60 t at 1454 ° C for 30 minutes. The sintering procedure produces a zone enriched in cobalt covering the mass having a porosity C3 / C4. The sintered samples are planed and polished to SNG433 standards, removing the zone enriched in cobalt.

The sintered wafers are placed in open graphite containers 65 lined with graphite flakes. This assembly is then hot pressed isostatically (HIP) at a temperature of 1371 to 1377 ° C for one hour under an atmosphere of 25% N2 and 75% He by volume, at a pressure of 8.76 x 108

9

653,055

dyne / cm2. Examination of the microstructure of a HIP sample reveals an area enriched in cobalt about 19.7 microns deep. A surface of 4 microns of cobalt and a surface of 2 microns of carbon were also produced as a result of the porosity of the substrates used, of type C.

Example 9

We pass a batch containing the following materials to the ball mill:

30.0%

WC (1.97 microns, medium size

750 kg

particles)

51.4%

WC (4.43 microns, medium size

1286 kg

particles)

6.0%

Co

150 kg

5.0%

WC-TiC carbide in solution in

124.5 kg

solid solution

6.1%

Carbide TaWC in solid solution

152 kg

1.5%

W

37.5 kg

This mixture was loaded with 6% total carbon. These materials are ground during 51,000 revolutions with 30,409 kg of cycloids and 798 liters of Naphta. This produces the final particle sizes of 0.82 microns.

500 grams of powder are separated from the ground mixture, to which the following materials are added:

1.9% TiN (previously ground to 96.9 gm approximately 1.4 to 1.7 microns)

0.2% C (Ravin 410) 9.4 gm

1500 ml Perchlorethylene

These materials are ground for 16 hours in a 190 m internal diameter cell loaded with tungsten carbide and containing 50% by volume of cycloids (17.3 kg). Once the grinding is finished, sieving in the wet phase on a 400 mesh screen, drying under partial vacuum in a mixer at 121 ° C and passing to Fitzmill through a 400 mesh screen.

SNG433 samples are pressed using a force of 3600 kg to produce a density of 8.24 gm / cm3 and a sample height of 5.84 to 6.10 mm.

These samples are sintered at 1454 ° C for 30 minutes on an NbC powder, under a vacuum of 10 to 25 microns, after which they are allowed to cool to oven temperature. The sintered samples have dimensions of 4.93 mm x 13.31 mm squared, a density of 13.4 gm / cm3 and an overall magnetic saturation of 146 to 150 gauss-cm3 / g Co. Evaluation of the microstructure of these samples shows a porosity A through the entire sample and a layer enriched in cobalt of about 21 microns thick.

The upper and lower surfaces of the plates are planed to a total thickness of 4.75 mm. These wafers are then heat treated at 1427 ° C for 60 minutes under a vacuum of 100 microns, followed by cooling to 1204 ° C at a rate of 56 ° C per hour, then at oven temperature.

The sides of each plate are planed to 12.7 mm squared and the polished edges to 0.064 mm radius.

These plates are then coated in the vapor phase with titanium carbide / aluminum oxide according to the following technique:

The wafers are placed in a coating reactor and heated approximately from 1026 to 1030 ° C while maintaining the pressure between 88 and 125 torr. Hydrogen gas is passed at the rate of 44.73 liters per minute through a vaporizer containing TiCU, at a temperature of 35 to

38 ° C under vacuum. The TiCU vapors are entrained by hydrogen and are admitted to the coating reactor. Simultaneously, hydrogen and methane are admitted to the reactor at the rate of 19.88 and 2.98 liters per minute respectively. These vacuum, temperature and flow conditions are maintained for 180 minutes to produce an adherent coating of TiC on the wafers. The flow of hydrogen in the vaporizer and the flow of methane in the reactor are interrupted. Hydrogen and chlorine io are then admitted into a generator containing aluminum particles, at a temperature of 380 to 400 ° C under a pressure of 0.034 atmospheres. Hydrogen and chlorine enter the generator at the rate of 19.88 liters per minute and 0.8 to 1 liter per minute respectively. The chlorine reacts with the aluminum 15 to form vapors of AlCb which are then admitted into the reactor. While hydrogen and AICh enter the reactor, CO2 is also admitted at the rate of 0.5 liters / minute. These flows are maintained for 180 minutes during which the platelets are maintained at a temperature of 1026 to 1028 ° C under an approximate vacuum of 88 torr. This process produces a dense coating of AI2O3 adhering to the inner coating of TiC.

The evaluation of the coated wafers gives the following results:

25

Porosity

Thickness of the zone enriched in cobalt (inclined surface) 30 Thickness of the zone depleted in solid solution (draft surface) Thickness of the TiC coating

35 AI2O3

Average hardness in Rockwell A of the mass of the substrate Coercive force Hc

Al in the enriched zone, Al with B dispersed in the mass approximately 39.3 microns up to 43.2 microns

5.9 microns 2.0 microns 91.9 microns

170 estreds

40 Example 10

We start from the initial batch described in Example 2, from which a 5000 g sample is taken. TiCN ground to 95.4 g (1.9%) and Ravin 410 carbon black at 1.98 g (0.02%) are added to this material. Mixed for 16 45 hours, sieved, dried, passed to Fitzmill in accordance with Example 9.

The test samples were passed through a sintered tablet press under vacuum at 1496 ° C. for 30 minutes, then cooled to oven temperature, according to the rate of cooling of said oven. The evaluation of the sintered samples gives the following result:

Porosity

Thickness of the zone enriched 55 in cobalt Thickness of the zone depleted in solid solution Average hardness in Rockwell A of the mass of the substrate 60 Magnetic saturation Coercive force

A-1, mass approximately 14.8 microns up to 19.7 microns 92.4

130 gauss-cm3 / g Co 230 œrsteds

Example 11

We start from the initial batch of Example 9 from which we take a sample of 5000 g. Pre-ground TiCN is added in an amount of 95.4 g (1.9%), then mixed for 16 hours, sieved, dried and passed through Fitzmill in accordance with Example 9. Des

653,055

10

test samples are then pressed and sintered at 1496 ° C, together with the samples of Example 10.

The evaluation of the sintered samples of this example gives the following results:

Porosity Al, mass with a heavy eta phase

Thickness of the enriched zone approximately 12.5

in cobalt microns

Thickness of the zone up to 16.4 microns depleted in solid solution

Average hardness in Rockwell 92.7

Has mass

Magnetic saturation 120 gauss-cmVg Co

Coercive force He 260 estreds

Example 12

We proceed as described above, according to a two-stage grinding cycle:

Stage I

The following materials are added to a mill cell with an inside diameter of 181 mm and a length of 194 mm loaded with 17.3 kg of WC-Co 4.8 mm cycloids. The cell is rotated around its cylindrical axis at 85 revolutions per minute for 48 hours (244,800 revolutions).

455 g

(6.5%)

Or

280g

(4.0%)

TaN

112g

(1.6%)

TiN

266g

(3.8%)

NbN

42.7g

(0.6%)

Carbon

14.0g

Ethomeen S-15

1500 ml

Perchlorethylene

Stage II

The following materials are then added to the cell and rotated for another 16 hours (81,600 revolutions):

5890 g (83.6%) WC 105 g Sunoco 3420

1000 ml Perchlorethylene

The mixture was calculated to produce a 10% W - 90% Ni binder alloy. The wet mixture is discharged from the cell, then sieved in the wet phase through a 400 mesh sieve (Tyler), dried at 93 ° C. under a nitrogen atmosphere and passed through a Fitzmill sieve. 40 Mesh.

The test samples are pressed in a sintered tablet press at 1454 ° C for 30 minutes under a nitrogen atmosphere at a pressure of 6.9 x 104 dyne / cm2. Then allowed to cool to the oven temperature, at the rate of cooling of said oven. After sintering, the samples are treated by isostatic hot pressing (HIP) at 1370 ° C for 60 minutes under a helium atmosphere at 1 x 109 dynes / cm2. The optical metallographic evaluation of the samples thus treated shows that the material has a porosity A-3 and has a zone depleted in solid solution with a thickness of approximately 25.8 microns.

Subsequently, the sample was re-prepared, which was examined by energy dispersive x-ray (EDX) analysis at various distances from the draft surface. FIG. 3 is a graphic representation of the variations in relative concentrations of nickel, tungsten, titanium and tantalum as a function of the distance from the draft surface. It is clearly seen that, near the surface, there is a layer where the titanium and tantalum, forming carbides are there in solid solution with tungsten carbide, are at least partially deficient in quantity. This zone depleted in solid solution extends inward over approximately 70 microns. The difference between this value and the value reported above is probably due to the fact that the sample was re-prepared between the measurements, so that, in each evaluation, different plans were examined.

We find a layer enriched with nickel (see Figure 3) corresponding to the depletion of titanium and tantalum. The concentration of nickel in the enriched layer decreases, as the distance from the draft surface decreases from 30 to 10 microns. This indicates that the nickel in this area was partially volatilized during the vacuum sintering.

It is believed that the 110 micron peak in the titanium and tantalum concentration is due to the random scanning of one or more large inclusions with a high concentration in these elements.

The two horizontal parallel lines show the typical dispersion obtained by analyzing the mass of the sample around the nominal chemical mixture.

Example 13

The following mixture was loaded, using the two-stage milling cycle described below:

Stage I

The following materials are ground according to step I of Example 12:

455 g

(6.4%)

Or

280g

(3.9%)

TaH

112g

(1.6%)

TiN

266g

(3.7%)

NbN

61.6g

(0.9%)

C Ravin 410, 502

14 g

Ethomeen S-15

2500 ml

Perchlorethylene

Stage II

The following materials are added to the molding cell, and the mixture is rotated for an additional 16 hours:

5980 g (83.6%) WC 140 g 'Sunoco 3420

The mixture was calculated to produce a 10% W and 90% Ni binder alloy.

After discharging the mixture, it is sieved, dried and passed through a Fitzmill according to example 12.

Test samples are sintered in vacuo, after pressing, at 1466 ° C for 30 minutes under a pressure of 35 microns. The sintered samples have a porosity A-3 and have an area depleted in solid solution of 13.1 microns thick.

Example 14

A mixture is treated according to the following two-stage milling cycle:

Stage I

The following materials are added to a mill cell with an internal diameter of 190 mm and a length of 194 mm loaded with 17.3 kg of WC-Co 4.8 mm cycloids. The mill is rotated around its axis at the rate of 85 revolutions per minute for 48 hours (244,800 revolutions):

5

10

15

20

25

30

35

40

45

50

55

60

65

11

653,055

177 g (2.5%) HfHi

182.3 g (2.5%) TiHi

55.3 g (0.8%) Carbon

459 g (6.4%) Co

14 g EthmeenS-15

2500 ml perchlorethylene

Stage II

The following materials are then added and the mill is rotated for an additional 16 hours (81,600 revolutions):

6328 g 140 g

(87.9%)

WC

Sunoco 3420

The mixture was calculated to produce a 10% W and 90% Co. binder alloy.

The wet material obtained is discharged, then sieved in the wet phase through a 400 mesh screen, dried at 93 ° C. under a nitrogen atmosphere and passed to the Fitzmill through a 40 mesh screen.

Wafer samples are pressed, then sintered at 1468 ° C for 30 minutes under a vacuum of 35 microns, which allows the volatilization of the majority of the hydrogen present in the samples. During sintering, the samples were deposited on an NbC powder.

The sintered samples have a porosity A-2 in the enriched zone and a porosity A-4 in the rest of the sample, not enriched. These samples have a medium hardness Rockwell

"A" of 90, a zone depleted in solid solution of 9.8 microns thick and a coercive force, He, of 150 estreds.

5 Example 15

A batch of materials having the composition described in Example 9 is mixed, ground and pressed into platelets. The plates are then sintered, planed, heat treated and planed (the sides only), according to, in practice, the hard process described in Example 9. However, a cooling rate of 69 ° C. was used. / hour in the final heat treatment.

A wafer is analyzed by X-ray analysis (EDX) at various distances from the deposition surfaces. The results of this analysis are shown in the graph in Figure 2. They indicate the existence of a cobalt-enriched layer extending inwardly from the draft surfaces to a depth of approximately 25 microns , followed by a layer of partially cobalt-depleted material extending inward approximately 90 microns from the draft surfaces. Although this is not shown in the graph of Figure 2, we have found in the layer enriched in cobalt, a depletion in solid solution, as well as, in the layer partially depleted in cobalt, a enrichment in solid solution.

The two horizontal lines indicate the typical dispersion, in the analysis, of the mass of the material around the nominal chemical mixture.

G

1 Blatt Zeichnungen

Claims (37)

653,055 1. Cemented carbide body, characterized in that it comprises a first carbide, a metal binder alloy, a solid solution of the first carbide with a second carbide and a layer enriched by binding near its peripheral surface, this body having essentially , in its mass, a porosity of type A to B. 2. Body according to claim 1, characterized in that the layer near its peripheral surface is partially depleted in solid solution of carbides. 2 3 653,055 mixture, in an amount sufficient to produce, in the sintered block, a cobalt binder poor in tungsten. 3. Body according to claim 1 or 2, characterized in that it comprises, under the layer enriched with binder, a layer partially depleted in binder. 4. Body according to claim 3, characterized in that the layer partially depleted in binder is enriched in solid solution of carbides. 5 5. Body according to claim 1, characterized in that the first carbide is tungsten carbide. 6. Body according to claim 1, characterized in that the second carbide is a carbide of a transition metal, carbide whose free energy of formation is more negative than that of the first carbide at a temperature above the point of melting of the binding alloy. 7. Body according to claim 6, characterized in that the second carbide is chosen from the group of transition metal carbides from groups IVB and VB. 8. Body according to claim 7, characterized in that the second carbide is chosen from the group comprising carbides of titanium, hafnium, tantalum and niobium. 9. Body according to claim 6, characterized in that the second carbide is present at a level of at least 0.5% by weight. 10 10. Body according to claim 1, characterized in that the binder is chosen from the group comprising cobalt, nickel, iron and their alloys. 11. Body according to claims 3, 4 or 10, characterized in that the binder is cobalt. 12. Body according to claim 11, characterized in that the cobalt-enriched layer, near the peripheral surface, has a cobalt content of 1.5 to 3 times the average content of the body proper. 13. Body according to claim 10, characterized in that the binder is a cobalt alloy having an overall magnetic saturation less than 158 gauss-cmVg of cobalt. 14. Body according to claim 13, characterized in that the overall magnetic saturation of the binder alloy is between 145 and 157 gauss-cmVg of cobalt. 15 15. Body according to claim 10, characterized in that the overall magnetic saturation of the binder alloy is less than 126 gauss-cmVg of cobalt. 16. Body according to claim 10, characterized in that the cobalt-enriched layer extends inwards from the peripheral face to a minimum depth of 6 microns. 17. Body according to claim 10, characterized in that the cobalt-enriched layer extends inwards from the peripheral surface to a depth between 12 and 50 microns. 18. Body according to claim 1, characterized in that the layer enriched with binder extends inward from the draft surface. 19. Body according to claim 1, characterized in that it comprises nitrogen present in the form of carbonitride in a solid solution of the first and second carbides. 20 20. Body according to claims 5 and 19, characterized in that the first carbide is tungsten carbide and that the solid solution is a carbonitride comprising tungsten and a metal chosen from the group of transition metals from groups IVB and VB . 21. Body according to claim 20, characterized in that the carbonitride in solid solution is a tungsten and titanium carbonitride. 22. Body according to claims 3,5,7 and 10, characterized in that it comprises tungsten carbide, cobalt, a solid solution of tungsten carbide with a second carbide chosen from the group comprising the carbides of the elements groups IVB and VB, a first layer enriched in cobalt and partially depleted in solid solution, this layer being located near the peripheral surface, and a second layer partially depleted in cobalt and enriched in solid solution, this second layer being located under the first. 23. Body according to one of claims 1 to 4, characterized in that it comprises a hard and dense refractory coating bonded to the peripheral surface, this coating having one or more layers. 24. Body according to claim 23, characterized in that the layer consists of a material chosen from the group containing carbides, nitrides, borides and carbonitrides of titanium, zirconium, hafnium, niobium, tantalum, germanium, as well than aluminum oxide and oxynitride. 25 25. Body according to claim 23, characterized in that the coating comprises a layer of titanium carbide or carbonitride. 26. Body according to claim 23, characterized in that the coating comprises a layer of titanium carbide and a layer of titanium nitride. 27. Body according to claim 26, characterized in that the coating also comprises a layer of titanium carbonitride. 28. Body according to claim 23, characterized in that the coating comprises a layer of aluminum oxide. 29. Body according to claim 28, characterized in that the coating also comprises a layer of titanium carbide. 30 30. A method for preparing a cemented carbide body according to claim 1, characterized in that a block of a first carbide is prepared having a substantially uniform distribution, a metal binder and a chemical agent chosen from the group comprising the metals, alloys, hydrides, nitrides and carbonitrides of the transition metals, the carbides of which have a free energy of formation more negative than the first carbide at a temperature above the melting temperature of the binder alloy, then that densify the block and transform, at least partially, the chemical agent in a solid solution with the first carbide by a heat treatment which increases the content of binder near the peripheral surface. 31. Method according to claim 30, characterized in that the block is prepared by grinding and mixing a powder of the first carbide, a powder of the binder alloy and a powder of the chemical agent, then forming a block by pressing and sintering this block at a temperature above the melting temperature of the binder alloy. 32. Process according to claim 30, characterized in that the second carbide resulting from the transformation of the chemical agent is migrated in a direction away from the peripheral surface. 33. Method according to claim 31, characterized in that, during sintering, an element chosen from the group comprising hydrogen and nitrogen is volatilized at least partially. 34. Process according to claim 31 for the preparation of the block according to claims 5 and 11, characterized in that free carbon is added during the milling and 35. The method of claim 30, for the preparation of a block according to claim 23, characterized in that is deposited on the peripheral surface a hard and adherent resistant coating having one or more layers. 35 40 45 50 55 60 65 36. Method according to claim 35, characterized in that one or the other layer is formed of a material chosen from the group comprising carbides, nitrides, borides and carbonitrides of titanium, zirconium, hafnium, niobium , tantalum and vanadium, as well as aluminum oxide and oxynitride. 37. Method according to claim 30, characterized in that the peripheral parts of the body are stripped of the layer enriched with binder.