FI74304B - MED BINDEMEDEL ANRIKADE HAORDMETALLKROPPAR OCH FOERFARANDE FOER FRAMSTAELLNING AV DESSA. - Google Patents

Description

1 74304

Binder - enriched, cemented carbide bodies and method of making them

The present invention relates to cemented carbide bodies having cobalt, nickel, iron or mixtures thereof as a binder, and to the manufacture of these bodies. More specifically, the present invention relates to cemented, carbide metal cutting pieces having a hard, refractory oxide, nitride, boride or carbide coating on the surface.

In the past, a variety of hard, refractory coatings have been deposited on the surface of cemented, carbide cutting pieces to improve the strength of the cutting edge and thus extend the shear life of the piece. See, e.g., U.S. Patent Nos. 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 Corrigendum 29,420. unfortunately, refractory coatings can reduce the toughness of cemented carbide hard pieces to varying degrees. The degree of deterioration depends at least in part on the structure and composition of the coating and the method used to deposit it. Thus, although refractory coatings have improved the wear resistance of metal cutting hard pieces, they have not reduced the tendency of the cutting edge to break by crushing or splitting, especially in intermittent cutting applications.

Previous efforts to improve edge strength in coated shear hard pieces have focused on providing a cobalt-enriched layer extending inwardly from the substrate-coating interface. It has been found that enrichment of cobalt in the surface layers of certain C-porous substrates can be achieved during vacuum sintering cycles. These cobalt-enriched zones were characterized by A-porosity, while most of the substrate 2 74304 had C-porosity. Decreases in solid solution carbide usually occurred to varying depths and degrees in these cobalt-enriched regions. Enrichment of cobalt is desirable in that an increase in cobalt content is known to improve the toughness of cemented carbides. Unfortunately, the level of enrichment achieved is difficult to control in C-porous media. Typically, a coating of cobalt and carbon was formed on the surface of the substrate. This cobalt and carbon coating was removed before the refractory layer was applied to the substrate to provide a permanent bond between the coating and the substrate. Sometimes the level of cobalt enrichment in the subsurface layers of the substrate was so high that it had a detrimental effect on side wear. As a result, the cobalt-enriched layers on the side surfaces of the substrate were sometimes ground off, leaving only cobalt enrichment on the pouring surfaces and the possibility of C-porous material on the side surface. Compared to A- or B-porosity type substrates, C-porous substrates are not as chemically homogeneous. This can lead to poorer control of the formation of the eta phase (hard and brittle phase that affects toughness) at the interface between the coating and the substrate, deterioration of the adhesion of the coating, and increased growth of non-uniform coating.

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

Type A when the pore diameter is less than 10 μm.

Type B »when the pore diameter is between 10 and 40 μm. Type Cf when the pores are irregular due to the presence of carbon content. These contents are drawn out of the sample during its metallographic production, leaving the above-mentioned irregular pores.

3 74304

In addition to the above classification, the observed porosity may be given a number ranging from 1 to 6 to indicate the frequency of the observed porosity. A method for making these classifications can be found in Cemented Carbides, authors dr. P. Schwarzkopf et al.

R. Kieffer, published by MacMillan & Co. New York (1960) pp. 116-120.

Cemented carbides can also be classified according to their binder carbon and tungsten contents. Tungsten carbide-cobalt alloys with an excess of carbon are characterized by C-pores, which, as already mentioned, are the actual contents of free carbon. Tungsten carbide-cobalt alloys, which are low in carbon and in which cobalt is saturated with tungsten, are characterized by the presence of an ethasic phase, meaning M12C or MgC carbide, where M is cobalt and tungsten. Between the extremes, i.e., C-porosity and the eta phase, is the region of the side alloy intermediate compositions containing tungsten and carbon dissolved to varying degrees, but with no free carbon or eta phase present. The level of tungsten present in tungsten carbide-cobalt alloys may also be characterized by the magnetic saturation of the bond alloy, since the magnetic saturation of the cobalt alloy is a function of its composition. The magnetic saturation of carbon-saturated cobalt is reported to be 3,158 Gauss-cm per g of cobalt, indicating C-type porosity, while 125 Gauss-cm 2 per g of cobalt and below indicates the presence of the eta phase.

Accordingly, it is an object of the present invention to provide an easily controllable and economical method of forming a binder-enriched layer close to the surface of a cemented carbide body.

It is a further object of the invention to provide a cemented 4 74304 carbide body having a binder-enriched layer near its surface so that substantially all of the porosity, throughout the body, is of either the A or B type.

It is also an object of the invention to provide cemented carbide bodies having carbon concentrations ranging from C-porosity to eta-phase and having a binder-enriched layer near their outer surface.

It is a further object of the invention to combine a refractory coating with the aforementioned cemented carbide bodies according to the invention so as to provide coated shear hard pieces which combine good wear resistance and good toughness.

These objects can be realized according to the invention and the main features of the invention appear from the appended claims.

According to the present invention, it has been found that a binder-enriched layer can be formed close to the outer surface of a cemented carbide body using the following method:

Grinding and mixing the first carbide powder, binder powder and chemical reagent powder selected from the group consisting of metals, alloys and hydrides, nitrides and carbonitrides of transition elements whose carbides have a more negative free energy than the first carbide near the melting point of the binder. then a sintered batch of this mixed material is sintered or subsequently heat treated so that said chemical agent is at least partially converted to a carbide.

According to the present invention, this method can be used to form a binder-enriched layer 5 74304 near the outer surface of a cemented carbide body having substantially only Λ- or B-type porosity throughout the body. Enrichment can also be achieved in cemented carbide bodies with carbon contents ranging from eta phase to C porosity.

In the cemented carbide body according to the present invention, a layer partially impoverished from the binder is also found under said binder-enriched layer.

The first carbide is tungsten carbide. The binder may preferably be cobalt, nickel, iron or mixtures thereof, but more preferably cobalt.

The chemical agent is preferably selected from the hydrides, nitrides and carbonitrides of the Group IVB and VB elements and is preferably added in a small but effective amount, most preferably 0.5-2% by weight of the powder charge. The chemical agent is preferably titanium nitride or titanium carbonitride.

The cemented carbide bodies of the present invention have also been found to have a layer that is at least partially depleted relative to the solid solution carbide near one of the outer surfaces of the body. The cemented carbide bodies according to the invention have also been found to have a layer enriched in solid solution carbides below this solid solution depleted layer.

The cemented carbide bodies of the present invention have, preferably at the junction of the pouring surface and the side surface, a cutting edge with a hard, dense refractory coating permanently bonded to these surfaces. The binder-enriched layer can be sanded off the side surface before coating.

6 74304

The refractory coating preferably consists of one or more layers of a metal oxide, carbide, nitride, boride or carbonitride.

The exact nature of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawing, in which:

Figure 1 is a schematic sectional view of an embodiment of a coated metal cutting hard piece according to the invention.

Figure 2 is a graphical representation of typical levels of cobalt enrichment in a cemented carbide body according to the present invention, as a function of the depth below the landfill surfaces.

Figure 3 is a graphical representation of the variation in the relative concentrations of binder and solid solution carbides as a function of the depth below the pour surface in the sample of Example 12.

The above objects of the invention are achieved by heat treating a cemented carbide compact containing an element having a carbide formation energy more negative than that of tungsten carbide at a high temperature near or above the melting point of the binder. In shear-hard piece applications, this element, i.e. a chemical agent, can be selected from Group IVB and VB transition metals, their alloys, nitrides, carbon nitrides and hydrides. It has been found that the layer of material near the outer surface of the cemented tungsten carbide body can be uniformly enriched with a binder and usually at least partially depleted of solid solution carbide during sintering and reheating at a temperature above the melting point of the binder alloy of nitride and

7 74304

During sintering, these additions of Group IVB and VB elements react with carbon to form carbide or carbonitride. These carbides or carbonitrides may be present in part or in whole in the form of a solid solution with tungsten carbide and any other carbides present. The amount of nitrogen present in the final sintered carbide is typically less than the amount of nitrogen added as nitride or carbonitride because these additions are unstable at high temperatures higher or lower than the melting point of the binder alloy and result in at least partial nitrogen evaporation from the sample. its equilibrium vapor pressure requires. Thus, if the chemical agent is added as a metal, alloy or hydride, it is converted to a cubic carbode, which is typically in solid solution with tungsten carbide and any other carbides that may be present. The hydrogen contained in the added hydride evaporates during sintering.

Tantalum, titanium, niobium and hafnium can be used as metals, hydrides, nitrides and carbonitrides, either alone or in combination, to achieve uniform cobalt enrichment in or after sintering tungsten carbide-cobalt-based alloys with a wide range of carbon contents. Additions totaling approximately 15% by weight have been found to be suitable. Zirconium and vanadium as metals, nitrides, carbonitrides and hydrides are also believed to be suitable for this purpose. In alloys of porosity classes A and B and in carbon-poor alloys containing eta-1 phase, cobalt enrichment takes place without extrusion of peripheral cobalt or carbon, so that there is no need to remove excess cobalt and carbon from cemented carbide surfaces before layering of the refractory coating.

s 74304

Additions of about 0.5-2% by weight, especially titanium, in the form of titanium nitride or titanium carbonitride, to tungsten carbide-cobalt-based alloys are preferred. Since titanium nitride is not completely stable during vacuum sintering but this causes at least partial evaporation of nitrogen, it is preferable to add half a mole of carbon per mole of starting nitrogen to maintain the carbon content necessary to obtain a tungsten-poor cobalt distillate alloy. It has been found that enrichment with cobalt by heat treatment of tungsten carbide-cobalt-based alloys occurs more readily when the alloy contains a tungsten-poor cobalt binder. The magnetic saturation of the tungsten-poor cobalt binder should preferably be 145-157 Gauss-cm / g Co. Titanium nitride additions, together with the necessary carbon additions to tungsten carbide-cobalt-based alloys, promote the formation of a cobalt binder alloy having a magnetic saturation of 145-157 and which is usually difficult to achieve. Although a cobalt-binder alloy with a magnetic impregnation of 145-157 Gauss-cm3 / g Co is preferred, alloys containing tungsten-impregnated cobalt binder alloys (less than 125 Gauss-cm3 / g Co) may also be enriched.

It has been found that a layer cobalt-enriched with a thickness greater than 6 μm provides a significant improvement in the edge strength of cemented carbide carbides with a refractory coating. Although as deep a cobalt enrichment as 125 microns has been achieved, a cobalt-enriched layer having a thickness of 12 to 50 microns is preferred for coated shear-hard piece applications. Preferably, the cobalt-enriched layer of the refractory coated hard piece has a cobalt content of between 150 and 300% of the average cobalt content measured from the surface by energy-dispersive X-ray analysis.

9 74304

Binder enrichment is believed to occur in all tungsten carbide binder cubic carbide (i.e., tantalum, niobium, titanium, vanadium, hafnium, and zirconium) alloys that do not sinter into continuous carbide rings. These alloys containing a binder from 3% by weight upwards should be enriched using the process according to the invention. However, for shear hardener applications, the binder content is preferably between 5 and 10% by weight of cobalt and the total cubic carbide content is 20% by weight or less. Although cobalt is the primary binder, it can be replaced by nickel, iron and their alloys with each other as well as cobalt. Other alloys containing nickel or cobalt should also be suitable.

The sintering and heat treatment temperatures used to achieve binder enrichment are typical liquid phase sintering temperatures. For cobalt-based alloys, these temperatures are 1285-1540 ° C. The length of the sintering cycles should be at least 15 min at this temperature. The results can be further improved by using controlled cooling rates from heat treatment temperatures down to below the melting point of the bond alloy. These cooling rates should be between 25-85 ° C per hour, preferably 40-70 ° C per hour. Most preferably, the heat treatment cycle for cutting hard pieces substrates with a cobalt binder is at 1370-1500 ° C for 30-150 min, followed by cooling at 40-70 ° C per hour to 1200 ° C. Pressure levels during heat treatment can range from 0.1 Bake to the high pressures (inclusive) typically used in isostatic hot pressing. The primary pressure range is 13-20 Pa. If nitride or carbonitride additions are used, the vapor pressure of the nitrogen in the sintering atmosphere is preferably less than its equilibrium pressure so that nitrogen can evaporate from the substrate.

74304

Although sintering results in initial enrichment, subsequent grinding steps in the metal-cutting hard piece manufacturing process may remove enriched zones. In these situations, heat treatment according to the above parameters can then be used to develop a new enriched layer under the outer surfaces.

Binder-enriched substrates intended for use in coated cutting hard pieces may have binder enrichment on both pouring and side surfaces. However, depending on the type of hard piece, the sidewall binder enrichment can sometimes be removed, but this is not necessary in all cases to achieve the optimum result.

Binder-enriched substrates can be coated using refractory coating methods well known to those skilled in the art. Although the layered refractory coating may have one or more layers of materials selected from the group consisting of carbides, nitrides, borides and carbonitrides of groups IVB and VB and alumina and oxynitride, it has been found that good shear edge strength and sidewall wear can be achieved. by combining a substrate having a binder-enriched layer of the present invention with a coating comprising: alumina on a titanium carbide inner layer or a titanium carbide inner layer bonded to a titanium carbonitride interlayer bonded to a titanium nitride outer layer, or titanium nitride bonded to a titanium nitride outer layer . A cemented carbide body having a binder-enriched layer in accordance with the invention, combined with a titanium carbide / alumina coating, is preferred. In this case, the total thickness of the coating should be 5-8 μm.

Figure 1 of the accompanying drawing schematically shows an embodiment 2 of a cut-hard piece 2 of a coated metal 11 74304 in accordance with the present invention. , which is chemically substantially similar to the original powder mixture.

The binder-enriched layer 14 is on the pour surfaces 4 of the cemented carbide body, but is sanded away from the side surfaces 6 of the body. by the method of the invention.

Said binder-poor layer 16 is partially depleted of the binder while being enriched in solid solution carbides. The enriched layer is partially depleted of solid-solution carbides. Inside the binder-depleted layer 16 there is a major portion 18 of substrate.

A cutting edge 8 is formed on the cutting line of the pouring surfaces and the side surfaces 6. Although the cutting edge 8 is shown here as a friction grind, friction grinding of the cutting edge is not necessary in all applications of the present invention. It can be seen from Figure 1 that the binder-enriched layer 14 extends into the region of this cutting edge and is preferably adjacent to most, if not all, of the ground edge 8. The binder depleted zone 16 extends to the side surface 6 immediately below the cutting edges 8. The refractory coating 10 is permanently bonded to the peripheral surface of the cemented carbide body 12.

These and other features of the invention will become more apparent upon consideration of the following examples.

12 74304

Example 1

The mixture containing 7,000 g of powders was ground and mixed for 16 h with paraffin, surfactant, solvent and cobalt-bound tungsten carbide cycloides in the following relative amounts: 10.3 wt% x Ta (C) 5, 85% by weight x Ti (C) 0.2% by weight x Nb (C) 8.5% by weight Co 7000 g

1.5 wt% x Ti (N) - 102.6 g WC

+ C to give a binder alloy containing 2% by weight of W and 98% by weight of Co 2% by weight of paraffin (Sunoco 3420) (Sun Oil Co.) 2.5 liters of solvent (perchlorethylene) 14 grams of surfactant (Ethomeen S- 15) (Armor Industrial Chemical Co.) χ% by weight based on the added metal.

Rectangular hard blank blanks measuring 15.1 mm x 15.1 mm x 5.8-6.1 mm and weighing 11.6 g were "pill-pressed using a force of 8200 kg. These hard pieces were vacuum sintered for € 149 ° At 30 min in C and then cooled under ambient conditions of the oven.After sintering, the hard pieces weighed 11.25 g and were 13.26 mm x 13.26 mm x 4.95 mm.These hard pieces were then processed to SNG433 grinding dimensions as follows: ( this identification number is based on the hard piece identification system developed by the American Standards Association and widely adopted by the cutting tool industry (international designation: SNGN 12 04 12).

1. The upper and lower surfaces (pouring surfaces) of the hard pieces were ground to a thickness of 4.75 mm.

2. The hard pieces were heat treated at 1427 ° C for 60 min under a vacuum of 13 Pa, then cooled at 56 ° C

13 7430 in 4 hours to 1204 ° C, after which they were cooled under oven ambient conditions.

3. The circumferential (side) surfaces were ground to a 12.70 mm square, and the cutting edges were rubbed to a radius of 0.064 mm.

The ground hard surfaces were then coated with a titanium carbide / titanium carbonitride / titanium nitride coating using the following chemical vapor deposition (CVD) method in the following order of application.

Table I

_Päällystys__Päällystysreaktiot_

Type Temperature Pressure_ 1. Tic 982-1025 ° C ~ 1 atm TiCl. + CH. ^ TiC,. + 4HCl 4 4 «- (S) 2. TiCN 982-1025 ° C ~ 1 atm TiCl4 + CH4 + 1 / 2N2 TiCN + 4HCl 3. TIN 982-1050 ° C ~ 1 atm TiCl4 + 2H2 + 1 / 2N2 -> TiN (g) + 4HCl

Together with the above-mentioned hard pieces, hard pieces made of the same powder mixture but without the addition of TiN and associated carbon were treated. The microstructural data obtained from the coated hard pieces are as follows:

Example 1 Example 1 without TiN with TiN

Porosity A-1 A-1, B2 (unenriched, total) A-1 (enriched)

Cobalt-rich belt - no ~ 22.9 μm thickness (dump surface only)

The thickness of the poor zone (only the landfill surface) is not ~ 22.9 μm from the solid solution

Intermediate-eta-phase thickness of TiC and substrate 4.6 x 3.3 .mu.m Coating thickness

TiC 5.6 μm 5.0 μm

TiCN 2.3 μm 3.9 '/ μm

TiN 1.0 μm 1.0 μm 14 74304

Example 2

Fresh pill compressed hard pieces were prepared according to Example 1 using mixtures of Example 1 without and with TiN and associated carbon additions. The hard pieces were sintered at 1496 ° C for 30 min under a vacuum of 3.3 Pa and then cooled under oven ambient conditions. They were then milled (to a radius of 0.064 mm) and then CVD coated with TiC / TiCN / TiN by the method of Table I. In this example, it should be noted that the cobalt-enriched layer was present on both the side and dump surfaces.

The coated hard pieces were then rated with the following results:

Example 2 Example 2 without TiN with TiN

Porosity A-1 at the edges in the A-2 enriched zone A-3 in the middle of the A-4 total

The thickness of the cobalt-enriched zone is not even 22.9 μm '

The solid solution is not partially and intermittently in the impoverished zone up to 21 μm thickness'

Thickness of the eta layer of the interface between TiC and the substrate up to 5.9 μm 3.3 μm Coating thickness

TiC 2.0, 1.3, um

TiCN 1.7 μm 1.0 ', μm

TiN 8.8 μm 7.9 μm

Average Rock- 91.2 91.4 well "A" hardness (total)

Coercive force, He 138 oerstedia 134 oerstedia

Example 3

A mixture comprising the following substances was charged to a cylindrical mill together with a surfactant, a vapor binder, a solvent and 114 kg of cycloids: 15 74304 ^ WC (2-2.5 .mu.m particle- 15,000 g 85 , 15% by weight (size) IWC (4-5 μm particle size 27,575 g size) 5.98% by weight TaC 2,990 g 2.6% by weight TiN 1,300 g 6.04% by weight % Co 3,020 g 0.23 wt% C (Ravin 410-Industrial 115 g

Carbon Corp. product) _ 50,000 g

The powder charge was equilibrated to give a total of 6.25% by weight of carbon in the charge. The mixture was stirred and ground for 90,261 revolutions to give an average particle size of 0.90. The mixture was then screened wet, dried and ground in a hammer mill. It was pressed from extrudates, which were then sintered at 145 ° C for 30 min and then cooled under ambient conditions of an oven.

This treatment resulted in a sintered preform with a total (i.e., measurement comprising both the bulk and the binder-enriched material) magnetic saturation of 117-121 3 Gauss-cm per g of cobalt. Microstructural examination of the sintered blank showed that the eta phase was present throughout the blank, that the porosity was A-2 to B3, that the thickness of the cobalt-enriched zone was approximately 26.9, and that the thickness of the solid solution depleted zone was approximately 31, 4 ^ um.

Example 4

Subsequent amounts of material were added to a vessel having an inner diameter of 190 mm and a length of 194 mm lined with a tungsten carbide-cobalt alloy. In addition, 17.3 kg of 3.2 mm tungsten carbide-cobalt cycloids were added to the vessel. These materials were ground and mixed together by rotating the mill vessel around its cylinder centerline at 85 rpm for 72 h (i.e., 367,200 rpm).

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The composition of the mixture was 283 g (4.1% by weight) of TaC

205 g (3.0% by weight) of NbC

105 g (1.5% by weight) of TiN

7.91 g (0.1% by weight) of C

381 g (5.5% by weight) of Co

5986 g (85.8% by weight) of WC

105 g Sunoco 3420 14 g Ethome S-15 2500 n perchlorethylene This mixture was equilibrated to give a binder alloy containing 2% by weight W -98% by weight of Co. After grinding and mixing, the slurry was screened wet to remove oversized particles and foreign matter, dried at 93 ° C under a nitrogen atmosphere, and then ground to break up the agglomerates in a Fitzpatrick Co. J-2 Fitzmill grinder.

Compacts were pressed from this powder, which were then Sint-wheeled at 1454 ° C for 30 min and cooled under ambient conditions.

The top and bottom surfaces of the hard piece (i.e., its pouring surfaces) were then ground to final thickness. Thereafter, the heat treatment was performed at 1427 ° C under a reduced pressure of 13 Pa.

After 60 min at this temperature, the hard pieces were cooled at 566 ° C per hour to 1204 ° C and then cooled in an oven at ambient conditions. The circumferential (i.e., side) surfaces were then ground to a 12.70 mm square and the cutting edges of the hard piece were ground ground to a radius of 0.064 mm. These treatments gave a hard piece of substrate in which only the pouring surfaces had a zone enriched in cobalt and depleted of solid solution, which zones were ground away from the side surfaces.

17 74 30 4

The hard pieces were then placed in a coating reactor and coated with a thin layer of titanium carbide, using the following chemical vapor deposition method. The hot zone containing the hard pieces was first heated from room temperature to 900 ° C. During this heating period, hydrogen gas was allowed to flow through the reactor at a rate of 11.55 liters per minute. The internal pressure of the reactor was kept slightly below atmospheric pressure. The hot zone was then heated from 900 ° C to 920 ° C. During this second heating cycle, the reactor pressure was maintained at 180 torr and a mixture of titanium tetrachloride and hydrogen and pure hydrogen gas was allowed to flow into the reactor at a rate of 15 liters and 33 liters per minute, respectively. A mixture of titanium tetrachloride and hydrogen gas was obtained by passing hydrogen gas through an evaporator containing titanium tetrachloride at 47 ° C. When 192 ° C was reached, methane was also introduced into the reactor at a rate of 2.5 liters per minute. The internal pressure of the reactor was reduced to 18.6 kPar. Under these conditions, titanium tetrachloride reacts with methane in the presence of hydrogen to form titanium carbide on the hot hardboard surface. These conditions were maintained for 75 min, after which the flow of titanium tetrachloride, hydrogen and methane was stopped. The reactor was then allowed to cool while argon was passed through the reactor at a flow rate of 1.53 liters per minute at a pressure slightly below atmospheric pressure.

Examining the microstructure of the final hard piece, a cobalt-enriched zone extending inwardly up to 22.9 μm and a depleted zone from the solid solution of cubic carbide extending inwardly up to 19.7 μm from the substrate pour surfaces were observed. The porosity / enriched zone and the rest of the substrate were estimated to be between A-1 and A-2.

74304 BC

Example 5 In this example, the material was mixed and ground using a two-step milling process and the following batch of material:

Phase I (489,600 laps)

141.6 g (2.0 wt%) TaH

136.4 g (1.9% by weight) of TiN

220.9 g (3.1% by weight) of NbC

134.3 g (1.9% by weight) of TaC

422.6 g (5.9% by weight) of Co

31.2 g (0.4% by weight) of C

14 g Ethomeen S-15 1500 ml Perchlorethylene

Phase II (81,600 laps)

6098 g (84.9% by weight) of WC

140 g Sunoco 3420 1000 ml Perchlorethylene This was equilibrated to give a binder alloy containing 2% by weight of W and 98% by weight of Co.

Test hard pieces were then prepared and coated with TiC in the same manner as the test blanks described in Example 4.

A microstructural examination of the coated hard pieces showed that the porosity in both the cobalt-enriched and the bulk of the material was A-1. The cobalt-enriched zone and the solid solution-depleted zone extended inward from the landfill to approximately 32.1 μm and a depth of 36 μm, respectively.

Example 6

The following substances were charged to a 190 mm inner diameter mill: 19 74304

283 g (4.1% by weight) of TaC

205 g (3% by weight) of NbC

105 g (1/5% by weight) of TiN

7.91 g (0.1% by weight) of C

381 g (5.5% by weight) of Co

5946 g (85.8% by weight) of WC

140 g Sunoco 3420 14 g Ethomen S-15 2500 ml Perchlorethylene This mixture was equilibrated to give a binder alloy containing 2% by weight and 98% by weight of Co.

In addition, cycloids were added to the mill. The mixture was then ground for four days. The mixture was dried in a sigma mixer at 121 ° C under partial vacuum and then treated in a Fitzmill through a 40 mesh screen.

SNG433 hard pieces were then prepared using the method described in Example 4. In this example, however, the hard pieces were CVD coated with TiC / TiN coating. The coating procedure was as follows: 1. TiC coating: the samples in the coating reactor were kept at approximately 1026-1036 ° C under a reduced pressure of 16.6 kPa. Hydrogen carrier gas was introduced to the TiCl 4 evaporator at a rate of 44.73 liters per minute. The evaporator was kept at 33-35 ° C, under reduced pressure. The TiCl 2 vapor was taken up with H 2 O stock gas and introduced with it into the coating reactor. Free hydrogen and free methane flowed into the coating reactor at a rate of 19.88 and 3.98 liters per minute, respectively. These conditions were maintained for 10 min and a dense TiC coating was obtained that was permanently bound to the substrate.

2. TiN Coating: The flow of methane into the reactor was stopped and N 2 was discharged into the reactor at a rate of 2.98 liters per minute. These conditions were maintained for 30 min to give a 20 7 4 3 0 4 dense TiN coating that was permanently bonded to the TiC coating.

Examination of coated hard pieces yielded the following results:

Porosity A-1, throughout

The thickness of the cobalt-enriched zone is 17.0-37.9

The thickness of the zone impoverished from the solid solution is up to 32.7

TiC-substrate interface up to 3.9 μm eta phase thickness Coating thickness

TiC 3.9 μm

TiN 2.6 μm The mean of the major part 91.0

Rockwell "A" hardness

Coercive force, He 98 oerstedia

Example 7

The material mixture was made using the following two-stage grinding cycle:

In step I, the following substances were added to a WC-Co-lined, 181 mm inner diameter and 194 mm long mill vessel together with 17.3 kg of 4.8 mm WC-Co cycloids. The mill vessel was rotated about its cylinder centerline at 85 rpm for 48 h (244,800 rpm).

140.8 g (2.0% by weight) of Ta

72.9 g (1.0 wt%) TiH

23.52 g (0.3% by weight) of C

458.0 g (6.5% by weight) Co 30 g Ethomeen S-15 120 g Sunoco 3420 1000 ml Soltrol 120 (solvent) 2i 74 30 4

In step II, 6314 g (90.2% by weight) of WC and 1500 ml of Soltrol 130 were added and the whole batch was rotated for a further 16 h (81,600 revolutions). This mixture was equilibrated to give 5 wt. B and 95% by weight of Co binder alloy. After milling, the slurry was wet screened through a 400 mesh screen, dried under nitrogen at 93 ° C for 24 h, and run through a 40 mesh Fitzmill screen.

The specimens were uniaxially compressed with a total force of 16,400 kg to a size of 15.11 mm x 15.11 mm x 15.28 mm (specific gravity).

O

8.6 kg / cm 3).

Fresh test specimens as above were sintered at 1468 ° C for 150 min under a vacuum of 0.1 Pa. The hard pieces were then cooled under ambient oven conditions. Flake graffiti was used as a separating agent between test hard pieces and graphite sintering substrates.

Once sintered, the hard pieces were milled to a radius of 0.064 mm. The hard pieces were then coated with TiC / TiCN / TiN according to the following procedure.

1. Hard pieces were placed in the reactor and air was removed from the reactor by passing hydrogen through it.

2. The hard pieces were heated to approximately 1038 ° C while maintaining the flow of hydrogen through the reactor. The pressure in the coating reactor was kept slightly higher than one atmosphere.

3. TiC coating; a mixture of H 2 and TiCl 4 was introduced into the reactor over a period of 25 minutes at a rate of approximately 92 liters per minute and methane at a rate of 3.1 liters per minute. The TiCl 2 evaporator was maintained at a pressure of approximately 40 kPa and a temperature of 30 ° C.

4. TiCN coating: H 1 + TiCl 3 flow remained essentially the same for 13 min; the methane flow was halved; and N 2 was introduced into the reactor at a rate of 7.13 liters per minute.

5. TiN coating: for 12 minutes the methane flow was stopped and the nitrogen flow was doubled. At the end of the TiN coating, the flow of both H 2 + TiCl 2 and ^ J was stopped, the heating elements of the reactor were closed and the reactor was purged with free 11a until it had cooled to approximately 250 ° C. At 250 ° C, the reactor was purged with nitrogen.

By determination, it was found that the porosity of the hard pieces substrates was A-1 to A-2 in their unenriched interior, i.e. in the main part of the substance. The cobalt-enriched zone and the solid solution-depleted zone extended within the surfaces to a depth of approximately 25 and 23 μm, respectively.

The average hardness of the unenriched interior was 91.7 Rockwell "A". The substrate coercive force They were found to be 186 oerstedia.

Example 8

260 kg of a powder mixture was prepared from which the carbon in the final substrate was equilibrated to C3 / C4 porosity using the following two-stage mixing and grinding procedure:

Phase I

The following batch mixture was ground for 96 h: 10,108 g TaC (6.08 wt% carbon) 7,321 g NbC (11.28 wt% carbon)

3,987 g TiN

1,000 g C (Molocco Black, an Industrial

Carbon Corprn product) 16 358 g Co 500 g Ethomeen S-15 364 kg 4.8 mm Co-WC cycloid naphtha 23 7 4 3 0 4

Phase II

The following substances were added to the above mixture and the mixture was ground for a further 12 h: 221.75 kg WC (6.06% by weight carbon) 5.0 kg Sunoco 3420 naphtha

The final mixture was then wet screened, dried and ground in a Fitzmill apparatus.

The hardwood blanks were then pressed, which were then sintered at 1454 ° C for 30 min. This sintering process gave a cobalt-enriched zone covering the main component with a porosity of C3 / C4. The sintered blanks were ground and then ground to SNG433 hard piece dimensions, removing the cobalt-enriched zone.

The sintered hard pieces were then packed with flake graphite inside an open graphite canister. This combination was then hot isostatically compressed (HIP) at 1371-1377 ° C for 1 h in an atmosphere of 8.76 x 10 dynes / cm containing 25% v / v Nj and 75% v / v He. Micro-structural examination of the HIP sample showed that a cobalt-enriched zone approximately 19.7 μm deep had developed during isostatic hot pressing. About 4 μm of surface cobalt and 2 μm of surface carbon also developed due to the C-type porosity of the substrate used.

Example 9

A batch containing the following substances was ground in a ball mill: 30.0% by weight WC (1.97 μm average particle size) 750 kg 51.4% by weight WC (4.43 μm average particle size) 1286 kg 6.0 weight -% Co 150 kg 5.0% by weight WC-TiC solid solution carbide 124.5 kg 6.1% by weight TaWC solid solution carbide 152 kg 1.5% by weight W 37.5 kg 24 74304 The total carbon content of this mixture was 6.00% by weight .

These substances were ground in 51,080 cycles together with 3409 kg of cycloids and 798 liters of naphtha. The final particle size became 0.82 μm.

Five thousand g of powder was separated from this mixed and ground batch and the following substances were added: 1.9% by weight of TiN (pre-ground to approximately 96.9 g to a particle size of 1.4-1.7 μm) 0.2% by weight C (Ravin 410) 9.4 g 1500 ml perchlorethylene These substances were then ground in a 190 mm inner diameter tungsten carbide lined milling vessel containing 50% by volume of cycloids (17.3 kg) for 16 h. , dried under partial vacuum in a sigma mixer at 121 ° C, and then passed through a 40 mesh screen on a Fitzmill.

The SNG433 preforms were compressed using a force of 3600 kg to give a preform density of 8.24 g / cm 3 and a preform height of 5.84-6.10 mm.

The blanks were sintered at 1454 ° C for 30 minutes on top of an NbC powder separating agent under a reduced pressure of 1.3-3.3 Pa and then allowed to cool in an oven. The dimensions 3 of the sintered samples were 4.93 mm x 13.31 mm x 13.31 mm, the density 13.4 g / cm and the total magnetic impregnation value 146-150 Gauss-cm3 / g Co. Microstructural examination of the samples showed A-porosity throughout, and a cobalt-enriched layer with a thickness of approximately 21 μm.

The top and bottom surfaces of the hard pieces were then ground to a total thickness of 4.75 mm. The hard pieces were then heat treated at 1427 ° C for 60 minutes under a reduced pressure of 13 Pa, cooled to 1204 ° C at 56 ° C per hour, and then cooled in an oven.

The side surfaces of each hard piece were ground to a square of 12.70 mm, and the edges were ground to a radius of 0.064 mm.

The pieces were then CVD-coated with titanium carbide-alumina using the following method.

The hard pieces were placed in a coating reactor, heated to approximately 1026-1030 ° C and kept under a reduced pressure of 12-17 kPa. Hydrogen gas was passed at a rate of 44.73 liters per minute through an evaporator containing TiCl 4 at 35-38 ° C under reduced pressure. The TiCl 4 vapor was triturated with hydrogen and passed to a coating reactor. Simultaneously, hydrogen and methane flowed into the reactor at a rate of 19.88 and 2.98 liters per minute, respectively. These vacuum, temperature, and flow conditions were maintained for 180 min to form a permanent TiC coating on the hard pieces. The flow of hydrogen to the evaporator and the flow of methane to the reactor were then stopped. Hydrogen and chlorine were now flowed into a generator containing aluminum particles at 380-400 ° C and 3.4 kPa. Hydrogen and chlorine flowed into the generator at a rate of 19.88 and 0.8 liters per minute, respectively. Chlorine reacted with aluminum to form AlCl 2 vapors, which were then introduced into the reactor. While hydrogen and AlCl 3 flowed into the reactor, also at a rate of 0.5 liters per minute, flowed into the reactor. These flows were maintained for 180 min, during which time the hard pieces were kept at 1026-1028 ° C, a vacuum of approximately 12 kPa. This procedure developed a dense Al 2 O 3 coating that was permanently bonded to the inner TiC coating.

Examination of the coated hard pieces gave the following results: 26 7 4 3 0 4

Porosity A-1 in the enriched zone A-1, and here and there in B si

Cobalt-enriched belt thickness of approximately 39.9 7um (dump surface) '

Thickness of the zone impoverished by the solid solution up to 43.2 μm (pouring surface) Coating thickness

TiCl 5.9 μm Al 2 O 3 2.0 μm

The average Rockwell “A” hardness of the main substrate is 91.9

Coercive force, He 170 oerstedia

Example 10

Another batch of 5000 g was separated from the original batch prepared according to Example 9. 95.4 g (1.9 wt%) of TiCN and 1.98 g (0.02 wt%) of Carbon 410 of Nutri were added to this material, stirred for 16 h, screened, dried and treated in a Fitzmill apparatus according to Example 9 .

The test pieces were pill pressed, sintered under reduced pressure at 1496 ° C for 30 min, and then cooled in an oven at the cooling rate around the oven. Examination of the sintered samples gave the following results:

Porosity A-1 throughout

Cobalt-enriched belt thickness of approximately 14.8 μm '

Thickness of the zone of the solid solution depleted by up to 19.7 μm '

The interior of the substrate is 92.4

average Rockwell A

hardness 3

Magnetic impregnation 130 Gauss-cm / g Co

Coercive force (He) 230 oerstedia 27 7 4 3 0 4

Example 11

Another batch of 5000 grams was separated from the original batch made according to Example 9. The pre-ground TiCN was added 95.4 g (1.9 wt%), stirred for 16 h, screened, dried and treated in a Fitzmill apparatus as in Example 9. The test pieces were then compressed and sintered at 1496 ° C together with the test pieces of Example 10. with.

Examination of the sintered samples thus obtained gave the following results:

Porosity A-1 together with the heavy eta phase throughout

The thickness of the cobalt-enriched belt is approximately 12.5 μm

Thickness of the impoverished zone up to 16.4 μm from the solid solution

I decorate an average of 92.7

Rockwell A hardness 3

Magnetic impregnation 120 Gauss-cm / g Co

Coercive force, He 260 oerstedia

Example 12

The following mixture was charged using the two-stage grinding cycle described below:

Phase I

The following substances were added to an 181 mm inner diameter, 194 mm long WC-Co lined mill vessel with 17.3 kg of 4.8 mm WC-Co cycloids. The mill vessel was rotated about its cylinder-blade centerline at 85 rpm for 48 h (244,800 rpm).

28 7 4 3 0 4 455 g (6.5% by weight) Ni

280 g (4.0% by weight) of TaN

112 g (1.6% by weight) of TiN

266 g (3.8% by weight) of NbN

42.7 g (0.6% by weight) of carbon 14.0 g Ethomeen S-15 1500 ml Perchlorethylene

Phase II

The following substances were then added to the mill vessel and rotated for an additional 16 h (81,600 revolutions):

5890 g (83.6% by weight) of V7C

105 g Sunoco 3420 1000 ml Perchlorethylene This mixture was equilibrated to give a binder alloy containing 10% to 90% by weight Ni. After removal of the mixture slurry from the mill vessel, it was screened wet through a 400 mesh screen (Tyler), dried at 93 ° C under a nitrogen atmosphere and treated in a Fitzmill apparatus through a 40 mesh screen.

The test samples were pill pressed, sintered at 1450 ° C for 30 min in a 6.9 x 10 6 dyne / cm 2 nitrogen atmosphere, and then cooled in an oven at the ambient cooling rate of the oven.

After sintering, the samples were HIP-treated at 1370 ° C for 9 ° 60 min in a 1 x 10 dynes / cm helium atmosphere. Optical metallographic examination of the HIP-treated samples showed that the material had A-3 porosity throughout, and a solid solution depleted band approximately 25.8 μm thick.

The sample was then reconstituted and examined by energy dispersive X-ray line segmentation (EDX) analysis at various distances from the landfill surface. Figure 3 is a graphical representation of variations in the relative concentrations of nickel, tungsten, titanium, and tantalum 29 74304 as a function of distance from the landfill surface of the sample. Clearly, there is a layer near the surface in which titanium and tantalum, which form carbides in solid solution with tungsten carbide, are at least partially depleted. This solid solution depleted zone extends inwardly by about 70. The discrepancy between this value and the value reported above is believed to be due to the fact that the sample was prepared between examinations, so that in each examination different levels of intersection of the samples were examined.

The depletion of titanium and tantalum is matched by a layer enriched in nickel (see Figure 3). The nickel content in this enriched layer decreases as the distance from the landfill surface decreases from 30 to 10. This indicates that some of the nickel in this zone has evaporated during vacuum sintering.

The peak at titanium and tantalum concentrations of 110 [mu] m is considered to be due to the fact that the partition has randomly hit a large grain or a grain with a high content of these elements.

The two parallel horizontal lines in the figure show the typical dispersion obtained in the analysis of the bulk of the sample on both sides of the nominal mixture chemistry.

Example 13

The following mixture was charged, using the two-stage grinding cycle outlined below:

Phase I

The following substances were ground according to Example 12, Step I: 30 7 4 3 0 4 455 g (6.4% by weight) Ni

280 g (3.9% by weight) of TaH

122 g (1.6% by weight) of TiN

266 g (3.7% by weight) of NbN

61.6 g (0.9% by weight) C Ravin 410, 502 14 g Ethomeen S-15 2500 ml Perchlorethylene

Phase II

The following materials were then added to the mill vessel and spun for an additional 16 h.

5980 g (83.6% by weight) of WC

140 g of Sunoco 3420 This was equilibrated to give a binder alloy containing 10% by weight of W and 90% by weight of Ni.

After removal, the mixture was screened, dried and treated in a Fitzmill apparatus according to Example 12.

Compressed test specimens were vacuum sintered at 1466 ° C for 30 min under a vacuum of 4.7 Pa. The sintered samples had A-3 porosity throughout and had a solid solution depleted zone with a thickness of up to 13.1 μm.

Example 14

A mixture was prepared using the following two-stage grinding cycle:

Phase I

The following substances were added to a 190 mm inner diameter and 195 mm long WC-Co lined mill vessel, with 17.3 kg of 4.8 mm WC-Co cycloids. The mill was rotated about its centerline at 85 rpm for 48 h (244,800 rpm): 31 74304 177 g (2.5 wt%) HfH 2 182.3 g (2.5 wt%) TiH 2 55.3 g (0.8 wt%) wt%) carbon 459 g (6.4 wt%) Co 14 g Ethomeen S-15 2500 ml Perchlorethylene

Phase II

The following substances were then added to the mill vessel and rotated for an additional 16 h (81,600 revolutions):

6328 g (87.9% by weight) of WC

140 g Sunoco 3420 This mixture was equilibrated to give a binder alloy containing 10% by weight of W and 90% by weight of Co.

After removal of the slurry from the mill vessel, it was wet screened through a 400 mesh screen, dried at 93 ° C under a nitrogen atmosphere, and treated on a Fitzmill apparatus through a 40 mesh screen.

The hard pieces were pressed and sintered at 1468 ° C for 30 min under a reduced pressure of 4.7 Pa, which allowed most of the hydrogen in the samples to evaporate. During sintering, the samples were supported on NfcC powder separation agent.

The porosity of the sintered sample was in the enriched zone of the A-2 sample and in the unenriched major part of the A-4 sample. The Rockwell MA "sample had an average hardness of 90; had a solid solution impoverishment of 9.8 .mu.m thick and a coercive force He of 150 oerstedia.

Example 15

A batch of material having the composition of the batch of Example 9 was mixed, ground and compressed into hard pieces. The blanks were then sintered, ground, heat treated, and ground (side surfaces only) essentially according to the procedures used in Example 9. However, a cooling rate of 69 ° C per hour was used for the final heat treatment.

One hard piece was analyzed by EDX line partitioning analysis at different distances from the hard disk dump surfaces. The results of this analysis are shown in the curve of Figure 2. It shows the existence of a cobalt-enriched layer extending inwards from the pouring surfaces to a depth of about 25 μm, followed by a bed material which is partially depleted relative to the cobalt and extends inwards from the pouring surfaces of approximately 90 μm. Although not shown in the curve of Figure 2, partial depletion relative to the solid solution has been observed in the cobalt-enriched layer and solid solution enrichment has been observed in the partially depleted cobalt layer.

The two horizontal lines in the curve show the typical scatter in the analysis of the interior material, on both sides of the nominal chemistry of the mixture.

The above description and detailed examples are provided to illustrate some of the possible alloys, products, methods and uses that fall within the scope of this invention as defined in the following claims.

Claims (17)

33 7 4 3 0 4 A cemented carbide body formed by sintering a substantially homogeneous mixture comprising as ingredients at least 70% by weight of tungsten carbide, a metallic binder and a metal carbide of Group IVB or VB transition metal carbide, the amount of metal carbide being less than the amount of tungsten carbide, known that the porosity of the body as a whole is essentially of the AB type, that the metal carbide together with the tungsten carbide forms a solid solution carbide and that there is a layer of material near the outer surface of the body which is at least partially depleted of the solid solution carbide. Cemented carbide body according to Claim 1, characterized in that the binder consists of cobalt, nickel, iron or an alloy thereof. 3. Cemented carbide body formed by sintering a substantially homogeneous mixture containing at least 70% by weight of tungsten carbide, a cobalt-bond alloy and a metal carbide which is a Group IVB or VB transition metal arbit, characterized in that the metal carbide together with tungsten carbide forms solid solution carbide, that there is a layer of material near the outer surface of the body which is at least partially depleted of solid solution carbide and that the total value of the magnetic impregnation 3 of the cobalt-bond alloy is less than 158 Gauss-cm / g of cobalt. A cemented carbide body comprising at least 70% by weight of tungsten carbide, cobalt and a metal carbide which is a Group IVB or VB transition metal carbide, characterized in that there is a cobalt-enriched layer near the outer surface of the body and that the porosity of the body is essentially of type A-B. 34 74304 Cemented carbide body according to Claim 4, characterized in that the concentration of the transition metal carbide in the cobalt-enriched layer is at least partially depleted. Cemented carbide body according to Claim 4 or 5, characterized in that the metal carbide is titanium, hafnium, tantalum or niobicarbide and that the metal carbide content is at least 0.5% by weight. Cemented carbide body according to one of Claims 4 to 6, characterized in that the cobalt-enriched layer extends inwards from the outer surface of the body to a depth of at least about 6 micrometers, preferably to a depth of 12 to 50 micrometers. Cemented carbide body according to one of Claims 4 to 7, characterized in that the outer surface of the body comprises a pouring surface connected to the side surface, the section of the pouring and side surface having a cutting edge, and that the enriched layer extends inwards from the pouring surface. Cemented carbide body according to one of Claims 4 to 8, characterized in that it further comprises a hard, dense refractory coating bonded to the outer surface of the body, the coating having one or more layers consisting of titanium, zirconium, hafnium, niobium, carbide, nitride, boride or carbonitride of tantalum or vanadium or oxide or oxide nitride of aluminum. Cemented carbide body according to Claim 9, characterized in that the coating comprises one or more layers of titanium carbide, titanium carbonitride, titanium nitride and alumina. 35 74304 A product made by a method of forming a binder-enriched layer close to one outer surface of a substantially AB-type cemented carbide body with a porosity, characterized in that the method comprises grinding and mixing the first carbide powder, the binder powder and the chemical reagent powder, which is a Group IVB or VB transition metal or an alloy, nitride or carbonitride thereof, to extrude these powders, to sinter the extrudate at a temperature higher than the melting temperature of the bond alloy so that the chemical reagent is at least partially converted to carbide in the binder enrichment layer that the binder-enriched layer is removed from selected areas of the product, that the extrudate is re-sintered at a temperature higher than the melting temperature of the bond alloy, so that the chemical reagent is at least partially converted to carbide in the layer near the outer surface of selected areas of the product. The article of claim 11, further comprising the step of depositing on the outer surface a durable, hard, wear-resistant, refractory coating comprising one or more layers of titanium, zirconium, hafnium, niobium. , carbide, nitride or carbonitride of tantalum or vanadium or alumina or oxynitride. Product according to Claim 11 or 12, characterized in that the first carbide powder is tungsten carbide and that the tungsten carbide constitutes at least 70% by weight of the product and that the binder consists of cobalt, nickel, iron or an alloy thereof. 14 · A method of forming a cobalt-enriched layer close to one of the outer surfaces of a substantially A-type cemented carbide body, 36 7 4 3 0 4 characterized by grinding and mixing tungsten micarbide powder, cobalt powder and a metal compound powder which is a Group IVB or VB transfer powder or carbonitride, extruding these powders into a compact, sintering the compact at a temperature higher than the melting point of the binder so that the metal compound is at least partially converted to the metal carbide in the layer where the binder is to be enriched. The method of claim 14, further comprising the step of removing the binder-enriched layer from selected areas of the outer surface. The method of claim 14, further comprising the step of depositing on the outer surface a durable, hard, wear-resistant, single or multi-layer coating of titanium, zirconium, hafnium, niobium, tantalum or vanadium carbide, nitride, boride or carbonitride or alumina or oxynitride. The method of claim 14, characterized in that the powders further comprise a second carbide powder which is a Group IVB or VB metal carbide or a solid solution thereof. 37 7 4 3 0 4