SE459100B - HEAVY METAL BODY WITH BINDING ENRICHED SURFACE AND FOE REFERENCES FOR ITS PREPARATION - Google Patents

Description

459 100 10 15 20 25 30 35 2 cobalt enrichment. Cobalt enrichment is desirable because it is well known that increasing the cobalt content increases the toughness or impact strength of cemented carbides. Unfortunately, it is difficult to regulate the formed enrichment level of substrates with C-porosity. In the typical case, a coating of cobalt and carbon formed on the surface of the substrate.

This coating of carbon and carbon was removed before depositing 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 surface of the substrate was so high that it had a detrimental effect on the wear of the release surfaces. As a result, the cobalt enrichment layer was sometimes abraded on the release surfaces of the substrate, leaving cobalt enrichment only on the chip surfaces and the presence of C-porosity material on the release surface. Compared to substrates with porosity of type A or B, substrates with C-porosity are not as chemically homogeneous.

This can result in less regulation of the formation of the eta phase at the coating-substrate interface (a hard and brittle phase, which affects the toughness), a reduction in the coating adhesion and an increase in non-uniform coating growth.

By definition, the porosity observed in cemented carbides can be classified into one of three categories, as recommended by the American Society for Testing and Materials (ASTM) as follows: Type A for more than 10 pm. a pore size with a diameter of smaller Type B for a pore size with a diameter of 10-40 μm.

Type C for irregular pores, which are caused by the presence of carbonaceous inclusions. These inclusions are extracted from the sample during metallographic preparation, leaving the above-mentioned irregular pores.

In addition to the above classifications, the observed porosity can be assigned a number ranging from 1 to 6 to indicate the degree or frequency of observed porosity. The method for making this classification is found. Cemented Carbides by Dr. Schwarzkopf and Dr. R. Kieffer, published by MacMillan Co., New York (1960), pp. 16-120.

Carbides can also be classified by their content of binders, carbon and tungsten. Tungsten carbide-cobalt alloys with excess carbon are characterized by the C-porosity, which, as already mentioned, is actually free carbon inclusions. Tungsten carbide-cobalt alloys with low carbon content and in which the cobalt is saturated with tungsten - an M C or 12 MGC carbide, where M means cobalt and tungsten. Between the extreme cases of C-porosity and eta-phase, there is characterized by the presence of eta-phase, an area with intermediate binder alloy compositions, which contain tungsten and carbon in solution-in varying content, but so that no free carbon or eta-phase exist. The tungsten content present in tungsten carbide-cobalt 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. Cobalt saturated with carbon is stated to have a magnetic saturation of 158 gauss-cm3 / g cobalt, indicating C-type porosity, while a magnetic saturation of 125 gauss-cm3 / g cobalt and below indicates the presence of eta phase.

It is therefore an object of the present invention to provide a simple controllable and economical method for producing a binder-enriched layer near the surface of a cemented carbide body.

It is a further object of the invention to provide a cemented carbide body having a binder-enriched layer close to its surface, substantially all of the porosity through the body being of the A or B type.

It is also an object of the invention to provide cemented carbide bodies with carbon contents ranging from C-porosity to eta-phase with a binder-enriched layer near the peripheral surface. It is a further object of the invention to combine the above-mentioned cemented carbide bodies according to the present invention with a refractory coating to create coated cutting inserts which have a combination of high abrasion resistance and high toughness.

These and other objects of the present invention will become more fully apparent upon consideration of the following description of the invention.

BRIEF SUMMARY OF THE INVENTION The present invention relates to a cemented carbide body characterized in that it comprises a metallic binder and a solid solution of a first carbide consisting of tungsten carbide, and a second carbide or carbonitride of a transition metal, whose carbide has a free energy of formation which is more negative than that of the first carbide near the melting point of the binder, and that the cemented carbide body has a binder-enriched and solid solution depleted layer which begins at and extends inwardly from a peripheral surface of the body, and the cemented carbide body preferably has substantially A- to B-type porosity throughout the body.

The cemented carbide body according to the invention can be produced by a process characterized in that a press body is produced with a substantially uniform distribution of a metallic binder, a first carbide consisting of tungsten carbide, and a chemical agent selected from metals, alloys, hydrides , nitrides and carbonitrides of transition metals, whose carbides have a free formation energy which is more negative than that of the first carbide near the melting point of the binder, that the compact is densified and heat treated, whereby the chemical is at least partially converted to solid solution carbide with the first carbide, and that during the heat treatment the binder content is increased towards the peripheral surface of the compact so that a layer is formed which begins at and extends inwards from the peripheral surface and which is enriched in binder and depleted in solid solution, and the compact preferably has substantially A- to B-type porosity throughout the whole body. Further features of the invention appear from the claims.

The method according to the present invention can be used to produce a layer of adhesive enrichment near a peripheral surface of a cemented carbide body, preferably with substantially only the A to B type porosity throughout the body. Enrichment can also be achieved in cemented carbide bodies which have carbon contents ranging from eta phase to C porosity.

Carbide bodies according to the present invention have also been found to have a layer below the binder-enriched layer which is partially binder depleted.

Preferably, the binder alloy may be cobalt, nickel, iron or their alloys, but is most preferably cobalt.

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

Carbide bodies in accordance with the present invention have also been found to have a layer which is at least partially depleted of carbide in solid solution near a peripheral surface of the body. Carbide bodies in accordance with the present invention have also been found to have a layer below the depleted layer of solid solution enriched in carbides in solid solution.

Cemented carbide bodies according to the present invention preferably have a cutting edge at the connecting line between a chip surface and a clearance surface with a hard, tight, refractory coating adhesively bonded to these surfaces. The adhesive-enriched layer can be ground away from the release surface before coating.

The refractory coating is preferably composed of one or more layers of a metal oxide, carbide, nitride, boride or carbonitride. 459 100 10 15 20 25 30 BRIEF DESCRIPTION OF THE DRAWINGS The exact nature of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

In these, Fig. 1 shows a schematic cross-section through an embodiment of a coated metal cutting insert according to the present invention. Fig. 2 is a graphical representation of the typical levels of cobalt enrichment created in a cemented carbide body according to the present invention, as a function of the depth below the chip surface. Fig. 3 is a graphical representation of the variation in relative concentrations of binder and carbides in solid solution as a function of the depth below the chip surface in a sample according to Example 12.

DETAILED DESCRIPTION OF THE INVENTION The above objects of the invention are achieved by heat treatment of a cemented carbide press body containing an element with a carbide having a more negative free formation energy than that of tungsten carbide at an elevated temperature near or above the melting point of the binder. For cutting insert applications, this element or chemical agent can be selected from Group IVB and VB transition metals, their alloys, nitrides, carbonitrides and hydrides. It has been found that the material layer adjacent to the periphery of a cemented carbide body can be reproducibly enriched in binder and usually at least partially depleted of solid carbide during sintering or reheating at a temperature above the melting point of the binder alloy by incorporating nitride, hydride and / or carbonitride additives of transition metals in groups IVB and VB to the powder charge.

During sintering, these group IVB and VB additives react with carbon to form a carbide or carbonitride. These carbides or carbonitrides may be present in whole or in part in solid solution with tungsten carbide and any other carbides present. 10 15 20 25 30 35 459 100 7 The nitrogen content present in the final sintered carbide is typically reduced from the nitrogen content added as a nitride or carbonitride, as these additives are unstable at elevated temperatures above and below the binder alloy. melting point and leads to at least partial volatilization of nitrogen from the sample if the sintering atmosphere contains a nitrogen concentration which is less than its equilibrium vapor pressure. If the chemical is added as a metal, alloy or hydride, it will also be converted - into cubic carbide, typically in solid solution with the tungsten carbide and any other carbides present.

The hydrogen in any hydride that is added evaporates during sintering.

The metals, hydrides, nitrides and carbonitrides of tantalum, titanium, niobium, hafnium can be used alone or in combination to promote continuous cobalt enrichment via sintering or subsequent heat treatment of tungsten carbide-cobalt base alloys with high carbon content. Additives of up to about 15% by weight have been found to be useful. It is believed that the metals, nitrides, carbonitrides and hydrides of zirconium and vanadium are also suitable for this purpose. In alloys with A and B porosity and carbon-depleted alloys containing eta phase, cobalt enrichment occurs without peripheral cobalt or carbon encapsulation, thus eliminating the need to remove excess T of cobalt and carbon from the cemented carbide surfaces before coating with refractory material. .

Additions of about 0.5-2% by weight, especially of titanium in the form of titanium nitride or titanium carbonitride, to tungsten carbide-cobalt base alloys are preferred. Since titanium nitride is not completely stable during vacuum sintering, but causes at least partial volatilization of the nitrogen, it is preferred to add half a mole of carbon per mole of starting nitrogen to maintain the carbon content necessary for a tungsten-rich cobalt binder alloy. It has been found that cobalt enrichment via heat treatment of tungsten carbide-cobalt base alloys occurs more easily when the alloy contains a tungsten-poor cobalt binder. The tungsten-poor cobalt binder should preferably have a magnetic saturation of 145-157 gauss-cm 3 / g cobalt. Titanium nitride additives together with the necessary carbon additives to tungsten carbide-cobalt base powder mixtures favor the formation of a cobalt binder alloy with a magnetic saturation of 145-157 gauss-cm 3 / g cobalt, which is usually difficult to achieve. Although a cobalt binder alloy having a magnetic saturation of 145-157 gauss-cm 3 / g cobalt is preferred, alloys containing tungsten-saturated cobalt binder alloys (less than 125 gauss-cm 3 / g cobalt) may also be enriched.

It has been found that a layer of cobalt enrichment thicker than 6 microns results in a significant improvement in the edge strength of cemented carbide inserts coated with solid material. While a cobalt enrichment as deep as 125 microns has been achieved, a cobalt enriched layer with a thickness of 12-50 μm for coated cutting insert applications. It is also preferred that the cobalt content of the cobalt-enriched layer of a refractory coated coating is 150-300% of the average cobalt content, measured on the surface by means of energy scattering X-ray analysis.

It is believed that binder enrichment should occur in all tungsten carbide-binder-cubic carbide alloys (ie, tantalum, niobium, titanium, vanadium, hafnium, zirconium) that do not sinter into a continuous carbide backbone.

These alloys, which contain binders from 3% by weight and above, should be enriched using the process described. For cutting insert applications, however, it is preferred that the binder content be 5-10% by weight of cobalt and that the total content of cubic carbide be 20% by weight or less. While cobalt is the preferred binder, nickel, iron and their alloys with each other and with cobalt can replace cobalt.

LH 15 20 25 30 35 459 100 9 Other binder alloys containing nickel or cobalt or iron should also be suitable.

The sintering and heat treatment temperatures used to achieve binder enrichment are the typical temperatures for liquid phase sintering. For cobalt base alloys, these temperatures are 1285-140 ° C.

The sintering cycles should be at least 15 minutes at this temperature. The results can be further optimized by using controlled cooling rates from the heat treatment temperatures down to a temperature below the melting point of the binder alloy. These cooling rates should be 25-85 ° C / h, preferably 40-70 ° C / h. It is most preferred that the heat treatment cycle for cutting insert substrates with a cobalt binder is 1370-1500 ° C for 30-150 minutes, followed by 40-70 ° C / h cooling to 120 ° C. The pressure level during heat treatment can vary from 10-3 torr up to and including the elevated pressures typically used in hot isostatic pressing. The preferred pressure level is 0.1-0.15 torr.

If nitride or carbonitride additives are used, the vapor pressure of the nitrogen in the sintering atmosphere is preferably below its equilibrium pressure to allow the volatilization of nitrogen from the substrate.

While initial enrichment occurs during sintering, subsequent grinding steps in the manufacturing process of the metal cutting insert can remove the enriched zones. In these situations, a subsequent heat treatment in accordance with the above parameters can be used to develop a new enriched layer below the peripheral surfaces.

Binder-enriched substrates, which are to be used in coated cutting inserts, can have adhesive enrichment on both the chip and the release surfaces. Depending on the type of insert, however, the adhesive enrichment on the release surface can be removed, but this is not necessary to achieve optimal performance in all cases. 459 100 10 20 25 30 10 The binder-enriched substrates can be coated using the techniques for coating refractory materials well known to those skilled in the art.

While the applied refractory coating may have one or more layers comprising materials selected from Group IVB and VB carbides, nitrides, borides and carbonitrides and the oxide or oxinitride of aluminum, it has been found that a combination of good strength of the cutting edge and abrasion of the release surface can be achieved by combining a substrate having a binder-enriched layer according to the present invention, with a coating of: alumina over an inner layer of titanium carbide; or an inner layer of titanium carbide bonded to an intermediate layer of titanium carbonitride bonded to an outer layer of titanium nitride, or titanium nitride bonded to an inner layer of titanium carbide. A cemented carbide body having an adhesive-enriched layer of the present invention in combination with a titanium carbide / alumina coating is most preferred. The coating should have a total thickness of 5-8 μm.

Fig. 1 schematically shows an embodiment of a coated metal cutting insert 2 according to the present invention. The insert 2 comprises a substrate or cemented carbide body 12, which has a binder-enriched layer 14, and a binder-depleted layer 16 over the main mass 18 of the substrate 12, which has substantially the same chemical composition as the original powder mixture.

A binder-enriched layer 14 is present on the chip surfaces 4 of the cemented carbide body and has been ground away from the release surfaces 6 of the body. Inside the binder-enriched layer 14 there may be a binder depleted zone 16. This binder depleted zone 16 has been found to develop together with the binder with the described procedure.

The binder depleted zone 16 is partially depleted of binder material, while it is enriched in carbides in solid solution. The enriched layer 14 is partially depleted of carbides in solid solution. Inside the binder depleted zone 16 is the bulk of substrate material 18.

Upon joining or cutting between the chip surfaces and the clearance surfaces 6, a cutting edge 8 is formed. While the cutting edge 8 shown here is downward, it is not necessary to hinge the cutting edge for all applications of the present invention. It can be seen from Fig. 1 that the adhesive-enriched layer 14 extends into the area of the cutting edge and is preferably arranged next to most if not the entire hinged edge 8. The adhesive-depleted zone extends to the release surface 6 just below the cutting edges 8. A refractory coating 10 is adhesively bonded to the peripheral surface of the cemented carbide body 12.

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

EXAMPLE 1 A mixture containing 7000 g of powder was ground and mixed for 16 hours with a paraffin, a surfactant, a solvent and cobalt-bound tungsten carbide cycloids in the amounts and proportions given below: 10.3% * Ta (c> 5, 85% * Ti 0.2%: Nb (c) 700 g 8.5% Co 1.5 s * T1 (N) ~ 102.6 g wc + c I to create a 2/98 wt% ~ W / Co binder alloy __l Weight% paraffin (Sunoco 3420) (Sun Oil Co) 2.5 liters solvent (perchlorethylene) 14 g surfactant (Ethomeen S-15) (Armor Industrial Chemical Co) x weight% of added metal 459 100 12 Square inputs with the dimensions 15.1 mm x 15.1 mm x 5.8 - 6.1 mm and a weight of 11.6 g was tablet pressed using a force of 8200 kg mass of vacuum vacuum insert at 149 ° C for 30 minutes and cooled then under sintering oven conditions.After sintering, the inserts weighed 11.25 g and had the dimensions 13.26 mm x 13.26 mm X 4.95 mm The inserts were treated to SNG433 ground dimensions as follows: (this identification number is based on the identification system for operations developed by the American Standards Association and generally accepted by the cutting tool industry. is: SNGN 12 04 12). 1. The top and bottom (chips) of the inserts were ground to a thickness of 4.75 mm.

The international designation 2. The inserts were heat treated at 124 ° C for 60 minutes at a vacuum of 100 ° C and then cooled at a rate of ss ° c / h to 120 ° C, oven conditions. followed by cooling under ambient 3. The periphery (clearance surfaces) were ground to form a 12.70 mm square and the cutting edges were drawn to a radius of 0.064 mm.

A titanium carbide / titanium carbonitride / titanium nitride coating was then applied to the ground inserts I \ J U1 using the following chemical vapor deposition (CVD) technique in the following order: TABLE 1 coating coating reactions Type Temperature Pressure Tic ä82-1o25 ° c ~ »1 arm. Ticl + cH §2Tic + 4Hc1 4 4+ (s) o. H2.

TiCN 982-1025 ° C. TiCl4 + CH4 + 1 / 2N2: T1CN (S) + 4HCl min 9s2 ~ 10o ° c -1 arm.

TiCl4 + 2H2 + l / 2Ná-> TiN (s) + 4HCl 459 100 13 Together with the above inserts, inserts were prepared which were prepared from the same powder mixture, but without TiN and its accompanying carbon additive. Microstructural data obtained from the coated inserts are given below: EXAMPLE 1 EXAMPLE 1 without TiN with TiN Porosity Al Al, B2 (non-enriched main mass) Al (enriched) Cobalt-enriched zone, thickness None ~ 22.9 μm (chip surface only ) Solid solution depleted zone, None ~ 22.9 μm thickness (chip surface only) TiC / substrate interface, 4.6 μm 3.3 μm Eta-phase thickness Coating thickness TiC 5.6 μm 5.0 μm TiCN 2.3 μm 3.9 μm TiN 1.0 μm 1.0 μm EXAMPLE 2 Raw, ie non-sintered, tablet-pressed inserts were prepared according to Example 1 using the mixtures of Example 1 with and without TiN and its accompanying carbon additives. These inputs were sintered at 1946 ° C for 30 minutes under 25 μ vacuum and then cooled under ambient oven conditions. They were then hung (0.064 mm radius) and TiC / TiCN / TiN-CVD were then coated according to the technique shown in Table 1. In this example, it should be noted that the cobalt-enriched layer was present on both the release and chip surfaces.

The coated inserts were mainly evaluated and the following results were obtained: 459 100 14 EXAMPLE 2 without Ti Porosity A-1 edges A-3 middle Cobalt enriched zone, thickness None Solid solution depleted zone, No thickness TiC / substrate interface, up to eta solid thickness 5 .9 pm Coating thickness TiC 2.0 pm TiCN 1.7 pm TiN 8.8 pm Average Rockwell "A" hardness (main 91.2 mass material) Coercive force, Hc 138 örsted EXAMPLE 3 EXAMPLE 2 with TiN A-2 enriched zone A-4 main mass up to 22.9 μm partial and intermittent up to 21 μm 3.3 μm 1.3 μm 1.0 μm 7.9 μm 91.4 134 örsted A mixture comprising the following materials was charged to a cylindrical grinder together with a surfactant, volatile binder, solvent and 114 kg of cycloids: 85.15 5.90 2.6 6.04 0.23 WC (2-2.5 μm grain size) weight% WC (4 -5 pm grain size) weight% Tac weight% Tin “weight% Co weight% C (Ravin 410, a product 15000 g 27575 2990 1300 3020 115 I-QUJKQKQÛ from Industrial Carbon Corp) 50000 g 10 15 20 25 30 459 100 The powder charge was balanced to give 6.25% by weight of total carbon in the charge. The mixture was mixed and ground for 90261 rpm to create an average grain size of 0.90 μm. The mixture was then wet sieved, dried and ground in a hammer mill. Compressors were pressed and then centrifuged at 1454 ° C for 30 minutes, followed by cooling under ambient oven conditions.

This treatment produced a sintered substance which had a total (ie the measurement included bulk material and binder-enriched material) magnetic saturation of 117-122 gauss-cm 3 / g cobalt. Microstructural evaluation of the sintered substance showed: eta phase occurred throughout the substance; the porosity was A-2 to B-3; the thickness of the cobalt-enriched zone was about 26.9 μm; and the thickness of the solid solution depleted zone was about 31.4 μm.

EXAMPLE 4 The following material was added to a mill drum having an inner diameter of 190 mm and a length of 194 mm, which drum was lined with a tungsten carbide-cobalt alloy. In addition, 17.3 kg of 3.2 mm tungsten carbide-cobalt cycloids were added to the drum. These materials were ground and mixed together by rotating the mill drum around its cylinder axis at 85 rpm for 72 hours (ie 367200 revolutions).

CHARGEN COMPOSITION 283 9 (4.1 wt%) TaC 205 Q (3.0 wt%) NbC 105 g (1.5 wt%) TiN 7.91 g (0.1 wt%) C 381 g (5.5 wt%) Co - 5946 9 (85.8 wt%) WC 105 g Sunoco 3420 14 g Ethomeen S-15 2500 ml Perchlorethylene 459 100 lO l5 20 25 30 35 l6 This mixture was balanced to give a 2/98 wt% W / Co-binder alloy. After grinding and mixing, the slurry was wet sieved to remove excessive particles and contaminants, dried at 93 DEG C. under a nitrogen atmosphere and then ground in a Fitzpatrick Co J hammer mill. 2 Fitzmill for breaking Using this powder, press bodies were pressed, which were then sintered at 1454 ° C for 30 minutes and cooled under ambient conditions.

The top and bottom of the insert (ie the chip surfaces) were then ground to the final thickness. This was followed by a heat treatment at 1247 ° C under a 100 μ vacuum. After 60 minutes at this temperature, the inserts were cooled at a rate of 5 ° C / h to 120 ° C and then oven-cooled under ambient conditions. The peripheral (or clearance surfaces) were then ground to a 12.70 mm square and the cutting edges of the insert were made to a radius of 0.064 mm.

These treatments resulted in an insert base in which only the chip surfaces had a cobalt-enriched and solid solution depleted zone, which zones had been ground away from the clearance surfaces.

The inserts were then introduced into a coating reactor and coated with a thin layer of titanium carbide using the following chemical vapor deposition techniques.

The hot zone containing the inserts 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 / min. The pressure in the reactor was maintained at slightly less than 1 atm. The hot zone was then heated from 900 ° C to 982 ° C. During this second heating step, the reactor pressure was maintained at 180 torr and a mixture of titanium tetrachloride and hydrogen as well as pure hydrogen gas was introduced into the reactor at a flow rate of 15 liters / min and 33 liters / min, respectively. The mixtures of titanium tetrachloride and hydrogen gas are obtained by passing the hydrogen gas through an evaporator which kept the titanium tetrachloride at a temperature of 47 ° C. When 982 ° C was reached, methane was also allowed to enter the reactor at a rate of 2.5 liters / min. The pressure in the reactor was reduced to 140 torr. Under these conditions, the titanium tetrachloride reacts with the methane in the presence of hydrogen to form titanium carbide on the hot insert surface. These conditions were maintained for 75 minutes, after which the flow of titanium tetrachloride, hydrogen and methane was stopped. The reactor was then allowed to cool while argon was allowed to pass through the reactor at a flow rate of 1.53 liters / min at a pressure of slightly less than 1 atm.

Examination of the microstructure of the final insert revealed a cobalt-enriched zone extending inwardly up to 22.9 μm and a cubic carbide solid solution depleted zone extending inwardly up to 19.7 μm from the chip surfaces of the substrate. The porosity in the enriched zone and the rest of the substrate were estimated to be between A-1 and A-2.

EXAMPLE 5 The material of this example was mixed and ground using a two step milling process with the following material batches: Step I (489600 rpm) 141.6 g (2.0 wt%) TaH 136.4 g (1.9 wt%) TiN 220.9 g (3.1 wt%) NbC 134 g (1.9 wt%) TaC 422.6 g (5.9 wt%) Co 31.2 g (0.4 wt%) C 14 g Ethomeen S-15 1500 ml Perchlorethylene Step II (81,600 rpm) 6098 g (84.9% by weight) WC 140 g Sunoco 3420 1000 ml Perchlorethylene 459 100 10 l5 20 25 30 35 18 This was balanced to give a 2/98 weight % W / Co-binder alloy.

The test batches were then prepared and TiC-coated in accordance with and together with the test substances described in Example 4. Microstructural evaluation of the coated batches revealed that the porosity of the cobalt-enriched as well as the main mass material was A-1.

The cobalt-enriched zone and the solid solution depleted zone extended inwardly from the chip surface to a depth of about 32.1 μm and 36 μm, respectively.

EXAMPLE 6 The following materials were charged to a mill drum with an inner diameter of 190 mm: 283 g (4.1% by weight) TaC 205 g (3.0% by weight) Nbc 105 g (1.5% by weight) TiN 7.91 g (0.1% by weight). wt%) C, 38l g (5.5 wt%) Co 5946 g (85.8 wt%) WC 140 g Sunoco 3420 14 g Ethomeen S-15 2500 ml Perchlorethylene This mixture was balanced to give a 2/98 wt% W / Co-binder alloy.

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 120 ° C under partial vacuum, after being ground in a Fitzmill screen. var- -mill through a 40 mesh SNG433 insert was then fabricated using the technique described in Example 4. However, the inserts in this example were CVD coated with a TiC / TiN coating. The coating process used was as follows: 459 100 19 l. TiC coating: The samples in the coating reactor were kept at about 1026-1036 ° C under a vacuum of 125 torr.

Hydrogen carrier gas flowed to a TiCl4 evaporator at a rate of 44.73 liters / min. The evaporator was kept at 33-35 ° C under vacuum. TiCl4 steam was entrained in the H2 carrier gas and carried into the coating reactor. Free hydrogen and free methane flowed into the coating reactor at a rate of 19.88 and 3.98 liters / min, respectively.

These conditions were maintained for 100 minutes to create a compact TiC coating which was adhesively bonded to the substrate. 2. TiN coating: The methane flow to the reactor was stopped and N2 was introduced into the reactor at a rate of 2.98 liters / min. These conditions were maintained for 30 minutes to create a compact TiN coating which was adhesively bound to the TiC coating.

Evaluation of the coated inserts gave the following results: Porosity Al, completely Cobalt-enriched zone, thickness Solid solution depleted zone, thickness TiC / substrate interface, eta solid thickness 17.0-37.9 μm up to 32.7 μm up to 3.9 pm Coating thickness TiC 3.9 pm TiN 2.6 pm Average Rockwell "A" - 91.0 hardness of the main mass Coercive force, Hc 98 örsted EXAMPLE 7 A material mixture was prepared using the following grinding cycle in two steps: In step I The following material was added to a WC-CO lined mill drum with an inner diameter of 18 mm and a length of 194 mm together with l7.3 kg of 4.8 mm WC-Co cycloids 459 100 10 15 20 25 30 35 20 The mill drum was rotated about its cylinder axis by 85 r / ml 48 hours (244,800 rpm) 140.8 g (2.0% by weight) Ta 72.9 g (1.0% by weight) TiH 23.52 g (0.3% by weight) C 458.0 g (6.5% by weight) Co 30 g Ethomeen S-15 120 g Sunoco 3420 1000 ml Soltrol 130 (one solvent) In step II, 6314 g (90.2% by weight) of WC and 1500 ml of Soltrol 130 were added and the whole charge rotated outer- li gare 16 h (8l600 rpm). This mixture was balanced to give a 5/95% by weight W / Co binder alloy.

After grinding, the slurry was wet sieved through a 400 mesh screen, tarkaaes unaer nitrogen at 93 ° C for 24 hours and ground in a Fitzmill grinder through a 40 mesh screen.

Samples were pressed uniaxially at a total force of 16,400 kg to 15, 11 mm x 1S, 11 mm x 5.28 mm (specific gravity 8.6 g / cm 3).

The above crude specimens were sintered at C for 150 minutes under 1 μ vacuum. The inserts were then cooled under ambient oven conditions. Fling graphite was used as a release agent between the provinces and the graphite sintering trays. 14680 The sintered inserts were made to a radius of 0.064 mm. The inserts were then coated with a TiC / TiCN / TiN coating according to the following procedure: 1. The inserts were located in the reactor and air was purged from the reactor by allowing hydrogen to flow through it. 2. The inserts were heated to about 1038 ° C while maintaining hydrogen flow through the reactor. the coating reactor pressure was maintained slightly above an atmosphere. 3. TiC coating: For 25 minutes a mixture of H 2 + TiCl 4 was introduced into the reactor at a rate of about 92 liters / min and methane was introduced into the reactor at a rate of 3.1 liters. /my. The TiCl4 evaporator was maintained at about 0.42 kg / cm 2 and 30 ° C. 4. TiCN ~ coating: For 13 min, the flow of H2 was maintained was reduced by half; and N + TiCl 4 mixture essentially; the methane stream 2 was introduced into the reactor at a rate of 7.13 liters / min. 5. TiN coating: During 12 minutes the methane flow was interrupted and the nitrogen flow rate doubled. At the end of the TiN coating, both the flow of the H2 + TiCl4 mixture was stopped and the heating element of the N reactor was switched off and the reactor was purged with free H2 until. it is cooled to about 25 ° C. at 20 DEG C. the reactor was purged with nitrogen.

It was determined that the insert pads had an A-1 to A-2 porosity in their non-enriched inner portion or material body mass. A cobalt-enriched zone and solid solution depleted zone extended from the surfaces about 25 microns and 23 microns, respectively. The non-enriched inner part had an average hardness of 91.7 Rockwell "A". The coercive force, Hc, of the substrate was found to be 186 örested.

EXAMPLE 8 A 260 kg mixture of powder having carbon balanced to C3 / C4 porosity in the final substrate was prepared using the following mixing and milling procedure in two steps: STEP I The following batch was ground in 96 hours: 10108 g TaC (6.08 wt% carbon) 7321 g NbC (11, 28 wt% carbon) 3987 g TiN 110 g * C (Molocco Black - a product of Industrial Carbon Corp) l6358 g Co 500 g Ethomeen S-15 364 kg 4, 8 mm Co-WC cycloids naphtha 459 100 10 15 20 25 30 35 22 STEP II The following was added to the above mixture and the mixture was ground for a further 12 hours: 221.75 kg WC 5.0 (6.06 wt% carbon) kg Sunoco 3420 naphtha The final mixture was then wet sieved, dried and ground in a Fitzmill grinder.

Inserts were then pressed and later sintered at 1454 ° C for 30 minutes. This sintering process created a cobalt-enriched zone, which was arranged over the material of the main mass with a C3 / C4 porosity. The sintered blanks were then ground and passed to SNG433 insert dimensions, resulting in removal of the cobalt enriched zone.

The sintered inserts were then packed with flake graphite inside an open graphite container. This was then subjected to hot isostatic pressing (HIP) at 1371-1377 ° C for 1 n 1 in an atmosphere of 25 vol1% NZ and '75 vol% He with a pressure of 8.76 x 108 dynes / cm 2.

Microstructural examination of a HIP-treated sample revealed that a cobalt-enriched zone with a depth of about 19.7 μm had been created during the HIP treatment. About 4 μm surface cobalt and 2 μm surface carbon were also created due to the C-type porosity substrate used.

EXAMPLE 9 A batch containing the following materials was ground in a ball mill: 30.0 wt% WC (average grain size 1.97 μm) 750 - kg 51.4 wt% WC (average grain size 4.43 μm) l286 kg 6.0 wt% co 150 kg 5.0 wt% WC-TiC carbide in solid solution 124.5 kg 6.1 wt% TaWC carbide in solid solution 152 kg l. 5 wt% W 37.5 kg 10 15 20 25 30 35 459 100 23 This mixture was charged to 6.00% by weight of total carbon.

These materials were ground for 5,1080 rpm with 3409 kg of cycloids and 798 liters of naphtha. A final grain size of 0.82 μm was achieved. 5000 g of powder were separated from the mixed and ground batch and the following materials were added thereto: 1.9% by weight of TiN (ground to about 1.4-1.7 μm) 96.9 9 0.2% by weight of C (Ravine 410) 9 , 4 g _ 1500 ml perchlorethylene These materials were then ground in a mill drum, which was lined with tungsten carbide and had an inner diameter of 190 mm and which contained 50% by volume of cycloids (l7.3 kg), for 16 hours. all through a 400 mesh screen, dried under partial vacuum in a sigma mixer at 21 ° C and then ground in a Fitzmill mill through a 40 mesh screen.

SNG433 blanks were pressed using a force of 3600 kg to create a blank density of 8.24 g / cm3 and a blank height of 5.84-6.10 mm. The substances were sintered at 1454 ° C for 30 minutes on an NbC powder release agent at a 10-25 μ vacuum and then allowed to cool in the oven. The sintered samples had sintered dimensions of 4.93 mm x 13.31 mm, a density of 13.4 g / cm 3 and a total magnetic saturation value of 146-150 gauss-cm 3 / g Co. Microstructural evaluation of the samples showed A-porosity throughout and a cobalt-enriched layer, which was about 21 microns thick.

The top and bottom of the inserts were then ground to a total thickness of 4.75 mm. The inserts were then heat treated at 124 ° C for 60 minutes at a vacuum of 100 μl, cooled to 120 ° C at a rate of 5 ° C / h and then oven cooled.

The clearance surfaces of each insert were ground to a square with the side 12.70 mm and the edges were drawn to a radius of 0.064 mm. 459 100 10 l5 20 25 24 The inserts were then CVD coated with titanium carbide / alumina using the following techniques.

The inserts were placed in a coating reactor and heated to about 1026-103 ° C and maintained at a vacuum of 88-125 torr. hydrogen gas was passed at a rate of 44.73 liters / min through an evaporator containing Tici4 at 35-3s ° C under vacuum. Tic14 vapor was entrained in the hydrogen gas and introduced into the coating reactor.

At the same time, hydrogen and methane flowed into the reactor at a rate of 19.88 and 2.98 liters / min. These conditions for vacuum, temperature and flow rate were maintained for 180 minutes, creating an adhesive TiC coating on the inserts. The hydrogen flow to the evaporator and the methane flow into the reactor were then stopped.

Hydrogen and chlorine were now allowed to flow to a generator, which contained an aluminum injection at 380 DEG-400 DEG C. and a pressure of 0.035 kg / cm @ 2. Hydrogen and chlorine flowed into the generator at a speed of 19.88 liters / min and 0.8-1.0 liters / min respectively. The chlorine reacted with the aluminum to form AlCl3 steam, which was then introduced into the reactor. While hydrogen and AlCl3 flowed into the reactor, CO2 also flowed into the reactor at a rate of 0.5 liters / min. These flow rates were maintained for 180 minutes, during which the inserts were maintained at 1026-1o28 ° C at a vacuum of about 88 torr. This process created a number 203 which was adhesively bonded to an inner coating of TiC. pact coating of A1 Evaluation of the coated inserts gave the following results: 459 100 25 Porosity Al in enriched zone, Al with scattered B in the main mass Cobalt enriched zone, thickness 39.3 pm play (chip surface) Solid solution depleted zone, up to 43.2 Pm thickness (chip surface) coating thickness TiC 5.9 μm Al2O3 2.0 μm _ Average Rockwell A- 91.9 hardness of the substrate main mass Coercive force, Hc l70 örsted EXAMPLE 10 An additional 5000 g of material was separated from the original batch of material obtained in Example 9.

Ground TiCN in an amount of 95.4 g (1.9% by weight) and 1.88 g (0.02% by weight) of Ravin 410 carbon black were added to this material, mixed for 16 hours, sieved, dried and ground in a Fitzmill. mill, as in Example 9.

The specimens were tablet pressed, vacuum sintered at 1946 ° C for 30 minutes and then oven cooled at ambient oven cooling rate. Evaluation of the sintered samples gave the following results.

Porosity Al throughout Cobalt-enriched zone, thickness approx. 14.8 pm Solid solution-depleted zone, up to 19.7 Pm thickness' Average Rockwell 92.4 A hardness of the substrate main mass Magnetic saturation l3O gauss-cm3 / g Co Coercive force (Hc ) 230 örsted 4 459 100 26 EXAMPLE 11 An additional 5000 g of material was separated from the original batch, prepared in Example 9.

Grinded TiCN in an amount of 95.4 g (1.9% by weight) was added, mixed for 16 hours, sieved, dried and ground in a Fitzmill mill, as in Example 9. Samples were then pressed and sintered at 1946. ° C together with the test pieces in Example 10.

Evaluation of the sintered samples gave the following results: - Porosity Al with strong eta phase throughout Cobalt enriched zone, thickness about 12.5 Fm Solid solution depleted zone, up to l6.4 μm thickness Average Rockwell 92.7 A hardness of the main mass Magnetic saturation 120 gauss-cm 3 / g Co Coercive force, Hc 260 örsted EXAMPLE 12 The following mixture was applied using the two-step grinding indicated below: STEP I The following material was added to a mill drum, was WC-Co- lined and had an inner diameter of 181 mm and was l94 mm long, together with 17.3 kg 4.8 mm WC ~ Co-cycloids. The mill drum was rotated about its cylinder axis at 85 rpm for 48 hours (24480 ° R). 455 g (6.5% by weight) Ni 280 g (4.0% by weight) TaN 12 g (1.6% by weight) TiN 266 g (3.8% by weight) NbN 42.7 g (0.6% by weight %) col 1410 9 Ethomeen S-15 1500 ml ;. perchlorethylene 10 15 20 25 30 35 459 100 27 STEP II The following was then added to the mill drum and this was rotated for a further 16 hours (81,600 rpm): 5890 g (83.6% by weight) WC 105 g Sunoco 3420 1000 ml perchlorethylene This mixture was balanced to After removing the mixture slurry from the mill drum, it was wet sieved through a 400 mesh screen (Tyler), dried at 93 DEG C. under a nitrogen atmosphere and ground with a Fitzmill grinder through a 40 mesh screen.

The specimens were tablet pressed, sintered at 145 DEG C. for 30 minutes in a nitrogen atmosphere at a pressure of 6.9 x 104 dynes / cm @ 2 and then oven cooled at ambient oven cooling rate.

After sintering, the samples were HIP-treated at 133 ° C for 9 dynes / cm 2. Optical 60 min in a helium atmosphere of 1 x 10 metallographic evaluation of the HIP-treated samples showed that the material had A-3 porosity throughout and a solid solution depleted zone with a thickness of about 25.8 μm.

The sample was then prepared again and examined by means of energy-scattering X-ray line scanning analysis (EDX) at different distances from the chip surface. Fig. 3 shows a graphical representation of the variation of the relative concentrations of nickel, tungsten, titanium and tantalum as a function of the distance from the chip surface of the sample. It is clear that there is a layer near the surface in which the titanium and tantalum, which form carbides which are in solid solution with tungsten carbide, are at least partially depleted. This solid solution depleted zone extends inward about 70 Pm. The discrepancy between this value and the value reported above is presumed to be due to the fact that the sample was rearranged between the evaluations so that different planes through the samples were examined at each evaluation. 459 100 10 15 20 25 30 35 28 Corresponding to the titanium and tantalum depletion, there is an enriched layer of nickel (see Fig. 3). The nickel concentration in the enriched layer decreases as the distance from the chip surface decreases from 30 to 10 μm.

This indicates that the nickel in this zone was partially volatilized during vacuum sintering.

The peak in the titanium and tantalum concentration at 110 Pm is thought to be due to scanning of one or more randomly large grains with a high concentration of these elements.

The two parallel horizontal lines show the typical scatter obtained in an analysis of the main mass of the sample around the nominal chemical mixture composition.

EXAMPLE 13 The following mixture was charged using the grinding cycle indicated below in two steps: STEP I v The following material was ground according to step l in Example 12 455 g (6.4 fold) Ni 280 g (3.9% by weight) TaH 112 g (1 , 6% by weight) TiN 266 g (3.7% by weight) NbN 61.6 g (0.9% by weight) C Ravine 410, 502 14 g Ethomeen S-15 2500 ml perchlorethylene STEP II The following was then added to the mill drum and rote was further stirred for 16 hours: 5980 g (s3.6 weighted wc 140 g Sunoco 3420 This mixture was balanced to give 10/90 wt% W / Ni binder alloy. 10 l 20 20 25 30 35 459 100 29 After discharging the mixture was sieved it, dried and ground in a Fitzmill mill according to Example 12.

Pressed specimens were vacuum sintered at 1446 ° C for 30 minutes under a 35 micron atmosphere. The sintered samples had an A-3 porosity throughout and a solid solution-depleted zone, which was up to 1.3 μm thick.

EXAMPLE 14 A mixture was charged using the following milling cycle in two steps: STEP I The following material was added to a mill drum, which was WC-Co lined and had an inner diameter of 190 mm and was 194 mm long, together with 17.3 kg 4 , 8 mm WC-Co-cycloids. The mill drum was rotated about its axis at 85 rpm for 48 hours (244,800 rpm): 177 g (2.5% by weight) HfH2 132.3 g (2.5% by weight) TiH2 55.3 g (0.8% by weight) carbon 459 9 (6.4% by weight) Co 14 g Ethomeen S-15 2500 ml perchlorethylene STEP II The following was then added to the mill drum and rotated for an additional 16 hours (81,600 rpm): 6328 g 140 g (87.9% by weight) WC Sunoco 3420 This mixture was balanced to give 10/90% by weight of W / Co binder alloy.

After removing the slurry from the mill drum, the slurry was screen sieved through a 400 mesh cross-section, dried at 93 ° C under a nitrogen atmosphere and ground in a Fitzmill grinder through a 40 mesh screen.

Inserts were compressed and then sintered at 458,468 ° C for 30 minutes under a 35 P vacuum, which allowed volatilization of a major portion of the hydrogen in the samples. During sintering, the samples were collected on an NbC powder release agent.

The sintered sample had A-2 porosity in the enriched zone and A-4 porosity in the non-enriched main mass of the sample. The sample had an average Rockwell "A" hardness of 90, a zone of solid solution depletion, which was 9.8 μm thick, 150 örsted.

EXAMPLE 15 and a coercive force, Hc, of A batch of material having a composition similar to that of the batch of Example 9, was mixed, ground and pressed into blanks. The blanks were then sintered, ground, heat treated and ground (only the release surfaces) essentially according to the procedure used in Example 9. However, a cooling rate of 69 ° C / h was used in the final heat treatment.

An insert was analyzed by EDX line scan analysis at different distances from the insert's chip surfaces.

The result of this analysis is shown in Fig. 2. Fig. 2 shows the presence of a cobalt-enriched layer extending inwards from the chip surfaces to a depth of about 25 μm, followed by a layer of material which is partially depleted of cobalt and which extends its up to about 90 pm from the chip surfaces. Although not shown in the diagram in Fig. 2, partial solid solution depletion has been found in the cobalt enriched layer and solid solution enrichment has been found in the partially depleted cobalt layer.

The two horizontal lines indicate the typical spread when analyzing the material of the main mass around the nominal chemical composition of the mixture.

The foregoing description and examples have been given to illustrate some of the possible alloys, products and processes as well as uses which fall within the scope of the invention as defined in the appended claims.

Claims (16)

10 15 20 25 30 459 100 31 PATENT REQUIREMENTS Carbide body, characterized in that it comprises a metallic binder and a solid solution of a first carbide, which is made of tungsten carbide, and a second carbide or carbonitride of a transition metal, the carbide of which has a free formation energy which is more negative than that of the first carbide near the melting point of the binder, and that the cemented carbide body has an adhesive-enriched and solid solution depleted layer which begins at and extends inwardly from a peripheral surface of the body, and the cemented carbide body preferably has substantially A- to B- type porosity throughout the body. Carbide body according to Claim 1, k n n e - t e c k n a d gang metal in group IVB or VB. that the transition metal is a transition metal Cemented carbide body according to Claim 1 or 2, characterized in that the transition metal is chosen from tantalum, titanium, niobium, hafnium, zirconium and vanadium. Cemented carbide body according to claim 3, characterized in that the transition metal is titanium. The cemented carbide body according to any one of claims 1 to 4, characterized in that the adhesive-enriched layer has a thickness of at least about 6 μm, preferably 12-50 μm. The cemented carbide body according to any one of claims 1-5, characterized in that the binder content of the binder-enriched layer is 150-300% thereof, the average binder content of the cemented carbide body. Cemented carbide body according to one of Claims 1 to 6, characterized in that the metallic binder is chosen from cobalt, nickel, iron or the like, alloys thereof. 459 100 10 15 20 25 30 35 32 Cemented carbide body according to claim 7, t o c k n a d is cobalt. k n n e - hence, that the metallic binder The cemented carbide body according to any one of claims 1 to 7, characterized in that the metallic binder is a cobalt alloy having a total magnetic saturation value of less than 155 gauss-cm 3 / g cobalt. The cemented carbide body according to claim 1, characterized in that it comprises a metallic binder of cobalt and a solid solution of tungsten carbide with a second carbide of a transition metal of group IVB or VB, and that the cemented carbide body has a layer near it which is enriched in cobalt and peripheral surface at least partially depleted in the solid solution, and below it a layer which is partially depleted in cobalt and enriched in the solid solution. 11. A process for producing a cemented carbide characterized in that a compact is produced with a substantially uniform distribution of a metallic binder, a first carbide consisting of tungsten carbide, and a chemical agent selected from metals, alloys, hydrides, nitrides and carbonitrides of transition metals whose carbides have a free formation energy which is more negative than that of the first carbide near the melting point of the binder, that the compact is densified and heat-treated, whereby the chemical is at least partially converted into solid carbide the first carbide, and that during the heat treatment the binder content is increased towards the peripheral surface of the compact so that a layer is formed which begins at and extends inwards from the peripheral surface and which is enriched in binder and depleted in solid solution, and the compact preferably has mainly A- to B-type porosity throughout the body. 12. l2. Process according to claim 11, characterized in that the compact is prepared by grinding and mixing powders of the metallic binder, the first carbide and the chemical agent, pressing the powders into a compact, and sintering. of the compact at a temperature above the melting temperature of the binder. 13. A process according to claim 11 or 12, characterized in that the chemical agent is selected from metals, alloys, hydrides, nitrides and carbonitrides of transition metals of Group IVB and VB. 14. A method according to any one of claims 11-13, characterized in that the metallic binder is selected from cobalt, alloys thereof. nickel, iron or of claims ll-14, that the chemical agent 15. A method according to any one of the following, is added in an amount of up to about 15% by weight, preferably 0.5-2% by weight of the compact. Process according to any one of claims 11-14, characterized in that the chemical agent is selected from the transition metals tantalum, titanium, niobium, hafnium, zirconium and vanadium or alloys, hydrides, nitrides and carbonitrides thereof.