KR20090107554A - Metal formulations - Google Patents

Abstract

The invention relates to a formulation which contains at least one hard material powder and at least two binder metal powders. Said formulation is characterized in that the cobalt is completely contained in the first binder metal powder and is prealloyed with one or more elements of groups 3 to 8 of the periodic system of elements, which are elements of the fourth period, and that at least one additional binder metal powder of the group of elementary powders including Fe, Ni, Al, Mn, Cr or the alloys thereof with each other is contained therein and the additional binder metal powders do not contain any cobalt in non-prealloyed form.

Description

Metal Formulations {METAL FORMULATIONS}

The present invention relates to metal formulations.

Formulations comprising a powdered hard material and a powdered binder metal are used industrially in particular to produce spray powders or carbide materials for surface coatings. In the case of carbides, the most commonly used carbide is tungsten carbide. Others, such as titanium, vanadium, chromium, tantalum and niobium carbide or mixtures with each other or with tungsten carbide, are generally used only as additives. In addition, nitrides can be used. Cobalt is the most commonly used binder metal, but binder systems containing 2 or 3 elements among Fe, Co and Ni are also used. In spray powders also binder systems are used which comprise, for example, two or three elements of Mn, Al, Cr. Further possible inorganic additives are metal powders such as tungsten, molybdenum, and also elemental carbon. If the cemented carbide material contains titanium carbonitride instead of tungsten carbide as its main component, it is referred to as "cermet". Further possible hard materials are borides.

As the binder metal in the cemented carbide material and spray powder, cobalt is generally used, but nickel or alloys of Fe, Co and Ni may also be used. In all cases, the binder phase after sintering or thermal spraying comprises a certain proportion of, for example, tungsten, chromium, molybdenum and carbon derived from hard materials as a result of the exchange of carbide phase and elements in liquid phase sintering or fusing. The powdered binder metal used is one of elemental powders such as iron, nickel, cobalt powder, or else alloy powder.

The binder phase of the spray powder contains the aforementioned elements and inorganic additives as well as other elements such as Al, rare earths, yttrium and the like.

Over the decades, the carbide material industry has observed a significant increase in the incidence of pulmonary fibrosis with certain patterns of pattern, and this increase in the incidence of pulmonary fibrosis is due to the handling of dust-type cemented carbide materials or the production of cemented carbide materials. It has been associated with the handling of dusty formulations. The disease is called "cemented carbide lung" and is the subject of numerous epidemiological studies and publications. In the customary production of cemented carbide materials by powder-metallurgical manufacturing processes, ie by pressing and sintering of powdered hard materials / binder formulations, the characteristics of the process free the breathable dust. When the carbide material is machined by grinding in the sintered or pre-sintered state, very fine breathable dust ("grinding dust") is likewise formed.

Thermal spraying of carbide containing spray powders likewise produces very fine dust (“overspray”).

Similarly, since about five years ago, it has been known that cemented carbide materials have additional severe toxic effects on rats after inhalation if the concentration is very sufficient. The exact mechanism of action has not been known to date. Two components, tungsten carbide and cobalt, do not show this effect to themselves. Thus, in order to improve occupational hygiene, there is a great interest in identifying mechanisms of action and alternatives that do not exhibit serious toxic effects or significantly reduce severe toxic effects.

It is an object of the present invention to provide a formulation with cobalt which reduces inhalation toxicity during thermal spraying of the formulation and grinding machining of presintered cemented carbide parts ("gray machining") and grinding machining of cemented carbide material. This object comprises at least one hard material powder and at least two binder metal powders, all cobalt present in the first binder metal powder and prealloyed with at least one element of groups 3 to 8 of the periodic table of elements, element Fe There is at least one further binder metal powder from the group consisting of powders of Ni, Al, Mn, Cr and alloys of one another with each other, the further binder metal powder containing no cobalt in an unalloyed form. It is achieved by a formulation characterized in that it does not.

It is surprising that the severe toxic effects of the dusty formulations of tungsten carbide with cobalt are based on the phenomenon of electrochemical corrosion which increases the bioavailability of cobalt after inhalation.

In addition, when the cobalt as a binder metal in the hard material / binder formulation is prealloyed with iron or other elements of groups 3 to 8 (transition groups IIIa to VIIa) of the periodic table of elements (these elements are not alloyed side by side with cobalt) It is surprising that the inhalation toxicity is lost, not when it is present. In principle, all metals located on the left side of the cobalt in the periodic table and preferably arranged in the same cycle result in a reduction in corrosion tendency as a result of the less inert properties, but more inactive elements, such as copper, even as additional phases The presence of copper in the present alloy state also has the opposite effect that can be seen.

The alloy partner of cobalt in the first binder metal powder is advantageously the fourth period of the periodic table and the elements of groups 3-8. It is particularly advantageous for the alloy partner of cobalt in the first binder metal powder to be an element selected from the group consisting of Fe, Ni, Cr, Mn, Ti and Al. The first binder metal powder may also further contain elements such as aluminum and / or copper.

The first binder metal powder is a separate matter and additional binder metals are generally needed. These metals are particularly advantageously selected from the group consisting of iron powder, nickel powder, FeNi alloy powder and prealloyed FeNi alloy powder.

Hard materials are typically titanium carbide, vanadium carbide, molybdenum carbide, tungsten carbide or mixtures thereof with each other. These compounds are also known as catalysts for the reduction of metals in aqueous media by catalysts for the reduction of oxygen, thus oxygen reduction mechanisms, ie Co + 1 / 2O ₂ + H ₂ O = Co (OH) ₂ .

In the case of spray powders, the at least one additional metal powder may contain Fe, Ni and additional elements such as Al, Cr, Mn, Nb, Ta, Ti, but not with cobalt except inevitable ranges. It does not contain impurities.

It is preferable that the first binder metal powder containing cobalt and mixed perfectly contains 10 wt% to 50 wt% of cobalt. The ratio of iron to cobalt is particularly preferred at 1: 1. Suitable compositions are, for example, FeCo 50/50, FeCoNi 90/5/5. This powder may additionally contain additional elements of the iron group.

Further binder metal powders or powders which do not contain any cobalt in prealloyed form are preferably iron or nickel based. That is, the total content of iron and nickel is at least 50%. The additional powder or the remainder of the powders contains at least 50% iron and nickel in total. As further binder metal powders, it is advantageous to use FeNi powders containing up to 30% Fe, alloy powders of the composition of FeNi 50/50, FeNi 95/5.

The weight ratio of the first binder metal powder to the additional powder or powders is preferably 1:10 to 10: 1, but particularly preferably 1: 5 to 5: 1. One skilled in the art can select the required ratio based on the desired stoichiometry and available alloy powders.

The further binder metal powder advantageously has a BET surface area of greater than 0.3 m ² / g, more advantageously greater than 0.5 m ² / g, in particular greater than 1 m ² / g.

In the cemented carbide materials and spray powder industry, the use of prealloyed powders containing two or more elements from the group consisting of Fe, Co, and Ni and exhibiting a composition on the binder with respect to these elements has led to the use of two or more to produce such formulations. It is a prior art because it uses three elemental powders. While the latter change does not reduce toxicity, the toxicity is reduced or eliminated by perfect mixing of the binder system. Such alloy powders from hydrogen reduction of oxides or other compounds are commercially useful but have significant disadvantages over elemental powders. For example, the oxygen content is high and the processability is poor. Ni and Fe powders, in particular, can be produced by the carbonyl process to achieve very low oxygen content because of the production of fine alloy powders with a specific surface area of which the reduction potential of carbon monoxide is greater than 1 m ² / g. This is because it is larger than hydrogen which is generally used.

Thus, advantageous formulations include, for example, a) at least one prealloyed powder selected from the group consisting of iron / cobalt and iron / nickel / cobalt, b) at least one elemental powder selected from the group consisting of iron and nickel or a) Using a pre-alloyed powder selected from the group consisting of iron / nickel different from the components, c) a hard material powder having a total composition of components a) and b) together containing up to 90% by weight of cobalt and up to 70% by weight of nickel Is a formulation achieved by a process of making a hard material / binder mixture. The iron content is advantageously at least 10% by weight.

In an advantageous embodiment of the invention, a method of preparing a hard material / binder mixture according to claim 1 is provided, wherein the total composition of the binder is up to 90% by weight of Co, up to 70% by weight of Ni and at least 10% by weight. Fe, where the iron content satisfies the following inequality,

(Wherein Fe: wt% iron content,% Co: wt% cobalt content,% Ni: wt% nickel content)

At least two binder powders are used, one binder powder having a lower iron content than the total composition of the binder, the other binder powder has a higher iron content than the overall composition of the binder, and the at least one binder powder is composed of iron, nickel and cobalt Prealloyed from at least two elements selected from

Although chemical exchange between the binder phase and the carbide phase and between the molten particles of the binder metal powder occurs during thermal spraying of the compacted formulations for producing cemented carbide materials and also during liquid phase sintering, it is sufficient to use elemental powders from a material standpoint. , From a toxicological point of view according to the above examples, it is sufficient to prealloy only the cobalt content with a minimum amount of iron, nickel, manganese, chromium or titanium, the remainder of the desired total composition on the binder metal, such as iron and / or nickel content Or the content of the additional metal is set in the form of the corresponding elemental powder or, for example, FeNi alloy powder. Such novel measures in formulation formulation can satisfy both aspects (toxicology and oxygen content or control of carbon content after sintering). In addition, there is an advantage that the workability is significantly improved by only partial use of the prealloyed powder over the exclusive use of the prealloyed powder.

Thus, the formulations shown in Tables 1a and 1b in which the first and second binder metal powders are provided in a ratio of 1: 1 are particularly advantageous.

Also preferred are the formulations of Tables 2 and 3.

Table 2: Table 2 presents 54 formulations with numbers 2.01 to 2.54, wherein the ratios of the alloying elements of the first binder metal powder, the additional binder metal powder and the first binder metal powder and the second binder metal powder are shown in Table 1 and The same, the first binder metal powder and the additional binder metal powder are provided in a ratio of 1: 2. This means that for formulation 2.01, the first alloy powder is FeCo 50/50, the additional alloy powder is FeNi 30/70, and the ratio of FeCo to FeNi is 1: 2.

Table 3: Table 3 presents 54 formulations with the numbers 3.01 to 3.54, wherein the ratio of the alloying elements of the first binder metal powder, the additional binder metal powder and the first binder metal powder and the second binder metal powder is shown in Table 1 and The same, the first binder metal powder and the additional binder metal powder are provided in a ratio of 2: 1. This means that for Formulation 3.01, the first alloy powder is FeCo 50/50, the additional alloy powder is FeNi 30/70, and the ratio of FeCo to FeNi is 2: 1.

Accordingly, the present invention provides a metal formulation comprising at least one hard material powder and at least two binder metal powders, wherein group 3 of the periodic table of elements is present in which all cobalt is present in the first binder metal powder and is an element of the fourth cycle. Pre-alloyed with at least one element of Groups 8 to 8, wherein at least one additional binder metal powder and alloys of these elements are present from the group consisting of powders of elements of Fe, Ni, Al, Mn, Cr and further binder metal powder Is characterized in that it does not contain any cobalt in prealloyed form;

A metal formulation comprising at least one hard material powder and at least two binder metal powders, wherein all cobalt is present in the first binder metal powder and prealloysed with one or more elements of groups 3 to 8 of the Periodic Table of the Elements, element Fe At least one additional binder metal powder is present from the group consisting of powders of Ni, Al, Mn, Cr and alloys of each other with each other and the additional binder metal powder does not contain any cobalt in prealloyed form, And the free corrosion potential between the hard material and the first binder metal powder measured in air saturated water at room temperature is less than 0.300 volts (preferably less than 0.280 volts), and the hard material has an anode;

A metal formulation comprising at least one hard material powder and at least two binder metal powders, wherein all cobalt is present in the first binder metal powder and prealloysed with one or more elements of groups 3 to 8 of the Periodic Table of the Elements, iron powder At least one additional binder metal powder selected from the group consisting of nickel powder, FeNi alloy powder and prealloyed FeNi alloy powder is used, and the additional binder metal powder is characterized in that it does not contain any cobalt in its non-alloyed form. . In all three metal formulations described above, especially hard materials advantageously have a BET surface area of greater than 0.3 m ² / g, preferably greater than 0.5 m ² / g, particularly preferably greater than 1 m ² / g Titanium carbide, vanadium carbide, molybdenum carbide or tungsten carbide.

In a further embodiment of the invention, the alloy partner of cobalt in the first binder metal powder of the metal formulation is an element of a fourth cycle;

The alloy partner of cobalt in the first binder metal powder of the metal formulation is an element selected from the group consisting of Fe, Ni, Cr, Mn, Ti, and Al,

The first binder metal powder in the metal formulation may contain additional alloyed elements, aluminum and / or copper (Cu) may be used as additional elements.

In a further embodiment of the present invention, at least one further binder metal powder selected from the group consisting of iron powder, nickel powder, FeNi alloy powder and prealloyed FeNi alloy powder is present in addition to the first binder metal powder.

In all of the metal formulations described above, the free corrosion potential between the hard material and the first binder metal powder measured in air saturated water at atmospheric pressure and room temperature is less than 0.300 volts, and the hard material has an anode.

The hard materials which may be present are, in particular, titanium titanium carbide, vanadium advantageously having a BET surface area of greater than 0.3 m ² / g, preferably greater than 0.5 m ² / g, particularly preferably greater than 1 m ² / g. Carbide, molybdenum carbide or tungsten carbide.

In all such metal formulations, the weight ratio of first binder metal powder to additional binder metal powder or powders is advantageously between 1:10 and 10: 1. All such metal formulations advantageously comprise a) at least one prealloyed powder selected from the group consisting of iron / cobalt and iron / nickel / cobalt, b) at least one elemental powder selected from the group consisting of iron and nickel or a A prealloyed powder comprising iron / nickel different from the components of c), c) a hard material powder containing a total composition of components a) and b) together containing up to 90% by weight of cobalt and up to 70% by weight of nickel can do. In such metal formulations, the iron content is advantageously at least 10% by weight.

In such metal formulations, the overall composition of the binder is advantageously at most 90% by weight of Co, at most 70% by weight of Ni and at least 10% by weight of Fe, wherein the iron content satisfies the following inequality,

(Wherein Fe: wt% iron content,% Co: wt% cobalt content,% Ni: wt% nickel content) and at least two binder powders are used, and one binder powder is made of iron rather than the entire composition of the binder. The content is low and the other binder powder has a higher iron content than the overall composition of the binder and the at least one binder powder is prealloyed from at least two elements selected from the group consisting of iron, nickel and cobalt.

Such metal formulations are advantageous for a variety of applications, and such metal formulations can be used to produce cemented carbide materials or sintered porous aggregates.

Such porous aggregates can be obtained by sintering without pressing one of the metal formulations described above.

Also suitable are thermal spray powders which contain such porous aggregates which can be obtained by sintering without pressing one of the above metal formulations and which contain Al, yttrium and / or rare earths.

The present invention also provides a method for controlling the toxic effects of cobalt containing metal formulations, wherein one of the metal formulations described above, advantageously one of the metal formulations set forth in Tables 1 to 3, produces a cemented carbide material or a sintered porous aggregate It is characterized by being used to.

In general, the present invention provides a method for controlling the toxic effects of cobalt containing metal formulations, characterized in that cobalt is prealloyed with one or more elements of Groups 3-8 of the Periodic Table of the Elements in the metal formulation.

Accordingly, the present invention provides a method for controlling the toxic effects of a cobalt-containing metal formulation, wherein the metal formulation according to the invention, the porous aggregate according to the invention or the thermal spray powder according to the invention is used to produce a shaped body or coating. Used for In the method for controlling the toxic effects of cobalt containing metal formulations, the toxic effects are especially pulmonary fibrosis and / or cemented carbide lung disease.

1 schematically shows the experimental setup used.

2 shows the aerosol concentrations plotted against mortality and assigned to the examples.

Since the high bioavailability of cobalt is based on electrochemical corrosion phenomena, the free corrosion potential between the hard material and the first binder metal powder measured in air saturated water at atmospheric pressure and room temperature is less than 0.380 volts according to the invention, preferably Is less than 0.330 volts, particularly preferably less than 0.300 and particularly very advantageously less than 0.280 volts, tungsten carbide has an anode. 1 schematically shows the experimental setup used. Reference numeral 1 designates an anode composed of tungsten carbide (or other hard material), reference numeral 2 designates a cathode composed of a binder metal, such as cobalt or a binder metal formulation according to the present invention, and reference numeral 3 is a reaction medium. Indicates tap air saturated water.

However, if cobalt is alloyed with iron, the contact voltage is greatly reduced even if iron is less inert than cobalt. The reason for this phenomenon is unknown. As the free corrosion potential decreases, it can be readily seen that the driving force of the corrosion phenomena decreases or the corrosion progresses more slowly and the bioavailability is likewise reduced. Thus, the free corrosion potential of the measurement setup described in Example 4 can serve as an indicator of inhalation toxicity of the expected hard material / binder metal formulation. An additional indicator of anticipated inhalation toxicity is the amount of dissolved binder metal that becomes solution as soon as the corresponding contact element comes into contact with water in the presence of oxygen over a predetermined time period.

The reason for the inhalation toxicity phenomenon, which can only be explained by the high interaction of the inhaled dust with the organism, is the synergy between the two components cobalt and the hard material, neither of which exhibits the behavior known from the literature. Because it turned out to be not. In addition, since the dependence of the two components on the geometric contact strength has been found in the present invention, the increase in the bioavailability caused by corrosion appears to be a reasonable explanation for the toxicological effects. Carbide materials have long been known as contact corrosion elements. For example, an aqueous cooling fluid preferentially dissolves cobalt from the cemented carbide material when used for grinding cemented carbide material. The theory by Megede (Universitaet Frankfurt a. Main, 1985) examines the mechanism in detail. Cobalt is corroded in the presence of water and oxygen by the oxygen reduction principle to form a hydroxide layer having a passivation effect on the surface. Tungsten carbide catalyzes electron transfer in the formation of hydroxide anions, which greatly accelerates corrosion and progresses in phase. As a result, the passivation effect of the hydroxide layer is impaired. Likewise, this explains why tungsten carbide is found in the section of cemented carbide lung disease but no cobalt is found. Cobalt is clearly corroded and reabsorbed in an accelerated form. The resulting increased bioavailability of cobalt at small doses / concentrations causes chronic disease (pulmonary fibrosis or "carbide alloy lung disease") at high concentrations for sensitive toxic phenomena. The bioavailability of cobalt has an adverse effect on the organism that has not been fully described to date. Description attempts include stabilization of reactive oxygen species, such as superoxides, by addition or complex formulation of ionic cobalt to DNA, for which cobalt is known.

In the case of cemented carbide materials and carbide spray powders, the corrosion resistance determined by chemical attack on the binder can be improved by adding Cr carbide or Cr metal to the formulation. In both cases, Cr is partially present in alloyed form in the binder after sintering or thermal spraying. If the concentration of Cr in the binder is high enough to be controlled by the carbon balance, the cemented carbide material or spray layer is significantly more corrosion resistant, from which WC-Co is purely toxic to dust when grinding such carbide material or overlay. Much less can be terminated. Further improvements in corrosion resistance can be achieved by partial replacement of cobalt with nickel, which is likewise an industrial practice in the case of cemented carbide materials.

In conclusion, the sensitive toxic effects of cemented carbide dust can be correlated with the rate of corrosion in the presence of water and oxygen. Free corrosion potential can be reduced by alloying cobalt with, for example, iron, so that cobalt containing formulations with cobalt prealloyed with iron are very less sensitive to inhalation toxicity. This is supported by the finding that the binder phase has a better corrosion resistance to oxidizing acids in the presence of air than cemented carbide materials containing cobalt and iron (TU Wien, Wittmann, 2002). Papers).

Some intermediates in the manufacture of cemented carbide materials can be expected to be particularly inhaling toxic, including dust from grinding machining ("gray machining") of presintered cemented carbide material parts. Here, the formulation is pressed so that sufficient mechanical strength of the sintered body to be machined by grinding is obtained as a result of the sintering bridge and sintered at a temperature below the melting eutectic point ("sintering"). In this state, the sintered body is still porous and no longer contains any organic additives, so the cobalt is still sufficiently present in elemental form since the powder used is not yet equilibrated in the formulation. This cobalt combined with the porous structure of the grinding dust means that very high inhalation toxicity is expected. Even if cobalt metal powders as well as ferrous metal powders are used to prepare the formulation, a reduction in toxicity may not be expected because virtually no interdiffusion (= alloy formulation) between cobalt particles and iron particles occurs during pretreatment.

Spray powders sintered from granular formulations are difficult to disperse in air due to their size, but breathable fine particles formed as a result of internal friction during handling of the powder are highly toxic (see Example 1e).

The formulations according to the invention can be used, for example, to produce cemented carbide materials or sintered porous aggregates, and the sintered porous aggregates can advantageously be used in thermal spray powders. Carbide materials with binder systems based on FeCoNi, in particular depending on the composition, are advantageous in accordance with the invention in many applications, providing technical advantages over purely cobalt-bonded materials.

According to the invention, the prealloyed powder is a metal powder containing the composition of the binder in terms of Fe, Co and Ni content in the form of atomic dispersion in each powder particle. Powders premixed within the meaning of the present invention may be obtained by precipitation and reduction as described in alloy powders subdivided from the melt or in the literature cited in US-B-6554885, EP-A-1079950 and these publications, or In principle, suitable powders may be alloy powders prepared by other processes such as carbonyl process, plasma process, CVD, etc., as described, for example, in US-B-6554885, EP-A-1079950 and the literature cited in these publications. Alloy powders obtainable by precipitation and reduction are advantageous. The manufacture of carbide spray powder corresponds to the preparation of granular formulations in the production of cemented carbide materials, but the granules are not pressed and instead are sintered on their own at a temperature below or slightly above the lowest shared temperature and then sorted. The organic additive in question is removed at that stage. The particles obtained in this way are still porous and have a sintered neck between the carbide material and the particles showing the binder metal phase.

The spray powder may contain other elements such as Al, rare earth, yttrium, in addition to the above-mentioned elements and the inorganic additive on the binder.

Formulations for the production of cemented carbide materials and spray powders generally aid in further processing and handling as well as the inorganic components described above, but no longer exist after firing of cemented carbide material or spray powder, such as paraffin, polyethylene glycols, inhibitors, etc. Also contains organic additives. These formulations can be subdivided, for example by spray drying. In addition, plasticizers such as polyethylene and paraffin wax, as used in extrusion, and binders such as carboxylic acids and dispersants may be provided.

Industrially customary formulations composed of hard materials and binder metals also always contain oxygen because the surface of the powder is treated with air, as a result of milling and mixing in aqueous liquids and subsequent drying. Because it is coated with. The oxygen in question reacts with the carbon present in the elemental form in the carbide or formulation during subsequent heat treatment to form carbon monoxide and carbon dioxide, thereby overturning the equilibrium between the metal content and the carbon content of the sinter or spray powder that must be correctly maintained. . In general, the oxygen content of the formulation should be kept as low as possible to better control the metal / carbon equilibrium.

Yes

On behalf of the applicant all examples were carried out by the inhalation study as defined by EEC (Appendix II.5.2.3) by Huntingdon Life Sciences, Cambridge, England. The powder under test was atomized as an aerosol and blown into a chamber in which 10 rats were present. The concentration of aerosol was reported in mg / l and the mean particle size in μm. The ratio is greater than 7 μm in percent and the abbreviation for time is h. The dust concentration in the chamber and the size distribution of the particles were measured (Marple cascade Impactor Mod. 298 manufactured by Graseby Andersen, Aklanta, GA). After 4 hours, the number of dead or dying mice was measured and the total number was reported as death.

Example 1 Inhalation Toxicity of WC / Co Formulations

a) Tungsten carbide-cobalt composites were prepared as described in WO 01/46484 A1. This composite contained 10% cobalt. This composite has very close contact between cobalt particles and tungsten carbide particles. The results of inhalation experiments at a concentration of 0.25 mg / l resulted in 100% mortality. The average particle size in the chamber was 2.5 μm and 90% of the particles were less than 7 μm.

b) A mixture of tungsten carbide and cobalt metal powder containing 10% by weight cobalt was prepared and the inhalation experiment was repeated at three concentrations.

Effective concentration death rate Average particle size Ratio <7 μm 0.24 30 4 75 0.52 100 4.2 74

c) A mixture of cobalt and tungsten carbide containing 6% cobalt was prepared. The results of inhalation experiments at an effective aerosol concentration of 0.26 mg / l were 0%, but 20% were stopped three days after the introduction of the aerosol into the chamber. The average particle size was 3.8 μm, with 79% of all particles smaller than 7 μm.

d) A mixture of tungsten carbide and cobalt containing 10% cobalt was milled and mixed as a dispersion in hexanes for 4 hours. Paraffin wax was added to finish 1 hour before milling and to assign 2% by weight of paraffin in the formulation based on the solids content. After milling and mixing for 4 hours, the hexanes were removed by vacuum distillation to form paraffin containing powder. This powder was used to test inhalation experiments at three concentrations. The result is as follows.

Effective concentration death rate Average particle size Ratio <7 μm 0.24 0% 3.2 87 1.08 20% 4.2 83

e) Sintered porous tungsten carbide-cobalt powder containing 17% cobalt and having a set particle size distribution of 5 to 30 mm was examined by suction test. the results are as follow. Effective aerosol concentrations varied from 1.01 to 0.93 mg / l, mortality was 60%, mean particle size in the chamber was determined to be 5.2 to 5.6 μm, and about 20% of the particles were less than 7 μm.

The results show that the inhalation toxicity of the WC / Co formulations depends on various influencing factors.

The highest toxicity is shown by example a). Due to the way it is produced, the maximum contact dimension is provided between the cobalt particles and the tungsten carbide particles.

Example b) with very low contact between cobalt and WC particles in the powder mixture is less toxic.

Likewise, example c) is a powder mixture but once again the effect is reduced as the cobalt content is reduced.

Example d) performed using two concentrations shows further reduced toxic effects. Since the contact between cobalt particles and tungsten carbide particles is very strong due to attritor milling, the reduced toxicity contributes to the hydrophobicization by the paraffin wax in question (2% by weight corresponding to 25% by volume).

Example e) shows the toxicity of conventional thermal spray powders. It should be noted here that only a fraction of the powder can reach the lungs because of the relatively coarse particles, but nevertheless significant deaths occur.

Comparing Examples a) to f), in addition to the ability to reach the lung and any content of hydrophobization agent, it can be seen that the contact strength between CO and WC is a major influence parameter on the degree of inhalation toxicity.

Example 2 Inhalation Toxicity of WC / FeCo Formulations

a) Conventional industrial cemented carbide grinding dust with a content of 70.6% tungsten carbide, 14.8% cobalt and 12.2% iron, as obtained from the final machining by grinding of cemented carbide, showed a mortality of 70% in suction experiments. . The effective aerosol concentration was 0.28 mg / l and the average particle size was 4.3 μm. 76% of all particles were smaller than 7 μm.

b) A mixture comprising 90% tungsten carbide, 5% iron powder and 5% cobalt metal powder was milled in the adapter as described in example d) but no paraffin was added. Due to the deformation process caused by milling, iron and cobalt fused and partially melted together, but did not alloy with each other. The results of two inhalation experiments using this powder are as follows.

Effective Aerosol Concentration death rate Average particle size Ratio <7 μm 0.25 0% 2.8 86 1.03 30% 3.2 85

c) A composite containing 5% iron, 5% cobalt and 90% tungsten carbide was prepared as described in WO 01/46484 A1. Here, iron and cobalt were perfectly alloyed with each other. The following results were obtained from the inhalation experiment.

Effective Aerosol Concentration death rate Average particle size Ratio <7 μm 0.988 0% 3 94 5.03 0% 3.7 84

As a typical industrial grinding dust obtained from final machining by grinding cemented carbide, example a) has a relatively very high toxicity. The iron content of 12% is due to wear of the grinding discs and other contaminants, not due to the final machining of cemented carbide with iron containing binder systems. Therefore, the iron content does not prealloy with the cobalt content. This grinding dust is not a formulation within the meaning of the present invention because the cobalt content is not prealloyed with iron because it is not produced in the targeted manner.

Example b) prepared using elemental powders Fe and Co shows a similar degree of toxicity as the attrition milling formulation containing 5% Co without additional additives.

Example c) did not show any toxicity at 5 mg / l, but in this case the contact between the WC particles and the premixed FeCo particles was as strong as a) in Example 1, and the composites were prepared similarly.

Example 3 Inhalation Toxicity of WC / FeNi Formulations

Inhalation experiments were performed using a mixture of 10% premixed FeNi 50/50 and 90% tungsten carbide. Here, 0% mortality occurred even at an effective aerosol concentration of 0.53 to 5.22 mg / l.

This example shows that sensitive inhalation toxicity does not occur, which contributes to the absence of cobalt.

Example 4): Free Corrosion Potential of WC / Co and WC / FeCo Contact Elements

Tungsten carbide powder was hot pressed at 2200 ° C. in a hot press to produce a solid having a density of 15.68 g / cm ³ , which corresponds to a logistic density. In addition, cobalt metal powder and prealloyed iron-cobalt metal powder (cobalt content: 50%) were pressed at 1000 ° C. to provide a compact having virtually theoretical density. In a first experiment, the contact voltage of tungsten carbide / cobalt, an electrochemical couple, by providing a power outlet electrode on two solid members to measure the contact voltage and partially immerse the structure in tap air saturated water. Was measured. Without mutual contact of the two solids, a difference of 330 volts was measured, with cobalt having a cathode for tungsten carbide. This difference represents the free corrosion potential. When the solid was in contact (short), a difference of 0.04 mV was measured, with the reverse of the polarity observed. The experiment was repeated and the cobalt member was replaced with one made from FeCo. The measured free corrosion potential was 0.240 volts with polarity preserved. When the solid body of FeCo and tungsten carbide was in contact, a difference of 0.007 mV was measured, and a polarity reversal occurred.

Comparing Examples 1) to 3), the presence of cobalt elements in contact with tungsten carbide is a necessary condition for inhalation toxicity to occur, but the required concentration is at least 20 when cobalt is prealloyed with the same wealth of iron. It becomes clear by the above factor that it is larger.

Example 4 demonstrates that the free corrosion potential or contact voltage between WC and cobalt, which depends critically on the concentration of molecular oxygen in water, according to the laws of electrochemistry known in the art makes a significant contribution. The 0.33 V measured here is compared with Mori et al. Of 0.301 to 0.384 V [R & HM 21, 135 (2003)] obtained from the potential difference measurement for the cemented carbide. However, if cobalt is alloyed with iron, the contact voltage is greatly reduced even if iron is less inert than cobalt. The reason for this phenomenon is unknown. As the free corrosion potential decreases, it can be readily seen that the driving force of the corrosion phenomena decreases or the corrosion progresses more slowly and the bioavailability is likewise reduced. Thus, the free corrosion potential of the measurement setup described in Example 4 can serve as an indicator of inhalation toxicity of the expected hard material / binder metal formulation. An additional indicator of anticipated inhalation toxicity is the amount of dissolved binder metal that becomes solution as soon as the corresponding contact element comes into contact with water in the presence of oxygen over a predetermined time period. 2 shows the aerosol concentrations plotted against mortality and assigned to the examples.

Claims (23)

A formulation comprising at least one hard material powder and at least two binder metal powders, wherein all cobalt is present in the first binder metal powder and is one or more of Groups 3 to 8 of the Periodic Table of Elements that is an element of the fourth cycle There is at least one additional binder metal powder from the group consisting of elements and prealloyed powders of elements Fe, Ni, Al, Mn, Cr and alloys of one another with each other, and the additional binder metal powder is not prealloyed. Formulations characterized in that they do not contain any cobalt in their raw form. A formulation comprising at least one hard material powder and at least two binder metal powders, wherein all cobalt is present in the first binder metal powder and prealloysed with one or more elements of groups 3 to 8 of the Periodic Table of the Elements, element Fe, There is at least one further binder metal powder from the group consisting of powders of Ni, Al, Mn, Cr and alloys of each other between these elements, the further binder metal powder does not contain any cobalt in prealloyed form, The free corrosion potential between the hard material and the first binder metal powder measured in air saturated water at atmospheric pressure and room temperature is less than 0.300 volts, and the hard material has an anode. A formulation comprising at least one hard material powder and at least two binder metal powders, wherein all cobalt is present in the first binder metal powder and prealloysed with one or more elements of groups 3 to 8 of the Periodic Table of the Elements, iron powder, Formulations characterized in that at least one additional binder metal powder selected from the group consisting of nickel powder, FeNi alloy powder and prealloyed FeNi alloy powder is used, and the additional binder metal powder does not contain any cobalt in unalloyed form. . The formulation of claim 2, wherein the alloy partner of cobalt in the first binder metal powder is an element of a fourth cycle. The formulation according to claim 1 or 2, wherein the alloy partner of cobalt in the first binder metal powder is an element selected from the group consisting of Fe, Ni, Cr, Mn, Ti and Al. 6. The formulation according to claim 1, wherein the first binder metal powder can contain additional elements in the form of alloys. The formulation of claim 6, wherein at least one of Al and Cu is used as additional element. 8. The at least one further binder metal powder of claim 1, wherein the at least one additional binder metal powder is selected from the group consisting of iron powder, nickel powder, FeNi alloy powder and prealloyed FeNi alloy powder. Is used in addition to the first binder metal powder. The free corrosion potential between the hard material and the first binder metal powder measured in air saturated water at atmospheric pressure and at room temperature is less than 0.300 volts, and the hard material is the positive electrode of claim 1. Formulations having a. The formulation according to claim 1, wherein the hard material contains titanium carbide, vanadium carbide, molybdenum carbide or tungsten carbide. The formulation of claim 10, wherein the hard material has a BET surface area of greater than 0.3 m ² / g, preferably greater than 0.5 m ² / g, particularly preferably greater than 1 m ² / g. The formulation of claim 1, wherein the weight ratio of first binder metal powder to additional binder metal powder or powders is 1:10 to 10: 1. The method of claim 1, wherein at least one prealloyed powder selected from the group consisting of a) iron / cobalt and iron / nickel / cobalt, b) at least one selected from the group consisting of iron and nickel Elemental powder of or a prealloyed powder consisting of iron / nickel different from the component of a), c) a hard composition comprising a total composition of components a) and b) together containing up to 90% by weight of cobalt and up to 70% by weight of nickel Formulations comprising a material powder. The formulation of claim 13, wherein the iron content is at least 10% by weight. The composition of claim 1, wherein the total composition of the binder is up to 90% by weight of Co, up to 70% by weight of Ni and at least 10% by weight of Fe, wherein the iron content satisfies the following inequality:

(Wherein Fe: wt% iron content,% Co: wt% cobalt content,% Ni: wt% nickel content), at least two binder powders are used, and one binder powder contains more iron than the total composition of the binder. Wherein the other binder powder has a higher iron content than the overall composition of the binder, and the at least one binder powder is prealloyed from at least two elements selected from the group consisting of iron, nickel and cobalt. Use of a formulation according to any one of claims 1 to 15 for producing a cemented carbide material. Use of a formulation according to any one of claims 1 to 15 for producing sintered aggregates. Porous aggregates obtainable by sintering without pressing of the formulation according to claim 1. A thermal spray powder comprising the porous aggregate according to claim 18 and also Al, yttrium and / or rare earths. 16. A method of controlling the toxic effects of a cobalt containing metal formulation, wherein the metal formulation according to any one of claims 1 to 15 is used to produce a cemented carbide material or a sintered porous aggregate. A method of controlling the toxic effects of a cobalt containing metal formulation, the method comprising the metal formulation according to any one of claims 1 to 15 and the aggregate according to claim 18 or the heat according to claim 19 for producing a shaped body or coating. A control method using spray powder. A method of controlling the toxic effects of a cobalt containing metal formulation, wherein the cobalt is prealloyed with one or more elements of Groups 3 to 8 of the Periodic Table of Elements in the metal formulation. The method of claim 20, wherein the toxic effect comprises pulmonary fibrosis and / or cemented carbide lung disease.

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