CH714312B1 - Powder metallurgy molding composition intended in particular for the manufacture of decorative or covering articles in sintered solid cermet and said decorative or covering particles in sintered solid cermet. - Google Patents

Abstract

The invention relates to a powder metallurgy molding composition intended in particular for the manufacture of decorative or covering articles in sintered solid cermet, comprising an inorganic powder intended to form the cermet and an organic binder. Said inorganic powder consists by weight of 35% to 95% of at least one ceramic phase based on ceramic chosen from the group consisting of TiC, TiCN, TiN and their mixtures, and from 5% to 65% of a phase metallic, said metallic phase being constituted by weight of at least 40% iron, 15% to 45% chromium, 0.1% to 25% molybdenum, 0.1% to 10% silicon, 0 to 10% of boron, and from 0 to 10% of niobium, the respective quantities of the elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase. The present invention also relates to a sintered solid cermet decorative or covering article made from such a molding composition as well as to a powder metallurgy manufacturing process of such a decorative or covering article or part of a sintered solid cermet clockwork mechanism.

Description

Field of the invention

The invention relates to a powder metallurgy molding composition intended for the manufacture of articles in sintered solid cermet, in particular decorative or covering articles, comprising an inorganic powder intended to form the cermet and an organic binder . The present invention also relates to an article of decoration or cover and a clockwork mechanism element in sintered solid cermet made from such a molding composition as well as a process for the manufacture by powder metallurgy of an article. in solid sintered cermet.

Background of the invention

In the manufacture of hard materials for making watch or jewelry parts, or even decorations for portable electronic devices (tablets, telephones, etc.), ceramic-metal composite materials, called cermets, are used. Such composite materials include a ceramic phase and a metallic phase or metallic binder. Solid cermets are obtained by powder metallurgy according to pressing or injection processes, followed by sintering, from a molding composition comprising an organic binder and an inorganic powder.

More specifically, the overall process for manufacturing a solid cermet article produced by powder metallurgy comprises at least the following steps: preparation of raw materials of inorganic powder; granulation; mixing with an organic binder to obtain the molding or feedstock composition; pressing or injection, in particular in a molding chamber, of a quantity of the feedstock obtained, for the production of a blank of the article, called a green part. The injection is carried out under pressure, in particular in a screw injector comprising means for heating this feedstock; debinding stoving for combustion and / or dissolution of certain components of the organic binder to obtain a brown body; heat treatment (sintering) of the blank or of the brown body at the end of debinding, giving its final consistency to the article obtained in solid and dense cermet. This heat treatment results in dimensional shrinkage, which makes it possible to obtain an article in finite dimensions; finishing treatment of the article's appearance (machining and / or polishing).

[0004] In watchmaking, solid cermets based on TiC, TiCN or TiN are used for their "scratch-resistant" characteristics (high hardness), for their metal splinters after polishing approaching those of steels and stainless steels (for TiC and TiCN bases) and for their low densities, approaching those of ceramics. These cermets show excellent resistance to salt corrosion. However, they have the drawback of all using nickel or cobalt as metal binder and therefore exhibit non-negligible nickel or cobalt release rates, which can sometimes exceed the maximum authorized rate (0.280 µg / cm <2>. Week depending on current RoHS and REACH standards).

For applications in watchmaking, jewelry and other portable electronic devices, and especially for decorative elements in contact with human skin, a material of the cermet type must absolutely guarantee the absence of release of allergenic elements. The alternative metal binders offered to date by manufacturers active in the field of cermets based on TiC, TiCN or TiN are mainly iron (Fe), iron-chromium (Fe-Cr) and iron- chromium-molybdenum (Fe-Cr-Mo), stainless steels and refractory steels.

[0006] In addition, applied to an element of horological decorations, all these cermets have resistance to corrosion in immersion in a saline environment as well as in saline mist which is extremely low, in particular after having undergone endings machining steps ( mechanical, laser) and / or polishing.

[0007] Applied to an element of a watch mechanism, these cermets are advantageous for their high hardness, but their low resistance to corrosion is detrimental in the event of the presence of condensation inside the watch mechanism or for trim parts in contact with the wearer's sweat.

Summary of the invention

The object of the present invention is to remedy these drawbacks by proposing a composition for molding by powder metallurgy making it possible to manufacture articles, in particular decorative or covering articles, in sintered solid cermet having no elements. allergens such as nickel and / or cobalt, traditionally used.

Another object of the present invention is to provide a powder metallurgy molding composition making it possible to manufacture articles, in particular decorative or covering articles and elements of watch mechanisms, in sintered solid cermet highly resistant to corrosion in immersion in a saline environment and under saline mist.

Another object of the present invention is to provide a powder metallurgy molding composition furthermore exhibiting the same properties of hardness, toughness, density, luster, and tints, as the cermets available on the market for the manufacture of decorative or dressing articles in the fields of watchmaking, jewelry, or portable electronic devices.

To this end, the invention relates first of all to a powder metallurgy molding composition intended for the manufacture of articles in sintered solid cermet, comprising an inorganic powder intended to form the cermet and an organic binder .

According to the invention, said inorganic powder consists by weight of 35% to 95% of at least one ceramic phase based on ceramic chosen from the group consisting of TiC, TiCN, TiN and their mixtures, and of 5 % to 65% of a metallic phase, said metallic phase consisting by weight of at least 40% iron, 15% to 45% chromium, 0.1% to 25% molybdenum, 0.1% to 10% of silicon, from 0 to 10% of boron, and from 0 to 10% of niobium, the respective quantities of said elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase.

Such a molding composition makes it possible to obtain articles in sintered solid cermet without an allergenic element such as nickel and / or cobalt, and highly resistant to salt corrosion. Said article may, for example, be an article of decoration or cover or an element of a watch mechanism.

The present invention also relates to a method of manufacturing by powder metallurgy of a sintered solid cermet article comprising a step of preparing a molding composition as defined above, a step of molding said composition of molding to produce a green part of the article, then debinding and sintering steps to obtain said solid sintered cermet article.

The present invention also relates to a decorative or covering article in sintered solid cermet, in which said cermet is obtained from an inorganic powder consisting by weight of 35% to 95% of at least one ceramic phase based on ceramic chosen from the group consisting of TiC, TiCN, TiN and their mixtures, and from 5% to 65% of a metallic phase, said metallic phase consisting by weight of at least 40% of iron, 15 % to 45% of chromium, from 0.1% to 25% of molybdenum, from 0.1% to 10% of silicon, from 0 to 10% of boron, and from 0 to 10% of niobium, the respective quantities of said elements of the phase metallic being such that their sum is equal to 100% by weight of the metallic phase.

The present invention also relates to a sintered solid cermet clockwork mechanism element, in which said cermet is obtained from an inorganic powder consisting by weight of 35% to 95% of at least one ceramic phase to ceramic base chosen from the group consisting of TiC, TiCN, TiN and mixtures thereof, and from 5% to 65% of a metallic phase, said metallic phase consisting by weight of at least 40% iron, 15% at 45% of chromium, from 0.1% to 25% of molybdenum, from 0.1% to 10% of silicon, from 0 to 10% of boron, and from 0 to 10% of niobium, the respective quantities of said elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase.

Detailed description of the preferred embodiments

The powder metallurgy molding composition according to the invention comprises an inorganic powder intended to form a cermet and an organic binder.

The organic binder used in the molding composition according to the invention comprises in a known manner a polymer structuring base of polyethylene and / or polypropylene type and / or copolymers, waxes of paraffin type which can be dissolved hot in organic solvents and / or polyethylene glycols which can be dissolved in hot water and at least one organic surfactant of the stearic acid or stearate type. Formulations of organic binders that are more complex and give excellent results can also be used. Such formulations are for example described in international application WO 2014/191304. For the manufacture of the feedstock, that is to say the hot mixing of organic and inorganic powders for molding, a mixer or a twin-screw extruder will preferably be used. More specifically, a heating mixer with high speed rotary knives, as described in application EP 2801560, makes it possible to obtain an intimate and homogeneous mixture of organic and inorganic powders.

Preferably, the molding composition according to the invention comprises from 4% to 24% by weight of organic binder and 76% to 96% by weight of inorganic powders.

Said inorganic powder consists by weight of 35% to 95% of at least one ceramic phase and 5% to 65% of a metallic phase, preferably 50% to 90% of the ceramic phase and of 10% to 50% of the metallic phase, more preferably from 65% to 85% of the ceramic phase and from 15% to 35% of the metallic phase, and more preferably from 70% to 80% of the ceramic phase and 20 % to 30% of the metallic phase.

The ceramic phase of the inorganic powder is based on ceramic chosen from the group consisting of TiC, TiCN, TiN and mixtures thereof. Preferably, the ceramic phase is based on TiC or TiN.

In the present description, the expression "ceramic phase based on an element" means that said ceramic phase contains at least 50% by weight of said element.

In the present description, all the percentages are given by weight. Advantageously, the ceramic phase of the inorganic powder consists by weight of 50% to 100% of a main ceramic phase based on ceramic chosen from the group consisting of TiC, TiCN, TiN, and mixtures thereof, and from 0 to 50% of at least one secondary ceramic phase chosen from the group comprising Cr3C2, CrN, NbC, NbN, TaC, TaN, and mixtures thereof.

Preferably, the ceramic phase of the inorganic powder consists by weight of 80% to 100% of said main ceramic phase, and from 0 to 20% of said secondary ceramic phase, and more preferably from 90% to 100% of said main ceramic phase, and from 0 to 10% of said secondary ceramic phase.

Advantageously, said main ceramic phase of the inorganic powder may consist solely of TiC or may consist of TiN, the secondary ceramic phase being NbN (for example 90/10).

According to the invention, the metallic phase of the inorganic powder consists by weight of at least 40% iron, 15% to 45% chromium, 0.1% to 25% molybdenum, 0.1% to 10% silicon, 0 to 10% boron, and 0 to 10% niobium, the respective amounts of the elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase.

The metallic phase of the inorganic powder consists predominantly of iron and chromium, and comprises by weight preferably from 40% to 70% of iron, and more preferably from 45% to 60% of iron, and 20% 40% chromium, and more preferably 25% to 35% chromium.

Preferably, the metallic phase of the inorganic powder comprises by weight from 1% to 20% of molybdenum, and more preferably from 5% to 10% of molybdenum.

Preferably, the metallic phase of the inorganic powder comprises by weight from 1% to 10% of silicon, and more preferably from 2% to 8% of silicon.

Preferably, the metallic phase of the inorganic powder comprises by weight from 0% to 5% of boron, and more preferably from 0% to 1% of boron.

Preferably, the metallic phase of the inorganic powder comprises by weight from 0% to 8% niobium, and more preferably from 0% to 5% niobium.

The metallic phase according to the invention is therefore an alloy consisting of Fe, Cr, Mo, Si and optionally of B and / or Nb.

The preferred contents of the various elements of the metallic phase of the inorganic powder mentioned above can be combined with each other as long as their sum is equal to 100% by weight of the metallic phase. If necessary, the iron is used to do the rest.

Preferably, the metallic phase of the inorganic powder consists of at least 40% iron (preferably at least 45% iron), 25% to 35% chromium, 5% to 10% iron. molybdenum, from 2% to 8% of silicon, from 0% to 1% of boron, and 0% to 5% of niobium, the respective quantities of the elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase.

Surprisingly, the combination of Mo and Si in the Fe-Cr metallic phase makes it possible to obtain good resistance to corrosion in a saline environment.

The addition of boron and / or niobium to the metallic phase Fe-Cr-Mo-Si makes it possible to increase the resistance to corrosion in a saline environment. The addition of boron also increases the toughness of the cermet.

In a particularly advantageous manner, the molding composition of the invention, and in particular the metallic phase, does not include nickel or cobalt. The metallic phase is also free of manganese and carbon.

The present invention also relates to a method of manufacturing by powder metallurgy of a sintered solid cermet article comprising a step of preparing a molding composition as defined above, a step of molding said composition of molding to produce a green part of the article, then debinding and sintering steps to obtain said solid sintered cermet article.

More specifically, the step of preparing a molding composition of the invention comprises the weighing of the powder of the main ceramic phase, optionally of the powders of the secondary ceramic phases, and of the elements constituting the metallic phase. The powders are then ground, for example by ball-milling or by attrition, in order to obtain an inorganic powder intended to form the cermet having a homogeneous distribution and comprising particles of final average size of a few microns. The components constituting the organic binder are then added to obtain the molding composition according to the invention, traditionally called feedstock. The feedstock can be put in the form of powder or granules to be preserved until the implementation of the step of molding the molding composition.

This molding step typically comprises a hot pressing or injection molding operation under pressure in a mold with cavities. We obtain a blank or a green part of the article to be produced. The green part is cooled in the cavity and then is ejected from the mold.

The green part is then debonded, to remove part of the components of the organic binder, in particular the waxes, before the sintering step. We get a brown body.

For the sintering step, the brown body is placed in a high temperature oven (for example 1350 ° C - 1550 ° C) to obtain a solid sintered and dense cermet article.

The method then comprises a step of finishing treatment of the appearance of the article, by machining (mechanical, laser, water jet, etc.) and / or by polishing.

Such a method of manufacturing by powder metallurgy is known to those skilled in the art and does not require further details here.

[0045] The article may be an article of decoration or of watchmaking or jewelry or of decorations of portable devices, or else an element of a clockwork mechanism.

The present invention also relates to a decorative or covering article made of sintered solid cermet, in particular a decorative or covering article obtained by the powder metallurgical manufacturing process using the molding composition described above. The decorative or covering article according to the invention is made of sintered solid cermet, said sintered solid cermet having been obtained from an inorganic powder consisting by weight of 35% to 95% of at least one ceramic phase based on ceramic chosen from the group consisting of TiC, TiCN, TiN and their mixtures, and from 5% to 65% of a metallic phase, said metallic phase consisting by weight of at least 40% of iron, 15 % to 45% of chromium, from 0.1% to 25% of molybdenum, from 0.1% to 10% of silicon, from 0 to 10% of boron, and from 0 to 10% of niobium, the respective quantities of the elements of the phase metallic being such that their sum is equal to 100% by weight of the metallic phase.

The present invention finally relates to an element of a clockwork mechanism in sintered solid cermet, in particular an element of a clockwork mechanism obtained by the powder metallurgy manufacturing process using the molding composition described above. The element of a watch mechanism according to the invention is made of sintered solid cermet, said sintered solid cermet having been obtained from an inorganic powder consisting by weight of 35% to 95% of at least one ceramic phase to ceramic base chosen from the group consisting of TiC, TiCN, TiN and mixtures thereof, and from 5% to 65% of a metallic phase, said metallic phase consisting by weight of at least 40% iron, 15% at 45% of chromium, from 0.1% to 25% of molybdenum, from 0.1% to 10% of silicon, from 0 to 10% of boron, and from 0 to 10% of niobium, the respective quantities of the elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase.

The final composition of the sintered solid cermet depending on the sintering parameters used (temperature, duration of the sintering stage, pressure in the sintering chamber), it is preferable here to characterize the decorative or covering article or the element of a clockwork mechanism of the invention by the composition of the cermet before sintering.

The molding composition of the invention makes it possible to obtain, by powder metallurgy, articles in sintered solid cermet, in particular decorative or covering articles, free of the allergenic elements traditionally used in cermets, such as nickel or cobalt.

In addition, the molding composition of the invention makes it possible to obtain, by powder metallurgy, articles in sintered solid cermet, in particular decorative or covering articles or elements of a watch mechanism, highly resistant to corrosion in a saline environment, even after having undergone a finishing treatment.

In addition, the decorative or covering articles or the watch mechanism elements in sintered solid cermet of the invention have a hardness of between 1000 and 1800 Vickers, and are therefore particularly resistant to scratches, in a similar manner to traditionally used cermets.

They also have sufficient tenacity to be easily machinable and polishable, similarly to cermets comprising nickel or cobalt traditionally used.

The various elements used to produce the decorative or covering articles of the invention make it possible to obtain sintered solid cermets of low densities, ie of densities of less than 10 g / cm <3>. The decorative or covering articles of the invention therefore exhibit pleasant wearing comfort, in particular when they relate to timepieces and consist, for example, of caps, middle pieces, watch cases or bracelets.

The decorative or covering articles in sintered solid cermet of the invention exhibit, after polishing, a beautiful metallic luster, like the cermets traditionally used.

The decorative or covering articles in sintered solid cermet of the invention have white to gray and gray-pink to pink tints for the cermets based on TiC and TiCN, and yellow to yellow-bronze tints for TiN-based cermets.

The decorative or covering articles in sintered solid cermet of the invention are decorative or covering articles for watches or jewelry, as well as articles for covering or protecting portable electronic devices, such as cell phones and tablets.

The elements of the sintered solid cermet clockwork mechanism of the invention are in particular functional elements. These elements according to the invention have a high hardness and are resistant to corrosion in the event of the presence of condensation inside the clockwork mechanism. Such an element can for example be a plate. This element is traditionally made from solid brass in which holes are machined for driving rubies with a small diameter hole in their center for inserting axle pivots. This brass must then be protected from corrosion by a surface deposit of nickel. A solid cermet plate according to the invention, having a high hardness, and produced according to pressure molding or injection molding processes in accordance with the manufacturing process of the invention, allows the direct insertion of the axle pivots, without driving in. nor the use of ruby and does not require the use of a surface treatment to protect it from corrosion.

The present invention will now be illustrated in more detail by the nonlimiting examples which follow.

Examples 1 to 10

Sintered solid cermet articles are made from molding compositions comprising the various inorganic powders indicated in Table I below, and as organic binder a binder comprising a polyethylene as structuring organic, a paraffin wax dissolving hot in heptane, in ethanol or in isopropanol, and as a surfactant for stearic acid.

The inorganic powders all comprise by weight 70% of a ceramic phase consisting of 100% TiC and 30% of a metallic phase nominally comprising by weight at least iron and 28% chromium before sintering.

By way of comparison, various articles are manufactured for which the Fe-Cr metallic phase does not contain molybdenum or no silicon (examples 1 to 9).

An article according to the invention is produced in the same way in which the Fe-Cr metal phase contains both molybdenum and silicon (Example 10).

The articles are obtained according to the following process: grinding of the mixture of powders of the ceramic phase and of the metallic phase by ball-milling allowing a significant reduction of the particle sizes while ensuring good homogeneity of the mixture after grinding in order to constitute the inorganic powder manufacture of the mixture of the organic binder and of the inorganic powder by hot mixing, preferably using a high speed knife mixer injection molding of 3D parts to obtain green parts ("green body") hot dewaxing in heptane at 70 ° C and for 24 hours green parts to dissolve the paraffin and a fraction of the surfactant present in the organic binder thermal debinding at a temperature of at least 600 ° C of the structuring organic compound of polyethylene type and of the surfactant residues to obtain a brown body sintering under inert gas (argon) of the brown body at a temperature of at least 1450 ° C in order to obtain a dense sintered solid cermet.

The raw sintering parts are then machined and polished mechanically or in bulk to obtain final parts.

For each article of Examples 1 to 10, the hardness, the toughness, the level of porosity and the corrosion resistance are measured.

The hardness is measured using a Wolpert durometer equipped with a Vickers point (square-based pyramid) and under an applied load of 30 kg. Beforehand, a calibration is carried out on a referenced standard of hardness comparable to that of cermets.

The hardness should be between 1000 and 1800 Vickers.

For the toughness measurements, these are extrapolated from the size of the cracks developing at the four corners of the hardness imprint.

The toughness value represents the ability of a material to resist the propagation of a crack following an impact. For ceramics traditionally used as horological decorations such as zirconia, in particular for the production of a watch case, it is considered that the toughness measured by Vickers indentations must be at least 4.5 MPa.m <1/2>.

The porosity rate is estimated using image acquisition software making it possible to discriminate on a polished surface and at 100x magnification, the different contrast zones. The measured porosity is therefore a surface porosity. A low porosity rate is directly linked to good quality and a beautiful shine of the surface after polishing.

The corrosion resistance is measured using a certified salt spray chamber (ASCOTT S120XP) in which the sample is positioned in an inclined manner and will then undergo a salt spray (5% NaCl) for 72 hours , at a temperature of 35 ° C.

The results obtained are shown in Table I below:

Table I

[0073] 1 70TiC-FeCr28 1487 9.2 0.08 low 2 70TiC-FeCr28Mo16 1612 7.4 0.17 low 3 70TiC-FeCr28Mo12 1593 7.3 0.14 low 4 70TiC-FeCr28Mo8 1578 8.6 0.09 low 5 70TiC-FeCr28Mo4 1555TiC-FeCr28Mo4 1555TiC-0.3Ci-low 6 low 7 70TiC-FeCr28Si2 1396 8.5 0.10 low 8 70TiC-FeCr28Si3 1448 7.4 0.29 low 9 70TiC-FeCr28Si4 1362 8.1 0.12 low 10 70TiC-FeCr28Mo8Si4 1481 6.1 0.13 good

The results of Table I show that only the molding composition according to the invention (Example 10) comprising a metallic phase Fe-Cr-Mo-Si makes it possible to obtain an article in sintered solid cermet, without nickel or cobalt, exhibiting good corrosion resistance in a saline environment. The comparative examples (Examples 1 to 9) without Mo or without Si show only low resistance to corrosion in a saline environment.

Examples 11-13

Articles according to the invention are produced according to the process of Examples 1 to 10. The inorganic powders all comprise by weight 70% of a ceramic phase consisting of 100% TiC and 30% of a metallic phase consisting nominally. by weight of iron, 28% of chromium, 8% of molybdenum, 4% of silicon and from 0.2% to 0.6% of boron before sintering.

The same measurements are carried out as for Examples 1 to 10.

The results are shown in Table II below:

Table II

[0078] 11 70TiC-FeCr28Mo8Si4B0.2 1441 7.2 1.58 Very good 12 70TiC-FeCr28Mo8Si4B0.4 1444 7.7 3.01 Very good 13 70TiC-FeCr28Mo8Si4B0.6 1422 7.9 1.55 Very good

Examples 11 to 13 of the invention show that the addition of a small amount of boron makes it possible to increase the resistance to corrosion in a saline environment. In addition, the addition of boron increases the toughness. Thus the measured tenacity of 6.1 MPa.m <1/2> for example 10 of the invention, without boron, passes to the maximum value of 7.9 MPa.m <1/2> for example 13 of invention, comprising a nominal quantity by mass of 0.6% of boron.

Example 14

An article according to the invention is produced according to the process of Examples 1 to 10. The inorganic powder comprises by weight 75% of a ceramic phase consisting of 100% TiC and 25% of a metallic phase consisting nominally of weight of 49.6% iron, 34% chromium, 8% molybdenum, 4% silicon, 4% niobium and 0.4% boron before sintering.

The same measurements are carried out as for Examples 1 to 10.

The results are shown in Table III below:

Table III

[0083] 14 75TiC-FeCr34Mo8Si4Nb4B0.4 1528 6.4 0.39 Very good

Example 14 of the invention shows that the addition of niobium also makes it possible to increase the resistance to corrosion in a saline environment. In addition, the addition of niobium makes it possible to improve the homogeneity of the metal phase and thus to reduce the porosity and increase the hardness of the cermet obtained.

Example 15

An article according to the invention is produced according to the process of Examples 1 to 10. The inorganic powder comprises by weight 80% of a ceramic phase constituted nominally by weight of 90% of TiN (main ceramic phase) and of 10 % NbN (secondary ceramic phase), and 20% of a metallic phase nominally constituted by weight of 59% iron, 28% chromium, 8% molybdenum, and 5% silicon, before sintering.

The hardness and the corrosion resistance are measured as for Examples 1 to 10.

The results are shown in Table IV below:

Table IV

[0088] 15 TiN-10NbN-FeCr28Mo8Si5 1108 good

Example 15 of the invention comprising a main ceramic phase TiN and a secondary ceramic phase NbN, as well as a metallic phase Fe-Cr-Mo-Si exhibits good resistance to corrosion in a saline medium.

The sintered solid cermet article obtained exhibits a metallic luster after polishing with a "bronze" yellow complexion with colorimetry indices L * = 74.1, a * = 5.1, b * = 20.2 measured using a Konica Minolta CM-3610 spectrophotometer for performing reflectance colorimetry measurements in the L * a * b reference space. Before each measurement, a calibration is made on a reference sample then three measurements are then carried out successively.

Claims (15)

1. Powder metallurgy molding composition intended for the manufacture of sintered solid cermet articles, comprising an inorganic powder intended to form the cermet and an organic binder, characterized in that said inorganic powder consists by weight of 35% to 95% of at least one ceramic phase based on ceramic chosen from the group consisting of TiC, TiCN, TiN and their mixtures, and from 5% to 65% of a metallic phase, said metallic phase consisting by weight of at least 40% iron, 15% to 45% chromium, 0.1% to 25% molybdenum, 0.1% to 10% silicon, 0 to 10% boron, and 0 to 10% niobium , the respective amounts of said elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase. 2. Molding composition according to claim 1, characterized in that the metallic phase comprises by weight from 40% to 70% iron, preferably 45% to 60% iron. 3. Molding composition according to one of the preceding claims, characterized in that the metallic phase comprises by weight from 20% to 40% of chromium, and preferably from 25% to 35% of chromium. 4. Molding composition according to one of the preceding claims, characterized in that the metallic phase comprises by weight from 1% to 20% of molybdenum, and preferably from 5% to 10% of molybdenum. 5. Molding composition according to one of the preceding claims, characterized in that the metallic phase comprises by weight from 1% to 10% of silicon, and preferably from 2% to 8% of silicon. 6. Molding composition according to one of the preceding claims, characterized in that the metallic phase comprises by weight from 0% to 5% of boron, and preferably from 0% to 1% of boron. 7. Molding composition according to one of the preceding claims, characterized in that the metallic phase comprises by weight from 0% to 8% of niobium, and preferably from 0% to 5% of niobium. 8. Molding composition according to one of the preceding claims, characterized in that the ceramic phase consists by weight of 50% to 100% of a main ceramic phase based on ceramic chosen from the group consisting of TiC, TiCN, TiN, and mixtures thereof, and from 0 to 50% of at least one secondary ceramic phase chosen from the group comprising Cr3C2, CrN, NbC, NbN, TaC, TaN, and mixtures thereof. 9. Molding composition according to one of the preceding claims, characterized in that said inorganic powder consists by weight of 50% to 90% of the ceramic phase and 10% to 50% of the metallic phase, and preferably of 65% to 85% of the ceramic phase and 15% to 35% of the metallic phase. 10. Molding composition according to one of the preceding claims, characterized in that it comprises by weight from 76% to 96% of inorganic powder and from 4% to 24% of organic binder. 11. A method of manufacturing by powder metallurgy a sintered solid cermet article comprising a step of preparing a molding composition according to one of claims 1 to 10, a molding step of said molding composition to produce a molding composition. green part of the article, followed by debinding and sintering steps to obtain said sintered solid cermet article. 12. A method of manufacturing by powder metallurgy an article in sintered solid cermet according to claim 11, characterized in that said article is an article of decoration or dressing, of watches or of jewelry or of decorations of appliances. portable. 13. A method of manufacturing by powder metallurgy a sintered solid cermet article according to claim 11, characterized in that said article is an element of a clockwork mechanism. 14. Article of decoration or dressing of watches or jewelry or decorations of portable devices, in sintered solid cermet, characterized in that said sintered solid cermet is obtained from an inorganic powder constituted by weight of 35 % to 95% of at least one ceramic phase based on ceramic chosen from the group consisting of TiC, TiCN, TiN and their mixtures, and from 5% to 65% of a metallic phase, said metallic phase being constituted by weight at least 40% iron, 15% to 45% chromium, 0.1% to 25% molybdenum, 0.1% to 10% silicon, 0 to 10% boron, and 0 to 10% niobium, the respective amounts of said elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase. 15. Clockwork mechanism element in sintered solid cermet, characterized in that said sintered solid cermet is obtained from an inorganic powder consisting by weight of 35% to 95% of at least one ceramic phase based on ceramic. chosen from the group consisting of TiC, TiCN, TiN and mixtures thereof, and from 5% to 65% of a metallic phase, said metallic phase consisting by weight of at least 40% of iron, from 15% to 45% of chromium, from 0.1% to 25% of molybdenum, from 0.1% to 10% of silicon, from 0 to 10% of boron, and from 0 to 10% of niobium, the respective quantities of said elements of the metallic phase being such that their sum is equal to 100% by weight of the metallic phase.