A process for manufacturing welding or hardfacing rods using a metallic superalloy as the filler material.

Abstract

A method for manufacturing welding or cladding rods whose filler material is a metallic superalloy. One aspect of the invention relates to a method for manufacturing cladding or welding rods, characterized in that it comprises the following successive steps: a step (E1) of supplying a mixture comprising 50 to 90% by volume of a powder of a metallic superalloy based on nickel and / or cobalt, and a powder of a binder based on wax and / or thermoplastic polymer; a step (E2) of forming a mixture wire from the mixture resulting from step (E1), this wire being designated as the "green" wire; a step (E3) of debinding the "green" wire resulting from step (E2) and obtaining a debinded wire designated as the "brown" wire; a step (E4) of sintering the "brown" wire resulting from step (E3) and obtaining a sintered wire usable as a cladding rod. or welding. Figure to be published with the abbreviation: Figure 3

Description

Title of the invention: Method for manufacturing welding or hardfacing rods whose filler material is a metallic superalloy. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of welding and cladding in which the material is supplied by a rod comprising a filler material, this filler material being a metallic superalloy.

[0002] The present invention relates to a new manufacturing process for such a welding or hardfacing rod. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Many welding or cladding processes use a filler material supplied in the form of a rod and a heat source.

[0004] As a reminder, welding is a technique for joining parts by adding a filler material at the junction between said parts. Hardfacing is a variant of welding that consists not of joining metal parts together, but of covering their surface with one or more layers of a filler material. Thus, the filler material of a welding or hardfacing rod either fills the gap between two parts to be joined, or adds material to the surface of a part.

[0005] The rods used for welding or cladding processes, hereinafter simply referred to as "rods", may have different diameters, usually between approximately 0.3 and 5 mm.

[0006] Nowadays, very few welding rods are available for supplying superalloy-based metal filler material. Furthermore, the available rods have a diameter greater than 2 mm. Therefore, rods with a small diameter, i.e., between 0.1 and 2 mm, are not available on the market.

[0007] This lack of availability for these rods results from the difficulty in producing them and the fact that the market share is quite small for this type of grade of metal filler material.

[0008] Indeed, nickel and / or cobalt-based metallic filler materials are complex to process by wire drawing due to their material properties generated by complex chemistries.

[0009] As a reminder, a superalloy or high-performance alloy is defined as a complex alloy of metallic materials, essentially nickel- or cobalt-based, exhibiting excellent mechanical strength and good resistance to wear. At high temperatures, it exhibits good surface stability as well as good resistance to corrosion and oxidation. This invention focuses particularly on nickel- and / or cobalt-based superalloys.

[0010] There is therefore a need for a new manufacturing process which makes it possible to produce rods, in particular rods of small diameters whose filler material is a superalloy based on nickel and / or cobalt. Summary of the invention

[0011] The invention offers a solution to the problems mentioned above, by providing a new method for manufacturing baguettes based on metal powder injection molding (MIM) technology, which belongs to the broader family of powder injection molding (PIM) technology, as does ceramic powder injection molding (CIM).

[0012] The MIM process consists of producing components by injecting a mixture of metal powder and a thermoplastic polymer binder, commonly referred to as feedstock. This mixture or feedstock is usually reduced to granules and then injected into a mold using equipment similar to that used for plastic injection molding. It then undergoes a step called debinding, aimed at removing the thermoplastic polymer binders by thermal and / or chemical means depending on the nature of said binders, followed by a step called sintering, aimed at generating strong bonds by diffusion of material, densifying the material, and eliminating porosity.

[0013] By way of example, [Fig.1] and [Fig.2] illustrate the use of a conventional MIM process for the production of a part 10 by injecting a material 20 based on metal powder and binder into a mold 30 through an injection nozzle 40.

[0014] Whereas in a conventional MIM process, an injection nozzle 40 injects a feed charge 20 into a mold 30 to produce a given part geometry 10, the invention proposes modifying the MIM process by eliminating the need for a mold, thus enabling the shaping of material into a rod, not necessarily straight. The process of the invention can, however, utilize the equipment typically used in a conventional MIM process, except for the mold 30, where the injection nozzle 40 then acts as an extrusion die.

[0015] Instead of injection, we can then speak of extrusion, the injection nozzle acting as a die and having an internal diameter greater than the cross-section of the rod to be obtained. Indeed, after extrusion of the feed charge 20, a rod with the desired dimensions is not obtained directly. Instead, a preform called the "green" part is obtained, which then undergoes a debinding step, at the end of which A "brown" or debinded part is obtained, which then undergoes a sintering step, resulting in a sintered part. These last two steps cause material shrinkage due to the removal of the binder and the densification of the material. This material shrinkage is linked in particular to the powder loading rate in the feedstock, which can be significant.

[0016] One aspect of the invention relates to a method for manufacturing a welding or hardfacing rod, which comprises the following successive steps: • a step El of supplying a mixture comprising: • 50 to 90% by volume of a powder of a nickel and / or cobalt-based metallic superalloy, and • a powder of a wax-based and / or thermoplastic polymer binder; • a step E2 of forming a mixture yarn 60 from the mixture resulting from step El, this yarn being designated as "green" yarn; • a step E3 of unbinding the "green" yarn resulting from step E2 and obtaining a unbound yarn designated as "brown" yarn; • a step E4 of sintering the "brown" wire 100 resulting from step E3 and obtaining a sintered wire usable as a re-hardening or welding rod.

[0017] The advantage of this process is that it allows shaping all the nuances of material (nickel base, cobalt, titanium, aluminum...).

[0018] Thanks to the invention, by adjusting the extrusion parameters (dimensions of the extrusion die, extrusion speed, extrusion pressure, temperature, etc.) and taking into account the shrinkage factor, it is advantageously possible to manufacture rods of different diameters, for example greater than 2 mm if necessary, and of different lengths, for example from 1 to 30 cm, the filler material of which is a superalloy based on nickel and / or cobalt.

[0019] Indeed, although it may seem counterintuitive to form rods that are not necessarily straight, the rods manufactured by the process according to the invention are sufficiently elongated to be advantageously used with conventional welding or hardfacing processes. Furthermore, any variations in the diameter of the rods thus formed, on the order of + / - 0.1 mm, remain largely acceptable for most welding or hardfacing applications. The rods produced according to the process of the invention can therefore be used like conventional rods during welding or hardfacing processes.

[0020] According to one aspect of the invention, the superalloy powder used has a particle size distribution of which the D50 is between 5 and 15 pm.

[0021] According to another aspect of the invention, during step El, the grains of the superalloy powder used are subspherical or spherical in shape.

[0022] According to a further aspect of the invention, during step E1, the superalloy powder and binder powder used are hot-mixed. The resulting mixture can be ground into granules after cooling and hardening. It can also be hot-extruded through a die.

[0023] According to one aspect of the invention, during step El, the binder mainly comprises polyethylene, polypropylene, polystyrene, polyoxymethylene or a mixture thereof.

[0024] According to another aspect of the invention, during step E2, the formation of a "green" yarn is carried out by extruding the mixture resulting from step E1 through a die.

[0025] According to a further aspect of the invention, during step E2, the main extrusion parameters are as follows: • Extrusion temperature: 50 to 250°C; • Extrusion speed: 10 to 100 cm3 / s; • Extrusion pressure: 50 to 1500 bars.

[0026] According to one aspect of the invention, during step E2, the die has a cross-section with a diameter between 0.1 and 10 mm.

[0027] According to another aspect of the invention, during step E3, the "green" wire resulting from step E2 is immersed for a period of between 10 and 200 hours in a solvent whose temperature is between 20 and 100 °C.

[0028] According to a further aspect of the invention, during step E3, the "green" wire resulting from step E2 is placed for a period of between 1 and 30 hours in an enclosure heated to a temperature between 50 and 250 °C.

[0029] According to one aspect of the invention, during step E4, sintering is carried out for a period of between 2 and 20 hours under a protective atmosphere or under vacuum, at a temperature between 1000 and 1500 °C.

[0030] An aspect of the invention also relates to a re-facing or welding process, using a re-facing or welding rod comprising a powder of a nickel and / or cobalt-based superalloy, said re-facing or welding rod being a product resulting from the process described above.

[0031] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0032] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0033] [Fig.1] and [Fig.2] schematically illustrate the use of a conventional MIM process for producing a part in a mold.

[0034] [Fig.3] schematically illustrates the different stages of the process according to the invention.

[0035] [Fig.4], [Fig.5] and [Fig.6] schematically illustrate an example of use of the process according to the invention for the production of a resurfacing or welding rod. DETAILED DESCRIPTION

[0036] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0037] Superalloys are complex alloys of metallic materials, primarily nickel- and / or cobalt-based, exhibiting good mechanical strength at high temperatures (above 500 to 550 °C) and some resistance to oxidation or hot corrosion. Indeed, their typical properties are as follows: • good resistance to flaking, • good corrosion resistance, • good resistance to oxidation, • good resistance to thermal fatigue and thermal shock, • an absence of excessive fragility, • an average density.

[0038] Superalloys are widely used for the production of industrial or marine gas turbines, aeronautical turbomachinery and, to a more limited extent, in the furnace industry and the chemical industry.

[0039] Several classes of superalloys exist today; however, the most widely used and important class is a priori that of nickel-based superalloys. Indeed, nickel as a basic element exhibits excellent plasticity and heat resistance properties. Moreover, its high-temperature resistance is greatly enhanced by alloying it with chromium, titanium, cobalt, and especially aluminum, with which it forms γ' precipitates that contribute to its structural hardening.

[0040] Superalloys are usually composed of: • primarily an austenitic matrix y in which Ni can be substituted by Co, Cr, Mo, W, as well as by Nb, Al, Ti, Ta; • ordered intermetallic precipitates y': Ni3(Ti,Al) or y": Ni3Nb which occupy 30 to 70% of the volume and whose dimensions vary between 10 nm and a few micrometers; or • primary (MC type) and secondary (M23C6 type) carbides, preferentially precipitated at grain boundaries.

[0041] Nickel and / or cobalt-based superalloys are widely known to those skilled in the art and will not be described here.

[0042] By way of example, some examples of compositions of nickel- or cobalt-based superalloys are nevertheless given in the table below where the values ​​indicated are % by mass:

[0043] [Tables 1] Type Fe Cr Ni Co Mo W Nb Ti Al Ta N-18 (nickel base) - 11.5 57 11.5 6.5 4.7 - 4.3 4.3 - CMS-X2 (nickel base) - 8 66 4.6 0.6 7.9 - 0.9 5.6 5.8 S-816 (cobalt base) 4 20 20 44 4 4 4 - - -

[0044] In the context of this description, by nickel-based superalloy, respectively by cobalt-based superalloy, means a high-performance alloy whose major component by mass is nickel, respectively cobalt; while by nickel- and cobalt-based superalloy means a high-performance alloy whose major component by mass is a mixture of nickel and cobalt.

[0045] There are several types of nickel-based superalloys, which often bear references or trade names such as: INCONEL®, RENE®, HASTELLOY®, NIMONIC®, MONEL®, MAR-M 246, MAR-M 247, MAR-M 200+Hf, MAR-M 002, UDIMET®, Triballoy®, SIEMET®, WASPALLOY®, PERMENDUR, KOVAR®, INVAR®, ALNICO®, etc.

[0046] There are also cobalt-based superalloys, which often bear references or trade names such as: HS25 (L605), HS30, HS31 (X40), HS188, FSX-414, X45, MAR-M 509, ECY 768, MP35N, MP159, ELGILOY, UMCO 50, UMCO 51, WL52, Hyperco®, Permendur®, etc.

[0047] The invention relates to a method for manufacturing a resurfacing or welding rod 50 (see [Fig.3]).

[0048] This process includes a first step of preparing a mixture to be formed into wire, for example by extrusion. This first step includes, in particular, a step 11 of supplying a mixture 60 comprising a metal powder and a powdered binder.

[0049] The volume proportion of metal powder in the mixture 60, also referred to as the filler content, is between 50 and 90%. Preferably, the filler content is between 60 and 80% in order to ensure both good extrusion capacity and good cohesion during debinding, as well as a high and homogeneous final density.

[0050] According to one embodiment of the invention, the mixture 60 may further comprise up to three additives, for example a minimum of 80% of a main binder, a binder secondary which represents 90% of the remainder and a dispersant type adjuvant which represents the last 10%.

[0051] The metal powder is preferably a nickel and / or cobalt-based metal superalloy, while the binder is preferably a wax and / or thermoplastic polymer-based binder.

[0052] The metal powder preferably has a particle size distribution with a D50 between 5 and 15 pm, meaning that 50% of the grains (by number) have a diameter less than a value d such that 5 < d < 15 pm. The superalloy powder grains are preferably subspherical or spherical in shape. As is known in the field of particle size analysis, a subspherical grain is defined as a grain whose shape is close to that of a sphere.

[0053] According to one embodiment of the invention, the particle size of the binder and the other additives is substantially equivalent. For these materials, pellets with a length and diameter between 1 and 4 mm can be used.

[0054] In the case where it is based on a thermoplastic polymer, the binder comprises, for example, predominantly polyethylene, polypropylene, polystyrene, polyoxymethylene, or a mixture thereof. As an additive, the thermoplastic polymer-based binder may include a fluidizing agent, such as paraffin or polyethylene glycol, or a wetting agent such as stearic acid.

[0055] In the case where it is wax-based, the binder comprises, for example, predominantly paraffin wax, camauba wax, or a mixture thereof. As an additive, the wax-based binder may include stearic acid.

[0056] The binder can also be a mixture of thermoplastic polymer and wax, which lowers the viscosity of the binder and opens a porosity facilitating its removal.

[0057] As an additive, the binder may also include surfactants to improve the miscibility of the components.

[0058] During the first preparation step, the metallic superalloy powder is preferably added gradually to the binder, which is preferably in a molten state. This addition is preferably carried out using mixers or extruders that allow for high shear rates, thus ensuring the homogeneity of the system. The resulting mixture 60, once homogeneous, is, for example, cooled and hardened, then formed into granules (also known as feedstock) so that it can subsequently be formed into wire, for example by extrusion. The resulting mixture 60, once homogeneous, can also be kept hot so that it can be extruded through a die 70 during step E2 of forming a wire from the mixture 60, before the mixture 60 cools and hardens.

[0059] After step El of supplying a mixture 60, the process according to the invention includes a step E2 of forming a mixture 60 yarn designated as "green" yarn, preferably by extrusion of the mixture 60 resulting from step El through a die 70 (see [Fig.4]).

[0060] If the mixture 60 is in the form of granules, it must be melted by heating before extrusion.

[0061] During step E2, the main preferred extrusion parameters are, for example, the following: • Extrusion temperature: 50 to 250°C; • Extrusion speed: 10 to 100 cm3 / s; • Extrusion pressure: 50 to 1500 bars.

[0062] The extrusion temperature corresponds to the temperature at which the mixture 60 is extruded. It is generally heated to this temperature upstream of the die 70, either, for example, during the formation of the mixture 60 or by melting said mixture 60 when it is in the form of granules. The extrusion die 70 can also be maintained at this extrusion temperature or at a temperature close to it.

[0063] The extrusion speed corresponds to the mixing flow rate 60 through the die 70 when it is extruded.

[0064] The extrusion pressure corresponds to the pressure to which the mixture 60 is subjected to be extruded through the die 70.

[0065] The internal diameter of the die 70 outlet orifice, i.e., the cross-section of the die 70, is preferably between 0.1 and 10 mm. The cross-section of the die 70 is preferably circular. It may also be oval, polygonal, star-shaped, or other. Apart from the shrinkage factor, the shape and diameter of the cross-section of the die 70 substantially determine the shape and diameter of the blended wire 60 obtained by the process of the invention. Depending on the diameter of the wire obtained, the term "cord" could also be used instead of "wire." The term "wire" is used here generically for a long, thin body extruded through an extrusion die.

[0066] The "green" yarn of mixture 60 obtained during step E2 can be cut to the desired length, this length being for example between 1 and 30 cm (cf. [Fig.5]).

[0067] After step E2 of forming a "green" yarn, the process according to the invention includes a step E3 of unbinding said "green" yarn (see [Fig.6]).

[0068] Debinding is a well-known step for those skilled in the art, which aims to eliminate the binder by thermal and / or chemical means, depending on the nature of the binder, in order to obtain a "brown" part. Indeed, the main debinding techniques are thermal degradation, dissolution in a solvent, or a combination of both.

[0069] The debinding parameters (temperature, atmosphere, etc.) depend not only on the nature of the binder, but also on the nature of the metal powder. The selection of these parameters is well known to those skilled in the art.

[0070] The debinding step must be perfectly controlled as it can cause damage to the part. Indeed, poorly controlled debinding risks leading to defects such as cracking, but also to chemical contamination due to carbon residues.

[0071] The term thermal debinding encompasses several techniques that can be distinguished and are well known to those skilled in the art, such as: • degradation; • evaporation under a controlled atmosphere or vacuum; or • drainage in liquid state on a porous substrate.

[0072] For binders that require thermal debinding, the "green" wire 60 is placed for a period of 1 to 30 hours in a heated chamber 80 with a temperature between 50 and 250 °C, depending on the case. This step can, for example, be carried out in an acidic atmosphere.

[0073] Among the binders which require thermal unbinding, we can notably mention polyoxymethylene and polypropylene.

[0074] For binders which require chemical unbinding, the "green" wire 60 is immersed for a period of 10 to 200 hours in a solvent 90 (organic solvent, aqueous solvent, neutral, basic or acidic...) whose temperature is between 20 and 100 °C depending on the case.

[0075] Among the binders which require chemical unbinding, polyoxymethylene can be notably mentioned.

[0076] After step E3 of unbinding the "green" wire 60, the process according to the invention includes a step E4 of sintering the unbound wire 100 or "brown" wire resulting from step E3 (see [Fig.6]).

[0077] Sintering is a well-known step to those skilled in the art, aimed at creating strong bonds between particles, eliminating porosity, and densifying the "brown" wire 100 so as to give it strength and a solid structure. Sintering is a manufacturing process for parts that involves heating a powder without melting it. Under the effect of heat, the grains bond together, forming the cohesion of the part.

[0078] The sintering parameters (temperature, duration, etc.) depend not only on the diameter of the "brown" wire 100, but also on the nature of the metal powder used in the mixture 60. The choice of these parameters is well known to those skilled in the art.

[0079] This sintering step E4 is preferably carried out in a sintering furnace 110 for a period of between 2 and 20 hours, under a protective atmosphere or under vacuum, for example at a temperature between 1000 and 1500 °C.

[0080] Following this E4 sintering step, the sintered wire obtained forms the re-hardening or welding rod 50 according to the invention.

[0081] The invention also relates to a resurfacing or welding process, which uses a 50 superalloy-based resurfacing or welding rod obtained by the process according to the invention.

[0082] Although described through a number of examples, variants and embodiments, the methods according to the invention include various variants, modifications and improvements which will be obvious to a person skilled in the art, it being understood that these variants, modifications and improvements form part of the scope of the invention.

Claims

Demands

1. A method for manufacturing a cladding or welding rod (50), characterized in that it comprises the following successive steps: - a step (E1) of supplying a mixture (60) comprising: • 50 to 90% by volume of a powder of a nickel and / or cobalt-based metallic superalloy, and • a powder of a wax and / or thermoplastic polymer-based binder; - a step (E2) of forming a mixture wire (60) from the mixture resulting from the step (E1) of supplying a mixture (60), this wire being designated as the "green" wire; - a step (E3) of debinding the "green" wire (60) and obtaining a debinded wire (100) designated as the "brown" wire; - a step (E4) of sintering the "brown" wire (100) resulting from the step (E3) of unbinding and obtaining a sintered wire usable as a re-hardening or welding rod (50).

2. A process according to claim 1, characterized in that during the step (El) of supplying a mixture (60), the superalloy powder used has a particle size distribution of which the D50 is between 5 and 15 pm.

3. A method according to claim 1 or 2, characterized in that during the step (El) of supplying a mixture (60), the grains of the superalloy powder used are of subspherical or spherical shape.

4. A method according to any one of the preceding claims, characterized in that during the step (E2) of forming a mixture yarn (60), the formation of a "green" yarn (60) is carried out by extruding the mixture resulting from the step (E1) of supplying a mixture (60) through a die (70).

5. A method according to the preceding claim, characterized in that during step (E2) of forming a blended yarn (60), the main extrusion parameters are as follows: - Extrusion temperature: 50 to 250 °C; - Extrusion speed: 10 to 100 cm3 / s; - Extrusion pressure: 50 to 1500 bars.

6. A method according to claim 4 or 5, characterized in that during the step (E2 of forming a blend wire (60)), the die (70) has a cross-section whose diameter is between 0.1 and 10 mm.

7. A method according to any one of the preceding claims, characterized in that during the debinding step (E3), the "green" yarn resulting from the mixing yarn (60) formation step (E2) is immersed for a period of between 10 and 200 hours in an organic or aqueous solvent (90) with a temperature between 20 and 100 °C.

8. A method according to any one of claims 1 to 6, characterized in that during the debinding step (E3), the "green" yarn resulting from the mixing yarn formation step (E2) (60) is placed for a period of between 1 and 30 hours in a chamber (80) heated to a temperature between 50 and 250 °C

9. V-. A process according to any one of the preceding claims, characterized in that during the sintering step (E4), the sintering is carried out for a period of between 2 and 20 hours under a protective atmosphere or under vacuum, at a temperature between 1000 and 1500 °C.

10. A re-facing or welding process, characterized in that it uses a re-facing or welding rod (50) comprising a powder of a nickel and / or cobalt-based superalloy, said re-facing or welding rod (50) being a product resulting from the process according to any one of the preceding claims.

Images