METHOD FOR SUPPLYING METALLIC MATERIALS

Abstract

 Method for supplying metallic material to a component (1),which comprises the following steps of a) supplying metallic material, by means of a thermal process for melting the metallic material, at least partially on the surface of said component (1), forming a layer (3) of metallic material and a thermally affected zone, and b) burnishing said layer (3) and wherein steps a) and b) are performed by means of at least one combined head (5) that comprises at least one device (2) for supplying said metallic material and at least one burnishing tool (4), the two steps being carried out with sufficient delay for the thermally affected zone to still be at a temperature at which the compressive creep stress is less than the burnishing pressure.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a method for supplying metallic material to a given component and the subsequent step of burnishing; as well as to the system for supplying the metallic material associated with said method. The invention falls within the technical sector of manufacturing processes by means of supplying material, applied to rotating components of different geometries, as well as for materials such as steels, special steels, nickel based and titanium based alloys and other metallic alloys.

BACKGROUND OF THE INVENTION

[0002] Different thermal processes for melting metallic material are known, such as laser material deposition (also known as Laser Cladding), which is a process of high industrial interest because it offers the possibility of supplying material on a base component with a high supply quality and a high selectivity in the treated zone. Laser cladding can be used as a technique for coating or as a fast layer-by-layer technique for manufacturing and forming. In particular, in any of the two variants, it is highly used in rotating components, since a device for laser cladding can be placed and the component can be rotated by means of a turning centre or the like.

[0003] One of the main difficulties posed by the laser cladding technique is guaranteeing the integrity of the coatings generated. In fact, on occasions, specific characteristics of these coatings are required, which are difficult to achieve directly by means of said laser cladding technique. The main problem stems from the actual process itself, which is based on the melting of a fraction of material of the base component onto which a fill material is injected, and which can also be melted. The movement of the component, rotational and/or longitudinal, causes the laser to fail to affect this zone and a fast cooling is produced that solidifies the previously melted material, thus creating a solid layer of coating diluted with part of the material of the base component. This process implies that there is a zone that has solidified once again after the melting and a thermally affected zone.

[0004] Furthermore, the presence of pores or gaps is common, as a result of the operation of laser cladding, despite working in optimal processing conditions such as working in vacuum and/or inert atmospheres. This reduces the mechanical properties of the components and on occasions requires a comprehensive control of the components manufactured using this technique, thus increasing the costs of maintenance and the prevention of service failures.

[0005] Moreover, there are processes for improving the surface properties of the fabricated components, by means of plastic deformation. One of these processes is that known as mechanical burnishing. The process of mechanical burnishing generally has two variants according to the type of tool that is used; roller burnishing, and ball burnishing. In both cases, a very hard tool is used. Roller burnishing uses a tool in the shape of a roller and is applied to rotating components, whilst in ball burnishing the tool is a sphere that is able to move in any direction and can be applied to any geometry of component. In turn, these processes can be carried out with different methods of generation of the necessary pressure: mechanical spring, hydraulic pump...

[0006] Regardless of the type of burnishing used, the process is based on plastically deforming a layer of material. The improvement achieved is two-fold: on the one hand the surface roughness is improved and on the other hand, compressive residual stress is introduced in the surface and below the surface, thus increasing the fatigue resistance of the parts treated by this technique.

[0007] Some systems, such as that presented in the application WO-2009124034 seek the application of a coating using burnishing techniques, which achieves a material deposit that is mechanically bonded to a base component.

[0008] On the other hand there are various solutions presented for both processes separately. Thus, there are solutions for the burnishing of different components such as roller paths, see application WO-2009109303; crankshafts, see application WO-2006135014; gears, see WO-2008088748; rotating components, see WO-2007045649; even the design of burnishing tools for geometries of specific components, such as applications WO-2008050012 and WO-2008037905. All of these applications are based on developing specific burnishing tools for their final use in already fabricated components.

[0009] Similarly, there are on the other hand various inventions regarding the processes of coatings for components, also in the equipment that carries out the process such as coaxial nozzles, powder entrainment elements, etc. See applications such as WO-2005028151, WO-2005084875, WO-2007022567 and US-7259353, as well as in the use of the coating process. These processes are performed in different fields for example, for hip replacements, see US-7632575; such as in biocompatible coatings, see ES-2143938; such as in repairing moulds for bottles, see WO-2009090622; and in repairing aeronautical turbines, see WO-200112381. Once more, all the inventions are focused on the process of coating.

[0010] There are some inventions closer in the state of the art, that combine the processes of coating by supplying material and the subsequent process of surface finishing, mainly abrasive polishing such as application JP-4083862, and grinding or machining. In some cases the combined use of the tools for material deposition and finishing is proposed, as in the United States application US-2005107003; but once again relating to processes of material removal by means of abrasive processes: polishing or grinding.

DESCRIPTION OF THE INVENTION

[0011] The present invention relates to a method for supplying metallic material onto a given component and the subsequent step of burnishing, wherein said method for supplying metallic material on a component comprises the following steps:

a) supplying the metallic material, by means of a thermal process for melting the metallic material; at least partially on the surface of said component, forming a layer of metallic material and a thermally affected zone, and

b) burnishing said layer,

wherein steps a) and b) are performed by means of at least one combined head that comprises at least one device for supplying said metallic material and at least one burnishing tool, the steps being carried out with sufficient delay for the thermally affected zone to still be at a temperature at which the compressive creep stress is less than the burnishing pressure.

[0012] The result is the improvement in the structural integrity of the components obtained, regardless of the metallic material that is being worked with, provided that the latter has a plastic deformation capacity susceptible to being mechanically burnished; since the device for supplying metallic material generates a layer of supplied material and where, subsequently, the burnishing tool plastically deforms the hot material, generating a layer of reduced surface roughness and increased structural integrity.

[0013] Upon plastically deforming the component obtained, the surface roughness is significantly improved and the compressive residual stresses are reduced in the surface itself, as well as below the surface; thus increasing the fatigue resistance of the components obtained by this procedure.

[0014] In addition, it can be observed that the supply device is produced in a combined manner, using the residual heat on the component so that the burnishing is performed in such a way that less pressure is required and whereby the energy requirement is less than that of the current state of the art.

[0015] The level of porosity after both steps is minimal thanks to the second step of burnishing and the completion time of the whole process is very short due to the use of a combined head in both procedures; taking into account that the process can be fully automated for producing components in this manner and in large numbers. Furthermore, the homogeneity of the metallic material coating is much greater than the operations of supplying metallic material in an isolated way.

[0016] Preferably, the surface layer to be plastically deformed and obtained by supplying metallic material varies between 5 and 350 microns in thickness.

[0017] It is considered that the part to be formed may be a rotating component; so it can be fixed by its ends and by means of a rotation shaft, both steps proceed to be performed by means of the combined head, with the possibility of the following movements:

• forward, by the combined head itself; that is, longitudinally and partially or completely covering the rotating component to be formed; or
• forward, by the rotating shaft; this option being the minority for the majority of cases.

[0018] The system for supplying metallic materials comprises at least one pulling system that regulates the distance between said, at least one, burnishing tool with respect to said, at least one, device for supplying metallic material.

[0019] In this way, and by means of a simple system, the delay of the application of said, at least one, burnishing tool can be regulated, according to the material to be formed or the metallic material to be supplied; allowing to reduce the distance for materials with a high degree of thermal conductivity and vice versa.

[0020] In addition, the supplying system can be guided by means of a type of turning center machine in the case of rotating components to be formed; a robot or any kinematic platform capable of guiding said, at least one, system for supplying metallic material.

[0021] Preferably, the pulling system comprises a graduated ruler with a slide positioned on it, so that the regulation is estimated using units of length, providing the assembly with high precision and being able to perform parameters that relate distance against holding time of the application of said, at least one burnishing tool.

[0022] The pulling system can be controlled in a fully automated manner, for example, for large numbers of components; or servo controlled by incorporating an additional shaft to the system object of the invention where said operations are performed.

[0023] Different options are considered in reference to the possibility of using one or another type of supply device, the possibilities being:

• a laser device and/or
• a plasma device.

[0024] Devices currently in use and that comprise a number of characteristics, which enable them to be used for supplying metallic material onto different types of components.

[0025] Additionally, different burnishing tools are considered, which may be:

• by means of a roller tool, and/or
• by means of a ball tool

wherein said, at least one, burnishing tool can be operated by means of an elastic element like a mechanical spring or a hydrostatic spring, since an excessive pressure is not necessary for correctly forming said, at least one, burnishing tool.

[0026] Therefore, according to the described invention, the method for supplying metallic material and the system associated thereof that the invention proposes, constitutes a development of the methods for supplying metallic material that have been used up until now, and solves the previously described problems in a completely satisfactory way, so as to allow the supply of metallic material, applied to rotating components as well as to components of different geometries, in a way that combines a procedure of surface forming that reduces porosity, improves the structural integrity of the components formed by said procedure and furthermore, it is able to automate it for producing components in large numbers.

DESCRIPTION OF THE DRAWINGS

[0027] In order to complete the description being made and with the objective of facilitating a better understanding of the characteristics of the invention, according to a preferred practical embodiment thereof, below, as an integral part of said description, a set of drawings is joined, wherein, by way of non-limitative example, the following has been represented:

Figure 1. - Shows a schematic view of the structure of the system, showing the combined action of its two main elements, the device for supplying metallic material and the burnishing tool that the invention proposes.

Figure 2. - Shows a more detailed schematic view, from the side, of the two elements and their arrangement.

PREFERRED EMBODIMENT OF THE INVENTION

[0028] In view of the described figures, it can be seen how in one of the possible embodiments of the system associated to the method for supplying metallic material that the invention proposes, comprises the following steps:

a) supplying metallic material, by means of a thermal process for melting the metallic material, on the entire surface of a component (1), forming a layer (3) of metallic material and a thermally affected zone, and

b) burnishing said layer (3),

wherein steps a) and b) are performed by means of a combined head (5) that comprises a device (2) for supplying said metallic material and a burnishing tool (4), the two steps being carried out with sufficient delay for the thermally affected zone to still be at a temperature at which the compressive creep stress is less than the burnishing pressure.

[0029] As represented in figure 1, the component is a cylinder-type rotating component; so as to facilitate the supply of metallic material as well as the subsequent step of burnishing.

[0030] Additionally, the supply system comprises a pulling system (6) that regulates the distance between said burnishing tool (4) and said supply device (2) of metallic material, said pulling system (6) comprising a graduated ruler with a slide positioned on it.

[0031] In view of both figures, it can be observed that the supply device (2) is a laser device and the burnishing tool (4) is a roller-type tool.

[0032] In view of the description herein and the set of figures, a person skilled in the art can appreciate that the embodiments of the invention that have been described may be combined in multiple ways within the object of the invention. The invention has been described according to some preferred embodiments of the invention, but for a person skilled in the art it would be apparent that multiple variations can be introduced in said preferred embodiments without departing from the object of the claimed invention.

Claims

1. Method for supplying metallic material to a component (1),which comprises the following steps:

a) supplying metallic material, by means of a thermal process for melting the metallic material, at least partially on the surface of said component (1), forming a layer (3) of metallic material and a thermally affected zone, and

b) burnishing said layer (3),
the method being characterized in that steps a) and b) are performed by means of at least one combined head (5) that comprises at least one device (2) for supplying said metallic material and at least one burnishing tool (4), the two steps being carried out with sufficient delay for the thermally affected zone to still be at a temperature at which the compressive creep stress is less than the burnishing pressure.

2. System for supplying metallic materials, according to the method defined by claim 1, characterized in that the component (1) is a rotating component.

3. System according to claim 2, characterized in that it comprises at least one pulling system (6) that regulates the distance between said, at least one, burnishing tool (4) and said, at least one, device (2) for supplying said metallic material.

4. System according to any one of claims 2 and 3, characterized in that said, at least one, supply device (2) comprises a laser device.

5. System according to any one of claims 2 to 4, characterized in that said, at least one, supply device (2) comprises a plasma device.

6. System according to any one of claims 2 to 5, characterized in that the burnishing tool (4) comprises a roller tool.

7. System according to any one of claims 2 to 6, characterized in that the burnishing tool (4) comprises a ball tool.

Drawing