JP2015518085A - Member with metallurgically bonded coating - Google Patents

Abstract

The present invention relates to a member (1) comprising a metallurgically bonded and sprayed and remelted coating (3). In order to avoid continuous wear phenomena when force is applied in the member (1) and further surface loading is applied, the present invention is provided with a sprayed layer (4) in the coating (3).

Description

  The present invention relates to metallurgically bonded, sprayed and remelted coatings.

  Furthermore, the invention relates to a method for producing a metallurgically bonded coating which has been sprayed and remelted on the surface of a member.

  The above types of components are known and well known to those skilled in the art, and in recent years it has been increasingly discussed in extensive scientific research to remelt a sprayed coating using laser technology.

  Metallurgically bonded coatings have high wear and corrosion resistance properties, combining the advantages of thermal spraying with the advantages of laser melting during their manufacture.

  For example, after applying a coating that exists in the form of an IN 625 HVOF layer onto the surface of a member such as a turbine blade, several melting lines may be rectangular or elliptical by intensive circles and nearly circular movements. Industrial processing is performed so as to generate light spots. The moving means required for this is a beam guide with high accuracy, which depends on the geometry of the melting point, the need for overlap of the melting lines and the required reproducibility of the production of the melting lines. To do.

  A metallurgically bonded coating of the type mentioned at the outset is disclosed, for example, in UK patent application No. 1039633, in which a layer sprayed with a laser device is re-applied. Melting takes place and the laser device guides the pointed light spots across the sprayed layer to melt them. In this case, each sprayed point and the entire layer are remelted using a laser. This results in improved mechanical properties of the coating, in particular the mechanical adhesion of the sprayed layer is improved by melting.

Metallurgically bonded coatings of the type described above are also discussed in a recently disclosed paper, and the remnants of IN 625 HVOF layers coated on steel and TI6A4V remelted using a laser. Stress has been discussed. In this paper, residual tensile stress has been identified in the remelted IN 625 layer. The disclosed paper shows the difficulty to achieve using laser remelting, the state of non-critical stress, i.e. unrestrained residual tensile stress, and residual compressive stress. CO ₂ in a circular shape of the laser point - when using laser, the laser is at a frequency of 200 Hz, over a length of 126 mm, which is guided over the surface of the member (Arif, A.F.M, Yilbas, B S., Surface Engineering, Volume 25, No. 3, April 2009, pp 249-256 (Non-Patent Document 1)).

  Similarly, in a recently disclosed paper, a 280 μm thick HVOF WC—CrC—Ni— layer was heat treated and compressed using a laser. In this case, the properties of porosity, hardness and wear resistance were improved. The laser spot was selected to have an elliptical shape of 5 mm × 4 mm with a degree of overlap of 30% at a moving speed of 400 mm / min for a laser output of 400 watts (Journal of the Korean Physical Society, Volume 54, No. 3). March 2009 (non-patent document 2)).

  A metallurgically bonded coating, known from this prior art, sprayed onto the surface of the part and remelted using laser technology, is forced into the part (Kraftaufschlagung) and further loaded onto the surface. When is added, there is a disadvantage that a wear phenomenon occurs.

British Patent Application No. 1039633

Arif, A.M. F. M, Yilbas, B.M. S. , Surface Engineering, Volume 25, No. 3, April 2009, pp 249-256 Journal of the Korean Physical Society, Volume 54, No. 3; March 2009

  The object of the present invention is therefore to avoid these drawbacks.

  This problem is solved by the features of claim 1. Advantageous embodiments of the invention are given in the dependent claims.

  The present invention provides for providing at least one sprayed layer on a metallurgically bonded coating.

  The core of the subject of the present invention is to provide a sprayed overlay layer on the metallurgically bonded coating. Surprisingly, it has been found that the coating is metallurgically bonded to the part, and when the part is expanded, only the top layer cracks due to the tolerance of the top layer. . Therefore, in the case of the coating of the present invention, cracks do not continue in the remelted coating. Therefore, a dense corrosion protection layer is provided and the basic material, i.e. the material of the component, is subsequently protected from corrosion attack.

  Specific members of any one of claims 1 to 10 are a twin barrel and a screw, which are used in an extruder for plastic processing. In twin barrels, two screws, among other things, feed and compress thermoplastic materials, such as PVC, at high pressures and temperatures. Plastic materials are subject to additional wearable materials such as glass fiber, wood flour and colorants. The proportion of the wear-active additional material may be greater than 50% by volume. Twin barrels and screws are subject to high wear, and the screws are supported on the inner surface of the barrel, which results in high surface pressure and bending stress on the surface. During PVC processing, PVC degradation can occur and hydrochloric acid can be generated which causes corrosion in the barrel and screw.

  As the coating, a hard metal layer based on metal-bonded tungsten carbide, for example WC-CoCr or WC-CrC-Ni, applied using the HVOF method is suitable for resisting abrasion.

  WC-based HVOF layers do not have metallurgical bonds but are sticky based on a mechanical sticking mechanism. Mechanical adhesion is primarily affected by the kinetic energy of the particles and the hardness of the substrate. When an HVOF layer is applied on a medium hardness basic material of 40-45 HRc, a shear strength of 250-350 MPa is obtained, and in the case of a substrate of 55-57 HRc hardness, a lower, 50-150 MPa Shear strength is obtained.

  For twin extrusion barrels, it was found that a coating with higher tack and shear strength of 250 MPa had to be applied on the substrate, so that the coating could withstand mechanical stress. In addition, there must be a support region at least 0.5 mm deep in the hardness of the coating below 55 HRc, so that a metal-bonded WC layer into the substrate due to high surface pressure and bending action. Will not be pushed in.

  The proposed coating system allows a hard metal coating with a shear stress of> 250 MPa on a support layer with a hardness of 55 HRc in the substrate. In this case, the former, a thin layer of medium hardness made of a Ni-based alloy is applied and remelted with a laser, and then a WC-HVOF coating is applied. According to the invention, the metallurgically bonded layer consists of a medium hardness, Ni-based alloy, for example a NiCrMo type alloy with boron, silicon and carbon parts, with a hardness of 40-45 HRc. It is a coating.

  In the case of higher hardness barrel materials, such as 42CrMo4 or X40Cr17Mo, a dense and corrosion-protective NiCrMo-BSiC coating by laser remelting of the Ni base layer coated by the former spraying Is brought about. By laser remelting, the base material under the former layer made of NiCrMo—BSiC alloy is cured. For the barrel and screw materials described above, the hard region having a hardness of 55-57 HRc occurs at a depth of about 0.5-2 mm. The former remelted layer is as thin as 5-30 μm and has an average altitude of 40-45 HRc. The high shear force and surface pressure on the thin, medium hardness metallurgically bonded Ni-based layer allows the substrate to be processed without causing severe plastic deformation and dents in the hard WC coating. It was found that it can be expressed in the cured region of

  The coating of the present invention enables a hard metal HVOF coating with a shear strength of 250 MPa applied on the inner surface of the twin barrel and the barrel surface of the screw, which is a coating of the former coated by thermal spraying. The substrate is cured by laser remelting and allows sufficient support of the coating. The coating allows protection against corrosion of the lower part by hydrochloric acid by a NiCrMo-BSiC alloy remelted with a laser when cracks due to high mechanical stress occur in the HVOF WC coating.

  Furthermore, it has been found that the coatings of the present invention have not only corrosion resistance, impact resistance and cracking resistance, but also high strain tolerance.

  For example, the present invention can be applied to a member having a complicated size and shape such as an inner surface of a pipe such as a turbine blade, a ball valve, a screw rotor, or a barrel.

The production of the coating of the present invention involves the following three steps:
1. Forming a thin coating, ie a coating having a thickness of preferably 5 to 300 μm, on the surface of the member using thermal spraying; As the material for the surface, in particular, an oxidation-resistant and / or corrosion-resistant material is used.
2. Remelting the coating applied by spraying; Here, the remelting is preferably performed using laser technology.
3. Spraying at least one other layer onto the remelted coating. Here, the layer is preferably a plasma layer made of an oxide ceramic material or an HVOF layer made of a metal-bonded carbide.
Is characterized by

  Plasma spraying and high-speed flame spraying are particularly suitable as thermal spraying variants.

  Preferably, the sprayed layer is remelted. Again, laser technology is suitable as a reliable instrument for remelting. The advantage of the remelted layer is that an alloy is formed in the underlying, metallurgically bonded, sprayed and remelted coating.

  A further advantageous embodiment of the invention provides a plasma layer, wherein the layer consists of an oxide ceramic material. Since this layer has a high hardness and low thermal conductivity, this layer is advantageously characterized by being particularly suitable for thermal insulation members.

  A practical variant of the invention provides a layer made of metal-bonded carbide, in particular an HVOF layer made of WC—CrC—Ni. This gives a layer with high hardness and fastness. Furthermore, the layer is electrically conductive and has a high thermal conductivity.

  Furthermore, the use of a layer sequence according to any one of claims 1 to 10 in an extruded twin barrel is provided.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. The drawings show the following schematics:

A conventional member provided with a metallurgically bonded and sprayed and remelted coating. FIG. 2a shows a member according to the invention with cracks. FIG. 2b shows the member according to the invention without cracks.

  FIG. 1 shows a conventional member provided with a coating 3.

  The coating 3 is metallurgically bonded to the surface 2 of the member 1 and remelted. The coating 3 is previously sprayed on the surface 2 of the member 1. The member shown in FIG. 1 is a screw rotor. The thickness of the coating 2 is 5 μm to 300 μm.

  In the essential method of the present invention, the metallurgically bonded coating 3 is further provided with a sprayed layer 4, as is further evident from FIG. 2a. 2a and 2b do not completely show the member 1 shown in FIG. 1 for the purpose of illustration. In the case of layer 4, the thickness is about 30 μm, which is a layer sprayed onto the metallurgically bonded coating 3. Layer 4 is a plasma layer made of an oxide ceramic material. Alternatively, the layer can be an HVOF layer made of WC—CrC—Ni.

  The advantages of the layer structure of FIG. 2a are illustrated in FIG. 2b. If cracking is caused due to the increased stress of the member, that cracking only occurs in layer 4. As can be seen from FIG. 1b, the crack 5 only spreads in the layer 4 and no cracks continue in the metallurgically bonded coating 3 are seen.

  As for this invention, those forms are not limited to the above-mentioned embodiment. Rather, many changes are possible and they utilize the indicated solution in the case of other modified embodiments.

  For example, the layer 4 may have a thickness of 5 μm to 300 μm, preferably 5 μm to 150 μm, and may particularly preferably have a thickness of 5 μm to 30 μm for reasons of cost reduction.

  Furthermore, the coating 3 can be made of a hot gas oxidation resistant material such as MGAlY or a corrosion resistant material such as NiGMo.

Furthermore, the following points can be contemplated within the scope of the present invention.
-Layer 4 on the hardened surface, limited to the inner coating of member 1, limited to twin barrel geometry, limited to spray with rotating burner,
The layer sequence according to claim 1, wherein the remelted layer 4 on the cured surface has <5 μm;
A rotary inner coating burner with RMTU,
HVOF inner coating burner for small inner diameters and for powders, twin combustion chambers, hydrogen atomization, kerosene, lambda <1, short spray distance, protection with active gas, powder plasma spheronization, <15 μm , Preferably 0.5-6 μm, 2-9 μm,
The inner coating of the member 1 made of metal-bonded tungsten carbide and molybdenum,
-Powder feeders for fine particles, vibrations, balls, spherical floors, vibration devices, delivery channels, grooves, hoppers or barrels, conveyor disks,
-Tubes with inner and outer coatings, combination lasers HVOF and HVOF, and laser HVOF, soft laser HVOF hard, corrosion resistant hard metal HVOF layer, eg powder WC-CrC-Ni containing a small amount of metal binder in the layer Consists of.

  Suggested here is that tungsten carbide powder for producing layers and bodies consists of spherical, plasma spheroidized tungsten, chromium, carbon and binders such as Fe, Co, Ni, and chromium. WC having, for example, WC-CrC-Ni with low metal binder content, miniaturized WC and miniaturized CrC, structures WC, W2C, (WCr) 2C, Cr3C2, Cr7C3, Cr23C6 with W content ((CrW) 23C6) , (WCr) 3NiC, (WCr) 4Ni2C, (WC) 6Ni6C, chromium carbide is a carbon supply material. In this case, carbon is present in excess and is liberated like graphite. This is advantageous for suppressing brittle n-carbide.

1 Member 2 Surface 3 Coating 4 Thermal Spray Layer 5 Crack

Claims (15)

A member (1) with a metallurgically bonded, sprayed and remelted coating (3),
Said member, characterized in that at least one sprayed layer (4) is provided on the coating (3).   2. Member according to claim 1, characterized in that the layer (4) has been remelted.   The member according to claim 2, wherein the layer (4) has a thickness of 5 to 500 μm.   The member according to claim 2 or 3, characterized in that the layer (4) has a thickness of 5 to 150 µm.   The member according to claim 3 or 4, characterized in that the layer (4) has a thickness of 5 to 30 m.   6. Member according to claim 1, characterized in that the layer (4) is a plasma layer from an oxide ceramic material.   6. The member according to claim 1, wherein the layer is a HVOF layer made of a metal bonded carbide, in particular WC—CrC—Ni.   The member according to any one of claims 1 to 7, wherein the coating (3) is made of a material resistant to oxidation of hot gases.   8. Member according to any one of the preceding claims, characterized in that the coating (3) is corrosion resistant.   10. A member according to any one of the preceding claims, characterized in that the coating (3) is on the surface (2) and / or on the inner surface of the member (1). A method of producing a metallurgically bonded coating (3) sprayed onto a surface (2) of a member (1) and remelted with a laser comprising:
Process as described above, characterized in that at least one further layer (4) is sprayed onto the coating (3).   12. Method according to claim 11, characterized in that the layer (4) is remelted.   13. Method according to claim 12, characterized in that the layer (4) is remelted using a laser.   14. Method according to any one of claims 11 to 13, characterized in that the layer (4) is applied using plasma spraying.   15. Method according to any one of claims 11 to 14, characterized in that the layer (4) is applied using high-speed flame spraying.

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