EP2825681A1

EP2825681A1 - Component with a metallurgically bonded coating

Info

Publication number: EP2825681A1
Application number: EP13709865.3A
Authority: EP
Inventors: Götz Matthäus
Original assignee: Thermico & Co KG GmbH
Current assignee: Thermico & Co KG GmbH
Priority date: 2012-03-13
Filing date: 2013-03-11
Publication date: 2015-01-21
Also published as: CA2867192A1; US20150017430A1; WO2013135638A1; JP2015518085A; DE102012102087A1

Abstract

The invention relates to a component (1) with a coating (3) which is metallurgically bonded, thermally sprayed, and remelted. The aim of the invention is to prevent signs of wear from continuing to arise due to an application of force in the component (1) and additional surface stress. According to the invention, this is achieved in that the coating (3) is provided with a thermally sprayed layer (4).

Description

Component with a metallurgically bonded coating

The invention relates to a component with a metallurgically bonded and thermally sprayed and remelted coating.

In addition, the invention relates to a method for producing a metallurgically bonded coating which is thermally sprayed onto a surface of a component and remelted.

Components of the type mentioned are known to the skilled worker and familiar, with the remelting of thermally sprayed layers by laser technology in extensive scientific work has been increasingly addressed in the recent past.

Metallurgically bonded coatings, whose production combines the advantages of thermal spraying with those of laser remelting, have high-quality wear and corrosion protection properties.

The industrial implementation is such that, after the coating, which for example is in the form of an IN 625 HVOF layer, is applied to a surface of a component, such as a turbine blade, individual melting lines are formed by the movement of a concentrated circle and approximately circular, rectangular or elliptical shaped light spot can be generated. The necessary movement devices of the beam guides require high accuracy, which depends on the geometry of the melting point, the requirements of the overlap of the melting lines and the required reproducibility of the generation of the melting line.

A metallurgically bonded coating of the type mentioned initially discloses, for example, GB 10 39 633, wherein the remelting of a thermally sprayed layer takes place by means of a laser device which guides a punctiform point of light over the sprayed-on layer and melts it. Here, both the respective spray position and the entire layer by means of the laser has been remelted. This results in improved mechanical properties of the coating, in particular, the mechanical adhesion of the thermal spray coating is improved by the melting.

Metallurgically bonded coatings of the type mentioned at the outset also address a recently published paper that deals with the residual stresses of laser-fused IN 625 HVOF layers applied to steel and TI6AI4V. In the process, residual tensile stresses were found in the remelted IN 625 layer. The publication shows the difficulties, uncritical stress states, i. E. Neutral and Druckeinspannung to achieve by means of laser remelting. A C0 ₂ laser with a round laser spot was used, which was guided at a frequency of 200 Hz over a length of 126 mm over the component surface (Arif, AFM, Yilbas, BS, Surface Engineering, Volume 25, No. 3, April 2009 , pp 249-256).

In a recent work as well, 280 μm thick HVOF WC-CrC-Ni layers were heat-treated and compacted by means of a laser. The properties of porosity, hardness and wear resistance were improved. The laser spot used was an oval geometry of 5 mm x 4 mm with an overlap of 30% at a travel speed of 400 mm / min at 400 Watt laser power (Journal of the Korean Physical Society, Volume 54, No. 3, March 2009).

These known from the prior art metallurgically bonded coatings that are thermally sprayed onto a surface of a component and remelted by laser technology, have the disadvantage that when Kraftaufschlagung in the component and further surface stress further wear phenomena occur.

It is therefore an object of the invention to avoid these disadvantages.

This object is achieved with the features of claim 1. advantageous Embodiments of the invention will become apparent from the dependent claims.

The invention provides that the metallurgically bonded coating is provided with at least one thermal spray coating.

The core idea of the invention is to provide the metallurgically bonded coating with a cover layer which is thermally sprayed on. Surprisingly, it has been found that when a component is stretched to which a metallurgical coating is bonded, only the top layer is torn over the value permitted for the top layer. In the coating according to the invention, therefore, no continuation of the crack takes place in the remelted coating. Thus, a dense anticorrosive layer is further provided, which is the base material, ie. the material of the component, protects against corrosion attack.

A concrete component according to one of claims 1 to 10 are double cylinders and screws, which are used in plastic processing extrusion machines. In the double cylinder, two screws, and the like, promote and compact. thermoplastic plastic material such as PVC under high pressure and temperature. The plastic materials are admixed with abrasive additives such as glass fiber, wood flour and dyes. The proportion of abrasive additives may be more than 50% by volume. The double cylinders and screws are exposed to heavy wear, in addition, the screws are based on the cylinder inner surface, which leads to a high surface pressure and flexing load of the surfaces. During the processing of PVC, decomposition of PVC can occur and hydrochloric acid can form, causing corrosion on the cylinder and screw.

As a coating applied by the HVOF process hard metal layer based on metal-bonded tungsten carbide such as WC-CoCr or WC-CrC-Ni, suitable to withstand the abrasive wear. HVOF coatings based on WC have no metallurgical bonding, but adhere due to mechanical adhesive mechanism. The mechanical adhesion is mainly influenced by the kinetic energy of the particles and the hardness of the base material. Applied to medium-hard base materials of 40-45HRc, the HVOF layers achieve a shear strength of 250-350 MPa and for hard base materials of 55-57 HRc a lower shear strength of 50-150 MPa.

It has been found that for double extrusion cylinders the high adhesion coating and a 250 MPa shear strength must be applied to the base material in order for the coating to withstand the mechanical stress. In addition, a supporting zone of at least 0.5 mm depth with a hardness of 55 HRc below the coating must be present, so that the metal-bound WC layer is not pressed into the base material by the high surface pressure and flexing work.

The proposed coating system allows a shear strength of> 250 MPa of the hard metal coating on a 55 HRc hard support layer in the base material. Here, a first, thin medium-hard layer of a Ni-based alloy is applied and remelted by laser and subsequently applied a WC-HVOF coating. The metallurgically bonded layer according to the invention is a medium-hard, 40-45 HRc hard coating of a Ni-based alloy, for example of the type NiCrMo with proportions of boron, silicon and carbon.

For harder cylinder materials such as 42CrMo4 or X40Crl7Mo, the laser remelting of the former thermally applied Ni base layer results in a metallurgically bonded, dense and corrosion-resistant NiCrMo-BSiC coating. The laser remelting causes hardening of the base material below the former layer of the NiCrMo-BSiC alloy. For the mentioned cylinders and screw materials, a hardness zone with a hardness of 55-57 HRc at a depth of approx. 0.5-2mm is used generated. The former remelted layer is thin, 5-30μη "und, and has an average hardness of 40-45 HRc.It has been shown that the high shear forces and surface pressures over the thin medium-hard, metallurgically bonded Ni-base layer, in the hardened Zone of the base material are passed without a critical plastic deformation and a depression of the hard WC coating occurs.

The coating according to the invention enables a hard metallic HVOF coating with a shear strength of 250 MPa, applied to the inner surface of the double cylinder and cylindrical surface of the screw, which causes a hardening of the base material by the laser remelting of the former thermally applied coating and enables a sufficient supporting effect of the coating. The coating allows protection against hydrochloric acid corrosion by the laser-remelted NiCrMo-BSiC alloy, if the high mechanical stress causes cracks in the HVOF WC coating.

In addition, it has been shown that the coating according to the invention is not only corrosion-resistant, impact-resistant and crack-resistant, but also has a high elongation tolerance.

Applications can be complex geometry components, such as turbine blades, ball valves, screw rotors, or the inner surfaces of tubes, such as cylinders.

The preparation of the coating according to the invention is characterized by three steps:

1. Generation of a thin coating by means of thermal spraying, ie a coating with a thickness preferably between 5 and 300 μm, on the surface of a component. The material of the surface is in particular an oxidation and / or corrosion resistant material. 2. Remelting of the thermally applied coating. The remelting takes place preferably by means of laser technology.

3. spraying at least one further layer on the remelted

Coating. The layer is preferably a plasma layer of oxide ceramic material or a HVOF layer of metal-bonded carbides.

As variants of thermal spraying, plasma spraying and high-speed flame spraying are particularly suitable.

Preferably, the thermal spray layer is remelted. As a tried and tested instrument for remelting, laser technology is also an option here. The advantage of the remelted layer is the formation of an alloy in the underlying metallurgically bonded, thermally sprayed and remelted coating.

A further advantageous embodiment of the invention provides that the layer is a plasma layer of oxide ceramic material. This layer is advantageously characterized by the fact that it has a high hardness and low thermal conductivity, so that this layer is particularly suitable for heat-insulating components.

A practicable variant of the invention provides that the layer of metal-bonded carbides, in particular a HVOF layer of WC-CrC-Ni is. As a result, a layer is given, which has a high hardness and toughness. In addition, it is electrically conductive and has a high thermal conductivity.

In addition, the use of the layer sequence according to one of claims 1 to 10 is provided in an extrusion double cylinder. In the following the invention will be explained in more detail with reference to the drawings. It shows in a schematic representation:

Fig. 1 is a conventional component with a metallurgical

Tailored and thermally sprayed and

remelted coating is provided and

Fig. 2a to 2b, a component according to the invention with and without cracking.

Fig. 1 shows a conventional component provided with a coating 3.

The coating 3 is metallurgically bonded to the surface 2 of the component 1 and remelted. Previously, the coating 3 was thermally sprayed onto the surface 2 of the component 1. The component shown in FIG. 1 is a screw rotor. The thickness of the coating 2 is 5 pm to 300 pm.

In a manner essential to the invention, the metallurgically bonded coating 3 is, as shown in FIG. 2a further shows, provided with a thermal spray coating 4. In the Figs. 2a, 2b is not the complete in FIG. 1 shown component 1 shown. In the layer 4, whose thickness is about 30 pm, it is a layer that has been thermally sprayed onto the metallurgically bonded coating 3. The layer 4 is a plasma layer of an oxide ceramic material. Alternatively, the layer may also be an HVOF layer of WC-CrC-Ni.

The advantage of the layer structure of FIG. 2a is shown in FIG. 2 B. If cracking occurs due to an increased load on the component, the crack formation takes place only in the layer 4. As shown in FIG. 1b, the crack 5 extends only in the layer 4, without it having a continuation in the metallurgically bonded coating 3 place. The present invention is not limited in its execution to the embodiment given above. Rather, a number of variants is conceivable, which make use of the solution shown in other types.

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

In addition, the coating 3 may be made of a hot gas oxidation resistant material such as MGAIY or a corrosion resistant material such as NiGMo.

Furthermore, it can be provided within the scope of the invention:

a layer 4 on a hardened surface, limited to the inner coating of the component 1, restricted to the geometry of double cylinders, restricted to the injection with rotating burner,

- A layer sequence according to claim 1 with a <5pm remelted

Layer 4 on a hardened surface,

a rotating interior coating burner with RMTU,

- An HVOF internal coating burner for small inner diameter and powder for this, a double combustion chamber, a hydrogen atomization, kerosene, lambda <1, short spray distance, protective effect by active gas, powder plasma sphered, <15pm, preferably 0.5-6 pm, 2-9 pm,

an inner coating of the component 1 of metal-bonded tungsten carbide and molybdenum,

a powder feeder for fine particles, vibrations, balls, a bed of balls, vibration direction, a conveying channel, groove, hopper or cylinder, a conveyor disc,

- a tube with inner and outer coating, combination LaserHVOF and

HVOF, and LaserHVOF soft and laser HVOF hard, a corrosion-resistant hard metallic HVOF layer, for example made of powder WC CrC Ni with low according to metallic binder content in the layer.

Also contemplated is a tungsten carbide powder for making layers and bodies, spherical, plasma sphered, of tungsten, chromium, carbon and a binder metal such as Fe, Co, Ni, WC with chromium, for example WCCrC Ni with a low metallic binder content, fine WC and fine CrC, structure WC, W2C, (WCr) 2C, Cr3C2, Cr7C3, Cr23C6 with W portions (CrW) 23C6, (WCr) 3NiC, (WCr) 4Ni2C, (WC) 6Ni6C, chromium carbide is carbon supplier. The carbon is in excess and released as graphite. This favors the suppression of embrittling n-carbides.

Bezuaszeichenliste:

1 component

2 surface

3 coating

4 sprayed layer

5 crack

Claims

claims:

1. component (1) with a metallurgically bonded and thermally injected and remelted coating (3),

characterized,

the coating (3) is provided with at least one thermal spray coating (4).

2. Component according to claim 1,

characterized,

that the layer (4) is remelted.

3. Component according to claim 2,

characterized,

the thickness of the layer (4) is between 5 and 500 μm.

4. Component according to claim 2 or 3,

characterized,

the thickness of the layer (4) is between 5 and 150 μm.

5. Component according to one of claims 3 to 4,

characterized,

the thickness of the layer (4) is between 5 and 30 μm.

6. Component according to one of the preceding claims,

characterized,

the layer (4) is a plasma layer of oxide ceramic material.

7. Component according to one of claims 1 to 5,

characterized,

the layer (4) is made of metal-bonded carbides, in particular an HVOF layer of WC-CrC-Ni.

8. Component according to one of the preceding claims,

characterized,

the coating (3) is made of a material resistant to hot gas oxidation.

9. Component according to one of claims 1 to 7,

characterized,

that the coating (3) is corrosion resistant.

10. Component according to one of the preceding claims,

characterized,

the coating (3) is located on the surface (2) and / or the inner surface of the component (1).

11. A method for producing a metallurgically bonded coating (3), which is thermally sprayed onto a surface (2) of a component (1) and remelted by means of laser,

characterized,

in that at least one further layer (4) is thermally sprayed onto the coating (3).

12. The method according to claim 11,

characterized,

that the layer (4) is remelted.

13. The method according to claim 12,

characterized,

that the layer (4) is remelted by means of laser.

14. The method according to any one of claims 11 to 13,

characterized,

that the layer (4) is applied by means of plasma spraying.

15. The method according to any one of claims 11 to 14,

characterized,

that the layer (4) is applied by means of high-speed flame spraying.