AT14988U1 - Component of a plastic processing machine - Google Patents

Abstract

The invention describes a component of a plastic processing machine made of a refractory metal (RM) selected from the group consisting of tungsten (W), W alloy, molybdenum (Mo) and Mo alloy, wherein at least one surface of the component at least partially a layer which is formed, at least in regions, from at least one compound of at least one element selected from the group consisting of carbon (C), boron (8) and nitrogen (N) with at least one element selected from the group consisting of W and Mo.

Description

description

COMPONENT OF A PLASTIC PROCESSING MACHINE

The invention relates to a component of a plastic processing machine made of a refractory metal (RM) selected from the group consisting of tungsten (W), W alloy, molybdenum (Mo) and Mo alloy. Furthermore, the invention relates to a method for producing such a component.

Plastic processing machines, such as extruding machines and injection molding machines, contain components such as extruder screws, hot runner nozzles, injection molds, mandrels, core inserts, etc.

These components are exposed during operation of the plastic processing machine high thermal and abrasive loads. Component damage occurs as a result of thermal stress as well as chemical and mechanical erosion. This leads to removal of material on the surface of the parts and it can lead to contamination of the plasticized plastic compound.

The failure of one of the components of such a plastic processing machine can lead to a standstill of the entire machine and thus has great impact on the economic operation of the plant.

The challenges in the operation of plastic processing machines consist in the reduction of the wear of the components. Developments are therefore aimed at increasing the resistance of the components to the prevailing conditions in order to achieve longer operating times. An increase in operating times also reduces, among other things, the operating costs of a plastics processing machine.

Some ways to increase the life of such components have already been described in the relevant literature.

Thus, WO 02007144303A1 discloses an extruder screw made of steel, which is provided with a wear protection layer, for example of tungsten carbide, as well as a sliding layer, for example of Mo.

For the processing of glass-fiber or particle-reinforced plastics refractory metals or their alloys are used as the base material for corresponding components. Such plastics, even in plasticized form, have a highly abrasive effect on the components used for their processing. The lifetime of components for plastics processing, in particular for the processing of glass fiber or particle-reinforced plastics is therefore often greatly reduced.

US20020092585 discloses a method for increasing the wear resistance of a base material by applying a refractory metal layer via electrochemical methods and subsequent thermal treatment with a boron-containing molten salt.

Further known from the prior art by means of gas phase reactions, such as chemical vapor deposition (CVD) or gas phase nitriding, on corresponding base materials of corresponding components deposited hard material layers to increase the wear resistance of the respective components.

However, the solutions known from the prior art often have poor adhesion to the base material, which can lead to material removal and contamination of the plasticized plastic mass.

Furthermore, it is often desirable not to provide the entire surface of the base material with a wear protection layer, which is very poor or impossible, for example, in deposited by a CVD method layers.

The object of the invention is therefore to provide a solution whereby the disadvantages described above can be avoided. In particular, it is an object of the invention to provide a solution in which the components of a plastics processing machine have a higher resistance to the mentioned loads and thereby the service life of the components and thus the plastic processing machine is increased. In particular, the present invention is intended to reduce the material removal of components, whereby contamination of the plasticized plastic material is reduced.

This object is solved by the independent claims. Preferred embodiments are given in the subclaims.

A component according to the invention of a plastics processing machine is made of a refractory metal (RM) selected from the group consisting of tungsten (W), W alloy, molybdenum (Mo) and Mo alloy and is characterized in that at least one surface of Component at least partially comprises a layer which at least partially from at least one compound at least one element selected from the group consisting of carbon (C), boron (B) and nitrogen (N) with at least one element selected from the group consisting of W and Mo, is formed.

The component according to the invention is preferably a hot runner nozzle, an extruder screw, a mandrel, a core insert or an injection mold.

The component is made of a refractory metal, wherein the refractory metal is selected from the group consisting of tungsten (W), W alloy, molybdenum (Mo) and Mo alloy. W, W alloys, Mo and Mo alloys are also abbreviated to RM in the following text. Therefore, an RM component is a component made of W, a W alloy, Mo, or a Mo alloy.

A surface of the RM component has at least partially on a layer which at least partially from at least one compound of at least one element selected from the group consisting of carbon (C), boron (B) and nitrogen (N), with at least one element selected from the group consisting of W and Mo is formed.

In the solution according to the invention, both the base body / the base material, as well as the layer on a RM. In the context of the invention, the basic bodies are the areas of the component which have no layer or no layer yet.

It has now been shown that layer adhesion problems, as can be observed in the prior art, do not occur due to the embodiment according to the invention. Furthermore, the components according to the invention are also significantly more resistant to a broad field of use conditions compared to uncoated components of W, W alloys, Mo or Mo alloys.

Particularly advantageous compounds are the carbides, borides and nitrides to mention. However, it is also excellent compounds that contain at least two elements of the group consisting of C, B and N in addition to W and / or Mo. For example, with compounds containing both C and B, excellent lifetime results could be achieved.

Preferably, the layer as RM that element which also forms the majority of the main body. So it is advantageous if, for example, the base body is made of molybdenum or a molybdenum alloy, that the layer is formed by a compound of molybdenum. For example, excellent results could be obtained if the main body of the component is made of Mo and the layer comprises M02B, MoB, MoC, M02C, M02N or MoN.

It is particularly advantageous if, in the production of the layer, the compound formation takes place by reaction of C, B and / or N with the W and / or Mo of the base body, since an excellent layer adhesion can thereby be achieved.

The layer may completely cover the base body or may also be applied only in places of highest stress. In addition, the layer may be single-layered or multi-layered and / or made up of mixed phases of varying composition. If a Mo-W alloy is used as the base body for the component, which represents an advantageous embodiment, then the compound may have metallic constituents Mo and W. Therefore, in the list of advantageous borides, carbides and nitrides given below, without adversely affecting the properties, W may be partially replaced by Mo or Mo partly by W.

Particularly advantageous binary compounds are W2B, WB, W2B5, Wi.xBa, WB4, WC, W2C, WN, W2N, W3N2, M02B, MoB, MO3B2, MO4, MoC, MO2C, MoN, MO2N and MO3N2 , In particularly advantageous ternary and quaternary compounds, the non-metallic constituent of the aforementioned binary compounds is partially replaced by one (for ternary compounds) or two (for quaternary compounds) further element (s) from group C, B and N. For example, for WC, the ternary compounds W (C, N) and W (C, B) and as the quaternary compound W (C, B, N).

In addition to the respective stoichiometric compositions of the compound, these may additionally contain other elements, for example C, B, N, W and / or Mo, in dissolved form.

A further advantageous embodiment is a composite layer. As Com-posite-Schioht is a Sohioht to understand, which is composed of at least two phase ranges. A particularly advantageous embodiment of the invention should be emphasized when the layer contains the phases WC and / or W2C. Another particularly advantageous embodiment is given if the layer contains WB and / or W2B. The combination of WC and / or W2C and WB and / or W2B represents a particularly advantageous embodiment of the invention. Thus, for example, the outermost region of the layer of WC and / or WB be formed, followed by an area, the W2B- and / or W2C phase. W2B and / or W2C are herebenaohbart to the body of W or a W alloy. In an analogous manner, for example, the outermost region of the layer can be formed from MoC and / or MoB, followed by a region which has M02B and / or M02C phases. M02B and / or M02C are adjacent to the main body of Mo or a Mo alloy.

In a further advantageous embodiment, the layer is interlocked with the adjoining region of the base body. This gearing effect is achieved in a simple manner by the reaction of C, B and / or N with Mo and / or W of the main body. For this purpose, C and / or B and / or compounds of C, B and / or N are applied to the surface of the base body. By heating C, B and / or N now diffuse into the main body, where it comes to the compound formation. The toothing is advantageously formed by grains of the layer (for example and advantageously by W2B, W2C, M02B and / or M02C grains). When applying C and B to tungsten or molybdenum forms, for example, as the top layer layer of a carbide or boride, which is particularly resistant to wear. The introduction of N into the layer is preferably carried out by annealing in an N-containing atmosphere (reaction annealing). NH 3 or a mixture of at least two gases of the group consisting of NH 3, H 2 and N 2 and also annealing temperatures, for example in the range from 700 to 1300 ° C., are preferably used.

The advantageous average layer thickness can be selected within a wide range, with a preferred range being 1 to 300 μm, preferably 3 to 200 μm.

As advantageous materials for the main body are pure W, W - 0.1 to 3 Ma% rare earth oxide, W heavy metal, pure Mo, Mo - titanium (Ti) - zirconium (Zr) - C (usual name: TZM), Mo - hafnium (Hf) - C (common name: MHC) or Mo-W alloys. As a particularly suitable rare earth oxide La203 is herauszustreiohen. W - La203 has a significantly improved cutting behavior compared to pure W, whereby the manufacturing cost of the component can be significantly reduced. Pure-W or Rein-Mo are to be understood as meaning the metals of the usual technical purity.

Advantageously, the component has at least one of the following properties: The compound is selected from the group a or b, with:

Group a: carbides, borides and nitrides;

Group b: compound containing W and / or Mo and at least two elements of the group consisting of C, B and N.

[0033] The compound is selected from the group consisting of W2B, WB, W2B5, Wi-xBa, WB4, WC, W2C, WN, W2N, W3N2; M02B, MoB, M03B2, M0B4, MoC, M02C, MoN, M02N and M03N2.

- The layer is designed as a composite layer.

The composite layer has at least one region of a boride and at least one region of a carbide.

The outermost layer layer is at least partially formed by WC or WB.

The layer is interlocked with the adjoining base body.

- The toothing is formed by grains of the layer.

[0039] The RM component has the layer at places of high stress.

At least one compound contains at least one element selected from the group consisting of B, C, N, W and Mo in dissolved form.

The RM component is of pure W, W-0.1 to 3% by mass rare earth oxide, W heavy metal, pure Mo Mo-Ti-Zr-C (TZM), Mo-Hf-C (MHC) or a Mo-W alloy.

The object of the invention is also achieved by a method for producing an RM component.

The method has at least the following steps: - Production of the geometry of the RM component by conventional methods; Applying at least one element and / or at least one compound of one

Elements selected from the group consisting of C, B and N, preferably in powder or slurry form; - Heat treatment for forming a compound with at least one RM in Vaku order, inert gas or reactive gas.

As a conventional method for the production of the RM component are pressing / sintering process with subsequent mechanical processing, near-net-shape pressing / sintering process, hot pressing, hot isostatic pressing, spark plasma sintering or metal injection molding to call.

After the geometry has been produced, at least one element or at least one compound of an element selected from the group consisting of C, B and N is applied in the regions which are to have the layer in use. The application can be done for example by dumping, by brushing, by dipping or by spraying. Particularly suitable is the application of a slurry to mention, since it is also possible to coat parts with complex geometries in a simple and advantageous manner. After application of C and / or B and / or a C, B and / or N-containing compound, the component is heat treated in vacuum, inert gas or reactive gas. Suitable reactive gases are, in particular, gases or gas mixtures which contain N (for example NH 3 or a mixture of at least two gases of the group consisting of NH 3, H 2 and N 2), C (for example CH 4) and / or B (for example BH 3). The temperature is advantageously 700 to 2,000 * Ό (annealing in vacuum) or 700 to 1,300 ° C (annealing in reactive gas), whereby the most suitable for each compound range can be determined by simple experiments. During the heat treatment, C, B and / or N diffuses / diffuses into the

Base material and forms with this the compound of the invention.

In conventional CVD method, a layer is deposited on the outside of the base material. As a result, it may be that tolerances of the components can no longer be met and the components must be reworked. In the coating according to the invention, this is not necessary since the dimensional stability is ensured in this method.

In contrast, for example, to a gas phase nitration in which the surface of the entire component, i. E. all areas which are achieved by the gas flow, nitrided and it is not possible to selectively expose certain areas, can be masked by the inventive method areas, whereby it is possible to apply the coating, for example, only in tribologically contaminated zones. By means of this targeted masking of the components, it is possible to realize hard or resistant as well as soft or tough regions on the same component.

A further advantage compared to gas-phase nitriding is that layer thicknesses in a wide range from 1 to 300 μm can be achieved with the method according to the invention. In gas phase nitriding only thicknesses of 1 to 15 pm can be achieved. Due to the higher layer thicknesses, the range of application or the duration of use of the coated components can be significantly extended.

The size of the components which can be coated, is another distinguishing feature for gas phase nitriding. In gas phase nitriding, not only the size of the system, but also the gas flow in this crucial. In the case of uneven gas conduction, as is increasingly the case with large components, it can happen that the components are coated only partially or inadequately. The coating according to the invention can be carried out largely geometry-independent, with only the size of the system for the required heat treatment is limiting.

In the method according to the invention, automation on a large scale can be carried out with manageable effort. This is difficult to carry out in the case of gas phase nitriding, since, in addition to the high manual effort for the charging, the system size also has a strongly limiting effect. By appropriate automation, it is possible to reduce the manufacturing cost per piece and at the same time to achieve an improvement in properties such as hardness and wear properties.

In addition to the methods described above, the layer can also be applied by other conventional methods such as PVD, CVD, thermal spraying or annealing in reactive gas (for example in the aforementioned gases / gas mixtures).

In the following the invention will be described in more detail by way of example and compared with the prior art.

Figure 1 shows a multilayer composite layer comprising areas of molybdenum carbide and areas of molybdenum boride.

Figure 2 shows a GDOES profile of the layer in Figure 1 Figure 3 shows a sketch of a hot runner nozzle with partial coating (thick

Lines).

FIG. 4 shows a further sketch of a hot runner nozzle with partial coating (thick lines).

FIG. 5 shows a partially coated tip of a TZM hot runner nozzle.

FIG. 6 shows an EBSD image of a two-layered tungsten boride / tungsten carbide

Layer on W.

Example 1 Basic bodies of W, W - 1 Ma% La203 (WL) and Mo were provided by diffusion processes with different layers. For this purpose, a slurry, the carbon and / or

Boron, applied by dipping on the surface of the body. The respective C and B components can be taken from Tables 1 and 2. Thereafter, the samples were subjected to annealing at 1500O / 10h in vacuum. The constituents C, B and N formed during the heat treatment, the corresponding compounds. As an example, this is reproduced for the sample 19 according to Table 2 in FIG.

The EBSD measurement was performed as follows.

- 120 pm Electron Beam Iris - High Current Mode, 20 kV Acceleration Voltage [0067] - Scanning Area 57 x 24 pm ^ [0068] - Magnification 1500x [0069] - Increment 0.05 pm [0070] - Binning 4x4 [0071] Camera Gain 17,06 [0072] - Camera Exposure 4,50 [0073] Substrate Correction: Static Subtract combined with Normalized

Intensity Histogram System: FEG-REM Zeiss Ultra plus 55 with EDAX Trident XM4 Analytical Package, Hikari EBSD Camera Tables 1 and 2 show an overview of the samples.

Table 1

Table 2

Example 2

Coated hot runner nozzle made of TZM

A hot runner nozzle made of TZM with an external thread was cleaned alkaline in the ultrasonic bath. Subsequently, the thread was covered with adhesive tape. The nozzle thus prepared was immersed in an aqueous suspension of graphite and boron (in a ratio of 20:80 by weight) and dried in air. Still in the green state, the tape was removed. This masking ensured that the coating takes place only at the desired locations of the nozzle and does not embrittle the thread. Sketches with the coated areas of such a coated hot runner nozzle (thick lines) are shown in Figures 3 and 4.

The heat treatment was carried out under vacuum at 1500 ° C for 4h, forming a multilayer of molybdenum carbides and molybdenum borides. A scanning electron micrograph of an edge region of the hot-runner nozzle thus treated is shown in FIG.

Claims (12)

claims 1. component of a plastic processing machine made of a refractory metal (RM) selected from the group consisting of tungsten (W), W alloy, molybdenum (Mo) and Mo alloy, characterized in that at least one surface of the component at least partially a Layer, which is at least partially formed of at least one compound of at least one element selected from the group consisting of carbon (C), boron (B) and nitrogen (N) with at least one element selected from the group consisting of W and Mo. , 2. Component according to claim 1, characterized in that the compound is selected from the group a or b, comprising: - Group a: carbides, borides and nitrides; Group b: compounds containing W and / or Mo and at least two elements of the group consisting of C, B and N. 3. Component according to claim 1 or 2, characterized in that the compound from the group consisting of WgB, WB, W2B5, Wi_xBa, WB4, WC, WgC, WN, WgN, W3N2, M02B, MoB, M03B2, M0B4, MoC, M02C, MoN, M02N and M03N2 is selected. 4. Component according to one of the preceding claims, characterized in that the layer is a composite layer having at least a portion of a boride and at least a portion of a carbide. 5. Component according to claim 4, characterized in that WC or WB at least partially forms the outermost layer layer. 6. Component according to one of the preceding claims, characterized in that the layer is interlocked with the adjoining region of RM. 7. Component according to claim 6, characterized in that the toothing is formed by grains of the layer. 8. Component according to one of the preceding claims, characterized in that the RM component has the layer in places of high stress. 9. Component according to one of the preceding claims, characterized in that at least one compound contains at least one element selected from the group consisting of B, C, N, W and Mo in dissolved form. 10. Component according to one of the preceding claims, characterized in that the RM component of pure W, W - 0.1 to 3 Ma% rare earth oxide, W heavy metal, pure Mo, a Mo - titanium (Ti) - zirconium (Zr) - C alloy (TZM), a Mo - hafnium (Hf) -C alloy (MHC) or a Mo-W alloy. 11. Component according to one of the preceding claims, characterized in that it is a hot runner nozzle, an extruder screw, a mandrel, a core insert or an injection mold. 12. A method for producing a component according to one of the preceding claims, characterized in that it comprises the following steps: - Production of the geometry of the RM component by conventional methods; - applying at least one element and / or at least one compound of an element selected from the group consisting of C, B and N, preferably in powder or slurry form; - Heat treatment to form a compound with at least one RM.