Carbide material for cutting devices and related manufacturing methods

Abstract

To provide a material suitable for cutting by a tungsten carbide material having enhanced brittleness, a breakage ratio and hardness of a material, and a method for manufacturing a device including the material.SOLUTION: A carbide material 34 contains 60-85 wt.% of a tungsten carbide, 10-25 wt.% of a titanium carbide, 0.5-20 wt.% of a metal matrix containing preferably, Fe, as needed, at least one or both of metal of Co and Ni. There are also provided a device including a material such as an iron substrate and a carbide, and a method for manufacturing the device. The method includes mixing powder containing a scavenger material such as carbon, tungsten and titanium, accumulating the mixed powder near the iron substrate 10, making an energy source 31 collide with the powder material, producing a melt pool 32 formed of the powder and the material of the substrate, solidifying the melt pool, and forming a carbide material 34 containing substantially no (W, Fe)6C and (W, Fe)12C type tungsten iron carbide.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a carbide material for deposition on an iron base and a method for manufacturing such a carbide material.

Background Art

[0002] In the case of carbide materials used as coatings, it is often desirable to achieve high hardness values. One common material is tungsten carbide in a cobalt or nickel metal matrix that provides optimal hardness and toughness together even under high-temperature or high-impact conditions.

[0003] Carbide materials can be deposited using an additive manufacturing process in which powders or wires are melted or sintered by a heat source that concentrates high energy such as a laser or an electron beam.

[0004] A known problem regarding the deposition of tungsten carbide on an iron base using additive manufacturing techniques is the formation of very brittle iron tungsten carbide (W, Fe)6C and (W, Fe)C that increases the brittleness of the material. Therefore, hitherto, there has been a limit to the toughness of the materials that can be achieved by the additive manufacturing method of depositing tungsten carbide on an iron base. This has hindered the application of the additive manufacturing method for generating tungsten carbide deposits on iron bases that may operate under high-impact conditions such as metal cutting tools and rotary cutting edges. 12 The adjustment of the material composition for the purpose of increasing hardness may cause other problems, particularly increasing the brittleness of the material and thereby increasing the fracture rate. Therefore, hitherto, there has been a limit to the hardness that can be achieved with tungsten carbide materials, but still, a material suitable for cutting is provided.

[0005]

Summary of the Invention

Means for Solving the Problems

Means for Solving the Problems

[0006] According to one aspect of the present invention, a carbide material is provided that includes 60 to 85% by weight of tungsten carbide and 10 to 25% by weight of titanium carbide.

[0007] The carbide material can further include a metal matrix of 0.5 to 20% by weight containing Fe.

[0008] The metal matrix can be in the range of 4.5 to 20% by weight, and in particular, another metal such as at least one of Co or Ni can be incorporated into the metal matrix. Therefore, it is preferable that the metal matrix can include Fe and at least one or both of metal Co or Ni.

[0009] In a preferred composition, it is preferable that the metal matrix can include Co and Fe.

[0010] The titanium carbide can consist of only TiC, or can include a combination of TiC and (Ti, W)C, that is, titanium carbide and titanium tungsten carbide.

[0011] The carbide material can further include an additional compound in the range of 0.5 to 8% by weight, and this additional compound is one or more of TaC, VC, NbC, HfC, ZrC, Cr3C2, and Cr7C3. These additional compounds improve the properties of the particles in the material.

[0012] The addition of tantalum is particularly preferred because it helps eliminate cracks during the solidification of the material from the molten state.

[0013] Spherical carbides in the material such as (Ti, W)C and WC preferably have a particle size with a diameter of 1 to 5 μm.

[0014] According to another aspect of the present invention, an apparatus is provided that includes an iron substrate such as a steel substrate and the aforementioned carbide material formed on at least a part of this substrate.

[0015] This device can be any device incorporating an iron substrate that requires the addition of a carbide material as a layer or edge, such as cutting devices like straight edge blades, circular blades, saws, drills, drill bits, etc., or steel substrates with carbide materials arranged for cutting purposes like lathes and milling machines, and further medical devices, medical implants, turbine blades, engine parts, electronic parts.

[0016] The carbide material is preferably formed on the upper surface of the iron substrate and can also be formed along the edge of the iron substrate.

[0017] According to a further aspect of the present invention, a method of manufacturing a device, particularly a cutting device, is provided. This method involves mixing carbon and tungsten as individual elements, namely tungsten carbide, or a mixture thereof, and a scavenger material, placing the mixed powder near the iron substrate, impinging an energy source on the powder material to create a melt pool formed by the powder and the substrate material, solidifying the melt pool to form a carbide material substantially free of (W, Fe)6C and (W, Fe) 12 C type iron tungsten carbide, that is, preferably (W, Fe)6C and (W, Fe) 12 C type iron tungsten carbide contains no more than 0.01%, more preferably (W, Fe)6C and (W, Fe) 12 C type iron tungsten carbide contains no more than 0.001%. The scavenger material reacts preferentially with the carbon in the iron substrate or steel substrate compared to the iron in the iron substrate or steel substrate reacting with carbon. This enables the scavenger material to react with carbon in the iron substrate or steel substrate before iron in the melt pool, thus preventing the formation of brittle iron tungsten carbide as there is no free carbon that could be used to form these harmful carbides. Therefore, the solidified material is substantially free of brittle carbides such as (W, Fe)6C and (W, Fe) 12 C and has improved toughness.

[0018] The scavenger material is preferably titanium at 10 - 25 wt% of the solidified carbide material.

[0019] Regardless of whether the powder is provided as a pure metal or compound, it preferably contains at least one of metallic Co or Ni or a mixture.

[0020] The powder can further contain one or more materials such as Ta, V, Nb, Hf, Zr, and Cr, either as elemental powder or compound. These serve to remove impurities from the particles within the material. Tantalum is particularly preferred as it prevents cracks from forming within the melt pool when the melt pool solidifies and further improves the structure of the formed carbide material.

[0021] Desirably, the melt pool is formed at a temperature of 1500 °C to 3000 °C.

[0022] The energy source can generate power between 300 W and 2 kW, and generally uses a laser such as a 1 kW continuous wave fiber laser that causes a laser beam to impinge on the substrate.

[0023] This method can further include moving the iron substrate relative to the energy source, preferably at a traverse speed of 0.01 m / min to 6 m / min, more preferably at a traverse speed of 1 m / min to 4 m / min.

Brief Description of the Drawings

[0024] The present invention will be described illustratively with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0025] FIG. 1 shows a method of forming a carbide material on a device such as a steel strip 10 that can be used as a blade within tools such as band saws, hacksaws, jigsaws, hole saws, etc. Teeth can be formed on the strip 10 if desired.

[0026] As the strip 10 moves relative to the workstation 12, a carbide material is formed along the upper edge 14 of the strip 10. The workstation 12 includes hoppers 20, 20' for supplying the material in powder form and a high-power energy source 22 that applies a continuous-wave fiber laser with an output range of 300 W to 2 kW, but typically applies an 800 W laser at 1 kW. One or more computing devices 24 control the movement of the strip 10 relative to the workstation 12 and the hoppers 20, 20', the supply of material from the hoppers 20, 20', and the output of the energy source 22. Typically, the strip 10 moves at a substrate traverse speed of 2 m / min, and the traverse speed can be varied between 0.01 m / min and 6 m / min.

[0027] Computer-executable instructions are possible that configure the workstation 12 to function as a 3D printer, and those instructions are present in a computer-readable medium that is within or removable from the device 24. Of course, one or more hoppers can be utilized.

[0028] The hoppers 20, 20' project the powder 30 onto the edge 14, and the incident laser beam 31 forms a hot melt pool 32 where the powder and the substrate are melted. The molten components react at a temperature of 1500°C to 3000°C, and as the strip 10 moves relative to the workstation 12, the melt pool 32 cools and a solid carbide material 34 is formed.

[0029] If desired, the carbide material can be deposited in a similar manner on drill bits, rotary blades, or other devices that require a carbide surface, such as turbine blades, engine parts, medical devices, and electronic components.

[0030] This method involves the formation of one or more of TaC, VC, NbC, Cr3C2, Cr7C3, ZrC, and HfC in the presence of carbides which are tungsten carbide and titanium carbide, and optionally further a metal matrix (Fe, and optionally Co and / or Ni). The carbides are produced by the reaction of elemental powders of carbon with elemental powders of W and Ti. The solid carbide material 34 contains 60 - 85 wt% tungsten carbide, 10 - 25 wt% titanium carbide, and 4.5 - 20 wt% metal matrix containing at least one or both of Fe and metal Co or Ni, and usually contains 0.5 - 8% of an additive for grain refinement consisting of one or more of TaC, VC, NbC, Cr3C2, Cr7C3, ZrC, HfC. The material 34 is formed using the powder elemental powders supplied from the hoppers 20, 20' or using powders of individual compounds, and the powders react with the molten components of the steel substrate 10 in the hot melt pool 32 to produce a carbide material of the desired composition on the substrate 10.

[0031] Before depositing on the substrate 10, the elemental powders of Ti, W, C, optionally the elemental powders of Co and / or Ni, and optionally the elemental powders of one or more of Ta, V, Nb, Cr, Zr, Hf are weighed, and the resulting carbide material is mixed so as to have a composition of 60 - 85 wt% WC, 10 - 25 wt% TiC, and optionally 4.5 - 20 wt% metal matrix (Fe and optionally Co and / or Ni) together with one or more of 0.5 - 8 wt% of TaC, VC, NbC, Cr3C2, Cr7C3, ZrC, HfC.

[0032] The powder is mixed and / or aggregated for at least 40 minutes to ensure a uniformly dispersed mixture, and then deposited on the substrate 10 to form a deposition bulk, or supplied through a nozzle from the hoppers 20, 20' together with an inert carrier gas such as argon or helium. In the case of pre - deposited powder, the laser beam 31 is focused on the top layer of the pre - deposited powder, while in the case of supply through a nozzle, the laser beam 31 is focused on the upper surface of the substrate or on the powder stream directly above the deposition area.

[0033] The laser beam 31 is focused and scanned over the entire deposited substrate area. The powder and the substrate in the area 32 are melted by the energy from the laser beam 31 to generate a melt pool 32. When discharging through a nozzle, the substrate melts to form a melt pool, and the powder 30 is discharged from the nozzle into the melt pool. Some of the particles of the supplied powder are preheated and partially melted before reaching the substrate 10 while the powder stream passes through the laser beam 31. The molten components in the melt pool 32 are the supplied powder and the substrate material.

[0034] In the process of creating carbide materials, to avoid material waste and achieve shortened manufacturing time and free net product shapes, the carbide materials are accurately deposited in net and near-net shapes. Small areas of carbide materials, such as those less than a few square millimeters, can be quickly and accurately deposited on small devices or circuit boards without causing distortion or softening the heat-affected zones.

[0035] By using a relatively large amount of titanium, 10 - 25 wt%, titanium functions as a scavenger material that preferentially reacts with any carbon when the carbide material is formed, preventing the carbon from reacting with the iron in the melt pool. This neutralizes the iron in the steel substrate, and (Fe, W) 12 C and the brittle carbides of (Fe, W)6C cannot be formed, and instead, these are replaced by titanium carbides such as TiC or (Ti, W)C. WC and W2C, which can be retained until reaching room temperature, also exist.

[0036] If necessary, as a grain refinement material, one of Ta, V, Nb, Hf, Zr, Cr or a mixture of these is added. By adding Ta, it prevents cracks from forming in the material when the melt pool 32 solidifies. After solidification, (Fe, W) 12 C and (Fe, W)6C carbides do not exist in the microstructure.

[0037] Figures 2 and 3 show micrographs of materials obtained from powders of Co, Ti, W, Ta, and C. Co was spherical powder with a purity of 99.8%, gas-sprayed, and a particle size of ≦45 μm. Ti was spherical powder with a purity of 99.9%, gas-sprayed, and a particle size of 15 - 45 μm. The W powder had a purity of 99.9% and a particle size of ≦25 μm. In the case of Ta powder, the purity was 99.97% and the particle size was 325 mesh (≦44 μm). For C, artificial graphite powder with a particle size of ≦20 μm was used. The ratio of the powders was 0.175 wt% Co, 0.16 wt% Ti, 0.5773 wt% W, 0.0094 wt% Ta, and 0.0783 wt% C by weight. This corresponds to 17.5 wt% Co, 20 wt% TiC, 61.5 wt% WC, and 1 wt% TaC, and a final material is obtained that has 4.5 - 20 wt% matrix (Fe and Co), 60 - 85 wt% WC, 10 - 25 wt% TiC, and optionally 0.5 - 8% (TaC, VC, NbC, CrC, ZcC, individual values or total values).

[0038] The deposited material 34 consists of a metal matrix of Fe and Co, and W, and a plurality of types of carbides such as TiC, WC, W2C, (Ti, W)C, and TaC. From Figure 2, it can be seen that the microstructure of the formed solid material 34 contains spherical and aggregated dendritic mixed carbides in a continuous matrix. (Fe, W) 12 The dendritic structures of C and (Fe, W)6C are not included. The matrix is continuous and contains Fe, Co, and unreacted W. Areas 1, 2, 3, and 5 show carbide aggregates, area 4 shows dendritic carbides, and area 6 shows spherical carbides. The light (white) carbides in Figure 2 are related to many hexagonal WC. The dark (gray) carbides in Figure 2 are related to the high content of FCC-type TiC and (Ti, W)C. The presence of TaC with an FCC structure can be observed in part of the carbide formation.

[0039] As shown at a higher magnification in Fig. 3, most of the globular carbides have an FCC structure (Ti, W)C carbide at the center and are surrounded by hexagonal WC. The particle size of the globular carbides of TiC is 1 to 5 μm when Ta, V, Nb, Cr, Zr are used as carbides TaC, VC, NbC, CrC, ZrC.

[0040] In alternative materials, they have a composition of 0.5 to 20 wt% metal matrix, 60 to 85 wt% WC, 10 to 25 wt% TiC, and optionally 0.5 to 8% additives. Pure tungsten carbide powder is deposited on a steel strip together with titanium powder, and the material composition at the strip edge after the melt pool has solidified is 60 to 85 wt% WC, 10 to 25 wt% TiC, and 0.5 to 20 wt% metal matrix obtained from the components of the steel strip when melted in the melt pool 32. Also in this case, titanium prevents the formation of (W, Fe)C. Optionally, one or more additives of Ta, V, Nb, Cr, Zr, and Hf can be added together with the tungsten carbide powder and titanium powder.

Claims

1. A carbide material comprising 60 to 85% by weight of tungsten carbide and 10 to 25% by weight of titanium carbide, wherein the carbide material contains spherical carbides, and the spherical carbides have an FCC structure (Ti, W)C carbide at the center and are surrounded by hexagonal WC, and the particle size is 1 to 5 μm in diameter.

2. The carbide material according to claim 1, further comprising a metal matrix of 0.5 to 20% by weight containing Fe.

3. The carbide material according to claim 2, wherein the metal matrix is in the range of 4.5 to 20% by weight.

4. The carbide material according to claim 2, wherein the metal matrix further contains at least one or both of metals Co and Ni.

5. The carbide material according to claim 2 or claim 3, wherein the metal matrix contains Co and Fe.

6. The carbide material according to any one of claims 1 to 5, further comprising an additional compound in the range of 0.5 to 8% by weight, and the additional compound is one or more of TaC, VC, NbC, HfC, ZrC, Cr3C2 and Cr7C3.

7. An apparatus comprising an iron substrate and the carbide material according to any one of claims 1 to 6 formed on at least a part of the iron substrate.

8. A method for manufacturing an apparatus, the manufacturing method comprising: mixing a powder containing carbon, tungsten, and a scavenger material; disposing the mixed powder near an iron substrate; colliding an energy source with the powder material to create a melt pool formed of the powder and the material of the substrate; and solidifying the melt pool to form a carbide material not containing iron tungsten carbides of (W, Fe)6C and (W, Fe)12C types, wherein the scavenger material is 10 to 25% by weight of titanium of the carbide material.

9. The manufacturing method according to claim 8, wherein the carbide material contains no more than 0.01% of iron tungsten carbides of (W, Fe)6C and (W, Fe)12C types.

10. The manufacturing method according to claim 8, wherein the carbide material contains no more than 0.001% of iron tungsten carbides of (W, Fe)6C and (W, Fe)12C types.

11. A method for manufacturing a cutting device, the manufacturing method comprising: a step of mixing powders containing carbon, tungsten, and titanium; a step of disposing the mixed powders near an iron substrate; a step of colliding an energy source with the powder material to create a melt pool formed of the powder and the material of the substrate; and a step of solidifying the melt pool to form a carbide material containing 60 to 85% by weight of tungsten carbide and 10 to 25% by weight of titanium carbide, wherein the melt pool is formed at a temperature of 1500°C to 3000°C.

12. The manufacturing method according to any one of Claims 8 to 11, characterized in that the powder further contains at least one of metal Co or Ni, or a mixture thereof.

13. The manufacturing method according to any one of Claims 8 to 12, characterized in that the powder contains one or more of Ta, V, Nb, Hf, Zr, and Cr.

14. The manufacturing method according to any one of Claims 8 to 13, characterized in that the energy source generates electric power between 300 W and 2 kW.

15. The manufacturing method according to any one of Claims 8 to 14, further comprising a step of moving the iron substrate at a traverse speed of 0.01 m / min to 6 m / min with respect to the energy source.

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