JP7506421B2 - Method for manufacturing hard metal member, hard metal member and raw material powder thereof - Google Patents

Description

The present invention relates to a method for manufacturing a hard metal component having a hard metal build-up layer on the surface of a metal substrate, a hard metal component obtained by the manufacturing method, and a raw material powder used in the manufacturing method.

Conventionally, one known surface treatment technique is to improve the wear resistance of the outermost surface by depositing a high-hardness material different from the metal substrate on the surface of the metal substrate. When this technique is used, hard metal components can be manufactured efficiently and inexpensively. Furthermore, even if the surface deposit layer formed using a high-hardness material wears away, the substrate can retain its original shape, so it can be reused by depositing the same material on the substrate again.

For example, the present inventors have also disclosed in Patent Document 1 (JP Patent Publication No. 2013-176778) a laser cladding method that uses a laser to form a high-hardness build-up layer on the surface of a metal substrate.

The laser cladding method described in Patent Document 1 above is characterized by including "a cladding process in which Fe-based high-speed tool steel powder is supplied as a cladding material to the surface of an Fe base material, and the Fe base material and the cladding material are integrated by scanning with a laser beam, and a heat treatment process in which the entire product is heated after the cladding process and then slowly cooled, so that the Vickers hardness of the laser-scanned portion is 700 to 1000," which can increase the hardness while suppressing cracking of the laser cladding layer.

Patent Document 2 (JP Patent Publication 2009-214110A) discloses "a hard-coating overlay welding rod, which is made of a mild steel pipe and cemented carbide particles filled in the mild steel pipe, and is characterized in that the cemented carbide particles are coated with copper."

In the commonly used hard-cladding overlay, a welding rod (hard-cladding overlay welding rod) in which cemented carbide particles are filled in a soft steel tube is used, and during overlay welding, molten iron (soft steel tube) penetrates the cemented carbide particle structure and deteriorates the inherent excellent properties of the cemented carbide. However, in the hard-cladding overlay welding rod described in Patent Document 2, iron does not easily form a solid solution with copper and copper alloys, and the property that iron does not melt with them is utilized, and the cemented carbide particles are protected with copper to prevent iron from penetrating into the inside of the cemented carbide particles. As a result, the dispersion of the cemented carbide particles in the hard-cladding layer is excellent, the inherent performance of the cemented carbide is maintained, and the molten metal is easily penetrated into the fine gaps to reduce pores, improving workability, and a hard-cladding overlay formed from cemented carbide particles with little deterioration can be obtained.

JP 2013-176778 A JP 2009-214110 A

Cemented carbide has extremely excellent hardness and fracture toughness, and it is expected that a layer of cemented carbide can be formed on the surface of a suitable metal substrate and used as a wear-resistant material. However, the large amount of hard particles (WC particles) contained in cemented carbide reacts with oxygen at high temperatures and deteriorates, and the CO gas generated by this reaction forms numerous void defects in the cemented carbide.

In contrast, the laser cladding method described in Patent Document 1 forms a cladding layer using high-speed tool steel powder as a raw material, and does not form a cladding layer made of cemented carbide.

The hard-cladding build-up welding rod described in Patent Document 2 is intended to form a build-up layer made of cemented carbide, but does not take into consideration the oxidation of hard particles (WC particles). In addition, it is a welding rod used for weld build-up, and cannot be used for additive manufacturing methods such as laser cladding (laser powder build-up welding), which has a higher degree of freedom in forming.

In view of the problems in the conventional technology as described above, the object of the present invention is to provide a simple and efficient method for manufacturing a hard metal component that can suppress the deterioration of hard particles (WC particles) due to oxidation and the formation of void defects caused by the oxidation, as well as a hard metal component obtained by the manufacturing method, and a raw material powder for additive manufacturing that can be suitably used in the manufacturing method.

In order to achieve the above objective, the inventors conducted extensive research into the composition and formation method of hard metal build-up layers, and discovered that adding a deoxidizing element to the molten region formed during additive manufacturing is extremely effective, leading to the invention.

That is, the present invention provides:
A method for manufacturing a hard metal member, comprising: forming a hard metal build-up layer on a surface of a metal substrate by an additive manufacturing method using a mixed powder containing hard particles including WC particles and a metal bonding phase as a raw material,
forming a molten region of the mixed powder by irradiating the mixed powder with a high energy beam and adding a deoxidizing element to the molten region;
The deoxidizing element has a standard free energy of formation lower than the standard free energy of formation of CO (ΔG _CO ) in the melting region;
The present invention provides a method for manufacturing a hard metal member, comprising the steps of:
The high-energy beam is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known high-energy beams that can be used in additive manufacturing methods can be used. As the high-energy beam, for example, a laser, an electron beam, a PTA (plasma transferred arc), etc. can be used, but it is preferable to use a laser.

In the manufacturing method of the hard metal component of the present invention, the oxidation of WC particles is suppressed by the deoxidizing element, so that the deterioration of WC particles and the formation of void defects in the hard metal cladding layer can be suppressed extremely effectively.

The deoxidizing element may be any element that oxidizes preferentially over WC in the molten region, and specifically, an element that has a standard free energy of oxide formation lower than the standard free energy of formation of CO in the molten region (ΔG _CO ) may be used. Here, the value of the standard free energy of formation depends on temperature, but it may be considered in the temperature range of "the temperature at which the metallic bonding phase of Co, Ni, etc. used in the cemented carbide melts to the maximum temperature of the molten region expected in high-energy beam irradiation." More specifically, for example, the standard free energy of formation may be compared in the range of 1500 to 2000°C.

In the manufacturing method of the hard metal member of the present invention, it is preferable to add the deoxidizing element to the mixed powder. The method of adding the deoxidizing element to the molten region is not particularly limited as long as it does not impair the effect of the present invention, but by adding the deoxidizing element to the mixed powder in advance, it is possible to add it to the molten region efficiently and easily. Furthermore, by adding the deoxidizing element to the mixed powder in advance, the action and effect of the deoxidizing element can be maintained constant even when forming a multi-layered hard metal overlay layer in the thickness direction.

For example, additive elements may be placed on the surface of the metal substrate, or an additive manufacturing method may be used to form a build-up layer made of additive elements. Also, additive elements may be added from outside during additive manufacturing using a nozzle that supplies powder, etc. Furthermore, by selecting a metal substrate containing a deoxidizing element, the deoxidizing element of the metal substrate may be supplied to the molten region.

In addition, in the method for manufacturing a hard metal member of the present invention, it is preferable that the mixed powder is a granulated powder. By using a granulated powder, the mixed state of each raw material powder can be homogenized, and a good hard metal buildup layer can be formed. In addition, when a deoxidizing element is contained, the deoxidizing element can be uniformly dispersed, and the deterioration of WC particles and the formation of void defects in the hard metal buildup layer can be more reliably suppressed.

In addition, in the manufacturing method of the hard metal member of the present invention, it is preferable to place the deoxidizing element on the surface of the metal substrate on which the hard metal buildup layer is formed. As described above, the method of adding the deoxidizing element is not limited, but when the desired thickness of the hard metal buildup layer is thin (for example, when forming a hard metal buildup layer of about one or two layers in the thickness direction), it is possible to simply and efficiently suppress the deterioration of WC particles and the formation of void defects in the hard metal buildup layer without using a special raw material powder.

In addition, in the manufacturing method of the hard metal member of the present invention, it is preferable that the hard metal build-up layer is a multi-layer build-up layer in the thickness direction. In the manufacturing method of the hard metal member of the present invention, a suitable method for adding a deoxidizing element can be selected, so that, for example, even if three or more layers of hard metal build-up layers are formed in the thickness direction, the effect of the deoxidizing element can be exerted.

Furthermore, in the manufacturing method of the hard metal member of the present invention, it is preferable that the deoxidizing element is one or more elements selected from Ca, Be, Mg, Ce, Al, Zr, Ti and Si. These elements are elements that oxidize preferentially over WC in the molten region, and can suppress the deterioration of WC particles and the formation of void defects in the hard metal cladding layer. More preferable deoxidizing elements are Al, Zr, Ti and Si, and the most preferable deoxidizing element is Al. Not only is Al oxidized preferentially over WC in the molten region, but it is also relatively inexpensive and easily available, and can be used suitably even when a large amount of raw material powder is required.

The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of:
A hard metal build-up layer is formed on the surface of the metal substrate,
The hard metal cladding layer contains hard particles including WC particles, a metal bonding phase and a deoxidizing element,
The deoxidizing element is one or more elements selected from Ca, Be, Mg, Ce, Al, Zr, Ti and Si;
Also provided is a hard metal member, characterized in that

In the hard metal member of the present invention, a deoxidizing element is used to suppress the oxidation of WC particles when forming the hard metal buildup layer, and the deoxidizing element is contained in the hard metal buildup layer, and more specifically, one or more elements selected from Ca, Be, Mg, Ce, Al, Zr, Ti, and Si are contained.

The metal bonding phase is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known metal bonding phases can be used, such as Co and Ni. In addition, the hard particles need only contain WC particles, and various conventionally known hard particles can be used.

In addition, in the hard metal member of the present invention, it is preferable that the porosity of the hard metal buildup layer is 5% or less. In the hard metal member of the present invention, the formation of void defects is suppressed by the deoxidizing element. A more preferable porosity is 4% or less, and a most preferable porosity is 3% or less.

Furthermore, the present invention provides
A mixed powder used in the method for producing a hard metal member of the present invention,
Contains hard particles including WC particles, a metal bonding phase and a deoxidizing element;
The deoxidizing element is one or more elements selected from Ca, Be, Mg, Ce, Al, Zr, Ti and Si;
Also provided is a feed powder for additive manufacturing, comprising:

The content and particle size of each component in the additive manufacturing raw material powder of the present invention are not particularly limited as long as they do not impair the effects of the present invention, and may be adjusted appropriately according to the desired characteristics of the hard metal cladding layer obtained by the additive manufacturing method.

In addition, it is preferable that the deoxidizing element of the additive manufacturing raw material powder of the present invention is Al, and the content of Al is 0.1 to 2.0 mass%. By making the content of Al 0.1 mass% or more, it is possible to suppress the deterioration of WC particles and the formation of void defects in the hard metal buildup layer. In addition, by making the content of Al 2.0 mass% or less, it is possible to suppress the formation of brittle intermetallic compounds formed by the reaction between Al and the metal base material (Fe), and to suppress cracking of the hard metal buildup layer caused by the formation of the intermetallic compounds.

The raw powder for the additive manufacturing method of the present invention is preferably granulated powder. By using granulated powder, the mixed state of each raw powder can be homogenized, and a good hard metal buildup layer can be formed. In addition, when a deoxidizing element is contained, the deoxidizing element can be uniformly dispersed, and the deterioration of WC particles and the formation of void defects in the hard metal buildup layer can be more reliably suppressed. Here, the shape, particle size, and particle size distribution of the granulated powder are not particularly limited as long as they do not impair the effects of the present invention, and may be appropriately adjusted according to the equipment and welding conditions used in the additive manufacturing method and the desired properties of the resulting hard metal buildup layer.

The present invention provides a simple and efficient method for manufacturing a hard metal component that can suppress the deterioration of hard particles (WC particles) due to oxidation and the formation of void defects caused by the oxidation, as well as a hard metal component obtained by the manufacturing method, and a raw material powder for additive manufacturing that can be suitably used in the manufacturing method.

FIG. 2 is a schematic diagram showing the formation of a hard metal cladding layer using a coaxial cladding torch. 1 is a graph showing the relationship between the standard free energy of formation of various oxides and temperature. 1 is a schematic cross-sectional view showing one embodiment of a hard metal member of the present invention. FIG. 2 is a schematic diagram of laser powder build-up welding in Example 1. 1 is a cross-sectional photograph of a hard metal buildup layer obtained in Example 1. 1 is a cross-sectional photograph of a hard metal build-up layer formed directly on a metal substrate in Example 1. 4A to 4C are cross-sectional photographs of hard metal buildup layers obtained at each laser output in Example 1. 4A to 4C are cross-sectional photographs of hard metal buildup layers formed directly on metal substrates at each laser output in Example 1. 1 is a graph showing the relationship between the porosity of the hard metal cladding layer and the laser output in Example 1. 1 is a SEM photograph of the hard metal build-up layer obtained in Example 1. 1 is a SEM photograph of a hard metal build-up layer formed directly on a metal substrate in Example 1. 1 shows the results of SEM-EDS analysis of the hard metal build-up layer obtained in Example 1. 1 is an XRD pattern of the hard metal cladding layer obtained in Example 1. 1 is a SEM photograph of a bonding interface between a hard metal buildup layer and a metal substrate obtained in Example 1. 1 is a SEM photograph of a bonding interface between a hard metal buildup layer formed directly on a metal substrate in Example 1 and the metal substrate. FIG. 11 is a schematic diagram of laser powder build-up welding in Example 2. 3 is a photograph showing the appearance and cross-section of the hard metal build-up layer obtained in Example 2. 1 is a Vickers hardness distribution in a cross section of a hard metal cladding layer obtained in Example 2. 4 is a photograph showing the appearance and cross-section of the hard metal build-up layer obtained in Example 3. 1 is a cross-sectional photograph of a hard metal buildup layer obtained in Example 4. 1 is a cross-sectional photograph of a hard metal build-up layer formed directly on a metal substrate in Example 4. 1 is a cross-sectional photograph of a hard metal buildup layer obtained in Example 5. 1 is a SEM photograph of a hard metal build-up layer obtained in Example 5. 1 shows an SEM photograph and SEM-EDS analysis results of the granulated powder obtained in Example 6. 4 is a cross-sectional photograph of each hard metal buildup layer obtained in Example 6.

Below, with reference to the drawings, a detailed description will be given of representative embodiments of the method for manufacturing a hard metal member of the present invention, and the hard metal member and its raw material powder. However, the present invention is not limited to those shown in the drawings, and since each drawing is intended to conceptually explain the present invention, ratios and numbers may be exaggerated or simplified as necessary for ease of understanding. Furthermore, in the following description, the same or equivalent parts are given the same reference numerals, and duplicate descriptions may be omitted.

1. Manufacturing method of hard metal components As one aspect of additive manufacturing, laser powder build-up welding using a coaxial cladding torch will be described.

(1) Additive manufacturing method FIG. 1 is a schematic diagram of a case where a hard metal cladding layer is formed using a coaxial cladding torch. The laser processing head 11 forms a hollow laser optical path 11a along the central axis, and the laser light 12 travels inside along this optical path. Specifically, the laser light 12 enters the laser processing head 11 from the entrance 11b, is reflected vertically downward by a mirror 21, and reaches a convex lens 22. The laser light 12 that reaches the convex lens 22 is focused and irradiated from the irradiation port 11d at the lower end of the laser processing head 11. Then, the laser light 12 is irradiated onto the surface of the metal substrate 13 with the focal point directly below the lower end of the laser processing head 12 on the optical axis 11c or defocused. At this time, the metal substrate 13 is irradiated with the laser light 12 by melting the irradiated surface of the laser light 12 to form a molten pool 13a that is liquefied, as in conventional laser powder overlay welding.

The laser processing head 11 is provided with, coaxially with the laser optical path 11a (coaxially with the optical axis 11c (coaxial)), a raw material powder supply pipe 14 that sends raw material powder 15 downward, a cooling water supply pipe 19 that sends cooling water 20 downward, and a shielding gas supply pipe 17 that sends inert gas 18 downward, in that order from the central axis side. In detail, the raw material powder supply pipe 14 is first arranged concentrically outside the laser optical path 11a in the horizontal plane, and converges from the upper end to the optical axis 11c side following the focusing of the laser light 12, and is connected to the vicinity of the irradiation port 11d at the lower end of the laser processing head 11.

Although not shown, the raw powder supply pipe 14 may be one or more pipes arranged at a predetermined angle on a horizontal plane, or may be a ring-shaped pipe connected around the entire circumference. Thus, the raw powder supply pipe 14 introduces raw powder 15 from its upper end and releases it into the position where the laser light 12 irradiates the surface of the metal base material 13, that is, into the molten pool 13a on the surface of the metal base material 13. The released raw powder 15 is heated by the laser light 12 and the molten pool 13a of the metal base material 13, and forms a hard metal build-up layer 16 on the surface of the metal base material 13 on the rear side in the movement direction of the laser processing head 11 (see arrow Y).

In particular, in laser powder build-up welding using a coaxial cladding torch, both the focus of the laser light 12 and the raw material powder 15 are emitted from the lower end of a single laser processing head 11, so there is no need to control the positioning of the irradiation position of the laser light 12 (position of the molten pool 13a) and the emission position of the raw material powder 15. Therefore, even if the laser processing head 11 scans the surface of the metal substrate 13, it is easy to control the thickness of the hard metal build-up layer 16, and the number of processing processes can be reduced, which is an advantage.

In addition, a shielding gas supply pipe 17 is arranged concentrically (coaxially) outside the raw material powder supply pipe 14 with respect to the laser light path 11a in the horizontal plane, and converges from its upper end toward the optical axis 11c in accordance with the convergence of the laser light 12, and is connected to the vicinity of the irradiation port 11d at the lower end of the laser processing head 11. Therefore, the shielding gas supply pipe 17 discharges an inert gas 18 such as argon gas that flows in from its upper end at its lower end. The discharged inert gas 18 is sprayed onto the raw material powder 15 (and thus the hard metal buildup layer 16), so that the hard metal buildup layer 16 is immediately subjected to oxidation prevention treatment while being deposited on the surface of the metal substrate 13. This shielding gas supply pipe 17 may be any pipe capable of spraying an amount of inert gas 18 sufficient to prevent oxidation of the hard metal buildup layer 16, and may be a multiple pipe or a ring-shaped pipe connected to the entire circumference.

In addition, a cooling water supply pipe 19 is arranged concentrically outside the shielding gas supply pipe 17, and its upper end is connected to a position a predetermined distance above the lower end of the laser processing head 11. Note that this cooling water supply pipe 19 is not an essential part of the laser processing head 11, but serves the cooling function of the laser processing head 11.

The type of laser used, laser output, laser focus size, scanning speed, scanning pattern, etc. are not particularly limited as long as they do not impair the effects of the present invention, and may be appropriately adjusted according to the desired shape, size, mechanical properties, etc. of the hard metal buildup layer 16.

The greatest feature of the manufacturing method of the hard metal member of the present invention is that a deoxidizing element is added to the molten pool 13a to suppress the oxidation of WC particles. Although there is no particular limitation on the method of adding the deoxidizing element to the molten pool 13a, it is preferable to add the deoxidizing element to the raw material powder 15. By adding the deoxidizing element to the raw material powder 15 in advance, the deoxidizing element can be added to the molten pool 13a efficiently and easily. Furthermore, by adding the deoxidizing element to the raw material powder 15 in advance, the effect of the deoxidizing element can be maintained constant even when multiple hard metal overlay layers are formed in the thickness direction.

For example, additive elements may be placed on the surface of the metal substrate 13, or an additive manufacturing method may be used to form a build-up layer made of additive elements. Also, additive elements may be added from outside during additive manufacturing using a nozzle that supplies powder, etc. Furthermore, by selecting a metal substrate 13 that contains a deoxidizing element, the deoxidizing element of the metal substrate may be supplied to the molten pool 13a.

By using a powder containing a deoxidizing element as the raw material powder 15, a buildup layer containing a deoxidizing element can be formed on the surface of the metal base material 13 as a preliminary treatment for forming the hard metal buildup layer 16. Alternatively, a wire or powder containing a deoxidizing element may be placed on the surface of the metal base material 13, and the laser light 12 may be irradiated to that area. In other words, the formation of the hard metal buildup layer 16 and the preliminary treatment thereof can be carried out by the same device.

(2) Raw Material Powder The raw material powder 15 of the hard metal buildup layer 16 is a mixed powder containing hard particles including WC particles and a metallic binder phase.

It is preferable to add a deoxidizing element to the mixed powder. The deoxidizing element may be any element that oxidizes preferentially over WC in the molten region, and specifically, an element that has a standard free energy of oxide formation lower than the standard free energy of formation (ΔG _CO ) of CO in the molten region can be used. Figure 2 shows the relationship between the standard free energy of formation and temperature of various oxides listed in the Metal Data Book. It can be seen that Ca, Be, Mg, Ce, Al, Zr, Ti and Si can be used as deoxidizing elements in the temperature range (1500 to 2000°C) of "the temperature at which the metallic bonding phase such as Co and Ni used in cemented carbide melts to the maximum temperature of the molten region expected by high-energy beam irradiation."

The content and particle size of the deoxidizing elements, hard particles including WC particles, and metal bonding phase are not particularly limited as long as they do not impair the effects of the present invention, and may be appropriately adjusted according to the desired characteristics of the hard metal buildup layer 16 obtained by the additive manufacturing method.

Here, the deoxidizing element is Al, and the Al content is preferably 0.1 to 2.0 mass%. By making the Al content 0.1 mass% or more, it is possible to suppress the deterioration of WC particles and the formation of void defects in the hard metal buildup layer 16. Furthermore, by making the Al content 2.0 mass% or less, it is possible to suppress the formation of brittle intermetallic compounds formed by the reaction between Al and the metal base material 13, and it is possible to suppress cracking of the hard metal buildup layer 16 caused by the formation of the intermetallic compounds.

The hard particles other than WC particles are not particularly limited as long as they do not impair the effects of the present invention, and various hard particles known in the art that are used in cemented carbides and cermets can be used. For example, hard particles such as carbides, nitrides, carbonitrides, borides, and oxides of metals IVa, Va _, and VIa in _the periodic table can be used. More specifically, for example, WC, TiC, VC, _Mo2C , ZrC, HfC, NbC, TaC, _Cr3C2 , SiC, _Si3N4 , and _TiB2 can be used.

The type of metal bonding phase is not particularly limited as long as it does not impair the effects of the present invention, and various metal bonding phases that are conventionally known and used in cemented carbides and cermets can be used. For example, Co and Ni can be preferably used.

The raw powder 15 is preferably granulated powder. By using granulated powder, the mixed state of each raw powder can be homogenized, and a good hard metal buildup layer 16 can be formed. In addition, when a deoxidizing element is contained, the deoxidizing element can be uniformly dispersed, and the deterioration of WC particles and the formation of void defects in the hard metal buildup layer 16 can be more reliably suppressed. Here, the shape, particle size, and particle size distribution of the granulated powder are not particularly limited as long as they do not impair the effects of the present invention, and may be appropriately adjusted according to the equipment and welding conditions used in the additive manufacturing method and the desired characteristics of the resulting hard metal buildup layer 16.

2. Hard Metal Member Fig. 3 is a schematic cross-sectional view showing one embodiment of the hard metal member of the present invention. The hard metal member 21 is
A hard metal build-up layer 16 is formed on the surface of a metal base material 13. The hard metal build-up layer 16 does not need to be formed on the entire region of the metal base material 13, and may be formed on any region.

The hard metal buildup layer 16 has hard particles including WC particles and a metallic bonding phase, and further contains deoxidizing elements (Ca, Be, Mg, Ce, Al, Zr, Ti, and Si). When Al is used as a deoxidizing element, the Al is dispersed in the hard metal buildup layer 16 as alumina, and the Al content is preferably 0.1 to 2.0 mass%.

Since the oxidation of WC particles is suppressed by the deoxidizing elements, the hard metal buildup layer 16 is in a dense state with very few void defects. The porosity of the hard metal buildup layer 16 is preferably 5% or less, more preferably 4% or less, and most preferably 3% or less.

Even when Al is used as a deoxidizing element, it is preferable that an intermetallic compound layer due to the addition of Al is not formed at the bonding interface between the metal substrate 13 and the hard metal buildup layer 16. Specifically, it is preferable that the bonding interface is similar to that when the hard metal buildup layer 16 is formed using the raw material powder 15 to which Al is not added.

The type and content of the hard particles, including WC particles, and the metal bonding phase are not particularly limited as long as they do not impair the effects of the present invention, and may be appropriately adjusted according to the desired characteristics of the hard metal buildup layer 16.

The hard particles other than WC particles are not particularly limited as long as they do not impair the effects of the present invention, and may be various hard particles known in the art that are used in cemented carbides and cermets. For example, hard particles such as carbides, nitrides, or carbonitrides of metals IVa, Va, and VIa in the periodic table may be used. More specifically, for example, WC, TiC, VC, _Mo2C , ZrC, HfC, NbC, TaC _{, Cr3C2} , _SiC , _Si3N4 , and _TiB2 may be used.

The thickness of the hard metal buildup layer 16 is not particularly limited, but it is preferable to have multiple buildup layers in the thickness direction. Even if the hard metal buildup layer 16 is formed of three or more buildup layers in the thickness direction, it is in a dense state with few void defects.

The metal substrate 13 is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known metal substrates can be used, but from the viewpoints of adhesion with the hard metal buildup layer 16 formed on the surface, mechanical properties, price, etc., it is preferable to use a steel material, and for example, tool steel or bearing steel can be suitably used. More specifically, for example, medium carbon steel (S45C, etc.), chromium molybdenum steel, alloy tool steel, high carbon chromium bearing steel, stainless steel, etc. can be used as the metal substrate 13.

3. Raw material powder for additive manufacturing The raw material powder for additive manufacturing of the present invention can be suitably used in the manufacturing method of the hard metal member of the present invention, and has the characteristics described in "(2) Raw material powder" above.

The method for producing the raw powder for additive manufacturing is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known powder production methods can be used.

The manufacturing method of the hard metal member of the present invention, the hard metal member, and the raw material powder thereof will be further explained in the following examples, but the present invention is not limited to these examples.

Example 1
A hard metal build-up layer was formed on the surface of a stainless steel (SUS304) substrate using a coaxial cladding torch as shown in FIG. 1. GTV WC-Co granulated powder (WC: 88% by mass, Co: 12% by mass, particle size: 45-90 μm) was used as the raw material powder, and the laser powder build-up welding conditions were laser output: 1400 W, laser scanning speed: 5 mm/s, raw material powder supply speed: 10 g/min. A semiconductor laser was used as the laser. The additive manufacturing method was performed in an argon chamber, and the oxygen in the chamber was set to 100 ppm.

As a pretreatment for laser powder buildup welding, a linear groove was machined using a fiber laser on the surface of the stainless steel base material on which the hard metal buildup layer was to be formed, and a φ0.5 mm pure aluminum wire was placed in the groove. Next, a semiconductor laser was irradiated to the area where the pure aluminum wire was placed under conditions of laser output: 1800 W, laser scanning speed: 3 mm/s, and the surface of the stainless steel base material was alloyed with Al, and then polished to form the treated area.

As shown in Figure 4, one pass of laser powder build-up welding was performed on the treated area to form a hard metal build-up layer. A cross-sectional photograph of the resulting hard metal build-up layer is shown in Figure 5. For comparison, Figure 6 shows a cross-sectional photograph of a hard metal build-up layer obtained by performing one pass of laser powder build-up welding directly on the surface of a stainless steel base material without forming a treated area. It can be seen that when Al was added to the surface of the stainless steel base material, a dense hard metal build-up layer was formed, whereas when Al was not added, numerous void defects were formed.

Figure 7 shows cross-sectional photographs of hard metal buildup layers obtained by performing one pass of laser powder buildup welding on the treated area with laser powers of 1200 W, 1400 W, and 1600 W. Figure 8 shows cross-sectional photographs of hard metal buildup layers obtained by performing one pass of laser powder buildup welding directly on the surface of a stainless steel substrate without forming a treated area using similar laser powder buildup welding conditions. At all laser powers, the addition of Al has a significant effect in suppressing void defects.

The porosity of each hard metal overlay shown in Figures 7 and 8 was measured by image analysis of cross-sectional optical microscope photographs. More specifically, analysis software ImageJ was used to calculate the area ratio from the ratio of the number of pixels in the overlay to the number of pixels in the pores, which was used as the porosity. The relationship between the obtained porosity and the laser output is shown in Figure 9. When Al was not added, the porosity was 20% or more at a laser output of 1,400 W or more, whereas when Al was added, the porosity was 5% or less under all conditions.

Scanning electron microscope (SEM) photographs of the microstructure of the hard metal cladding layer obtained with a laser output of 1400 W, with and without the addition of Al, are shown in Figures 10 and 11, respectively. When Al was not added, the WC particles were coarsened and the formation of a harmful phase ( _W2C phase) was observed. On the other hand, when Al was added, fine WC particles were uniformly dispersed and no formation of a harmful phase ( _W2C phase) was observed.

Figure 12 shows the results of SEM-EDS analysis of the hard metal buildup layer obtained by adding Al with a laser output of 1400 W. It can be seen that fine aluminum oxides are dispersed in the hard metal buildup layer (arrows in element mapping). In addition, the Al content of the Al alloyed region of the metal substrate and the hard metal buildup layer was measured and found to be 0.8 mass% and 0.5 mass%, respectively.

XRD measurements were performed on the raw material powder and the hard metal build-up layer obtained with a laser output of 1400 W (with and without the addition of Al). The obtained XRD patterns are shown in Figure 13. It can be seen that the constituent phases of the hard metal build-up layer obtained with the addition of Al have not changed significantly from the raw material powder. Furthermore, no Al-based compounds due to the addition of Al were detected. On the other hand, in the case where no Al was added, the peak intensity due to the harmful phase ( _W2C phase) indicated by ◆ in the figure became larger, and it can be seen that the deterioration of the WC particles was progressing.

Figures 14 and 15 show the results of SEM observations of the bonded interface between the hard metal cladding layer and the metal substrate when the laser output was 1400 W, with and without the addition of Al, respectively. No significant differences were observed apart from the observation of aluminum oxide (arrow in the figure) when Al was added, and no formation of an intermetallic compound layer due to the addition of Al was confirmed.

Example 2
A hard metal build-up layer was formed in the same manner as in Example 1, except that one pass of laser powder build-up welding was performed on the treated area as shown in Fig. 16 (laser output: 1400 W). Appearance and cross-sectional photographs of the obtained hard metal build-up layer are shown in Fig. 17. It can be seen that the hard metal build-up layer formed on the treated area to which Al was added was densified, whereas a large number of void defects were formed in the hard metal build-up layer formed directly on the metal substrate.

Micro Vickers hardness measurements were performed on the cross section of the hard metal buildup layer shown in Figure 17 (measurement load: 300 gf). The results are shown in Figure 18. The hardness of the hard metal buildup layer did not change significantly, and no significant effect was observed due to the addition of Al. This result shows that the addition of Al can reduce void defects without impairing the properties of the cemented carbide.

Example 3
A hard metal build-up layer was formed in the same manner as in Example 2, except that the deoxidizing element was Zr. Appearance and cross-sectional photographs of the obtained hard metal build-up layer are shown in FIG. 19. It can be seen that the hard metal build-up layer formed in the treated area to which Zr was added was densified, whereas the hard metal build-up layer formed directly on the metal substrate had many void defects. In addition, when the porosity of the hard metal build-up layer was measured in the same manner as in Example 1, the porosity of the hard metal build-up layer formed in the treated area to which Zr was added was 1.9%, and the porosity of the hard metal build-up layer formed directly on the substrate was 25.7%.

Example 4
A hard metal build-up layer was formed in the same manner as in Example 1, except that WC-Ni granulated powder (WC: 88 mass%, Ni: 12 mass%, particle size: 45-90 μm) manufactured by GTV was used as the raw material powder (laser output: 1600 W). A cross-sectional photograph of the obtained hard metal build-up layer is shown in FIG. 20. For comparison, a cross-sectional photograph of the hard metal build-up layer in the case where laser powder build-up welding was directly performed on the surface of the stainless steel base material without forming a treated region is shown in FIG. 21. It can be seen that even when the metallic bonding phase is Ni, the addition of Al significantly suppresses void defects in the hard metal build-up layer.

Example 5
The metal substrate was a SACM645 substrate containing about 0.8% by mass of Al, and laser powder build-up welding was performed directly on the SACM645 substrate without adding additional Al. The processing conditions and raw powder of the laser powder build-up welding were the same as those in Example 1 (laser output: 1600 W).

Figure 22 shows cross-sectional photographs of the hard metal buildup layer when one pass of laser powder buildup welding is performed, when two passes of laser powder buildup welding are superimposed in the thickness direction, and when three passes of laser powder buildup welding are superimposed in the thickness direction. The formation of void defects is suppressed up to the second layer by the supply of Al, but void defects are formed in the third layer.

Figure 23 shows an SEM photograph of the cross section of the hard metal buildup layer when the three passes of laser powder buildup welding shown in Figure 22 were superimposed. EDS analysis was performed on the first, second, and third layers shown in Figure 23, and the Al content was measured. The results were: first layer: 0.235 mass%, second layer: 0.159 mass%, third layer: 0.089 mass% (SACM645 base material: 0.845 mass%). This result indicates that the addition of at least 0.1 mass% Al is necessary to suppress void defects.

Example 6
WC-Co granulated powder (WC: 88% by mass, Co: 12% by mass, particle size: 15 to 45 μm) was mixed with Al particles having a diameter of about 3 μm and granulated to obtain granulated powders with Al contents of 0.5% by mass, 1.0% by mass, and 2.5% by mass. The granulated powders were produced by manually mixing the raw material powders, spraying an aqueous PVA solution as a binder, and then drying and classifying the powders.

The SEM photograph and SEM-EDS mapping of the obtained granulated powder (Al content: 1.0 mass%) are shown in Figure 24. It can be seen that the obtained granulated powder is composed of roughly spherical WC-Co granulated powder and fine Al particles.

The resulting granulated powders were used as raw material powders, and hard metal build-up layers were formed in the same manner as in Example 1, except that no Al was added to the metal substrate (laser output: 1600 W).

Cross-sectional photographs of each of the hard metal buildup layers obtained are shown in Figure 25. Densification due to the addition of Al is observed in all of the hard metal buildup layers. On the other hand, when the Al content of the granulated powder is set to 2.5 mass%, cracks are observed in the hard metal buildup layer. This result indicates that in order to suppress cracks in the hard metal buildup layer, the upper limit of the Al content of the granulated powder needs to be set to approximately 2.0 mass%.

11...laser processing head,
11a...laser optical path,
11b: entrance port,
11c...optical axis,
12...laser light,
13... Metal substrate,
13a...molten pool,
14: Raw powder supply pipe,
15... Raw material powder,
16...Hard metal overlay layer,
17...Shielding gas supply pipe,
18... inert gas,
19...cooling water supply pipe,
20...cooling water,
21...Hard metal member.

Claims (9)

A method for manufacturing a hard metal member, comprising: forming a hard metal build-up layer on a surface of a metal substrate by an additive manufacturing method using a mixed powder containing hard particles including WC particles and a metal bonding phase as a raw material,
forming a molten region of the mixed powder by irradiating the mixed powder with a high energy beam and adding a deoxidizing element to the molten region;
The deoxidizing element has a standard free energy of formation lower than the standard free energy of formation (ΔG _CO ) of CO in the range of 1500 to 2000° C. ,
The deoxidizing element is Al or Zr;
A method for manufacturing a hard metal member, comprising the steps of: adding the deoxidizing element to the mixed powder;
The method for producing a hard metal part according to claim 1, characterized in that The mixed powder is made into a granulated powder.
3. The method for producing a hard metal part according to claim 1 or 2, characterized in that disposing the deoxidizing element on the surface of the metal substrate on which the hard metal cladding layer is to be formed;
The method for producing a hard metal member according to any one of claims 1 to 3, characterized in that The hard metal cladding layer is a multi-layer cladding layer in the thickness direction;
The method for producing a hard metal member according to any one of claims 1 to 4, characterized in that A hard metal cladding layer is formed on the surface of the metal substrate,
The hard metal cladding layer has hard particles including WC particles, a metal bonding phase and a deoxidizing element,
The deoxidizing element is Al or Zr ;
A hard metal member characterized by: The porosity of the hard metal buildup layer is 5% or less;
7. The hard metal member according to claim 6 , A mixed powder used in the method for producing a hard metal member according to any one of claims 1 to 5 ,
Contains hard particles including WC particles, a metal bonding phase and a deoxidizing element;
The deoxidizing element is Al or Zr ;
A raw material powder for additive manufacturing, characterized by: The content of Al is 0.1 to 2.0 mass %;
The additive manufacturing feed powder according to claim 8 ,