A gradient functional hard alloy powder for selective laser melting additive manufacturing and preparation and application thereof
By constructing a gradient metal binder phase layer on top of the WC core, the problems of easy decomposition and grain coarsening of WC in selective laser melting additive manufacturing were solved, and high-density and high-performance cemented carbide parts were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHUZHOU SANXIN HARD ALLOY PRODN CO LTD
- Filing Date
- 2026-02-03
- Publication Date
- 2026-06-16
AI Technical Summary
In selective laser melting additive manufacturing, existing technologies struggle to effectively address issues such as WC decomposition, grain coarsening, and metallurgical defects in cemented carbide powders. Traditional methods, such as optimizing process parameters and using a single coating layer, are not ideal.
Using gradient functional cemented carbide powder, a gradient metal bond layer was designed to be constructed outside the WC core, including a tungsten-cobalt alloy wetting layer, a Co-W-Ni ternary alloy transition layer, and a nickel-cobalt alloy melting layer. The composition and thickness were precisely controlled by chemical vapor deposition process to achieve a smooth transition and stable connection of properties.
It effectively inhibits the decomposition and grain coarsening of WC, improves the density and mechanical properties of the parts, reduces metallurgical defects, and enhances the forming quality of the SLM process.
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Figure CN122210035A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of additive manufacturing technology, specifically to a graded functional cemented carbide powder for selective laser melting additive manufacturing, its preparation and application. Background Technology
[0002] Cemented carbide is a high-performance material typically composed of a refractory metal carbide hard phase (such as tungsten carbide, chemical formula WC) and a metallic binder phase (such as cobalt, chemical formula Co). With its excellent comprehensive properties, including high hardness, high strength, and high wear resistance, cemented carbide plays a crucial role in numerous fields and is widely used in the manufacture of cutting tools, mining and oil drilling tools, molds, and wear-resistant parts.
[0003] Selective laser melting (SLM) falls under the category of advanced additive manufacturing technology. It can directly utilize metal powder to create dense metal parts with complex geometries through a layer-by-layer melting and solidification process. This characteristic opens up entirely new technological pathways for the integrated, complex, and customized manufacturing of cemented carbide parts. However, applying traditional cemented carbide powder directly to the SLM process presents a series of significant technical challenges.
[0004] The fundamental reason lies in the significant differences in physical properties between the hard phase WC and the metallic binder phase Co, specifically in melting point, thermal conductivity, and coefficient of thermal expansion. During the SLM process, a high-energy laser beam acts on micron-sized powder particles within microseconds, instantly generating extremely high temperatures and creating a large temperature gradient. Under these extreme non-equilibrium thermodynamic conditions, the physicochemical incompatibility between WC and Co is drastically amplified, making them highly susceptible to various metallurgical defects.
[0005] Specifically, on the one hand, WC is prone to decomposition and melting under high temperature conditions. This not only leads to the loss of carbon, but also causes carbon to react with Co to form a brittle η phase (chemical formula Co). x W This change (C2) severely deteriorates the mechanical properties of the material. On the other hand, WC particles in the molten pool aggregate and grow through a dissolution-reprecipitation mechanism, resulting in a coarsened microstructure of the final part, thereby reducing the material's hardness and wear resistance. Furthermore, during rapid solidification, the enormous thermal stress can cause microcracks and pores to form inside the part, thus affecting its density and service reliability.
[0006] To address the aforementioned issues, existing technologies have made numerous attempts. One approach is to optimize SLM process parameters, such as adjusting laser power, scanning speed, and scanning strategy; another is to perform post-processing on the formed parts, such as hot isostatic pressing. However, these methods can only improve the problem to a certain extent and cannot fundamentally solve the inherent instability of WC during the SLM process. Some studies have focused on modifying the powder, such as coating the WC powder surface with a single nickel (Ni) or cobalt (Co) layer. Although this single coating layer can protect the WC core to some extent, the effect is not ideal. This is because a single metal layer cannot simultaneously meet the requirements of good wettability with the WC core, rapid melting during the SLM process, and high fluidity. Moreover, due to the abrupt change in composition, new interfacial stresses may be generated between the coating and the core.
[0007] In conclusion, developing a novel cemented carbide powder material specifically designed for the characteristics of SLM (Simplified Chinese Luminescent Laminate) process is of great significance for promoting the industrialization of cemented carbide additive manufacturing technology. Summary of the Invention
[0008] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a graded-function cemented carbide powder, which can be used in SLM additive manufacturing of cemented carbide and can better overcome the problems of easy WC decomposition, grain coarsening and metallurgical defects existing in traditional graded-function cemented carbide powders.
[0009] The present invention also proposes a method for preparing the above-mentioned powder.
[0010] The present invention also provides an apparatus for preparing the above-mentioned powder.
[0011] The present invention also proposes applications of the above-mentioned powder.
[0012] According to one aspect of the present invention, a gradient functional cemented carbide powder is provided, comprising a tungsten carbide core and a gradient metal binder layer covering the tungsten carbide core. The gradient metal binder layer comprises, from the inside out, a tungsten-rich cobalt alloy wetting layer, a Co-W-Ni ternary alloy transition layer, and a nickel-rich cobalt alloy melting layer, wherein the mass content of tungsten and nickel in the Co-W-Ni ternary alloy transition layer varies in a continuous reverse gradient along the radial direction.
[0013] The graded-function cemented carbide powder according to embodiments of the present invention has at least the following beneficial effects: Traditional graded-function cemented carbide powders, when applied to selective laser melting (SLM) additive manufacturing, often suffer from problems such as WC decomposition, grain coarsening, and metallurgical defects. To solve these problems, the present invention designs a powder by constructing a graded metal binder phase layer outside the WC core. This powder not only solves the above problems but also has the following advantages:
[0014] 1) A wetting layer, a melting layer, and a transition layer are sequentially deposited on the surface of the WC core. The wetting layer enhances the interfacial bonding between the coating and the core, forming a strong metallurgical bond; the melting layer rapidly melts during the SLM process and encapsulates the WC core, preventing it from being directly exposed to high-energy laser light, thereby effectively suppressing the decomposition and melting of WC and reducing the formation of brittle η phase.
[0015] 2) The molten layer in the gradient binder phase has a low melting point and high fluidity, which can shorten the residence time of WC at high temperatures and inhibit grain coarsening through the dissolution-reprecipitation mechanism. At the same time, good fluidity helps the molten pool spread and intergranular filling, thereby improving the density of the part.
[0016] 3) The introduction of the transition layer enables a smooth transition of the binder phase composition and physical properties from the inside to the outside, avoids interface stress concentration caused by abrupt changes in material properties, and enhances the stability of the coating and the mechanical properties of the final part.
[0017] According to some embodiments of the present invention, the tungsten-rich cobalt alloy wetting layer is directly adjacent to a tungsten carbide core.
[0018] According to some embodiments of the present invention, the mass content of tungsten in the Co-W-Ni ternary alloy transition layer decreases radially from the inside to the outside, while the mass content of nickel increases radially from the outside to the inside.
[0019] According to some embodiments of the present invention, the mass content of tungsten in the Co-W-Ni ternary alloy transition layer decreases from 10% to 0% radially from the inside to the outside, the mass content of nickel increases from 0% to 30% radially from the outside to the inside, and the balance is Co.
[0020] According to some embodiments of the present invention, the mass fraction C of tungsten in the Co-W-Ni ternary alloy transition layer is... W (r) The distribution of radial position r follows the following relationship: In the formula, r inner r represents the inner radial position of the Co-W-Ni ternary alloy transition layer. outer The outer radial position of the Co-W-Ni ternary alloy transition layer, C W,inner For the Co-W-Ni ternary alloy transition layer in r inner The tungsten mass fraction at position r is given by n1, where n1 is the gradient exponent, ranging from 0.5 to 3. The distribution of the tungsten mass fraction at radial position r in the transition layer follows a predefined power function relationship. It is the thickness of the transition layer. : The inner radial position of the transition layer (i.e., the interface radius between the wetting layer and the transition layer). : Outer radial position of the transition layer (i.e., the interface radius between the transition layer and the molten layer). The length of the transition layer in the radial direction, i.e., the thickness of the transition layer.
[0021] According to some embodiments of the present invention, the mass fraction of nickel in the Co-W-Ni ternary alloy transition layer... The distribution of radial position r follows the following relationship: In the formula, The inner radial position of the Co-W-Ni ternary alloy transition layer. The outer radial position of the Co-W-Ni ternary alloy transition layer, C Ni,outer For the Co-W-Ni ternary alloy transition layer in r outer The nickel mass fraction at position r is given by n2, where n2 is the gradient exponent, ranging from 0.5 to 3. The distribution of the nickel mass fraction at radial position r in the transition layer follows a predefined power function relationship.
[0022] Gradient exponent and The value range is limited to 0.5 to 3 to cover the main nonlinear variation trend from concave to convex gradients. Its specific presupposition principle is based on the SLM forming mechanism of cemented carbide and the functional requirements of the gradient layer: the function of the gradient layer is to achieve a smooth transition in performance, with the core being to suppress the decomposition and coarsening of WC while ensuring good fluidity of the molten pool. Its presupposition principle is as follows: Suppressing WC decomposition (inner side): A higher tungsten content should be maintained on the inner side near the WC core (through...). Regulation (to reduce the rate of decrease), thereby enhancing the protective effect of the wetting layer on WC and inhibiting the decomposition of WC at high temperatures.
[0023] To ensure fluidity (outer side): Near the outer side, the nickel content should be increased rapidly (through...). Regulation The rate of increase (the rate of rise) is used to ensure that the melt layer has enough low-melting-point metal to melt rapidly during the SLM process and form a highly fluid molten pool. Optimization can be achieved through a combination of finite element simulation and small-batch experiments. For example, when... When the tungsten content decreases more slowly on the inner side, the protective effect is stronger; when At that time, the nickel content rises faster on the outer side, allowing for a quicker attainment of high fluidity.
[0024] According to some embodiments of the present invention, n1 and n2 are independently selected from 0.8 to 2.
[0025] According to some embodiments of the present invention, n1 is not greater than n2.
[0026] According to some embodiments of the present invention, the value of n2 / n1 is 1.1 to 1.3. and The value of is an independently adjustable parameter used to independently control the gradient curves of tungsten and nickel. However, in practical applications, to ensure the smoothness of the transition layer composition, it is generally recommended to... and The values should be coordinated to ensure that the cobalt content (as the main binder phase) remains relatively stable or varies as needed in the transition layer. In the examples... and Taking similar values (such as n1 being 1.5 and n2 being 1.8) is precisely to achieve this coordinated and smooth transition.
[0027] According to some embodiments of the present invention, n1 is 1 and n2 is 1.2.
[0028] According to some embodiments of the present invention, n1 is 1.5 and n2 is 1.8.
[0029] According to some embodiments of the present invention, n1 is 0.8 and n2 is 1.0.
[0030] make and Similar numerical values help achieve a uniform distribution of cobalt (Co) within the transition layer and ensure a smooth transition in the rate of composition change. For example, when and During the coordinated matching process, the rate of decrease in tungsten content balances the rate of increase in nickel content, ensuring the stability of the binder phase composition in the intermediate region of the transition layer and preventing localized enrichment of cobalt. This maintains consistency with adjacent layers in terms of melting point, wettability, etc., thereby promoting a smooth transition of interfacial properties and reducing problems such as stress concentration or uneven melting caused by abrupt changes in material properties.
[0031] According to some embodiments of the present invention, the average particle size of the tungsten carbide core is 0.5 to 15 micrometers.
[0032] According to some embodiments of the present invention, the total thickness of the gradient metal bonding phase layer is 2 to 12 micrometers.
[0033] According to some embodiments of the present invention, the mass fraction of tungsten in the tungsten-rich cobalt alloy wetting layer is 3% to 20%.
[0034] According to some embodiments of the present invention, the mass fraction of nickel in the nickel-rich cobalt alloy melt layer is 15% to 50%.
[0035] According to some embodiments of the present invention, the thickness of the tungsten-rich cobalt alloy wetting layer is 0.5 to 3 micrometers.
[0036] According to some embodiments of the present invention, the thickness of the Co-W-Ni ternary alloy transition layer is 1 to 6 micrometers.
[0037] According to some embodiments of the present invention, the thickness of the nickel-cobalt alloy molten layer is 0.5 to 3 micrometers.
[0038] According to some embodiments of the present invention, the thickness ratio of the tungsten-rich cobalt alloy wetting layer, the Co-W-Ni ternary alloy transition layer, and the nickel-rich cobalt alloy melting layer is 1:0.5~5:0.5~3. The thickness ratio of the three layers is controlled based on interfacial stress testing and wettability analysis. The wetting layer is mainly used to ensure complete coverage of the WC core, the transition layer is mainly used to smooth the composition gradient and alleviate thermal stress, and the melting layer is mainly used to ensure rapid melting and densification.
[0039] According to some embodiments of the present invention, the thickness ratio of the tungsten-rich cobalt alloy wetting layer, the Co-W-Ni ternary alloy transition layer and the nickel-rich cobalt alloy melting layer is 1:0.5~1:0.5~0.8.
[0040] According to some embodiments of the present invention, the thickness ratio of the tungsten-rich cobalt alloy wetting layer, the Co-W-Ni ternary alloy transition layer, and the nickel-rich cobalt alloy molten layer is 1:0.5~0.6:0.5~0.6. For example, it is 1:0.55:0.53.
[0041] According to another aspect of the present invention, a method for preparing the above-mentioned powder is also provided, comprising the following steps: A tungsten carbide particle is placed in a fluidized state, and a gradient metal binder phase layer is formed on the surface of the tungsten carbide particle by chemical vapor deposition; wherein the chemical vapor deposition process includes, in sequence, a tungsten-rich cobalt alloy wetting layer deposition step, a Co-W-Ni ternary alloy transition layer deposition step, and a nickel-rich cobalt alloy melting layer deposition step.
[0042] A fluidized bed chemical vapor deposition process is used to precisely control the introduction timing and flow rate of various precursors in three stages to sequentially deposit the wetting layer, transition layer and melting layer on the surface of tungsten carbide particles.
[0043] According to some embodiments of the present invention, the tungsten-rich cobalt alloy wetting layer deposition step includes introducing a first set of precursors for forming the wetting layer.
[0044] According to some embodiments of the present invention, the first group of precursors includes a cobalt carbonyl precursor and a tungsten carbonyl precursor.
[0045] According to some embodiments of the present invention, the nickel-cobalt alloy melt layer deposition step includes introducing a second set of precursors to deposit and form the nickel-cobalt alloy melt layer.
[0046] According to some embodiments of the present invention, the first group of precursors includes a cobalt carbonyl precursor and a nickel carbonyl precursor.
[0047] According to some embodiments of the present invention, the Co-W-Ni ternary alloy transition layer deposition step includes continuously adjusting the flow ratio of the first group of precursor bodies and the second group of precursor bodies to deposit and form the transition layer.
[0048] According to some embodiments of the present invention, the chemical vapor deposition is performed at 500~1000°C.
[0049] According to some embodiments of the present invention, the gradient metal binder layer is formed on the surface of the tungsten carbide particles by chemical vapor deposition. The process includes: a first deposition stage in which a first set of precursors for forming the wetting layer is introduced into the fluidized bed reactor; a second deposition stage in which the flow rate ratio of the first set of precursors to a second set of precursors for forming the molten layer is continuously adjusted to deposit and form the transition layer; and a third deposition stage in which the second set of precursors is introduced into the fluidized bed reactor to deposit and form the molten layer.
[0050] According to another aspect of the present invention, an apparatus for preparing the above-mentioned powder is also provided, comprising a fluidized bed reactor, a gas supply system connected to the fluidized bed reactor, the gas supply system being connected to a flow control system and a program control unit, the program control unit being used to control the flow control system.
[0051] The powder of this invention is produced using a fluidized bed chemical vapor deposition process. Through programmed control, the composition, thickness, and distribution characteristics of the gradient layer can be precisely controlled. This process has the capability for large-scale, homogenized production, good process repeatability, and significant industrial application value.
[0052] According to some embodiments of the present invention, the flow control system is used to perform three deposition stages, and in the second deposition stage, the precursor flow ratio is adjusted according to the power function relationship.
[0053] According to another aspect of the invention, applications of the above-mentioned powder are also provided, including applications in selective laser melting additive manufacturing.
[0054] According to some embodiments of the present invention, a specific application includes an article in which at least some components of the article are prepared from the powder described above, and the article includes cutting tools, mining and oil drilling tools, molds or wear-resistant parts.
[0055] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0056] Figure 1 This is a schematic diagram of the structure of the gradient functional cemented carbide powder particles in Examples 1-4 of the present invention.
[0057] Figure 2 This is a process flow diagram of the graded functional cemented carbide powder preparation method in Examples 1-4 of the present invention.
[0058] Figure 3 This is a schematic diagram of the radial elemental composition distribution of the gradient metal bonding phase layer in Embodiment 4 of the present invention.
[0059] Figure 4 This is a SEM cross-sectional image of the powder particles obtained in Example 1 of the present invention.
[0060] Figure 5 This is an EDS line scan analysis image of the powder particles obtained in Example 1 of the present invention.
[0061] Figure 6 The image shows the microstructure of SLM parts prepared using the cemented carbide powder obtained in Example 1 and Comparative Example 1 of this invention.
[0062] Explanation of reference numerals in the attached figures: 100, graded functional cemented carbide powder; 101, tungsten carbide (WC) core; 102, graded metal binder phase layer; 103, tungsten-rich cobalt alloy wetting layer; 104, Co-W-Ni ternary alloy transition layer; 105, nickel-rich cobalt alloy molten layer. Detailed Implementation
[0063] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available. Unless otherwise specified, the same parameter value is the same in all embodiments. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0064] In the description of this invention, references to terms such as "some embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0065] In the description of this invention, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.
[0066] In some embodiments of the present invention, the mass fractions of tungsten and nickel in the Co-W-Ni ternary alloy transition layer vary in a gradient along the radial direction, specifically C W (r) The distribution of radial position r follows the following relationship: , The mass fractions of tungsten and nickel exhibit a gradient power function relationship with their corresponding positional distributions. The design principle, basis, and calculation method of this relationship are explained below: 1. The principle and basis of the formula: The power function relationship described in this invention is one of the standard mathematical models used in the field of functionally graded materials to describe the continuous variation of material composition along a specific direction. Its principle lies in: A smooth, continuous transition of the binder phase composition is achieved from the inner tungsten-rich cobalt alloy (wetting layer) to the outer nickel-rich cobalt alloy (melting layer). This gradient distribution aims to eliminate interfacial stress concentration caused by abrupt compositional changes in traditional multilayer coatings, improve coating stability and bonding strength with the core, and optimize melting behavior during the SLM process.
[0067] power function It allows for flexible control over the rate of gradient change and the shape of the curve. This is achieved by adjusting the gradient exponent. and The value of can achieve a linear gradient ( ), convex gradient ( ) or concave gradient ( This allows for precise control of material properties (such as coefficient of thermal expansion, melting point, and wettability) to achieve optimal SLM forming results. The model is based on the fundamental theory of FGM design in materials science.
[0068] 2. Calculation method of the formula: The formula in this invention is a normalized power function form, the purpose of which is to clearly express the radial position of the component within the transition layer. and outer radial position The changing patterns between them.
[0069] For the mass fraction of tungsten :
[0070] when hour, ,but (Tungsten content is the highest, and it is connected to the wetting layer).
[0071] when hour, ,but (The tungsten content is the lowest, and it is connected to the molten layer).
[0072] For the mass fraction of nickel :
[0073] when hour, ,but (Minimum nickel content, connected to the wetting layer).
[0074] when hour, ,but (It has the highest nickel content and is connected to the molten layer).
[0075] Therefore, the formula in this invention accurately describes the tungsten content from the inside. The content continuously decreases to 0 on the outer side, while the nickel content continuously increases from 0 on the inner side to 0 on the outer side. The gradient change process.
[0076] Example 1 This example provides a graded functional cemented carbide powder with the following structure: Figure 1 As shown, the powder particle 100 has a core-shell structure, consisting of a tungsten carbide (WC) core 101 and a gradient metallic binder layer 102 covering it. The WC core 101 is made of spherical tungsten carbide powder with an average particle size of 5 micrometers. The gradient metallic binder layer 102 has a total thickness of 5 micrometers, and from the inside out, it consists of a tungsten-rich cobalt alloy wetting layer 103, a Co-W-Ni ternary alloy transition layer 104, and a nickel-rich cobalt alloy melting layer 105. In the Co-W-Ni ternary alloy transition layer 104, the mass content of tungsten and nickel exhibits a continuous reverse gradient along the radial direction.
[0077] The tungsten-rich cobalt alloy wetting layer 103 is a tungsten-rich cobalt alloy with a thickness of 1 micrometer, wherein the mass fraction of tungsten is 10%. This wetting layer has excellent chemical affinity and wettability with the WC core 101, ensuring a stable interfacial bond between the two.
[0078] The nickel-cobalt alloy melt layer 105 is a nickel-cobalt alloy with a thickness of 1 micrometer, in which the mass fraction of nickel is 30%. This melt layer has a low melting point and good high-temperature fluidity, which is beneficial for the rapid formation of a molten pool and filling of interparticle gaps during the SLM process.
[0079] The Co-W-Ni ternary alloy transition layer 104, with a thickness of 3 micrometers, is located between the tungsten-rich cobalt alloy wetting layer 103 and the nickel-rich cobalt alloy molten layer 105. In this layer, the mass fraction of tungsten smoothly decreases from 10% on the inner side to 0% on the outer side, while the mass fraction of nickel smoothly increases from 0% on the inner side to 30% on the outer side, with corresponding variations in cobalt content. Its compositional distribution follows a specific power function relationship, where the gradient exponent n1 for tungsten is 1 and the gradient exponent n2 for nickel is 1.2. This achieves a smooth transition in composition and properties from the wetting layer to the molten layer, avoiding interfacial stress concentration caused by abrupt changes in composition.
[0080] This embodiment also provides a method for preparing the above-mentioned powder, such as... Figure 2 As shown, the specific steps are as follows: Step S301: Pre-treat spherical tungsten carbide powder with an average particle size of 5 micrometers, including reduction treatment at 500 degrees Celsius in a hydrogen atmosphere to remove surface oxides, followed by drying.
[0081] Step S302: The pretreated tungsten carbide powder is loaded into a fluidized bed chemical vapor deposition (FB-CVD) reactor. Argon gas is introduced as the fluidizing gas, and the gas flow rate is controlled to keep the powder in a bubbling fluidized state. The reactor is then heated to 750 degrees Celsius.
[0082] Step S303: Deposit tungsten-rich cobalt alloy wetting layer 103. A first set of precursor gases containing carbonyl tungsten (W(CO)6) and carbonyl cobalt (Co(CO)3NO) is introduced into the reactor. The flow rate ratio of the two gases is precisely controlled so that the mass fraction of tungsten in the deposited tungsten-rich cobalt alloy is 10%. Deposition continues until the coating thickness reaches 1 micrometer.
[0083] Step S304: Deposit the Co-W-Ni ternary alloy transition layer 104. Using a program control unit, while keeping the cobalt carbonyl flow rate essentially constant, the tungsten carbonyl flow rate is gradually decreased according to a preset power function relationship (n1=1, n2=1.2), while the nickel carbonyl (Ni(CO)4) flow rate is gradually increased simultaneously. By precisely controlling the fluctuations in the flow rates of the two precursors, the coating composition smoothly transitions from a tungsten-rich cobalt alloy to a nickel-rich cobalt alloy, continuing deposition until the transition layer thickness reaches 3 micrometers.
[0084] Step S305: Deposit nickel-cobalt alloy molten layer 105. Completely stop the introduction of carbonyl tungsten, continue to introduce carbonyl cobalt and carbonyl nickel, control the flow rate ratio so that the mass fraction of nickel in the deposited nickel-cobalt alloy is 30%, and continue deposition until the molten layer thickness reaches 1 micrometer.
[0085] Step S306: After deposition, stop the introduction of all precursor gases, cool the reactor to room temperature under argon protection, and remove the powder to obtain the gradient functional cemented carbide powder of the present invention.
[0086] Example 2 This example provides a graded functional cemented carbide powder, which is basically the same as that in Example 1, except that: the average particle size of the WC core is 1 micrometer, the total thickness of the graded metal binder layer 102 is 3 micrometers, including a wetting layer thickness of 0.5 micrometers, a transition layer thickness of 2 micrometers, and a molten layer thickness of 0.5 micrometers. The mass fraction of tungsten in the wetting layer is 15%, and the mass fraction of nickel in the molten layer is 40%. The gradient index n1 of tungsten in the transition layer is 1.5, and the gradient index n2 of nickel is 1.8. The reactor temperature during preparation is 800 degrees Celsius.
[0087] Example 3 This example provides a gradient functional cemented carbide powder, which is basically the same as that in Example 1, except that: the average particle size of the WC core 101 is 10 micrometers, the total thickness of the gradient metal binder layer 102 is 8 micrometers, including a 2-micrometer wetting layer, a 4-micrometer transition layer, and a 2-micrometer molten layer. The mass fraction of tungsten in the wetting layer is 5%, and the mass fraction of nickel in the molten layer is 20%. The gradient index n1 of tungsten in the transition layer is 0.8, and the gradient index n2 of nickel is 1.0. The reactor temperature during preparation is 700 degrees Celsius.
[0088] Example 4 This example provides a gradient functional cemented carbide powder, which is basically the same as that in Example 1, except that: the total thickness of the gradient metal binder layer 102 is 1.5 micrometers, and the thicknesses of the tungsten-rich cobalt alloy wetting layer 103, the Co-W-Ni ternary alloy transition layer 104, and the nickel-rich cobalt alloy melting layer 105 are 1:5:4. Specifically, the mass content of tungsten and nickel in the Co-W-Ni ternary alloy transition layer 104 exhibits a continuous reverse gradient change along the radial direction, as detailed below. Figure 3 As shown.
[0089] Comparative Example 1 This example provides a cemented carbide powder, specifically WC-12Co powder prepared by a conventional ball milling mixing method.
[0090] Comparative Example 2 This example provides a cemented carbide powder, specifically a powder in which a 12% mass fraction Ni layer is coated onto the surface of WC powder using a single chemical nickel plating method.
[0091] Test case The cemented carbide powders prepared in Examples 1-4 and Comparative Examples 1-2 were used in SLM additive manufacturing experiments. Specifically, cubic samples with dimensions of 10 mm × 10 mm × 10 mm were prepared using the same SLM process parameters (laser power 350 W, scanning speed 800 mm / s, layer thickness 30 μm, scanning spacing 80 μm). The density (Archimedes displacement method, referring to GB / T 3850-2015 "Method for Determination of Density of Dense Sintered Metallic Materials and Cemented Carbide"), microstructure (SEM-EDS), and Vickers hardness (micro Vickers hardness tester, 10 kgf) of the samples were tested. The test results of Examples 1-3 and Comparative Examples 1-2 are shown in Table 1 below: Table 1
[0092] As can be seen from the data in the table above, the SLM samples prepared using the gradient functionalized cemented carbide powder provided by this invention have significantly higher densities than those prepared using traditional mixed powders and single-coated powders, and show no obvious internal cracks. Microstructural observation revealed that the WC grain size growth in the samples prepared by this invention was effectively controlled, with no significant coarsening and no obvious η-phase formation. Therefore, its Vickers hardness is also much higher than that of the comparative samples. The experimental results fully demonstrate the significant advantages of the technical solution of this invention in suppressing SLM forming defects, improving microstructure, and enhancing mechanical properties; at the same time, it also proves that the powder of this invention can effectively suppress the decomposition and coarsening of tungsten carbide during selective laser melting, resulting in dense, high-performance cemented carbide parts.
[0093] The SEM cross-sectional image and EDS line scan analysis image of the powder particles obtained in Example 1 are shown below. Figure 4 and 5 As shown in the figure, the prepared powder particles have a three-layer gradient structure consisting of a WC core and an outer layer, and the radial variation trends of W, Ni, and Co elements in the powder particles are consistent with the design. This indicates that the operation steps of the present invention can successfully prepare cemented carbide powder with a gradient coating. The test results of other embodiments are similar, and are not shown one by one to avoid redundancy.
[0094] The microstructure of SLM parts prepared using the cemented carbide powders obtained in Example 1 and Comparative Example 1 of this invention is as follows: Figure 6 As shown. From Figure 6As can be seen from the microstructure, the SLM part prepared using gradient functional cemented carbide powder in Example 1 of this invention exhibits a uniform and dense microstructure, with uniform WC grain distribution, no obvious grain coarsening, and no obvious cracks or pores. In contrast, the SLM part prepared using conventional WC-12Co mixed powder in Comparative Example 1 shows significant microstructural defects, including WC grain coarsening, the formation of brittle η phase, and metallurgical defects such as internal microcracks and pores. This demonstrates the significant advantages of the gradient functional cemented carbide powder of this invention in suppressing WC decomposition, preventing grain coarsening, and reducing metallurgical defects, verifying the effectiveness of the gradient coating design.
[0095] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.
Claims
1. A graded functional cemented carbide powder, characterized in that: It includes a tungsten carbide core and a gradient metal binder layer covering the tungsten carbide core. The gradient metal binder layer includes, from the inside to the outside, a tungsten-rich cobalt alloy wetting layer, a Co-W-Ni ternary alloy transition layer and a nickel-rich cobalt alloy melting layer. In the Co-W-Ni ternary alloy transition layer, the mass content of tungsten and nickel changes in a continuous reverse gradient along the radial direction.
2. The graded functional cemented carbide powder according to claim 1, characterized in that: The tungsten-rich cobalt alloy wetting layer is directly adjacent to a tungsten carbide core; and / or, the tungsten mass content of the Co-W-Ni ternary alloy transition layer decreases radially from the inside to the outside, and the nickel mass content increases radially from the outside to the inside.
3. The graded functional cemented carbide powder according to claim 1, characterized in that: The wetted layer contains 3% to 20% tungsten by mass; and / or the molten layer contains 15% to 50% nickel by mass.
4. The graded functional cemented carbide powder according to claim 1, characterized in that: The tungsten content in the transition layer of the Co-W-Ni ternary alloy decreases from 10% to 0% radially from the inside to the outside, while the nickel content increases from 0% to 30% radially from the outside to the inside, with the balance being Co.
5. The graded functional cemented carbide powder according to claim 1, characterized in that: The mass fraction C of the tungsten in the Co-W-Ni ternary alloy transition layer W (r) The distribution of radial position r follows the following relationship: In the formula, r inner r represents the inner radial position of the Co-W-Ni ternary alloy transition layer. outer The outer radial position of the Co-W-Ni ternary alloy transition layer, C W,inner For the Co-W-Ni ternary alloy transition layer in r inner The tungsten mass fraction at the given point, where n1 is the gradient exponent, ranging from 0.5 to 3; And / or, the mass fraction of nickel in the Co-W-Ni ternary alloy transition layer The distribution of radial position r follows the following relationship: In the formula, The inner radial position of the Co-W-Ni ternary alloy transition layer. The outer radial position of the Co-W-Ni ternary alloy transition layer, C Ni,outer For the Co-W-Ni ternary alloy transition layer in r outer The nickel mass fraction at the given point, where n2 is the gradient exponent, ranging from 0.5 to 3.
6. The graded functional cemented carbide powder according to claim 1, characterized in that: The average particle size of the tungsten carbide core is 0.5 to 15 micrometers; and / or the total thickness of the gradient metal bonded phase layer is 2 to 12 micrometers.
7. A method for preparing graded functional cemented carbide powder as described in any one of claims 1 to 6, characterized in that... Includes the following steps: A tungsten carbide particle is placed in a fluidized state, and a gradient metal binder phase layer is formed on the surface of the tungsten carbide particle by chemical vapor deposition; wherein the chemical vapor deposition process includes, in sequence, a tungsten-rich cobalt alloy wetting layer deposition step, a Co-W-Ni ternary alloy transition layer deposition step, and a nickel-rich cobalt alloy melting layer deposition step.
8. An apparatus for preparing graded functional cemented carbide powder as described in any one of claims 1 to 6, characterized in that: The system includes a fluidized bed reactor and a gas supply system connected to the fluidized bed reactor. The gas supply system is connected to a flow control system and a program control unit, and the program control unit is used to control the flow control system.
9. The application of the graded functional cemented carbide powder as described in any one of claims 1 to 6 in selective laser melting additive manufacturing.
10. An article, characterized in that: The raw materials for preparing at least some components of the article include graded functional cemented carbide powder as described in any one of claims 1 to 6, and the article includes cutting tools, mining and oil drilling tools, molds or wear-resistant parts.