Design / preparation method and application of corrosion-resistant multi-principal-element binder phase cemented carbide

Abstract

The application discloses a design / preparation method and application of a corrosion-resistant multi-principal-element binder phase hard alloy. The design method comprises the following steps: obtaining a target corrosive service environment, and formulating a target hard alloy system; establishing a phase diagram thermodynamic database; performing Pourbaix diagram calculation to obtain a presumed corrosion product and an immune region and a passivation region, and selecting a multi-principal-element alloy as a binder phase; performing phase diagram calculation to obtain phase composition and phase parameters; and taking the multi-principal-element alloy, the phase composition and the phase parameters as design outputs. The design method provided by the application can clearly determine the element composition and phase structure in the binder phase, uses the Pourbaix diagram and the phase diagram to guide the design of a reasonable corrosion-resistant hard alloy preparation process, improves the preparation efficiency of the hard alloy, and establishes an internal connection among the composition-structure-performance of the corrosion-resistant hard alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of cemented carbide, and in particular to a design / preparation method and application of a corrosion-resistant multi-principal-element binder phase cemented carbide. Background Art

[0002] Currently, the increasing demand for energy has promoted deep drilling activities in the continental and oceanic crusts, posing new challenges to the durability of drilling tools. Cemented carbide is widely used in marine drilling equipment due to its high hardness, wear resistance, heat resistance, and corrosion resistance. For typical WC-Co cemented carbide, excessive corrosion may lead to damage to the bonding phase, destroying the overall structural integrity, resulting in reduced strength and premature fracture of the carbide skeleton. Therefore, optimizing the corrosion resistance of cemented carbide is crucial to ensure the service life of drilling components. The corrosion behavior of cemented carbide is affected by the phase structure and chemical composition of the metal bonding phase. In recent years, multi-principal element alloys have attracted much attention due to their excellent corrosion resistance due to the combination of the benefits of controlled phase structure (such as FCC) and chemical composition (such as Cr) on surface passivation. CoCrNi multi-principal element alloys have good corrosion resistance and strong toughness, but their application as a bonding phase in cemented carbide has not been studied. Co, as a traditional binder phase, provides good wettability and bonding, Ni offers greater ductility and corrosion resistance, Cr offers better oxidation and corrosion resistance, and the CoCrNi alloy binder phase exhibits good wettability with the hard phase WC. Therefore, the introduction of a CoCrNi multi-component alloy as a binder phase into cemented carbide systems is considered to enhance the corrosion resistance of cemented carbide.

[0003] The corrosion behavior of cemented carbide is also related to the corrosive medium. Different corrosive environments will result in differences in corrosion mechanisms and corrosion products. It is well known that for the corrosion of typical WC-Co cemented carbide, Co is easily soluble in acidic and neutral solutions, while WC is relatively stable and not prone to corrosion. In alkaline solutions, there is no consensus on the dissolution process of Co and WC. In addition, the formation of passivation film in the corrosive medium will also affect the corrosion resistance of cemented carbide. In the preparation process of corrosion-resistant cemented carbide, it is difficult to obtain satisfactory results by simply adding elements. Therefore, it is crucial to rationally design cemented carbide by introducing a new multi-element bonding phase and combining it with theoretical calculations. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a design / preparation method and application of a corrosion-resistant multi-principal-element binder phase cemented carbide.

[0005] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0006] In a first aspect, the present invention provides a design method for a corrosion-resistant multi-principal-element binder phase cemented carbide, comprising:

[0007] Obtaining a target corrosive service environment, and formulating a target cemented carbide system according to the target corrosive service environment, wherein the target cemented carbide system includes hard elements corresponding to hardness and bonding elements corresponding to bonding;

[0008] Establishing a phase diagram thermodynamic database of the target cemented carbide system;

[0009] performing a Pourbaix diagram calculation on the target cemented carbide system based on the phase diagram thermodynamic database to obtain inferred corrosion products of the target cemented carbide system under the target corrosive service environment and immune zones and passivation zones corresponding to the inferred corrosion products, and selecting a multi-principal alloy as a bonding phase from the bonding elements;

[0010] performing a phase diagram calculation on the target cemented carbide system according to the phase diagram thermodynamic database to obtain phase composition and phase parameters, wherein the phase composition includes the ratio of the bonding elements and the ratio of the hard phase to the bonding phase, and the phase parameters include heat treatment temperature;

[0011] The multi-principal component alloy, phase composition and phase parameters are used as design outputs for the corrosion-resistant multi-principal component bonding phase cemented carbide.

[0012] In a second aspect, the present invention further provides a method for preparing a corrosion-resistant multi-principal-element binder phase cemented carbide, comprising:

[0013] The above design method is used to obtain the design output under the target corrosive service environment;

[0014] According to the design output, a corrosion-resistant multi-principal-element bonding phase cemented carbide is prepared.

[0015] In a third aspect, the present invention further provides the use of the corrosion-resistant multi-principal-element binder phase cemented carbide prepared by the above preparation method in the manufacture of marine drilling equipment.

[0016] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least:

[0017] The technical solution provided by the present invention establishes a thermodynamic database and a method for calculating Pourbaix diagrams and phase diagrams based on the electrochemical Nernst equation. It predicts possible corrosion products, corrosion-immune zones, and passivation zones, and verifies these predictions through micro-area electrochemical experiments. The optimal multi-principal component bonding phase is selected based on the basic electrochemical corrosion characteristics of cemented carbides with different bonding phases, thereby obtaining a multi-principal component bonding phase WC-based cemented carbide with excellent corrosion resistance. The provided design method can clarify the elemental composition and phase structure of the bonding phase, and uses the Pourbaix diagram and phase diagram to guide the design of a reasonable corrosion-resistant cemented carbide preparation process, thereby improving the preparation efficiency of the cemented carbide and establishing the intrinsic relationship between the composition, structure, and performance of the corrosion-resistant cemented carbide. Micro-area electrochemical testing is used to verify and provide a basis for the efficient design of cemented carbides with improved corrosion resistance, guiding the design and preparation of high-performance corrosion-resistant multi-principal component cemented carbides from the perspective of corrosion product prediction.

[0018] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of this application and implement them according to the contents of the specification, the following is an explanation of the preferred embodiments of the present invention with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the process of designing and verifying a corrosion-resistant multi-principal-element binder phase cemented carbide according to a typical embodiment of the present invention;

[0020] Figure 2a This is a Pourbaix diagram of a W-Co system at different electrode potentials and pH values ​​provided by a typical embodiment of the present invention;

[0021] Figure 2b This is a Pourbaix diagram of a W-Co-Cr-Ni system at different electrode potentials and pH values ​​provided by a typical embodiment of the present invention;

[0022] Figure 3 It is a vertical cross-sectional diagram of the composition of the W-Co-Cr-Ni-C system at different temperatures according to a typical embodiment of the present invention;

[0023] Figure 4a -g is a composition and structure diagram corresponding to the TEM of a WC-CoCrNi system cemented carbide prepared in a typical embodiment of the present invention;

[0024] Figure 5a This is a SVET test graph of a WC-CoCrNi system in 3.5% NaCl at pH = 10 provided by a typical embodiment of the present invention;

[0025] Figure 5b This is a typical embodiment of the present invention provided by the comparison of the classic WC-Co system cemented carbide sample in 3.5% NaCl at pH = 10 SVET test graph

[0026] Figure 5c This is a LEIS test graph of a WC-CoCrNi system in 3.5% NaCl at pH = 10, provided by a typical embodiment of the present invention;

[0027] Figure 5d This is a LEIS test chart of a comparative classic WC-Co system cemented carbide sample in 3.5% NaCl at pH = 10, provided by a typical embodiment of the present invention. DETAILED DESCRIPTION

[0028] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0030] In the field of cemented carbide preparation, some existing technologies use traditional enumeration methods to prepare corrosion-resistant cemented carbide with excellent performance. For example, Chinese invention patent publication number CN101974715A discloses a WC-Co cemented carbide and its preparation method. This method is mainly targeted at WC cemented carbide, in which the traditional binder phase Co is used, mixed with a small amount of Y powder. It provides a reference for the preparation process of cemented carbide, but cannot systematically adjust or redesign the corresponding alloy for different corrosion-resistant environments. Chinese invention patent publication number CN102031436A discloses a method for improving the corrosion resistance of WC-Co cemented carbide by introducing rare earth components to enhance the corrosion resistance, but does not explain the material design, and the corrosion detection method is relatively traditional, without revealing the corrosion mechanism and the fundamental reason for the improvement in corrosion resistance.

[0031] Therefore, based on the existing research in this field, the present invention realizes the integration of WC cemented carbide material system design and preparation by combining theoretical calculations with micro-area characterization methods, aiming to achieve low-cost, efficient and rapid material design.

[0032] The purpose of the present invention is to provide a design and verification method for a corrosion-resistant multi-principal-element binder phase cemented carbide.

[0033] Cemented carbide is mainly composed of a hard phase and a binder phase. When cemented carbide composite materials are in a corrosive service environment, due to the difference in potential between the binder phase and the hard phase, the two are prone to galvanic corrosion, which causes the binder phase to corrode and dissolve. The hard phase's role as a skeleton support is weakened, which ultimately affects the performance match between the hard phase and the binder phase, leading to failure. Corrosion-resistant multi-principal alloys are introduced as a binder phase to improve the overall corrosion resistance of cemented carbide and improve the shortcoming of traditional cemented carbide's short service life in corrosive environments. The Pourbaix diagram is a reliable tool for studying the corrosion characteristics of material alloys. Using Pourbaix calculations to guide experiments can help speed up material design and make up for the shortcomings of intelligent design of corrosion-resistant cemented carbide materials.

[0034] In addition, using the CALpHAD method to calculate the phase diagram can further accelerate the design of cemented carbide materials. The phase structure of the binder phase also affects the corrosion resistance. The phase diagram guides the reasonable phase range and sintering temperature during the sample preparation process.

[0035] Based on the above technical concept, see Figure 1 As shown, an embodiment of the present invention provides a design method for a corrosion-resistant multi-principal-element binder phase cemented carbide, which includes the following steps:

[0036] Obtaining a target corrosive service environment, and formulating a target cemented carbide system according to the target corrosive service environment, wherein the target cemented carbide system includes hard elements corresponding to hardness and bonding elements corresponding to bonding;

[0037] Establishing a phase diagram thermodynamic database of the target cemented carbide system;

[0038] performing a Pourbaix diagram calculation on the target cemented carbide system based on the phase diagram thermodynamic database to obtain inferred corrosion products of the target cemented carbide system under the target corrosive service environment and immune zones and passivation zones corresponding to the inferred corrosion products, and selecting a multi-principal alloy as a bonding phase from the bonding elements;

[0039] performing a phase diagram calculation on the target cemented carbide system according to the phase diagram thermodynamic database to obtain phase composition and phase parameters, wherein the phase composition includes the ratio of the bonding elements and the ratio of the hard phase to the bonding phase, and the phase parameters include heat treatment temperature;

[0040] The multi-principal component alloy, phase composition and phase parameters are used as design outputs for the corrosion-resistant multi-principal component bonding phase cemented carbide.

[0041] As a typical application example, the overall design method described above can be implemented in the following steps:

[0042] (1) Select the type of binder phase elements in the multi-principal alloy according to the corrosive service environment and determine the target cemented carbide system;

[0043] (2) establishing a phase diagram thermodynamic database of the target cemented carbide system;

[0044] (3) performing a Pourbaix diagram calculation based on the thermodynamic database to obtain a relationship diagram between the potential and pH of the corresponding system and the immune zone and passivation zone corresponding to the corrosion product;

[0045] (4) Based on the constructed thermodynamic database of cemented carbide system, phase diagram calculation is performed to obtain the composition range corresponding to different phase compositions.

[0046] In a more specific application example, the WC-Co-Cr-Ni quinary system is used as an example. The present invention addresses the corrosion-resistant WC cemented carbide system, which comprises a WC hard phase with excellent toughness and strength, and a CoCrNi binder phase with excellent corrosion resistance. This system forms a thermodynamic database for the quinary system containing the five elements W, C, Co, Cr, and Ni. Based on this established database and incorporating the CALpHAD method, a corrosion-resistant WC cemented carbide system was designed.

[0047] Regarding the specific optional range of elements, in some embodiments, the hard elements include any combination of W, Ti, C, and N.

[0048] In some embodiments, the bonding element includes any combination of Co, Cr, Ni, Fe, Al, and Mn.

[0049] Furthermore, regarding how to guide the design based on the Pourbaix diagram and phase diagram, in some embodiments, the selection rules for the multi-principal alloy specifically include:

[0050] Select the required hard phase and binder phase elements and their proportions according to the applicable environment;

[0051] The immune area and passivation area of ​​the system are obtained by calculating the Pourbaix diagram;

[0052] The immune zone is the non-corrosion area (blue) in the thermodynamically stable state below the equilibrium line of the Pourbaix diagram. The larger the immune zone, the stronger the material's ability to resist corrosion and the better its corrosion resistance.

[0053] The passivation zone is the area where corrosion products of oxides and hydroxides are generated (orange). Since an insoluble, dense protective film is formed on the metal surface in the passivation zone, it provides a certain degree of protection for the sample surface and can also greatly reduce metal corrosion. A large passivation zone (the passivation film can be generated in a wider range of pH and potential, which is more conducive to protecting the sample surface) is beneficial to the corrosion resistance of the material.

[0054] Compare the Pourbaix plots of different systems to predict their corrosion resistance, and select one or more samples with relatively larger immune and / or passive zones.

[0055] In some embodiments, the selection rules of phase composition and phase parameters specifically include:

[0056] Calculate the phase diagram based on the corresponding system composition;

[0057] Based on the phase diagram calculation results, the normal structure of cemented carbide, WC+γ, is selected to avoid the adverse effects of abnormal structures (carbide, graphite phase) on the performance of cemented carbide;

[0058] Since the phase diagram calculation results show that there is no region containing only WC + γ, the C content closest to the carbon-poor phase to graphite phase transformation line is selected to avoid the influence of carbides as much as possible;

[0059] The liquidus of the corresponding system is determined based on the phase diagram calculation results to guide the determination of the sintering temperature.

[0060] In addition, regarding the process of establishing the Pourbaix diagram and the phase diagram, in some embodiments, the process of establishing the phase diagram thermodynamic database may specifically include:

[0061] Acquiring thermodynamic data of a low-element system, where the elements in the low-element system are part of the elements in the target cemented carbide system;

[0062] Establishing a thermodynamic model to calculate the Gibbs free energy of multiple phases in the low-element system;

[0063] All calculation results are integrated and expanded to form a phase diagram thermodynamic database of the target cemented carbide system.

[0064] Still taking the WC-Co-Cr-Ni quinary system as an example, step (2) above may specifically include:

[0065] (2-1) collecting thermodynamic data of all pure components, binary components, and ternary components of the target cemented carbide system;

[0066] (2-2) Evaluate and screen the collected thermodynamic data;

[0067] (2-3) Based on reliable experimental phase diagrams and thermodynamic information, select appropriate thermodynamic models to describe the Gibbs free energy of different phases;

[0068] (2-4) By integrating the above-evaluated thermodynamic parameters and making reasonable extrapolations, a self-consistent thermodynamic database of the Co-Cr-Ni-WC quinary system phase diagram was obtained.

[0069] In the above process, the thermodynamic database of pure component, binary system, ternary system and other systems of the target cemented carbide system is first collected; then the system phase diagram is drawn from low to high based on the phase diagram calculation method, and compared and corrected. After evaluation and optimization, all the above parameters are organically integrated until a reliable Co-Cr-Ni-WC five-element thermodynamic database of the target cemented carbide is obtained.

[0070] In some embodiments, the process of calculating the Pourbaix diagram specifically includes:

[0071] Importing the phase diagram thermodynamic database into the calculation software, using the point calculation module to input the target composition of the target cemented carbide system, and obtaining the chemical potential corresponding to each element in the target composition;

[0072] Based on the Gibbs free energy of pure elements, the energy difference of each element in the target component is obtained through the electrochemical reaction equation and the Nernst equation and converted into a potential difference value;

[0073] A multivariate Pourbaix diagram is obtained based on superimposed pure element Pourbaix diagrams, the change in Gibbs free energy caused by alloying is calculated, and the immune region and the passivation region of the multivariate Pourbaix diagram are delineated.

[0074] The specific exemplary process of the above steps is:

[0075] Calculating the single element Pourbaix diagram involved in the target cemented carbide system by combining the thermodynamic database and Pourbaix diagram calculation software;

[0076] The calculation process is to select the elements involved in the system, input the electrode potential range and temperature parameters, and output all possible products;

[0077] After selecting and optimizing the product, a single element Pourbaix diagram is generated;

[0078] Import the system thermodynamic database into the phase diagram calculation software, use the point calculation module to input the target component, and obtain the chemical potential corresponding to the single element of the target component. Based on the Gibbs free energy of the pure element, the energy difference of each element in the target component is obtained through the electrochemical reaction equation and the Nernst equation and converted into a potential difference value;

[0079] The Nernst equation is expressed as:

[0080] For any electrochemical reaction equation aA+bB=cC+dD

[0081]

[0082] Among them, E θ represents the standard electrode potential; R represents the gas constant 8.31441 J / (K.mol); T represents the temperature; n represents the number of electron transfers in the electrode reaction; F represents the Faraday constant 96.487 kJ / (V.mol);

[0083] The calculated potential difference value is brought into the Pourbaix diagram for correction;

[0084] The Pourbaix diagrams of different single elements obtained by the above method are superimposed to obtain the Pourbaix diagram of the target system.

[0085] Furthermore, in step (4) described above, the phase diagram of the target cemented carbide system can be calculated by combining the thermodynamic database and the phase diagram calculation software;

[0086] Then, the composition ranges of different binder phases of the target cemented carbide system under different conditions are calculated based on the phase diagram, such as Figure 2a and Figure 2b As shown;

[0087] Then, according to the relationship between the phase structure and the composition and temperature obtained from the phase diagram calculation results, the liquid phase sintering temperature and the carbon content range of the system are determined, such as Figure 3 As shown;

[0088] Finally, a cemented carbide sample was prepared by a powder metallurgy method based on the phase structure.

[0089] The structure of the prepared cemented carbide samples was verified and the corrosion electrochemical properties were tested, and finally the composition and preparation conditions of a corrosion-resistant multi-component bonding phase cemented carbide were determined.

[0090] The phase diagram intuitively reflects the relationship between the composition, temperature and structure of the reaction material. Starting from the expected structure and performance of the material, the phase relationship of the target cemented carbide system under different sintering temperatures and carbon contents is obtained based on the phase diagram calculation method. By selecting a reasonable composition range, the ideal corrosion-resistant cemented carbide can be efficiently screened.

[0091] In some embodiments, the design method may further include the following verification steps:

[0092] preparing a verification sample by powder sintering according to the multi-principal alloy, phase composition and phase parameters;

[0093] The micromorphology and corrosion pattern of the verification samples are characterized to verify the effectiveness of the design output.

[0094] In some embodiments, the characterization method of the micromorphology includes transmission electron microscopy observation, and the characterization method of the corrosion mode includes micro-electrochemical experiments. TEM analysis of the designed and prepared samples reveals the rationality of the design of the sample composition and structure. The micro-electrochemical experiment reveals the improvement of the electrochemical corrosion performance of the prepared samples from a microscopic scale, thereby guiding the development and design of corrosion-resistant cemented carbide. For example, based on the phase diagram of the thermodynamic database, the composition and structure of the cemented carbide system are calculated and predicted, and the composition and structure of the prepared cemented carbide system are verified by TEM. The galvanic corrosion relationship between the hard phase and the binder phase is measured using a micro-electrochemical test method, and the galvanic corrosion tendency is experimentally verified to reveal the improvement of the corrosion resistance of the sample.

[0095] A second aspect of the embodiments of the present invention further provides a method for preparing a corrosion-resistant multi-principal-element binder phase cemented carbide, comprising the following steps:

[0096] Using the design method provided in any of the above embodiments to obtain a design output under a target corrosive service environment;

[0097] According to the design output, a corrosion-resistant multi-principal-element bonding phase cemented carbide is prepared.

[0098] In some embodiments, the preparation method may specifically include:

[0099] preparing a binder phase powder and a hard phase powder according to the design output;

[0100] Mixing powder according to the ratio of hard phase and binder phase outputted by the design, ball milling and pressing to obtain cemented carbide block sintered blank;

[0101] The cemented carbide block sintered blank is vacuum sintered to obtain the corrosion-resistant multi-principal-element bonding phase cemented carbide.

[0102] As a specific example, the design and preparation process of a complete corrosion-resistant multi-principal element binder phase cemented carbide includes the following steps:

[0103] (1) Select a suitable multi-element alloy as the binder phase based on the Pourbaix diagram calculation;

[0104] (2) Determine the appropriate carbon content and sintering temperature based on the phase diagram;

[0105] (3) mixing the binder phase powder and the hard phase powder to obtain a mixed powder;

[0106] (4) wet-milling the mixed powder and pressing the mixed powder to obtain a cemented carbide block sintered blank;

[0107] (5) Cemented carbide samples were obtained by vacuum sintering.

[0108] Specific forming and sintering processes include:

[0109] By adding the binder phase powder and the hard phase powder to perform high energy ball milling, wherein the powder is selected from WC, CoCrNi, Co, C powder;

[0110] The pre-mixed powders were wet-milled, with alcohol as the milling medium, a ball-to-material mass ratio of 8:1N12:1, and a milling time of 10-20 hours;

[0111] The ball-milled powder is molded and sintered, the ball-milled mixed slurry is dried and sieved, and then pressed into shape at a pressing pressure of 120-180 MPa;

[0112] The maximum liquid phase sintering temperature is determined by the phase diagram and is kept at this temperature for 0.5 to 3 hours;

[0113] The complete typical preparation process is as follows:

[0114] WC, CoCrNi and Co powders were used to prepare cemented carbide, where the ratio of cemented carbide powder to binder phase powder was 8:2;

[0115] The mixed powder is added to the molding agent paraffin; and placed in a carbide ball mill with a ball-to-material mass ratio of 10:1, and alcohol is added as a ball milling medium, and the ball milling time is 16 hours;

[0116] The pressing pressure during the subsequent press-forming process was 150 MPa;

[0117] The maximum sintering temperature was determined to be 1450℃ according to the phase diagram and kept at that temperature for 90min to obtain the cemented carbide sample.

[0118] After preparing the sample, the composition and structure of the corresponding cemented carbide system can be predicted based on the constructed cemented carbide system thermodynamic database. Combined with the TEM characterization results of the prepared cemented carbide, the rationality of the thermodynamic database in predicting the cemented carbide system can be verified, thereby promoting the efficient design of the cemented carbide system.

[0119] The required electrochemical test solution pH and electrochemical test potential are selected in combination with the Pourbaix diagram; electrochemical tests are performed on cemented carbide samples to obtain the overall and corrosion kinetics information of the cemented carbide, evaluate its corrosion resistance, and verify the corrosion resistance of the cemented carbide.

[0120] In a typical embodiment of the present invention, a corrosion-resistant multi-principal-element binder phase cemented carbide is designed and the corrosion resistance of the cemented carbide sample is further verified. The composition and phase structure of the cemented carbide are fully considered. The Pourbaix diagram is used to calculate and predict the corrosion products of the corresponding cemented carbide system. The cemented carbide system that produces the target protective corrosion products is screened. The corrosion product prediction results of the WC-CoCrNi system correspond to the expansion of the immune zone and the generation of passivation corrosion products Cr2O3 and NiO. Figure 3 As shown, the phase structure of the cemented carbide system was preliminarily screened through phase diagram calculations combined with first-principles calculations. The phase diagram calculation results show that WC and FCC structures CoCrNi and the corresponding metal carbides are generated in the corresponding sintering temperature and composition ranges. The selected phase structure combined with the phase diagram composition range further guides the design of the experimental powder ratio. At the same time, combined with the powder metallurgy preparation method and electrochemical testing of corrosion resistance, the composition structure of the prepared cemented carbide was characterized by TEM, and the galvanic corrosion characteristics of the hard phase and binder phase were verified by micro-electrochemical testing. The design and rationality of the prepared cemented carbide system and the performance improvement revealed by Pourbaix calculations, phase diagram calculations, experimental design, powder metallurgy, TEM, and micro-electrochemical corrosion testing are of great significance to the design of new corrosion-resistant multi-principal component binder phase cemented carbides.

[0121] A third aspect of the present invention also provides for the application of the corrosion-resistant multi-component binder phase cemented carbide produced by the aforementioned preparation method in the manufacture of marine drilling equipment. For example, the technical solution provided by the present invention can produce a corrosion-resistant multi-component binder phase cemented carbide comprising a hard phase comprising WC and a binder phase comprising CoCrNi. The excellent compatibility and low corrosion tendency of the two phases provide excellent corrosion resistance suitable for future drilling environments. More importantly, the validation conditions for the corrosion-resistant multi-component binder phase cemented carbide are also determined based on the aforementioned design method.

[0122] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0123] Example 1

[0124] This embodiment illustrates the overall process of designing and experimentally verifying a corrosion-resistant multi-principal-element binder phase cemented carbide, as shown below:

[0125] (1) Determine the type of alloying elements based on the target multi-principal binder phase to obtain the target cemented carbide system;

[0126] (2) Establish a thermodynamic database for the target cemented carbide system;

[0127] (3) calculating the Pourbaix diagram of the W-Co-Cr-Ni system at different electrode potentials and pH values ​​based on the thermodynamic database to obtain the immune zone and the passivation zone;

[0128] (4) calculating a cemented carbide phase diagram based on the thermodynamic database W-Co-Cr-Ni-C to obtain composition intervals for different phase formations;

[0129] (5) Prepare cemented carbide samples by powder metallurgy method;

[0130] (6) Structural characterization and corrosion performance testing of the prepared cemented carbide samples;

[0131] (7) The composition structure of the cemented carbide system is calculated based on the phase diagram of the thermodynamic database, and the prepared cemented carbide system is verified by TEM;

[0132] (8) The galvanic corrosion relationship between the hard phase and the bonding phase was measured using a micro-area electrochemical test method. The galvanic corrosion relationship was experimentally verified to reveal the differences in the corrosion resistance of cemented carbide.

[0133] Regarding the implementation details, in step (1), the type and composition of the multi-component bonding phase alloy elements are determined according to the corrosion resistance of the target cemented carbide; by consulting relevant cemented carbide and its related thermodynamic calculation literature, the wetting relationship between the hard phase and the bonding phase is fully considered, and the electrochemical corrosion characteristics of the corresponding metal elements of the corresponding cemented carbide system are calculated, and a reasonable multi-component alloy is selected as the bonding phase to prepare the cemented carbide.

[0134] In step (2), the main steps for establishing the thermodynamic database of the target multi-component binder phase cemented carbide system are:

[0135] Step 2-1: Consult the literature to obtain specific thermodynamic data of binary, ternary and other low-element systems related to the target system, evaluate and screen the data in the literature, and discard unreliable data;

[0136] Step 2-2: Based on the obtained phase diagram, thermodynamic experimental information, and phase equilibrium conditions, combined with an appropriate thermodynamic model, determine the adjustable parameters, then optimize them using the least squares method to obtain appropriate parameter values. The obtained parameter values ​​are then used to calculate the phase diagram and thermodynamic data.

[0137] Step 2-3: Self-consistency verification, that is, from simple binary systems to complex multi-component systems, the phase diagram is calculated through the thermodynamic database to obtain the composition structure corresponding to the target system, and the parameters are modified through multiple evaluations and optimizations until a reliable and reasonable thermodynamic database of the target cemented carbide system is finally obtained.

[0138] Steps 2-4: Using the established thermodynamic database for multi-component systems, a phase diagram is constructed using pressure, temperature, and composition as variables. Different regions in the phase diagram correspond to different compositions and phases. Based on the correspondence between performance and structure, the composition of the corrosion-resistant cemented carbide can be rationally designed according to the phase diagram, thereby producing a cemented carbide with the desired structure and performance.

[0139] In step (3), thermodynamic calculation and Nernst equation are used to calculate the Pourbaix diagram of the corresponding system, predict the corrosion resistance of the cemented carbide system, and screen the composition of the corresponding multi-component alloy binder phase cemented carbide;

[0140] Step 3-1: Calculate the Gibbs free energy of the target cemented carbide system elements after solid solution by combining the thermodynamic database and phase diagram calculation software Pandat;

[0141] Step 3-2: Based on the Gibbs free energy of the corresponding element, the corrosion Pourbaix diagram of the corresponding system is calculated in combination with the Nernst equation. The Pourbaix diagram calculation process is to select the elements involved in the system, input the electrode potential range and temperature parameters, and output all possible products; after selecting and optimizing the products, a single-element Pourbaix diagram is generated, and the different single-element Pourbaix diagrams obtained by the above method are superimposed to obtain the Pourbaix diagram of the target system.

[0142] In step (4), the main steps to select a reasonable system phase interval are:

[0143] Step 4-1: Calculate the cemented carbide system phase diagram;

[0144] Step 4-2: Calculate the composition range of different carbon contents of cemented carbide system under different conditions based on the phase diagram;

[0145] Step 4-3: Determine the liquid phase sintering temperature and the corresponding sintering range based on the relationship between the phase structure, carbon content and temperature obtained from the phase diagram calculation results.

[0146] In step (5), a cemented carbide sample is prepared by a powder metallurgy method, the steps of which are:

[0147] Step 5-1: Determine the corresponding ratio of WC to the multi-principal alloy binder phase CoCrNi and the system carbon supplementation content according to the calculated phase interval;

[0148] Step 5-2: The ball-to-material mass ratio during the wet milling mixing process is 8:1 to 12:1, and the ball milling time is 10 to 20 hours;

[0149] Step 5-3: The pressing pressure during the pressing process is 120 to 180 MPa;

[0150] Step 5-4: The temperature of liquid phase sintering is determined according to the phase diagram, and the liquid phase sintering time is 1 to 2 hours;

[0151] Step 5-5: Combine the sample after liquid phase sintering with the phase diagram to obtain the cemented carbide in the corresponding phase range.

[0152] In step (6), the structure characterization and corrosion performance test of the prepared cemented carbide sample are carried out, and the steps are as follows:

[0153] Step 6-1: Prepare the sample and polish the sample surface to meet the requirements of subsequent morphology test and electrochemical corrosion test;

[0154] Step 6-2: Use TEM to verify the structural composition of the designed cemented carbide. Perform TEM testing on the prepared sample to characterize the internal structure and composition of the sample. Compare the compositional structure with the corresponding intervals obtained by the phase diagram calculation design to verify the rationality of the phase diagram calculation prediction design.

[0155] In step (7), the prepared cemented carbide sample is subjected to a micro-area electrochemical corrosion test, the steps of which are as follows:

[0156] Step 7-1: Place the prepared electrochemical sample in a micro-area electrochemical device for regional scanning to characterize the microscopic electrochemical corrosion performance of the micro-area and corresponding different components, and characterize the corrosion resistance of the corresponding multi-component alloy binder phase. This reveals the differences in corrosion resistance between different components at the micron scale.

[0157] Step 7-2: The sample surface was subjected to SVET (Scanning Vibrating Electrode Test) test and LEIS (Micro-area Electrochemical Impedance Test) test respectively. The micro-area electrochemical characterization results showed that the hard phase and bonding phase in the cemented carbide system had different corrosion current density and electrochemical impedance, which verified the galvanic corrosion effect and also reflected that the WC-CoCrNi system had better corrosion resistance.

[0158] Step 7-3: The current density and impedance information show a differential distribution between the hard phase and the bonding phase, verifying the galvanic corrosion effect on the surface. At the same time, the low corrosion current density and high impedance value of the bonding phase characterize the excellent corrosion resistance of the corresponding system.

[0159] Of course, the specific processes, means and items of material preparation and material characterization testing may be different from the above examples. All modified implementation methods that utilize the main design ideas are within the scope of the present invention.

[0160] Example 2

[0161] This embodiment utilizes the technical solution provided in Example 1 to illustrate a design method for a WC-CoCrNi corrosion-resistant multi-principal element binder phase cemented carbide, as shown below:

[0162] 1. Determine the type and composition of alloying elements based on the target cemented carbide's corrosion resistance. By reviewing relevant literature on corrosion-resistant cemented carbide and its design, and fully considering the wetting relationship between the hard phase and the binder phase, a reasonable multi-principal alloy binder phase is selected to prepare the cemented carbide. Because the prepared cemented carbide requires excellent corrosion resistance, the W-Co-Cr-Ni-C quinary system is selected as the target cemented carbide based on literature research.

[0163] 2. Consult the literature to obtain thermodynamic data related to the target system; the thermodynamic data of the known systems in this system are: based on the collected binary, ternary and even quaternary databases such as C-Co, C-Cr, CW, Co-W, Cr-W, C-Co-Cr, Co-Cr-W, C-Co-W, C-Ni-W, C-Co-Ni-W, etc., integrate them through the CALpHAD method based on the thermodynamic database, draw the phase diagram through Thermo-Ca1c software and verify the accuracy of the low-element database, compare the combined phase diagram with the original phase diagram, continue to consult the literature for correction until the drawn phase diagram is accurate; repeat the above verification process until the thermodynamic database of the W-Co-Cr-Ni-C quinary system is obtained.

[0164] 3. Based on the thermodynamic database, Pourbaix diagram calculations were performed. The Pourbaix diagram of the W-Co-Cr-Ni system was calculated using thermodynamic calculations and the Nernst equation. The immune and passivation zones of the system were determined, and the corrosion tendency was compared with that of the classic W-Co system. Based on the thermodynamic database and the Nernst equation, the energy difference between each element in the target component was calculated using the electrochemical reaction equation and the Nernst equation, with the Gibbs free energy of the pure element as the benchmark. The energy difference was converted into a potential difference to evaluate the galvanic corrosion tendency.

[0165] 4. Based on the thermodynamic database, the cemented carbide phase diagram was calculated using the phase diagram calculation software Pandat. By fixing the ratio of the hard phase to the binder phase and changing the carbon content of the system, a vertical interface phase diagram was obtained, in which the content of the hard phase WC was 80 wt.%, and the content of the binder phase CoCrNi was 20 wt.%. The composition ranges for the generation of various different phases in the multi-component alloy system were calculated, and the guiding range was screened based on the composition ranges and their corresponding phase structures.

[0166] 5. Use powder metallurgy method to prepare gold cemented carbide.

[0167] According to the expected structure of the binder phase, the required composition range of the binder phase is determined in combination with the phase diagram, and the powder ratio is determined according to the composition of this range.

[0168] By adding the binder phase powder and the hard phase powder for high energy ball milling;

[0169] Mix 80% WC powder with 20% CoCrNi and a trace amount of carbon black powder; add carbide grinding balls with a ball-to-material mass ratio of 10:1, and add alcohol as a ball milling medium. The ball milling time is 16 hours.

[0170] The mixed slurry after ball milling was dried and sieved, and then the pressing pressure in the pressing process was 150MPa;

[0171] The crushing sintering temperature was 1450℃ and kept at this temperature for 90min to obtain the cemented carbide sample;

[0172] 6. Conduct structural verification and corrosion resistance testing on the manufactured cemented carbide.

[0173] TEM was used to verify the composition and phase structure of the designed cemented carbide;

[0174] By selecting a simulated drilling fluid with a pH of 10 as the electrolyte, hoping to be applied in a drilling environment, corrosion experiments were carried out at 25°C using the electrochemical three-electrode technique.

[0175] Combined with the micro-area electrochemical test results, the galvanic corrosion differences and corrosion resistance of the sample surface are revealed, and the corrosion products on the sample surface calculated by Pourbaix and the corresponding corrosion resistance improvement are verified.

[0176] 7. Micro-area electrochemical experiments are used to experimentally verify the galvanic corrosion tendency.

[0177] The SVET technique was used to test the local corrosion current of the hard phase and bonding phase planes. The current difference between the hard phase and bonding phase of WC-CoCrNi and WC-Co samples was compared to intuitively obtain the corrosion rate between the hard phase and bonding phase.

[0178] The LEIS technology was used to test the local corrosion resistance of the hard phase and bonding phase planes. The impedance values ​​between the hard phase and bonding phase of WC-CoCrNi and WC-Co samples were compared respectively to intuitively obtain the corrosion resistance between the hard phase and bonding phase.

[0179] Based on the above embodiments, it can be clearly seen that the technical solution provided by the embodiments of the present invention, through the establishment of a thermodynamic database and a method based on Pourbaix calculation and phase diagram calculation, combined with a unique means of micro-area electrochemical characterization of the corrosion resistance of cemented carbide, evaluates and selects the basic characteristics and corrosion resistance of the bonding phase, obtains the optimal bonding phase composition structure corresponding to the cemented carbide system, and matches the optimal test conditions, thereby obtaining a closed loop between the design, preparation, and verification of multi-principal component corrosion-resistant cemented carbide materials. The provided design method can clarify the type of corrosion-resistant bonding phase, use Pourbaix diagram calculation and phase diagram calculation to guide the design of a reasonable cemented carbide preparation process, improve the research and development efficiency of corrosion-resistant cemented carbide, and enhance the understanding of the relationship between cemented carbide phase structure and performance through TEM testing and micro-area electrochemical verification.

[0180] The composition and structure of the prepared cemented carbide were obtained by TEM test, which corresponds to the system calculated by phase diagram, indicating the efficiency and rationality of the design of cemented carbide by phase diagram calculation. Figure 4a-4g The TEM results shown in the figure show that the composition structure of the corresponding cemented carbide system is consistent with the results of phase diagram calculation and prediction. Figure 4a and Figure 4e The high-angle annular dark field (HAADF) images of two different regions inside the WC-CoCrNi were characterized respectively. As shown in the figure, W elements and C elements are enriched in the WC region, and the elements contained in the CoCrNi binder phase are enriched in the binder phase region. Figure 4b and Figure 4f The high-resolution TEM (HR-TEM) images at the interface between WC and CoCrNi were characterized respectively, and the interplanar spacing of the WC hard phase was measured to be 0.25 nm, corresponding to the (100) crystal plane, and the d spacing of the CoCrNi binder phase was 0.20 nm, corresponding to the (111) crystal plane. Figure 4c 、 4d 4g and 4g are selected area electron diffraction (SAED) patterns of the CoCrNi binder phase, the WC hard phase, and the Cr3C, respectively, characterizing the FCC structure of the CoCrNi binder phase and the HCP structure of the WC particles. TEM characterization results demonstrate the efficiency and rationality of phase diagram calculation in designing cemented carbides.

[0181] Combined with micro-electrochemical technology, the microscopic corrosion dynamics information can be detected, which facilitates intuitive comparison of the bonding phase type and cemented carbide system with excellent corrosion resistance. The corrosion test results are as follows: Figure 5a-5d shown.

[0182] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A design method for corrosion-resistant multi-principal element binder phase cemented carbide, characterized in that: include: Obtaining a target corrosive service environment, and formulating a target cemented carbide system according to the target corrosive service environment, wherein the target cemented carbide system includes hard elements corresponding to hardness and bonding elements corresponding to bonding; Establishing a phase diagram thermodynamic database of the target cemented carbide system; performing a Pourbaix diagram calculation on the target cemented carbide system based on the phase diagram thermodynamic database to obtain inferred corrosion products of the target cemented carbide system under the target corrosive service environment and immune zones and passivation zones corresponding to the inferred corrosion products, and selecting a multi-principal alloy as a bonding phase from the bonding elements; performing a phase diagram calculation on the target cemented carbide system according to the phase diagram thermodynamic database to obtain phase composition and phase parameters, wherein the phase composition includes the ratio of the bonding elements and the ratio of the hard phase to the bonding phase, and the phase parameters include heat treatment temperature; The multi-principal component alloy, phase composition and phase parameters are used as design outputs for the corrosion-resistant multi-principal component bonding phase cemented carbide.

2. The design method according to claim 1, characterized in that: The hard elements include any combination of W, Ti, C, and N; And / or, the bonding element includes any combination of Co, Cr, Ni, Fe, Al, and Mn.

3. The design method according to claim 1, characterized in that: The selection rules of the multi-principal alloy specifically include: Selecting the required hard phase and binder phase element types and proportions according to the target corrosive service environment; The immune zone and passivation zone of the system are obtained by calculating the Pourbaix diagram. The immune zone is the thermodynamically stable non-corrosion region below the equilibrium line of the Pourbaix diagram. The passivation zone is the area where corrosion products of oxides and hydroxides are generated. The corrosion product film has a certain protective effect and reduces corrosion. In some embodiments, the selection rules of phase composition and phase parameters specifically include: Calculating a phase diagram based on the target cemented carbide system composition; Based on the phase diagram calculation results, the normal structure WC+γ area of ​​cemented carbide is selected; When the phase diagram calculation results show that there is no region containing only WC+y, the region with the C content closest to the transition line from the carbon-poor phase to the graphite phase is selected; The liquidus of the target cemented carbide system is determined based on the phase diagram calculation result, and the sintering temperature is determined based on the liquidus.

4. The design method according to claim 1, characterized in that: The process of establishing the phase diagram thermodynamic database specifically includes: Acquiring thermodynamic data of a low-element system, where the elements in the low-element system are part of the elements in the target cemented carbide system; Establishing a thermodynamic model to calculate the Gibbs free energy of multiple phases in the low-element system; All calculation results are integrated and expanded to form a phase diagram thermodynamic database of the target cemented carbide system.

5. The design method according to claim 1, characterized in that: The process of calculating the Pourbaix diagram specifically includes: Importing the phase diagram thermodynamic database into the calculation software, using the point calculation module to input the target composition of the target cemented carbide system, and obtaining the chemical potential corresponding to each element in the target composition; Based on the Gibbs free energy of pure elements, the energy difference of each element in the target component is obtained through the electrochemical reaction equation and the Nernst equation and converted into a potential difference value; A multivariate Pourbaix diagram is obtained based on superimposed pure element Pourbaix diagrams, the change in Gibbs free energy caused by alloying is calculated, and the immune region and the passivation region of the multivariate Pourbaix diagram are delineated.

6. The design method according to claim 1, characterized in that: Also includes: preparing a verification sample by powder sintering according to the multi-principal alloy, phase composition and phase parameters; The micromorphology and corrosion pattern of the verification samples are characterized to verify the effectiveness of the design output.

7. The design method according to claim 6, characterized in that: The characterization method of the micromorphology includes transmission electron microscopy observation, and the characterization method of the corrosion mode includes micro-area electrochemical experiment.

8. A method for preparing a corrosion-resistant multi-principal-element binder phase cemented carbide, characterized in that: include: Using the design method described in any one of claims 1 to 7 to obtain a design output in a target corrosive service environment; According to the design output, a corrosion-resistant multi-principal-element bonding phase cemented carbide is prepared.

9. The preparation method according to claim 8, characterized in that Specifically include: preparing a binder phase powder and a hard phase powder according to the design output; Mixing powder according to the ratio of hard phase and binder phase outputted by the design, ball milling and pressing to obtain cemented carbide block sintered blank; The cemented carbide block sintered blank is vacuum sintered to obtain the corrosion-resistant multi-principal-element bonding phase cemented carbide.

10. Use of the corrosion-resistant multi-principal-component binder phase cemented carbide prepared by the preparation method according to any one of claims 8 to 9 in the manufacture of marine drilling equipment.

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