Preparation method of CrFe-based hard alloy
By employing spark plasma sintering (SPS) technology and rapid sintering process, combined with an isolation layer design, the problems of binder phase loss and brittle phase in CrFe-based cemented carbide during induction plasma spheroidization were solved, resulting in the preparation of a high-performance WC-CrFe-based cemented carbide with excellent hardness and toughness.
Patent Information
- Application Number
- CN202511835968.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-08
- Publication Date
- 2026-03-06
AI Technical Summary
Induction plasma spheroidization technology has problems such as binder phase loss and WC decarburization forming brittle phase in the preparation of CrFe dual binder phase cemented carbide, which increases the difficulty of subsequent sintering process and makes it difficult to prepare cemented carbide with high comprehensive performance.
By employing spark plasma sintering (SPS) technology, combined with a sintering process that involves rapid heating and shortened heating and holding times, and by inserting pure carbon paper as an isolation layer between the graphite mold and the chromium-based powder, a segmented heating process and pressure control were designed to prepare CrFe-based cemented carbide.
A WC-CrFe-based cemented carbide with excellent comprehensive mechanical properties was successfully prepared, with a hardness HV10 of 2033±21 and a fracture toughness of 8.4±0.3 MPa·m1/2. The problems of binder phase loss and brittle phase in the induction plasma spheroidization process were solved, and the sintering of high-performance alloys was realized.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of cemented carbide preparation technology, and specifically to a method for preparing CrFe-based cemented carbide. Background Technology
[0002] The statements in this section provide only background information relevant to the disclosure of this application and may not constitute prior art.
[0003] Cemented carbide is a class of composite materials with excellent comprehensive properties, including high hardness, high wear resistance, good toughness, and stable chemical properties. It is widely used in many industrial fields such as cutting tools, mining drills, and mold making. This alloy consists of a hard phase (such as tungsten carbide (WC) and titanium carbide (TiC)) and a metallic binder phase (such as cobalt (Co, Ni, and Fe)). The hard phase particles are firmly bonded together by the binding effect of the cobalt and other binder phases, thus providing both high strength and good fracture toughness.
[0004] With the continuous development of modern industry, various sectors have placed higher and more diversified demands on the performance of cemented carbide tools, which has brought new challenges to cemented carbide development. To meet diversified market demands, overcome the shortcomings of traditional cobalt-based binders such as high cost and potential environmental hazards, and improve the performance of cemented carbide products, powder pretreatment has become a key step in its preparation process. Common powder spheroidization technologies include atomization, plasma rotating electrode method, and induction plasma spheroidization. Among them, induction plasma spheroidization, with its advantages of high temperature, high enthalpy, and controllable atmosphere, can prepare high-performance spherical powders with high sphericity, low impurity content, and narrow particle size distribution, and is particularly suitable for the preparation of high-melting-point metal spherical powders. Currently, there is limited research on inductive plasma spheroidization in the preparation of high-performance cemented carbide powders, and the focus is mainly on the preparation of spherical powders of traditional Co-based cemented carbide. Research on CrFe dual-binder phase cemented carbides is almost nonexistent. While higher plasma torch temperatures bring high sphericity and good powder properties, they also lead to problems during spheroidization, such as binder phase loss and WC decarburization forming brittle phases, which are detrimental to the subsequent applications of cemented carbide powders. The binder phase loss during spheroidization of CrFe dual-binder phase cemented carbides is difficult to predict, increasing the difficulty of subsequent sintering. Therefore, achieving the successful preparation of such high-performance alloys is of great research value. Summary of the Invention
[0005] The purpose of this invention is to address the problems of binder phase loss and WC decarburization leading to brittle phase formation caused by current plasma technology, and to provide a method for preparing CrFe-based cemented carbide. Specifically, for cemented carbide spherical powder prepared by plasma spherical technology, a sintering method is designed to adaptively compensate for the defects brought about by the spherical process, and to prepare cemented carbide with excellent comprehensive mechanical properties.
[0006] The technical solution of the present invention is as follows: A method for preparing CrFe-based cemented carbide, using CrFe-based cemented carbide spherical powder prepared by plasma spheroidization as raw material, and employing a rapid sintering process, wherein the rapid sintering process has the following characteristics: rapid heating and shortened heating and holding time.
[0007] According to a preferred embodiment, the rapid sintering process is spark plasma sintering (SPS).
[0008] According to a preferred embodiment, the spark plasma sintering technology specifically includes the following steps: Pre-sintering: Hold at 900-1100℃ for 5-8 minutes for pre-sintering; Sintering: Hold at 1300-1400℃ for 3-15 minutes.
[0009] According to a preferred embodiment, the sintering temperature is 1300-1350℃ and the holding time is 6-10 min.
[0010] According to a preferred embodiment, a layer of pure carbon paper (C) approximately 50 micrometers (μm) thick is inserted between the graphite mold / punch and the chromium-based (CrFe) powder in the spark plasma sintering apparatus as an isolation layer. By setting the isolation layer, the generation of brittle phases caused by decarburization during sintering is effectively reduced, while it also acts as a lubricant during high-temperature sintering, preventing damage to the mold during subsequent demolding.
[0011] According to a preferred embodiment, the spark plasma sintering technology employs the following segmented heating process:
[0012] Step 1 is the program-set pressurization process, gradually increasing the pressure on the sample until the target pressure is reached within two minutes at room temperature. Step 6 is the process of cooling down from the sintering temperature to room temperature within two minutes after the sintering and holding temperature is completed in Step 5.
[0013] According to a preferred embodiment, the pre-sintering temperature is 1100°C and the time is 6 minutes.
[0014] According to a preferred embodiment, the CrFe-based cemented carbide spherical powder prepared by plasma spheroidization includes a Cr and Fe dual binder phase, and the hard phase is WC.
[0015] According to a preferred embodiment, the pressure in the pre-sintering section and the sintering section is 20-60 MPa.
[0016] According to a preferred embodiment, the vacuum level in the pre-sintering section and the sintering section is 0.1 to 0.3 mbar.
[0017] Compared with existing technologies, the advantages of this invention are: 1. A method for preparing CrFe-based cemented carbide, which realizes the successful sintering of spherical WC-CrFe powder with excellent mechanical properties prepared by induction plasma spheroidization technology, which has a spherical structure and excellent powder properties but suffers from the loss of binder phase and brittle phase, as raw material to obtain WC-CrFe-based cemented carbide with excellent mechanical properties. By innovatively designing the SPS sintering process, it fills the gap in the application field of novel binder cemented carbide powder WC-CrFe-based cemented carbide prepared by induction plasma spheroidization. 2. A method for preparing CrFe-based cemented carbide, employing SPS (Sintered Plasma Phosphate Sintering) technology to prepare WC-CrFe-based cemented carbide. Appropriate process parameters are crucial for obtaining cemented carbide with superior performance. By controlling the appropriate SPS sintering temperature, sintering pressure, and holding time, cemented carbide with excellent mechanical properties can be obtained. These parameters are designed for specific spherical powders and differ from the sintering process required for conventional powder sintering. By incorporating a pre-sintering process before sintering, material densification is achieved while effectively solving the problem of WC decarburization and brittle phase formation caused by the induction plasma spheroidization process. The main mechanical properties of the obtained spheroidized WC-CrFe cemented carbide are: hardness HV10 of 2033±21 and fracture toughness of 8.4±0.3 MPa·m. 1 / 2 . Attached Figure Description
[0018] Figure 1 The morphology of CrFe-based cemented carbide powder after plasma spheroidization of the raw material; Figure 2 SPS sintering process curves for WC-CrFe powder prepared by ball milling; Figure 3 The image shows the SPS sintering process curve of the plasma-spheroidized WC-CrFe-based cemented carbide powder of this application. Detailed Implementation
[0019] The specific embodiments listed in this invention are merely examples, and the invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of this invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of this invention should be covered within its scope. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are commercially available conventional products. To better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.
[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Unless otherwise specified, all units used in this specification are International Standard Units (SI), and all numerical values and ranges appearing in this invention should be understood to include systematic errors unavoidable in industrial production.
[0021] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0022] Example 1: A method for preparing a CrFe-based cemented carbide Step 1: Take out the spheroidized WC-CrFe powder and pour it into the graphite mold of the SPS device (place a 50μm thick layer of pure carbon paper between the graphite mold / punch and the chromium powder as an isolation layer) for sintering.
[0023] Step 2: Set the pre-sintering temperature to 1100℃, and the sintering temperature to 1350℃ (the specific sintering process is shown in the table below):
[0024] Once the target temperature is reached, maintain that temperature for 6 minutes to ensure complete sintering of the powder. Throughout the process, apply a pressure of 40 MPa to the graphite mold to promote molding.
[0025] Step 3: After the heat preservation is completed, wait for the furnace body to cool naturally to room temperature to obtain chromium-based nano-hard alloy material.
[0026] The prepared spherical CrFe-based cemented carbide was subjected to performance testing, and the following properties were obtained: hardness HV10 of 2033±21 and fracture toughness of 8.4±0.3 MPa·m. 1 / 2 The density is 13.86 g / cm³.3 -14.98 g / cm 3 .
[0027] Raw material morphology as Figure 1 As shown. The process curves during sintering are as follows. Figure 3 As shown.
[0028] By adjusting the pre-sintering temperature and sintering temperature, multiple experiments were conducted to obtain Examples 1-8 and Comparative Examples 1-3. Specific parameters are shown in Table 1 below. The prepared spherical CrFe-based cemented carbide was subjected to performance testing, and the performance data are shown in Table 1 below. Table 1. Sintering process parameters and mechanical properties of chromium-based cemented carbides in Examples 1-8 and Comparative Examples 1-3.
[0029] Comparative Example 4 Using the same gradient heating method as in Example 1, SPS sintering was performed on WC-CrFe powder prepared by conventional ball milling. The sintering process curve is shown below. Figure 2 As shown. Comparison Figure 2 and Figure 3 As can be seen from the curves, the Y-axis change of WC-CrFe powder prepared by conventional ball milling when entering the pre-sintering stage during sintering using the same method is inconsistent with the trend of the process curve of the spheroidized powder described in this application when entering the pre-sintering stage. The densification stage of WC-CrFe powder prepared by conventional ball milling occurs in a lower temperature range. For WC-CrFe powder prepared by conventional ball milling, the control of phase transformation may need to be done after sintering. This is completely different from the sintering process approach and technical problems overcome by the plasma spherical powder of this application.
[0030] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.
Claims
1. A method of producing a CrFe-based cemented carbide, characterized in that, The CrFe-based hard alloy spherical powder prepared by plasma spheroidization is used as raw material, and a rapid sintering process is adopted, wherein the rapid sintering process has the following characteristics: rapid heating, shortening of heating and holding time.
2. A method of producing a CrFe-based cemented carbide according to claim 1, characterized in that, The rapid sintering process is a spark plasma sintering technology.
3. A method of producing a CrFe-based cemented carbide according to claim 2, c h a r a c t e r i s e d in that The spark plasma sintering technology specifically comprises the following steps: Pre-sintering: pre-sintering at 900-1100℃ for 5-8 min; Sintering: sintering at 1300-1400℃ for 3-15 min.
4. A method of producing a CrFe-based cemented carbide according to claim 3, characterized in that, The sintering temperature is 1300-1350℃, and the holding time is 6-10 min.
5. The method of claim 1, wherein the CrFe-based cemented carbide is prepared by the steps of: preparing a CrFe-based cemented carbide powder; and sintering the CrFe-based cemented carbide powder. In the pre-sintering section and sintering section, pure carbon paper is inserted as a separation layer between the graphite mold / punch of the spark plasma sintering device and the CrFe-based powder.
6. A method of producing a CrFe-based cemented carbide according to claim 3, characterized in that, The spark plasma sintering technology adopts the following segmented heating process: 。 7. The method of producing a CrFe-based cemented carbide according to claim 3, characterized in that, The pre-sintering temperature is 1100℃, and the time is 6 min.
8. The method of claim 1, wherein the CrFe-based cemented carbide is prepared by the steps of: preparing a CrFe-based cemented carbide powder; and sintering the CrFe-based cemented carbide powder. The CrFe-based hard alloy spherical powder prepared by plasma spheroidization comprises Cr and Fe double binder phases, and the hard phase is WC.
9. The method of claim 1, wherein the CrFe-based cemented carbide is prepared by the steps of: preparing a CrFe-based cemented carbide powder; and sintering the CrFe-based cemented carbide powder. The pressure in the pre-sintering section and sintering section is 20-60 MPa.
10. The method of claim 1, wherein the CrFe-based cemented carbide is prepared by the steps of: preparing a CrFe-based cemented carbide powder; and sintering the CrFe-based cemented carbide powder. The vacuum degree in the pre-sintering section and sintering section is 0.1 to 0.3 mbar.