Rare earth oxide modified high-entropy hard alloy and preparation method thereof

Abstract

The invention discloses a rare earth oxide modified high-entropy hard alloy and a preparation method thereof. A high-entropy hard phase (high-temperature calcination), a high-entropy binding phase and rare earth oxide are adopted, grinding, pressing and air pressure sintering at the temperature of 1450-1550 DEG C are conducted, and the high-entropy hard phase is prepared from tungsten carbide, titanium carbide, zirconium carbide, yttrium carbide, manganese carbide, chromium carbide and molybdenum carbide; the high-entropy binding phase comprises the following components: cobalt and a CoCrFeNi-series high-entropy alloy; and the component of the rare earth oxide is Y2O3 or Nd2O3. The prepared rare earth oxide modified high-entropy hard alloy has the advantages of high strength, high compactness, high hardness, high wear resistance and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of cemented carbide materials, and particularly relates to a rare earth oxide-modified high-entropy cemented carbide and a preparation method thereof. Background Art

[0002] Cemented carbide is an alloy material prepared by powder metallurgy process with refractory metal carbides such as WC as hard phase and transition metals such as Co as bonding phase. It has excellent properties such as high hardness, strength, wear resistance and corrosion resistance. It is used to manufacture cutting tools, cutting tools, drilling tools and wear-resistant parts, etc., and is widely used in military industry, aerospace, mechanical processing, metallurgy, oil drilling, mining tools, electronic communications, construction and other fields.

[0003] In order to further improve the performance of cemented carbide, many researchers are currently committed to the research of high entropy cemented carbide. CN102796933A discloses a nitrogen-containing cemented carbide based on a high entropy alloy binder phase, wherein the binder phase is a high entropy alloy, and the hard phase is a uniformly distributed WC and carbonitride solid solution, wherein the high entropy alloy binder phase is at least four of iron, cobalt, nickel, chromium, aluminum, vanadium, titanium, copper, zirconium, molybdenum, and manganese, and the preparation method is: ball milling and mixing WC powder, high entropy alloy binder phase, and carbonitride solid solution powder, and completing low-pressure sintering at 1400°C-1480°C, wherein the binder phase is a real high entropy alloy, thereby preparing a high entropy alloy binder phase cemented carbide. CN109161773A discloses a method for preparing a high entropy alloy binder phase cemented carbide. First, an amorphous high entropy alloy binder phase powder of Fe:Co:Ni:Cu:Cr=1:1:1:(0.4-0.6):(0.4-0.6) is prepared by intermittent planetary ball milling; then the amorphous high entropy alloy binder phase powder and the hard phase powder are mixed by roller ball milling, and the prepared mixture is still amorphous; finally, SPS sintering is performed at 1400-1450°C to prepare a high entropy alloy binder phase cemented carbide.

[0004] It can be seen that the existing high entropy cemented carbide only has a high entropy alloy as the bonding phase, while the hard phase is not, and further research and development is needed to improve the performance of the cemented carbide. Summary of the invention

[0005] In view of the above problems, the present invention provides a rare earth oxide modified high entropy cemented carbide and a preparation method thereof. The present invention adopts high entropy hard phase (high temperature calcination) + high entropy bonding phase + rare earth oxide, and obtains rare earth oxide modified high entropy cemented carbide after grinding, pressing and 1450℃~1550℃ gas pressure sintering, which has the advantages of high strength, high density, high hardness, high wear resistance, etc., and can be used to manufacture cutting tools, knives, drilling tools and wear-resistant parts, etc., and has good application prospects.

[0006] The technical solution of the present invention is: a rare earth oxide modified high entropy cemented carbide, characterized in that it is prepared by grinding, pressing and gas pressure sintering at 1450°C to 1550°C of high entropy hard phase + high entropy bonding phase + rare earth oxide; wherein the high entropy hard phase is ground after high temperature calcination;

[0007] The components and mass ratio of the high entropy hard phase are as follows: 15-35% tungsten carbide (WC), 10-20% titanium carbide (TiC), 10-20% zirconium carbide (ZrC), 10-20% yttrium carbide (YC2), 0-20% manganese carbide (Mn3C), 0-20% chromium carbide (Cr3C2), and 0-20% molybdenum carbide (MoC); the components and mass ratio of the high entropy bonding phase are as follows: 3%-15% cobalt (Co), and 8%-20% CoCrFeNi-based high entropy alloy; the total mass of the high entropy hard phase and the high entropy bonding phase is 100%;

[0008] The rare earth oxide component is: Y2O3 or Nd2O3, and the added amount thereof is 0.3-0.7% of the total mass of the high entropy hard phase and the high entropy bonding phase.

[0009] Among them, the CoCrFeNi-based high entropy alloy is prepared from HEA alloy powder (CoCrFeNi, AlCoCrFeNi, CoCrFeNiMo or CoCrFeNiMn) by a gas atomization method. During the preparation, high-pressure gas is used to crush the heated liquid alloy, and the CoCrFeNi-based high entropy alloy is obtained after cooling.

[0010] Table 1 List of components of CoCrFeNi-based high entropy alloys (mass ratio)

[0011]

[0012] Preparation method:

[0013] 1) High-entropy hard phase high temperature calcination

[0014] After dry grinding and mixing the components of the high entropy hard phase according to the ratio, the high-temperature calcination (calcination temperature 2200-2400°C) in a carbonization furnace for 2-3 hours is performed, and the calcined material is crushed and dry-ground to prepare powder. The purpose of high-temperature calcination is mainly to promote the solid solution of various hard phases through high temperature to achieve the purpose of improving the solid solution strength.

[0015] 2) Grinding

[0016] The hard phase powder prepared in step 1) and the binder phase cobalt powder are wet-milled and then dried; the dried powder is then mixed with the CoCrFeNi-based high entropy alloy powder and wet-milled, and finally rare earth oxide is added and wet-milled for further processing and then dried;

[0017] 3) Suppression

[0018] The dried mixed powder is sieved with a 100-mesh screen, then 1-15% of liquid paraffin by weight of the powder is added and stirred evenly, and then dried and pressed;

[0019] 4) Gas pressure sintering

[0020] The rare earth oxide modified high entropy cemented carbide is prepared by gas pressure sintering process, the sintering temperature is 1450℃~1550℃, and the sintering time is 30~35h.

[0021] Furthermore, the sintering curve is divided into the following three stages:

[0022] ① Forming dewaxing stage: 0-15h is the forming dewaxing stage, during which the sintering temperature rises in stages; when the sintering temperature reaches 260-300℃, H2 is charged, and when the sintering temperature reaches 430-470℃, H2 is gradually discharged to achieve dewaxing of high entropy cemented carbide;

[0023] ② Pre-sintering stage: 15h~18h is the pre-sintering stage, the temperature is raised to 780~820℃, and then maintained for 0.5~1.5h;

[0024] ③ Sintering stage: gradually increase the temperature to 1450℃~1550℃ (first increase the temperature to 1100~1200℃, and then maintain for 3~4h; then increase the temperature to 1300~1400℃, and then maintain for 1~2h; then increase the temperature to 1450℃~1550℃, and then maintain for 1.5~2.5h), at this time, fill in 4~6MPa argon gas pressurization to improve the density of the product, then stop heating in the sintering furnace and gradually cool to room temperature, and finally obtain sintered dense high entropy cemented carbide.

[0025] The technical effects of the present invention are:

[0026] 1. Most of the current high-entropy cemented carbides have a high-entropy alloy as the bonding phase, but not the hard phase. However, the hard phase and the bonding phase of the present invention are both high-entropy, and the components of the high-entropy hard phase + high-entropy bonding phase are carefully selected and assembled, especially using CoCrFeNi-based high-entropy alloys with good hardness, strength and corrosion resistance to improve product performance. On this basis, rare earth oxides are further added as toughening agents to improve the wettability and strength of the bonding phase and the hard phase, so that the mechanical properties such as strength and hardness are significantly improved. Then, by calcining the high-entropy hard phase at high temperature, various hard phases can be caused to solid-dissolve with each other by high temperature, thereby achieving improved solid solution strength. Combined with the gas pressure sintering process (specially designed staged heating program + argon gas pressurization method), the mechanical properties such as density of the product are further improved, thereby obtaining a high-entropy cemented carbide with high strength, high density, high hardness and high wear resistance.

[0027] 2. Different from the general mechanism of adding rare earth oxides to cemented carbide (hard phase is hard materials such as WC, TiC, etc.) to improve hardness and strength, the present invention adds rare earth oxides as toughening agents in high-entropy cemented carbide (although it is called cemented carbide, it is obviously different from traditional cemented carbide in terms of component composition. It is a mixture of various hard carbides using the high entropy concept, which is different from the hard phase of traditional cemented carbide) in which both the hard phase and the bonding phase are high entropy alloys, to improve the wettability and strength of the bonding phase and the hard phase, so that the mechanical properties such as strength and hardness are significantly improved. This is the first technology of adding rare earth oxides to high-entropy cemented carbide in which both the hard phase and the bonding phase are high entropy alloys, which has been explored by the research team through theoretical research and experiments. It is creative in terms of the phase composition and toughening mechanism of cemented carbide. Experiments have proved that the cemented carbide prepared by high-entropy hard phase and high-entropy bonding phase modified with rare earth oxides has the advantages of high strength, high density, high hardness, high wear resistance, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Gas pressure sintering curve of high entropy cemented carbide modified with rare earth oxides;

[0029] Figure 2 Metallographic organization diagrams of high entropy cemented carbide (Figure a), yttria-enhanced high entropy cemented carbide (Figure b) and YG10 cemented carbide (Figure c); in the figure, G (binder phase-HEA), H (hard phase) and HEA (high entropy alloy). DETAILED DESCRIPTION

[0030] The effects are described below in conjunction with the embodiments and drawings.

[0031] Embodiment 1:

[0032] 1. Raw material formula

[0033] High entropy hard phase: tungsten carbide (WC) 18%, titanium carbide (TiC) 10%, zirconium carbide (ZrC) 10%, yttrium carbide (YC2) 10%, manganese carbide (Mn3C) 10%, chromium carbide (Cr3C2) 5%, molybdenum carbide (MoC) 5%;

[0034] High entropy bonding phase: 12% cobalt (Co), 20% CoCrFeNi-based high entropy alloy;

[0035] Rare earth oxide: Y2O3 0.3%.

[0036] 2. Preparation process:

[0037] 1) High-entropy hard phase high temperature calcination

[0038] After dry-grinding and mixing the components of the high-entropy hard phase in accordance with the proportion, the materials were calcined at high temperature in a carbonization furnace (calcination temperature: 2300° C.) for 2.5 hours, and the calcined materials were crushed and dry-grinded to prepare powders.

[0039] 2) Grinding

[0040] The hard phase powder and the binder phase Co powder prepared in step 1) are placed in a cemented carbide ball mill according to a ratio, and then cemented carbide grinding balls and anhydrous ethanol with a ball-to-material ratio of 10:1 are added, and the ball milling is performed for 4-6 hours; then the mixture and the grinding balls are poured into a tray and placed in a vacuum drying oven for drying.

[0041] After drying, the dried powder is mixed with CoCrFeNi-based high entropy alloy powder (prepared by gas atomization of CoCrFeNi alloy powder), and then carbide grinding balls and anhydrous ethanol with a ball-to-material ratio of 10:1 are added, and ball milling is performed for 6-8 hours; finally, rare earth oxides are added, and then after ball milling for 2-3 hours, the mixture and the grinding balls are poured into a tray and placed in a vacuum drying oven for drying.

[0042] 3) Suppression

[0043] The dried mixed powder was taken out and sieved using a 100-mesh screen, then cooled to room temperature, added with 8% liquid paraffin by weight of the powder, and after being stirred evenly, sent to a drying oven and dried for 20 minutes. Then, it was pressed using a 200MPa press.

[0044] 4) Gas pressure sintering

[0045] The rare earth oxide modified high entropy cemented carbide was prepared by gas pressure sintering process. The sintering temperature was 1490℃. The sintering curve is as follows: Figure 1 As shown, it is divided into the following three stages:

[0046] ① Forming and dewaxing stage: 0 to 15 hours is the forming and dewaxing stage, during which the sintering temperature rises in stages (first to 280°C, then maintained for 6.5 hours; then to 450°C, then maintained for 4.5 hours); when the sintering temperature reaches 280°C, H2 is charged, and when the sintering temperature reaches 450°C, H2 is gradually discharged to achieve dewaxing of high entropy cemented carbide.

[0047] ② Pre-sintering stage: 15h~18h is the pre-sintering stage, first raising the temperature to 800℃ and then maintaining it for 1h.

[0048] ③ Sintering stage: 18h~33h is the sintering stage. First, the temperature is raised to 1150℃ and then maintained for 3.5h; then raised to 1350℃ and then maintained for 1.5h; then raised to 1490℃ and then maintained for 2h. When the sintering temperature reaches 1490℃, 5MPa argon gas is filled for pressurization to improve the density of the sample. After 33h, the sintering furnace stops heating and gradually cools to room temperature, and finally a sintered and dense high-entropy cemented carbide sample is obtained.

[0049] Embodiment 2:

[0050] The rare earth oxide uses Nd2O3 instead of Y2O3, and the rest is the same as in Example 1.

[0051] Comparative Example 1:

[0052] No rare earth oxide is added, and the preparation method omits the step of ball milling after adding rare earth oxide. The rest is the same as Example 1.

[0053] Comparative Example 2:

[0054] Ordinary YG10 cemented carbide gold with hard phase WC (90%) + Co (10%).

[0055] The hardness, flexural strength and fracture toughness K of Examples 1-2 and Comparative Examples 1-2 IC The test results are shown in Table 2. The hardness is measured by Rockwell hardness test method, in accordance with GB / T 3849.1-2015 Cemented Carbide Rockwell Hardness Test (A Scale) Part 1: Test Method; the flexural strength is measured by transverse fracture strength test method, in accordance with GB / T 3851-2015 Cemented Carbide Transverse Fracture Strength Determination Method; the fracture toughness K IC The indentation test was carried out according to GB / T 44304-2024 Test method for fracture resistance of fine ceramics at room temperature - indentation (IF) method.

[0056] Table 2 Hardness, flexural strength and fracture toughness K of Examples 1-2 and Comparative Examples 1-2 IC Test results

[0057]

[0058] The test results are shown in Table 2. Compared with Comparative Example 1, Comparative Example 2 uses high entropy hard phase (68%) + Co (12%) + high entropy bonding phase (20%), and its hardness is significantly improved, but the flexural strength and fracture toughness K IC The hard alloy prepared by adding rare earth oxides into the high entropy hard phase and high entropy binder phase modified by rare earth oxides has a lower hardness, bending strength and fracture toughness K IC There is a significant improvement.

[0059] like Figure 2 From the metallographic organization diagrams of the high entropy cemented carbide prepared in Comparative Example 1 (Figure a), the yttria-enhanced high entropy cemented carbide prepared in Example 1 (Figure b), and the YG10 cemented carbide of Comparative Example 2 (Figure c), it can be seen that the metallographic structure of Example 1 with yttria added is more uniform in grain size and denser in arrangement than that of Comparative Example 1 without yttria added, so that the mechanical properties of the alloy are higher. Compared with the high entropy cemented carbide prepared in Example 1, the ordinary YG10 cemented carbide of Comparative Example 2 has coarser grains and uneven grain size.

[0060] Example 3

[0061] 1. Raw material formula

[0062] High entropy hard phase: tungsten carbide (WC) 25%, titanium carbide (TiC) 12%, zirconium carbide (ZrC) 11%, yttrium carbide (YC2) 10%, manganese carbide (Mn3C) 10%;

[0063] High entropy bonding phase: 12% cobalt (Co), 20% CoCrFeNi-based high entropy alloy;

[0064] Rare earth oxide: Y2O3 0.5%.

[0065] The rest is the same as in Example 1.

[0066] Example 4

[0067] High entropy hard phase: tungsten carbide (WC) 20%, titanium carbide (TiC) 10%, zirconium carbide (ZrC) 10%, yttrium carbide (YC2) 10%, manganese carbide (Mn3C) 10%, chromium carbide (Cr3C2) 6%, molybdenum carbide (MoC) 6%;

[0068] High entropy bonding phase: Cobalt (Co) 10%, CoCrFeNi-based high entropy alloy 18%;

[0069] Rare earth oxide: Nd2O3 0.4%.

[0070] The rest is the same as in Example 1.

Claims

1. A rare earth oxide modified high entropy cemented carbide, characterized in that: It is made by grinding, pressing and gas pressure sintering of high entropy hard phase + high entropy bonding phase + rare earth oxide at 1450℃~1550℃; wherein, the high entropy hard phase is ground after high temperature calcination; The components and mass ratio of the high entropy hard phase are: 15-35% tungsten carbide, 10-20% titanium carbide, 10-20% zirconium carbide, 10-20% yttrium carbide, 0-20% manganese carbide, 0-20% chromium carbide, and 0-20% molybdenum carbide; the components and mass ratio of the high entropy bonding phase are: 3%-15% cobalt, 8%-20% CoCrFeNi-based high entropy alloy; the total mass of the high entropy hard phase and the high entropy bonding phase is 100%; The rare earth oxide component is: Y2O3 or Nd2O3, and the added amount thereof is 0.3-0.7% of the total mass of the high entropy hard phase and the high entropy bonding phase.

2. A rare earth oxide modified high entropy cemented carbide as claimed in claim 1, characterized in that: The CoCrFeNi-based high entropy alloy is prepared from alloy powder of CoCrFeNi, AlCoCrFeNi, CoCrFeNiMo or CoCrFeNiMn by gas atomization.

3. The method for preparing a rare earth oxide modified high entropy cemented carbide according to claim 1 or 2, characterized in that: The following steps are involved: 1) High-entropy hard phase high temperature calcination After dry grinding and mixing the components of the high entropy hard phase according to the proportion, the components are calcined at high temperature in a carbonization furnace at a temperature of 2200-2400°C for 2-3 hours, and the calcined materials are crushed and dry ground to prepare powder; 2) Grinding The hard phase powder prepared in step 1) and the binder phase cobalt powder are wet-milled and then dried; the dried powder is then mixed with the CoCrFeNi-based high entropy alloy powder and wet-milled, and finally rare earth oxide is added and wet-milled for further processing and then dried; 3) Suppression The dried mixed powder is sieved with a 100-mesh screen, then 1-15% of liquid paraffin by weight of the powder is added and stirred evenly, and then dried and pressed; 4) Gas pressure sintering The rare earth oxide modified high entropy cemented carbide is prepared by gas pressure sintering process. The sintering temperature is 1450℃~1550℃ and the sintering time is 30~35h. When the temperature is raised to 1450℃~1550℃, 4~6MPa argon gas is filled for pressurization to improve the density of the product.

4. The preparation method according to claim 3, characterized in that: The sintering curve is divided into the following three stages: ① Forming dewaxing stage: 0-15h is the forming dewaxing stage, during which the sintering temperature rises in stages; when the sintering temperature reaches 260-300℃, H2 is charged, and when the sintering temperature reaches 430-470℃, H2 is gradually discharged to achieve dewaxing of high entropy cemented carbide; ② Pre-sintering stage: 15h~18h is the pre-sintering stage, the temperature is raised to 780~820℃, and then maintained for 0.5~1.5h; ③ Sintering stage: gradually increase the temperature to 1450℃~1550℃, at this time, fill in 4~6MPa argon gas for pressurization to improve the density of the product, then stop heating in the sintering furnace and gradually cool to room temperature, finally obtaining sintered dense high entropy cemented carbide.

5. The preparation method according to claim 4, characterized in that: The sintering stage gradually heats up to 1450°C-1550°C, specifically: first heat up to 1100-1200°C, then maintain for 3-4 hours; then heat up to 1300-1400°C, then maintain for 1-2 hours; then heat up to 1450°C-1550°C, then maintain for 1.5-2.5 hours.

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