Powder metallurgy wear and corrosion resistant double strengthened phase precipitation hardened high speed steel

Abstract

The application provides a powder metallurgy wear-resistant and corrosion-resistant dual-strengthening-phase precipitation-hardened high-speed steel, which comprises the following components in percentage by mass: C: 2.2%-3.0%; Si: 0%-0.4%; Cr: 2.0%-8.0%; Co: 10.0%-30.0%; Ni: 0%-2.5%; (1.39Co+1.4Ni): 13.0%; V: 6%-13.0%; W: 5%-12%; Mo: 5%-16.0%; (Mo+W / 2): 10.0%-22.0%; and the balance is iron and impurities, wherein the steel is a dual-strengthening-phase precipitation-hardened high-speed steel, the strengthening phase comprises intermetallic compound (IMC) μ phase, MC carbide and (Cr, Fe) C type carbide, wherein the μ phase is (Fe, Co) 7 (Mo+W / 2) 6 type, and the type of the MC carbide is V(C, N) type. The μ phase and the carbide of the prepared precipitation-hardened high-speed steel are small in size and uniform in distribution, and the prepared precipitation-hardened high-speed steel has excellent comprehensive performance, especially outstanding wear resistance and corrosion resistance, and can meet the requirements of different working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to a precipitation hardening high speed steel, in particular to a powder metallurgy wear and corrosion resistant double strengthening phase precipitation hardening high speed steel. BACKGROUND

[0002] In the field of manufacturing tools for high speed cutting of difficult-to-cut materials, the tools or parts not only need to withstand working stress loading and impact, but also need to withstand wear caused by direct contact with hard abrasive particles in moving parts or working media. In order to be suitable for these working conditions and have a long service life at the same time, the material must have a good strength and toughness match and high wear resistance.

[0003] Precipitation hardening steel is a carbon-free ferritic martensitic precipitation hardening tool alloy. Due to the low content of C in the composition, no carbide is precipitated, and the structure is mainly Fe-based matrix and Fe-Co-Mo-W intermetallic compound (i.e. IMC). The hardening effect is due to the precipitation of IMC particles during aging process. This kind of precipitation hardening high speed steel has good grindability and resistance to temper softening, and good dimensional stability.

[0004] The wear resistance of the steel depends on the hardness of the matrix and the content, morphology and particle size distribution of the hard second phase precipitated in the steel. When prepared by traditional casting and forging process, the alloy composition is prone to segregation during solidification process due to the characteristics of slow cooling of molten steel during the process. This undesirable structure cannot be effectively solved by hot working method, which will adversely affect the performance of the alloy, resulting in low levels of strength, toughness, grindability and other properties of high speed steel, which is difficult to meet the requirements of high-end manufacturing on material performance and service life. The corrosion resistance of existing precipitation hardening steel is also difficult to meet the use in high-end fields. SUMMARY

[0005] Therefore, the present application provides a powder metallurgy wear and corrosion resistant double strengthening phase precipitation hardening high speed steel with good structure and excellent performance.

[0006] To achieve the above purpose, the technical scheme of the present application is as follows:

[0007] A powder metallurgy wear and corrosion resistant double strengthening phase precipitation hardening high speed steel, characterized in that the steel comprises the following chemical components in mass percentage:

[0008] C: 2.2%-3.0%;

[0009] Si: 0%-0.4%;

[0010] Cr: 2.0%-8.0%;

[0011] Co: 10.0%-30.0%;

[0012] Ni: 0% - 2.5%;

[0013] (1.39Co + 1.4Ni) ≥ 13.0%;

[0014] V: 6% - 13.0%;

[0015] W: 5% - 12%;

[0016] Mo: 5% - 16.0%;

[0017] (Mo + W / 2): 10.0% - 22.0%;

[0018] balance being iron and impurities;

[0019] and, the precipitated phase in the precipitation hardening high speed steel includes intermetallic compound (IMC) μ phase, MC carbide and (Cr, Fe) C type carbide, wherein the μ phase is (Fe, Co)7(Mo + W / 2)6 type, and the type of MC carbide is V(C, N) type.

[0020] The present application promotes the precipitation of μ phase when preparing the precipitation hardening high speed steel by powder metallurgy process through the reasonable design of alloy composition and ratio, thereby improving the wear resistance and corrosion resistance of the steel.

[0021] The role of Co (Cobalt) is to be dissolved in the matrix, so that the alloy becomes a martensitic steel, thereby increasing the hardness and strength of the alloy by one level compared with ferrite alloy. The increase of Co content will appropriately reduce the toughness of the steel. In the present application, the content of Co element is 10.0% - 30.0%, preferably 10.0% - 28.0%.

[0022] The melting point of W (Tungsten) is high, which increases the strength and tempering stability of the steel, the high temperature creep resistance, and the anti-tempering softening capacity of the steel, so that the surface layer of the steel has less temperature rise and less hardness drop during processing and use. In the present application, the content of W element is 5% - 12.0%, preferably 5% - 9.0%.

[0023] The role of Mo (Molybdenum) is the same as W, and the price is lower than W. In the present application, an appropriate amount of Mo is added to replace W. However, it should be noted that the higher the Mo content, the higher the starting precipitation temperature of μ phase, and the larger the particle size of μ phase. In order to ensure the small particle size of μ phase, the content of Mo element in the present application is 5% - 16.0%, preferably 5% - 15.7%.

[0024] A small amount of C (carbon) is added to the steel, part of which is dissolved in the matrix to improve the strength of the matrix, and the other part of C combines with the carbide forming element to improve the wear resistance of the material. The content of C is not less than 0.5% to ensure that the carbide forming element can participate in the precipitation of carbide to form a double strengthening phase mechanism; at the same time, the content of C should not exceed 3.0% to avoid excessive C dissolved in the matrix leading to a decrease in toughness. Within the above-mentioned C content range of 2.2%-3.0%, the preferred range is 2.2%-2.8%, which can obtain a good combination of wear resistance and toughness.

[0025] V (vanadium) as a strong carbide forming element, its main role is to form MC type carbide with the steel, to improve the wear resistance of the steel. To ensure that the steel is a double phase strengthening mechanism of μ phase and MC carbide, and to ensure the grindability of the steel, the content of V element in the present application is 6%-13.0%, preferably 6%-11.8%.

[0026] Cr (chromium) is added to the steel, which can coarsen the particles, reduce the red hardness, and improve the processability. On the other hand, part of Cr is dissolved in the matrix, which can improve the corrosion resistance and hardenability of the steel. In the present application, the content of Cr element is 2.0%-8.0%, preferably 2.0%-7.5%.

[0027] Si (silicon) is not a carbide forming element, but is used as a deoxidizer and matrix strengthening element to improve the strength and hardness of the steel. However, too much Si will reduce the plasticity and toughness of the matrix. The Si content in the present application is controlled at 0.4% or less, and preferably ≤0.32%.

[0028] Ni (nickel) can replace Co to improve the thermal plasticity of the double strengthening phase steel in the spray forming process, but too much Ni will reduce the hardening effect of the steel. In the present application, the content of Ni element is 0%-2.5%, preferably 0%-2.3%.

[0029] As a limitation of the above-mentioned manner, the powder metallurgy wear-resistant and corrosion-resistant double strengthening phase precipitation hardening high-speed steel comprises the following chemical components by mass percentage:

[0030] C: 2.2%-2.8%;

[0031] Si: 0%-0.32%;

[0032] Cr: 2.0%-7.5%;

[0033] Co: 10.0%-28.0%;

[0034] Ni: 0%-2.3%;

[0035] (1.39Co+1.4Ni)≥15.0%;

[0036] V: 6% - 11.8%;

[0037] W: 5% - 9%;

[0038] Mo: 5% - 15.7%;

[0039] (Mo+W / 2): 10.0% - 20.2%;

[0040] balance: iron and impurities.

[0041] In order to achieve better comprehensive performance, the chemical components in the powder metallurgy wear-resistant and corrosion-resistant double-strengthening phase precipitation hardened high-speed steel should be controlled within the required range.

[0042] Further, at least 80% of the volume fraction of the μ phase has a particle size ≤1.5 μm, the maximum particle size of the μ phase is not more than 6.0 μm, and the volume fraction of the μ phase in the powder metallurgy wear-resistant and corrosion-resistant double-strengthening phase precipitation hardened high-speed steel is 10-20%.

[0043] Further, at least 80% of the volume fraction of the MC carbide has a particle size ≤2.0 μm, the maximum particle size of the MC carbide is not more than 3.0 μm, and the volume fraction of the MC carbide in the powder metallurgy wear-resistant and corrosion-resistant double-strengthening phase precipitation hardened high-speed steel is 1%-5%.

[0044] Further, the (Cr, Fe) C type carbide is a Cr-rich carbide.

[0045] Further, at least 80% of the volume fraction of the (Cr, Fe) C type carbide has a particle size of 1-5 μm, the maximum particle size of the (Cr, Fe) C type carbide is not more than 10.0 μm, and the volume fraction of the (Cr, Fe) C type carbide in the powder metallurgy wear-resistant and corrosion-resistant double-strengthening phase precipitation hardened high-speed steel is 3%-10%.

[0046] The present application adopts a powder metallurgy process to prepare a precipitation hardened steel, which can solve the problem of element segregation and obtain a uniform microstructure, and the main steps of the powder metallurgy process for preparing a precipitation hardened high-speed steel include: atomization and powdering → hot isostatic pressing forming, the steel liquid is rapidly cooled into powder, the alloy elements in the steel liquid cannot segregate and completely solidify, and the powder is consolidated into a material with a fine and uniform microstructure, compared with the traditional casting or electroslag process for producing a precipitation hardened high-speed steel, the performance is greatly improved.

[0047] The present application also provides a preparation method of the powder metallurgy wear-resistant and corrosion-resistant double-strengthening phase precipitation hardened high-speed steel as described above, and the preparation method specifically includes the following steps:

[0048] s1. Prepare the liquid steel of precipitation hardening steel according to the chemical composition requirements and transfer it to the ladle;

[0049] s1.1. Maintain the superheat of the liquid steel by heating the protective slag covering the upper surface of the liquid steel in the ladle; introduce inert gas into the bottom of the ladle to stir the liquid steel;

[0050] s1.2. Flow the liquid steel into the preheated tundish through the flow guide pipe at the bottom of the ladle at a stable flow rate, and apply protective slag to the upper surface of the liquid steel when the liquid steel enters the tundish and covers the lower end surface of the flow guide pipe;

[0051] s1.3. Continuously compensate the heating of the tundish to maintain the superheat of the liquid steel;

[0052] s1.4. After the liquid steel enters the atomization chamber from the tundish, inert gas is used for atomization and powdering, and the obtained metal powder is settled at the bottom of the atomization chamber and then enters the powder storage tank with a protective atmosphere. After being screened by the protective screening device, the metal powder enters the powder storage tank for storage;

[0053] s1.5. Under the protection of inert gas, the metal powder in the powder storage tank is transferred to the hot isostatic pressing jacket. After the metal powder is vibrated and packed tightly, the hot isostatic pressing jacket is subjected to vacuum degassing treatment, the end part is sealed and welded, and then the metal powder is completely densified and solidified by hot isostatic pressing, and the powder metallurgy process is completed.

[0054] The above-mentioned powder metallurgy process includes non-vacuum melting, atomization and powdering, and hot isostatic pressing. The whole process is protected to control the oxygen content and the morphology of precipitated phase, and to optimize the performance of the precipitation hardening steel.

[0055] The protective slag of the ladle has the functions of air insulation and conductive heating. Inert gas is introduced into the bottom of the ladle through the air hole to balance the temperature of the liquid steel at different positions in the ladle, and to accelerate the removal of harmful inclusions. The flow guide pipe at the bottom of the ladle plays a role in guiding the flow of the liquid steel, reducing turbulence during the flow of the liquid steel, avoiding slag entrainment and preventing inclusions from entering the next process. On the other hand, the flow guide pipe prevents the liquid steel from being exposed to air, preventing the increase of oxygen content in the liquid steel. Before the liquid steel enters the tundish, the tundish needs to be preheated to prevent local condensation or premature precipitation of the second phase when the liquid steel enters the tundish.

[0056] The inside of the powder storage tank has the functions of atmosphere protection and forced cooling. The powder protective screening device plays a protective role in the powder screening process and prevents the powder from floating. The powder storage tank is sealingly connected with the hot isostatic pressing jacket. Inert gas is introduced into the hot isostatic pressing jacket before powder loading to expel air, which can prevent the increase of oxygen content in the powder.

[0057] The precipitated hardening high-speed steel is prepared by adopting a powder metallurgy process, the component design is reasonable, various effective protection means are adopted in the preparation process to prevent the molten steel and the powder from being polluted, the precipitated intermetallic compound μ phase and carbide are small and uniform, the precipitated hardening high-speed steel has excellent mechanical properties, especially high wear resistance and corrosion resistance, and can obtain a hardness of more than 64HRC after solid solution aging treatment, and is suitable for use in the working condition with hard particles and corrosive medium. BRIEF DESCRIPTION OF DRAWINGS

[0058] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and serve as an explanation of the illustrative embodiments of the present application, and are not intended to limit the present application. In the drawings:

[0059] Figure 1 A microstructure diagram of the precipitated hardening high-speed steel prepared in Example 1 of the present application;

[0060] Figure 2 A microstructure diagram of the precipitated hardening high-speed steel prepared in Example 2 of the present application;

[0061] Figure 3 A microstructure diagram of the precipitated hardening high-speed steel prepared in Example 4 of the present application;

[0062] Figure 4 A microstructure diagram of the precipitated hardening high-speed steel prepared in Example 5 of the present application;

[0063] Figure 5 A microstructure diagram of the precipitated hardening high-speed steel prepared in Example 6 of the present application;

[0064] Figure 6 A microstructure diagram of the precipitated hardening high-speed steel prepared in Example 7 of the present application;

[0065] Figure 7 A microstructure diagram of the electroslag process high-speed steel prepared in Comparative Example A of the present application;

[0066] Figure 8 A microstructure diagram of the powder metallurgy process corrosion-resistant high-speed steel prepared in Comparative Example B of the present application. DETAILED DESCRIPTION

[0067] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0068] The present application relates to a group of powder metallurgy wear-resistant and corrosion-resistant double-strengthening phase precipitation hardened high-speed steel, which comprises the following chemical components by mass percentage: C: 2.2%-3.0%; Si: 0%-0.4%; Cr: 2.0%-8.0%; Co: 10.0%-30.0%; Ni: 0%-2.5%; (1.39Co+1.4Ni)≥13.0%; V: 6%-13.0%; W: 5%-12%; Mo: 5%-16.0%; (Mo+W / 2): 10.0%-22.0%; and the balance is iron and impurities.

[0069] As a preferred scheme by mass percentage, the precipitation hardened high-speed steel of the present application comprises the following chemical components: C: 2.2%-2.8%; Si: 0%-0.32%; Cr: 2.0%-7.5%; Co: 10.0%-28.0%; Ni: 0%-2.3%; (1.39Co+1.4Ni)≥15.0%; V: 6%-11.8%; W: 5%-9%; Mo: 5%-15.7%; (Mo+W / 2): 10.0%-20.2%; and the balance is iron and impurities. The precipitation hardened high-speed steel composed of the above components can obtain ideal microstructure and excellent performance to meet the requirements.

[0070] Secondly, the present application also relates to a method for preparing the above-mentioned precipitation hardened high-speed steel. When prepared by using traditional ingot or electroslag process, segregation is prone to occur due to slow solidification speed, which leads to performance decline. Therefore, in order to ensure that the prepared precipitation hardened high-speed steel ingot has uniform composition and microstructure, fine precipitates and high purity, the powder metallurgy process is used to prepare the steel ingot, and then the required rod product is obtained through forging.

[0071] Specifically, the preparation method of the present application comprises the following steps:

[0072] s1. The molten steel of the present application is poured into a melting ladle, and the molten steel loading weight is 1.5-8 tons;

[0073] s1.1. The protective slag covering the upper surface of the molten steel in the ladle is heated by electric current using a graphite electrode, and the molten steel is stirred by introducing argon or nitrogen gas at the bottom of the ladle, and the molten steel overheat degree is opened to 100-200℃ by opening the molten steel flow guide pipe;

[0074] s1.2. The molten steel is flowed into the tundish preheated to 800-1200℃ through the flow guide pipe at the bottom of the ladle at a flow rate of 10-50 Kg / min, and the protective slag is applied when the molten steel enters the tundish and covers the lower end surface of the flow guide pipe;

[0075] s1.3. The tundish is continuously compensated and heated during the atomization and powder preparation process, and the overheat degree of the molten steel is maintained at 100-200℃;

[0076] s1.4 The molten S1.4 steel enters the atomization chamber through the bottom of the tundish, the atomization gas injection valve is opened, nitrogen is used as the gas medium for atomization, the purity of the nitrogen is ≥99.999%, the oxygen content is ≤2ppm, and the outlet pressure of the gas nozzle is 1.0-5.0MPa; the molten steel is broken into droplets under the action of nitrogen injection and is rapidly cooled into metal powder, flies to the bottom of the atomization chamber, and then enters the powder storage tank body with a protective atmosphere; after the atomization powdering is completed, the metal powder in the powder storage tank body is sieved through a protective sieving device; a positive pressure inert protective gas is introduced into the cavity of the protective sieving device, and the powder storage tank is in a positive pressure inert gas protective atmosphere;

[0077] s1.5 The metal powder in the powder storage tank body is filled into the hot isostatic pressing sleeve, inert gas is introduced into the hot isostatic pressing sleeve to discharge air, then the hot isostatic pressing sleeve and the powder storage tank body are tightly connected, vibration operation is performed during the filling process to increase the filling density of the metal powder; after completion, the hot isostatic pressing sleeve is subjected to vacuum degassing treatment, the hot isostatic pressing sleeve is heated and kept at 200-600℃ during the vacuum process, degassing is performed to 0.01Pa, then heating and keeping are continued for more than 2h, then the end part of the sleeve is subjected to sealing welding treatment, finally the sleeve is subjected to hot isostatic pressing treatment, the hot isostatic pressing temperature is 1100-1180℃, the pressure is ≥100MPa, and the holding time is ≥1h, so that the metal powder is completely densified and consolidated, then the furnace is cooled, and the powder metallurgy process is completed.

[0078] s2. Open the forging billet

[0079] The precipitation hardening high speed steel according to the application is further forged and deformed as needed to obtain a rod or a forging with a certain shape and size, different properties are obtained by using different heat treatment systems, and the heat treatment used includes annealing, solid solution and aging. The annealing treatment involves heating the rod or forging to 870-890℃, keeping for ≥2h, then cooling to below 530℃ at a speed of ≤15℃ / h, and then furnace cooling or static air cooling to below 50℃; the solid solution treatment involves preheating the annealed rod or forging at a temperature of 810-850℃, uniformly heating, then placing in a temperature of 1170-1200℃ for 15-40min, and then oil cooling; then aging at a temperature of 580-650℃, keeping for 3-4h, and then air cooling to 50℃.

[0080] The powder metallurgy wear-resistant and corrosion-resistant double-strengthening-phase precipitation hardening high speed steel and the preparation thereof according to the application will be further described below with specific preparation examples and comparative examples and corresponding performance detection.

[0081] The strengthening phase particle size and volume fraction, heat treatment hardness, wear resistance and corrosion resistance of the powder metallurgy wear-resistant and corrosion-resistant double-strengthening phase precipitation hardened high-speed steel involved in the present application are verified, wherein the mu phase and carbide particle size and volume fraction are analyzed based on the microstructure images obtained by scanning electron microscopy, and the heat treatment hardness, wear resistance and corrosion resistance are tested according to GB / T 230.1, GB / T 12444, JB / T 7901 and GB / T 17899 respectively.

[0082] Eight kinds of precipitation hardened high-speed steels with different component compositions, cast and forged tool steels (alloy A) and powder metallurgy tool steels (alloy B) are obtained by the above preparation method, and the results are as follows:

[0083] Table 1: Alloy composition:

[0084] Alloy C Si Mn Cr Co Ni V W Mo Mo + W / 2 1.39 Co + 1.4 Ni Fe Example 1 2.27 0.31 - 4.00 15.52 0.11 6.22 10.71 5.88 11.23 21.73 Balance Example 2 2.44 0.30 - 3.78 14.91 0.42 6.08 10.35 5.86 10.13 21.31 Balance Example 3 2.27 0.31 - 4.00 15.52 0.11 6.22 8.0 14.0 18.0 21.73 Balance Example 4 2.27 0.31 - 4.00 10.0 2.0 6.22 10.71 5.88 11.23 16.70 Balance Example 5 2.20 - - 2.0 10.0 - 6.0 12..0 5.0 11.0 13.90 Balance Example 6 3.0 0.40 - 8.0 30.0 2.5 13.0 5.0 16.0 18.5 45.20 Balance Example 7 2.8 0.32 - 7.5 28.0 2.3 11.8 9.0 15.7 20.2 42.14 Balance Example 8 2.9 0.35 - 7.8 29 2.4 12 11.0 15.8 20.3 41.06 Balance Comparative Example A 1.09 0.33 0.31 3.84 7.95 0.13 1.11 1.47 9.35 10.08 11.23 Balance Comparative Example B 1.61 0.42 0.34 4.72 7.97 0.17 5.05 10.22 2.15 7.26 11.31 Balance

[0085] (I) Microstructure analysis

[0086] Based on the microstructure images obtained by scanning electron microscopy, Figures 1 to 6 are the microstructure diagrams of the prepared precipitation hardened steel forgings of examples 1, 2, 4, 5, 6 and 7, Figure 7 is the microstructure diagram of alloy A, Figure 8 is the microstructure diagram of alloy B.

[0087] It is obvious that, Figures 1 to 6 The hardened phase in grayish white color is distributed in the matrix in a fine and dispersed manner, which can significantly improve the wear resistance, toughness and service life of the material. Figure 7 and Figure 8 Contains two kinds of precipitates, one is bright white and large in size, and the other is grayish white and small in size.

[0088] Table 2 shows the comparison of precipitate content and particle size in examples 1 to 8 and alloys A and B after heat treatment:

[0089] Table 2: Content and particle size of precipitates

[0090]

[0091] The solid solution system of examples 1 to 8 is 1190℃×30 minutes, and the aging system is 600℃×3 hours; the quenching system of comparative example A is 1160℃×15 minutes, and the tempering system is 550℃×3 hours; the quenching system of comparative example B is 1170℃×15 minutes, and the tempering system is 550℃×3 hours.

[0092] The precipitated phase analysis of the high speed steel prepared in the examples 1 to 8 in the present application is carried out: the precipitated phase in the examples 1 to 8 is mainly IMC and carbide, wherein the IMC is mainly μ phase, the type is (Fe, Co)7(Mo+W / 2)6, the carbide is divided into two types, VC type carbide and Cr-rich (Cr, Fe)C type carbide; the detected strengthening phase in the alloy A and the alloy B is mainly Cr-rich (Cr, Fe)C type carbide, in addition, there is VC type carbide.

[0093] The μ phase volume fraction of the precipitation hardening high speed steel in the present application reaches 10%-20%, the particle size is small, most of the μ phase particle size is less than 1.5 μm, the maximum size is not more than 6.0 μm, meanwhile, another type of strengthening phase exists in the precipitation hardening steel in the present application, wherein the MC carbide type is V(C, N) type, the volume fraction is 1%-5%, the particle size is small, most of the MC carbide particle size is less than 2.0 μm; the (Cr, Fe)C type carbide is Cr-rich carbide, the volume fraction reaches 3%-10%, most of the (Cr, Fe)C type carbide size is 1-5 μm.

[0094] The MC type carbide in the alloy B prepared by the powder metallurgy process is the smallest, most of the MC type carbide is 0.5-1.5 μm, the volume fraction is 2-6%, but there is a large number of (Cr, Fe)C type carbide with the size range of 3-12 μm in the structure. The coarse carbide has the adverse effect of cutting the matrix. In the A alloy produced by the traditional electroslag process, the MC type carbide size is close to the example, but there is a large number of (Cr, Fe)C type carbide with the size range of 5-30 μm in the structure, the coarse carbide has the adverse effect of cutting the matrix.

[0095] (II) Hardness and wear resistance performance analysis after heat treatment

[0096] In order to verify the influence of the heat treatment system on the performance of the precipitation hardening high speed steel prepared in the present application, the heat treatment process with different solid solution temperatures and aging temperatures is set to heat treat the prepared rod.

[0097] The high speed steel prepared in the examples 1 to 8 and the alloys A and B are heat treated, and the following hardness and wear resistance performance comparison results are shown in table 3.

[0098] Table 3: mechanical property comparison

[0099]

[0100] As can be seen from table 3, the hardness of the precipitation hardening steel in the present application can reach more than 64HRC, and at the same time, excellent wear resistance performance is shown, which can withstand long time high strength wear in the use process, thereby greatly improving the service life of the material.

[0101] (III) Corrosion resistance analysis

[0102] The alloys A, B and the steels of Examples 1 to 8 were immersed in a 5% HNO3+1% HC1 solution at room temperature, and then the corrosion rate was measured. Then the polarization curve was measured in a 1% NaCl solution, and finally the corrosion potential was obtained. The comparison results of corrosion resistance are shown in Table 4.

[0103] Table 4: Comparison of corrosion resistance

[0104] Alloy Quench and temper / solution age Corrosion rate mm / y Self-corrosion potential E corr ]]> Example 1 1190°C oil quench + 600°C * 3h ≤150 -0.477 Example 2 1190°C oil quench + 600°C * 3h ≤150 -0.462 Example 3 1190°C oil quench + 600°C * 3h ≤150 -0.470 Example 4 1190°C oil quench + 600°C * 3h ≤150 -0.491 Example 5 1190°C oil quench + 600°C * 3h ≤150 -0.432 Example 6 1190°C oil quench + 600°C * 3h ≤150 -0.502 Example 7 1190°C oil quench + 600°C * 3h ≤150 -0.495 Example 8 1190°C oil quench + 600°C * 3h ≤150 -0.487 Comparative Example A 1160°C oil quench + 550°C * 1h * 3 times ≤300 -0.222 Comparative Example B 1170°C oil quench + 550°C * 1h * 3 times ≤300 -0.261

[0105] As can be seen from the comparison data in Table 4, the precipitation hardening steel of the present application exhibits excellent corrosion resistance. According to the requirements of corrosion resistance in different application scenarios, a suitable heat treatment system should be selected. In a relatively wide heat treatment temperature range, the precipitation hardening high-speed steel of the present application can have good strength and toughness and wear and corrosion resistance, thereby meeting the application requirements in the working conditions with wear and corrosion.

[0106] In addition, due to the limitation of the precipitated phase particle number statistical image analysis software, in the above implementation conditions, the precipitation hardening steel of the present application may have individual μ phase and carbide with a size exceeding the maximum size, but due to the extremely small number, it has no substantial effect on the toughness and other mechanical properties of the precipitation hardening steel, and thus can be ignored. Many more fine μ phases cannot be identified by the analysis software, and the statistical results of volume fraction and particle size are only for comparison.

[0107] In summary, the powder metallurgy wear and corrosion resistant dual strengthening phase precipitation hardening high-speed steel of the present application has the characteristics of μ phase and carbide dual strengthening phase due to the specific alloy composition design and powder metallurgy process used in the present application. The precipitated phase has fine particle size and high dispersion, so that the material has good strength and toughness ratio and excellent comprehensive performance, especially good wear and corrosion resistance. The tools and parts produced have a longer service life and can meet different types of application requirements, and can be used to make (1) cutters for cutting difficult-to-machine materials at high speed; (2) high-precision gauges; (3) corrosion-resistant parts, etc.

[0108] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel, characterized in that, Its chemical components, by mass percentage, include: C：2.2%-3.0%； Si: 0%-0.4%; Cr：2.0%-8.0%； Co: 10.0%-30.0%; Ni: 0%-2.5%; (1.39Co + 1.4Ni) ≥ 13.0%; V：6%-13.0%； W：5%-12%； Mo: 5%-16.0%; (Mo+W / 2): 10.0%-22.0%; The balance consists of iron and impurities; Furthermore, the precipitated phases in the powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel include intermetallic compound (IMC) μ phase, MC carbide and (Cr,Fe)C type carbide, wherein the μ phase is of type (Fe,Co)7(Mo+W / 2)6 and the MC carbide is of type V(C,N). The powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel has at least 80% volume fraction of the μ phase with a particle size ≤1.5μm, and the maximum particle size of the μ phase does not exceed 6.0μm. The volume fraction of the μ phase in the powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel is 10-20%. The powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel has at least 80% volume fraction of MC carbides with a particle size ≤ 2.0 μm, the maximum particle size of the MC carbides not exceeding 3.0 μm, and the volume fraction of the MC carbides in the powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel is 1%-5%.

2. The powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel according to claim 1, characterized in that, Its chemical components, by mass percentage, include: C：2.2%-2.8%； Si: 0%-0.32%; Cr：2.0%-7.5%； Co: 10.0%-28.0%; Ni: 0%-2.3%; (1.39Co + 1.4Ni) ≥ 15.0%; V：6%-11.8%； W：5%-9%； Mo: 5%-15.7%; (Mo+W / 2): 10.0%-20.2%; The balance consists of iron and impurities.

3. The powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel according to claim 1, characterized in that: The (Cr,Fe)C type carbide is a Cr-rich carbide.

4. The powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation-hardening high-speed steel according to claim 1, characterized in that: The particle size of the (Cr,Fe)C type carbide is 1-5 μm, with at least 80% by volume. The maximum particle size of the (Cr,Fe)C type carbide is no more than 10.0 μm. The volume fraction of the (Cr,Fe)C type carbide in the powder metallurgy wear-resistant and corrosion-resistant dual-strengthened precipitation hardening high-speed steel is 3%-10%.

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