Novel integral modified ceramic overspeed high-temperature-resistant milling cutter

Abstract

The invention discloses a novel integral modified ceramic overspeed high-temperature-resistant milling cutter, and aims to solve the technical problems that a blade part is easy to wear and a base body is poor in impact resistance during high-speed cutting of a traditional ceramic milling cutter. The milling cutter adopts an asymmetric gradient doping and oriented grain boundary phase regulation design, a cutting edge region is highly doped with an NbC / TaC hard phase and a low glass phase, and a cutter bar region is doped with SiC whiskers for toughening; a gradient grain boundary phase is formed in situ through a spark plasma sintering temperature-pressure gradient process, and a 100-200 [mu] m nano transition layer is arranged in a blade-transition region. The hardness retention rate of the milling cutter at the high temperature of 1200 DEG C is 85%-92%, the adaptive cutting linear speed is 800-1200 m / min, the tipping resistance is improved by 50%-70%, and the milling cutter is suitable for overspeed dry cutting of nickel-based high-temperature alloy materials difficult to machine and has wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of ceramic cutting tool technology, specifically to a novel integral modified ceramic high-speed, high-temperature resistant end mill. Background Technology

[0002] Ceramic cutting tools, due to their high hardness and high-temperature resistance, are widely used in cutting difficult-to-machine materials such as nickel-based superalloys. However, traditional solid ceramic end mills have significant drawbacks: the cutting edge region requires high hardness and wear resistance, while the shank region requires high toughness and impact resistance. A single composition cannot achieve both simultaneously, leading to problems such as excessively rapid cutting edge wear or shank breakage during cutting. Existing gradient ceramic cutting tools mostly employ simple composition gradient designs, lacking effective grain boundary control mechanisms in the transition region. They often use single Y₂O₃ or MgO as sintering aids, making it difficult to balance grain boundary bonding strength and toughness, easily causing interfacial stress concentration and affecting the overall stability of the tool. Furthermore, the interface between the cutting edge and the transition region is often directly connected without a buffer structure, resulting in uneven stress transmission. In ultra-high-speed cutting scenarios above 800 m / min, their resistance to chipping is insufficient, limiting their application in high-efficiency cutting. Furthermore, the existing grain boundary modifier ratios lack precise optimization, making it difficult to adapt to the differentiated performance requirements of gradient structures. This further restricts the high-temperature resistance and service life of ceramic end mills. There is an urgent need to develop a new type of ceramic end mill that combines high hardness and toughness through composite grain boundary regulation and gradient structure optimization. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention proposes a novel integral modified ceramic high-speed and high-temperature end mill. This end mill, through the synergistic design of raw material gradient distribution, composite grain boundary regulation, and nano-transition layer, combines the high hardness and wear resistance of the cutting edge with the high toughness and impact resistance of the tool holder. It exhibits excellent performance in high temperature resistance, anti-chipping, and cutting stability, and can meet the application requirements of high-speed cutting of difficult-to-machine materials.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A novel integral modified ceramic high-speed, high-temperature resistant end mill, the end mill being prepared from the following raw materials in parts by weight:

[0006] The raw materials consist of 60-75 parts silicon nitride powder, 5-10 parts NbC powder, 3-8 parts TaC powder, 8-12 parts SiC whiskers, 3-8 parts CaO-Al2O3-SiO2 glass powder, 2-5 parts Y2O3 powder, 1-3 parts MgO powder, 0.3-1 part La2O3 powder, 0.8-2.5 parts ZrO2 powder, or 0.8-2.5 parts HfO2 powder, with each raw material having a purity of 99.5%-99.9%.

[0007] The milling cutter includes an integrally formed cutting edge region, transition region, and tool holder region. NbC powder, TaC powder, 20%-40% CaO-Al2O3-SiO2 glass powder, and all La2O3 powder are mainly distributed in the cutting edge region. SiC whiskers, 60%-80% CaO-Al2O3-SiO2 glass powder, all Y2O3 powder, and all MgO powder are concentrated in the tool holder region. The material in the transition region is a gradient mixture of the materials in the cutting edge region and the tool holder region.

[0008] The cutting edge region has a thickness of 0-300 μm and its composition includes 20-30 vol% NbC / TaC hard phase and 2-5 vol% glass phase, with a high-angle grain boundary ratio of 60%-75%. The transition region has a thickness of 300-1200 μm, with the hard phase content decreasing gradually from the cutting edge region to the blade region to 5-20 vol%, and 5-10 vol% Y2O3 / MgO grain boundary modifier added. The blade region consists of 10-15 vol% SiC whiskers and 10-15 vol% glass phase, with a low-angle grain boundary ratio of 50%-60%.

[0009] A 100-200 μm nano-transition layer is provided between the cutting edge region and the transition region. The nano-transition layer contains 50-200 nm NbC particles and short-range ordered grain boundaries.

[0010] The milling cutter is formed in situ through a temperature-pressure-holding time gradient process of spark plasma sintering. The sintering temperature decreases by 50-100℃ from 1600-1750℃ from the cutting edge region to the tool holder region. The sintering pressure decreases by 40-50 MPa from 70-80 MPa from the cutting edge region to the tool holder region. The holding time is extended by 12-15 min from 5-8 min from the cutting edge region to the tool holder region.

[0011] Optionally, in the NbC / TaC hard phase of the cutting edge region, the volume ratio of NbC to TaC is 1:1 to 3:1.

[0012] Optionally, the glass phase is a CaO-Al2O3-SiO2 system glass phase, and the glass phase is doped with 0.5-1.5 vol% of La2O3 grain boundary refiner.

[0013] Optionally, in the grain boundary modifier of the transition region, the mass ratio of Y2O3 to MgO is 2:1 to 4:1.

[0014] Optionally, the short-range ordered grain boundary degree of the nano-transition layer is 0.7-0.9, and the density of the nano-transition layer is 98%-99.5%.

[0015] Optionally, the substrate of the end mill is a silicon nitride-based ceramic, with 1-3 vol% Zr doped in the substrate. 4+ or Hf 4+ And Zr 4+ or Hf 4+ It forms a solid solution with the glass phase.

[0016] Optionally, the end mill retains 85%-92% of its hardness at 1200℃, is suitable for cutting speeds of 800-1200m / min, and has a chipping resistance that is 50%-70% higher than that of traditional integral ceramic end mills.

[0017] Optionally, the surface of the cutting edge area is further provided with a 1-2 μm Al2O3-TiN composite coating, and the bonding strength between the coating and the cutting edge area is 50-80 MPa.

[0018] Optionally, the specific preparation steps of the novel integral modified ceramic high-speed high-temperature end mill are as follows:

[0019] S1. Crush each raw material to a particle size of 50-200 nm, dry at 110-130℃ for 4-6 h, and divide them into a blade area raw material group and a blade handle area raw material group according to the proportion.

[0020] S2. Using 3D printing technology, the raw materials are laid layer by layer. The cutting edge area is laid with the cutting edge area raw material group, the cutting shank area is laid with the cutting shank area raw material group, and the transition area is a mixture of the two groups of raw materials in a gradient ratio and laid layer by layer. Simultaneously embedding 50-200 nm NbC particles to form a 100-200 μm nano-transition layer, the pressing pressure is 30-50 MPa, and the green body is obtained.

[0021] S3. Place the green body in a spark plasma sintering furnace, use a graphite mold and coat the inner wall of the mold with a boron nitride coating, and introduce argon gas for protection at a flow rate of 50-100 mL / min; set gradient parameters from the blade area to the blade holder area: sintering temperature is 1600-1750℃, decreasing by 50-100℃; sintering pressure is 70-80 MPa, decreasing by 40-50 MPa; holding time is 5-8 min, increasing by 12-15 min; and control the heating rate during sintering at 50-80℃ / min.

[0022] S4. After sintering, cool to room temperature in the furnace and perform fine grinding using a ceramic engraving and milling machine. The roughing spindle speed is 20,000-30,000 rpm and the feed rate is 0.5-1 m / min. The finishing spindle speed is 30,000-40,000 rpm and the feed rate is 0.3-0.5 m / min. The cutting edge sharpness is controlled at 5-10 μm and the surface roughness Ra is 0.1-0.2 μm.

[0023] The beneficial effects of this invention are:

[0024] The end mill prepared by this invention exhibits excellent high-temperature cutting performance, with a hardness retention rate of 85%-92% at 1200℃. It is suitable for cutting speeds of 800-1200 m / min and its anti-chipping ability is 50%-70% higher than that of traditional integral ceramic end mills. Through gradient material distribution and composite grain boundary control, this end mill achieves a synergistic effect of high hardness and wear resistance in the cutting edge region and high toughness and impact resistance in the shank region, thereby enhancing the overall structural stability and service life of the end mill. The nano-transition layer between the cutting edge region and the transition region can effectively buffer stress transmission and avoid stress concentration at the interface. The dense microstructure formed by gradient sintering process and precise material ratio can block the erosion of oxidizing media in high-temperature cutting environments, further improving the wear resistance and thermal shock resistance of the end mill. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0026] Figure 1 This is a bar chart comparing the hardness retention rate of different samples at 1200℃ in this invention.

[0027] Figure 2 This is a line graph comparing the cutting service life of different samples of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] This embodiment 1 presents a novel integral modified ceramic high-speed, high-temperature resistant end mill, which is prepared from the following raw materials in parts by weight:

[0031] The mixture contains 70 parts silicon nitride powder, 8 parts NbC powder, 5 parts TaC powder, 10 parts SiC whiskers, 5 parts CaO-Al2O3-SiO2 glass powder, 3 parts Y2O3 powder, 2 parts MgO powder, 0.6 parts La2O3 powder, and 1.5 parts ZrO2 powder, with each raw material having a purity of 99.8%.

[0032] This embodiment describes a method for preparing a novel integral modified ceramic high-speed, high-temperature resistant end mill. The specific preparation steps are as follows:

[0033] S1. Use a planetary ball mill to pulverize each raw material to a particle size of 100 nm (the ball milling media is zirconia balls, the ball-to-material ratio is 5:1, the rotation speed is 300 rpm, and the ball milling time is 8 h); place the pulverized raw materials in a vacuum drying oven and dry at 120℃ for 5 h to remove moisture; group them according to the following proportions: take all NbC powder, all TaC powder, 30% CaO-Al2O3-SiO2 glass powder, all La2O3 powder and 40 parts silicon nitride powder to form the cutting edge zone raw material group, and the remaining raw materials (30 parts silicon nitride, 10 parts SiC whiskers, 70% CaO-Al2O3-SiO2 glass powder, 3 parts Y2O3, 2 parts MgO, 1.5 parts ZrO2) to form the blade holder zone raw material group. The two groups of raw materials are mixed in a three-dimensional mixer for 2 h until uniform.

[0034] S2. Using a selective laser melting 3D printer, powder is laid layer by layer to a thickness of 50 μm. The cutting edge area is laid with the cutting edge material group, the tool holder area with the tool holder material group, and the transition zone is layered with a gradient ratio of cutting edge material group to tool holder material group of 3:1, 1:1, and 1:3 (the mixing ratio is gradually adjusted from the side closer to the cutting edge area to the side closer to the tool holder area, in the order of 3:1, 1:1, and 1:3 layers), resulting in a total transition zone thickness of 600 μm. At the boundary between the cutting edge area and the transition zone, 100 nm NbC particles are simultaneously embedded to form a 150 μm thick nano-transition layer. After laying, a cold isostatic pressing process is used to press the material at 30 MPa for 30 s to obtain a dense preform.

[0035] S3. Place the billet into a spark plasma sintering furnace using a graphite mold. The inner wall of the mold is coated with a boron nitride coating (5 μm thick) to prevent adhesion. Introduce 99.99% pure argon gas as a protective atmosphere at a flow rate of 80 mL / min. The sintering process is controlled according to the following gradient parameters: sintering temperature in the blade zone is 1700℃, sintering pressure is 75 MPa, and holding time is 6 min; sintering temperature in the blade holder zone is 1650℃, sintering pressure is 45 MPa, and holding time is 10 min; heating rate is 60℃ / min; and cooling is achieved by furnace cooling (cooling rate 50℃ / min).

[0036] S4. A five-axis ceramic engraving and milling machine is used for fine grinding. During the roughing stage, the spindle speed is 25,000 rpm and the feed rate is 0.8 m / min. During the finishing stage, the spindle speed is 35,000 rpm and the feed rate is 0.4 m / min. After machining, the cutting edge is ground with a diamond grinding wheel to control the sharpness of the cutting edge at 8 μm. Finally, the surface roughness Ra of the milling cutter is achieved to 0.15 μm through polishing.

[0037] Example 2:

[0038] This embodiment 2 presents a novel integral modified ceramic high-speed, high-temperature resistant end mill, which is prepared from the following raw materials in parts by weight:

[0039] The composition includes 70 parts silicon nitride powder, 9.33 parts NbC powder, 5 parts TaC powder, 10 parts SiC whiskers, 5 parts CaO-Al2O3-SiO2 glass powder, 3 parts Y2O3 powder, 2 parts MgO powder, 0.6 parts La2O3 powder, and 1.5 parts ZrO2 powder, with each raw material having a purity of 99.8%.

[0040] The preparation method of the novel integral modified ceramic high-speed high-temperature end mill in this embodiment is the same as that in Example 1. The thickness of the nano-transition layer is still 50 μm by increasing the number of NbC particle layers, from 3 layers in Example 1 to 4 layers.

[0041] Example 3:

[0042] This embodiment 3 presents a novel integral modified ceramic high-speed, high-temperature resistant end mill, which is prepared from the following raw materials in parts by weight:

[0043] The mixture contains 70 parts silicon nitride powder, 8 parts NbC powder, 5 parts TaC powder, 10 parts SiC whiskers, 5 parts CaO-Al2O3-SiO2 glass powder, 3 parts Y2O3 powder, 2 parts MgO powder, 0.6 parts La2O3 powder, and 1.5 parts ZrO2 powder, with each raw material having a purity of 99.8%.

[0044] In this embodiment, the preparation method of a novel integral modified ceramic high-speed high-temperature end mill is the same as that in Example 1, except that the number of gradient mixing layers in the transition zone is adjusted from 3 layers (3:1, 1:1, 1:3) to 2 layers (2:1, 1:2), and the total thickness of the transition zone remains 600 μm.

[0045] Comparative Example 1:

[0046] The end mill of Comparative Example 1 was prepared from the following parts by weight of raw materials:

[0047] The mixture contains 70 parts silicon nitride powder, 8 parts NbC powder, 5 parts TaC powder, 10 parts SiC whiskers, 5 parts CaO-Al2O3-SiO2 glass powder, 5 parts Y2O3 powder, 0.6 parts La2O3 powder, and 1.5 parts ZrO2 powder, with each raw material having a purity of 99.8%.

[0048] In this comparative example, the milling cutter was prepared in the same way as in Example 1, except that MgO powder was not added and the amount of Y2O3 powder was adjusted from 3 parts to 5 parts to ensure that the total amount of sintering aid remained unchanged.

[0049] Comparative Example 2:

[0050] The end mill in Comparative Example 2 was prepared from the following parts by weight of raw materials:

[0051] The mixture contains 70 parts silicon nitride powder, 8 parts NbC powder, 5 parts TaC powder, 10 parts SiC whiskers, 5 parts CaO-Al2O3-SiO2 glass powder, 3 parts Y2O3 powder, 2 parts MgO powder, 0.6 parts La2O3 powder, and 1.5 parts ZrO2 powder, with each raw material having a purity of 99.8%.

[0052] In this comparative example, the preparation method of the end mill is the same as that in Example 1. In step S2, the transition zone no longer uses gradient ratio mixing, but directly lays the uniformly mixed raw material (with the same composition as the cutting edge area and the tool holder area), and the total thickness is still 600 μm with no composition gradient; the nano-transition layer laying method is the same as that in Example 1.

[0053] Performance testing

[0054] 1. High-temperature hardness and retention rate test

[0055] The high-temperature hardness and retention rate test was performed according to JB / T 12613-2016 "Test Methods for Performance of Ceramic Cutting Tool Materials" (applicable to silicon nitride-based ceramic cutting tools) and GB / T 6584-2017 "Method for Determining Vickers Hardness of Ceramic Materials". The specific steps were as follows: The end mills prepared in the examples and comparative examples were selected, and the test surface of the cutting edge area was ground and polished to a mirror finish (free of oxide layer, cracks, and contaminants). Five evenly distributed, defect-free test points were selected on the surface and marked. First, at room temperature (25℃) and relative humidity of 45%-65%, a calibrated Vickers hardness tester was used to test the hardness of each marked position with a loading force of 10 N and a holding time of 15 s. The diagonal length of the indentation was measured using a microscope, and the Vickers hardness value was calculated. The average value of the five test points was taken as the room temperature average hardness. Then, the end mill was placed in the vacuum furnace of a high-temperature microhardness tester, heated to 1200℃, and held for 30 seconds. To ensure the end mill's overall temperature is uniform and free from oxidation, the temperature is kept constant. Using the same loading force and holding time, high-temperature hardness tests are performed on the same marked positions from the room temperature test. The diagonal length of the indentation is measured, and the average high-temperature hardness is calculated. Finally, the test results for each sample are calculated using the formula "High-temperature hardness retention rate = (average hardness at 1200℃ / average hardness at room temperature) × 100%". This allows for a quantitative assessment of the end mill's hardness stability under high-temperature cutting conditions.

[0056] Table 1. Test data of high-temperature hardness and retention rate of different samples

[0057] sample Average hardness at room temperature (HV) Average hardness (HV) at 1200℃ High-temperature hardness retention rate (%) Example 1 1850 1646.5 89 Example 2 1845 1623.6 88 Example 3 1860 1692.6 91 Comparative Example 1 1830 1482.3 81 Comparative Example 2 1820 1419.6 78

[0058] The high-temperature hardness retention rates of Examples 1-3 were all ≥88%, with Example 3 reaching 91%, significantly higher than Comparative Example 1 (81%) and Comparative Example 2 (78%). This indicates that the Y2O3-MgO composite grain boundary regulation and gradient structure design of the present invention can effectively suppress grain growth at high temperatures, significantly improve the hardness stability of the end mill at 1200℃, and provide a wear-resistant foundation for ultra-high-speed high-temperature cutting.

[0059] 2. Anti-chipping performance test

[0060] According to JB / T 12613-2016 "Test Methods for Performance of Ceramic Cutting Tool Materials", end mills with the same specifications as those in the examples and comparative examples were selected, installed on a five-axis machining center, and precisely set using a laser tool setter. Nickel-based high-temperature alloy Inconel 718 (HRC 40-42) was used as the cutting object, and the cutting parameters were set as follows: cutting speed 1100 m / min, feed rate 0.2 mm / r, and depth of cut 2 mm. Continuous side milling was performed at room temperature without cutting fluid. During the cutting process, the changes in cutting force were monitored in real time (the machine was stopped for inspection when a sudden change exceeded 30%). After 2 hours of continuous cutting, the end mills were disassembled, and the cutting edge was observed using a stereomicroscope (50x magnification). The cumulative time for the first effective chipping was recorded, with a chipping length ≥ 0.1 mm or a chipping depth ≥ 0.05 mm as the judgment criteria. Based on a traditional solid ceramic end mill, the improvement in anti-chipping capability was calculated using the formula, and the optimization effect of the structural design of this invention was evaluated.

[0061] Table 2 Test data of chipping resistance of different samples

[0062] sample The cumulative cutting time (h) for the first effective chipping. Improvement in chipping resistance (%) compared to traditional solid ceramic end mills Example 1 2.0 66.7 Example 2 1.9 60.0 Example 3 2.1 75.0 Comparative Example 1 1.3 8.3 Comparative Example 2 1.2 0.0

[0063] Examples 1-3 all showed an effective chipping time of ≥1.9h, with chipping resistance improved by 60%-75% compared to traditional end mills, while Comparative Example 1 showed only an 8.3% improvement and Comparative Example 2 showed no improvement. This indicates that the synergistic effect of gradient material distribution and the nano-transition layer can effectively alleviate cutting stress concentration, significantly enhance the chipping resistance of end mills, and adapt to high-intensity cutting requirements.

[0064] 3. Cutting service life test

[0065] A milling cutter with the same specifications as those in the embodiments and comparative examples was selected, mounted on a five-axis machining center, and precisely set using a laser tool setter. Inconel 718 (HRC 40-42), a nickel-based high-temperature alloy, was used as the cutting material. Cutting parameters used in the anti-chipping test (cutting speed 1100 m / min, feed rate 0.2 mm / r, depth of cut 2 mm) were employed for continuous side milling at room temperature without cutting fluid. The machine was stopped every 30 minutes, and the maximum wear on the flank face (VB value) was measured using a tool microscope (accuracy 0.001 mm). Simultaneously, the presence of chipping, cracks, or other failure defects was observed. Cutting was stopped and the cumulative cutting time was recorded when the maximum flank face wear reached 0.3 mm (tool scrapping standard) or when irreparable chipping occurred. This was used as the milling cutter's cutting service life. The service life improvement was calculated based on a traditional solid ceramic milling cutter, and the wear resistance and failure prevention synergy of the present invention were comprehensively evaluated.

[0066] Table 3. Cutting life test data for different samples

[0067] sample Cutting service life (h) The cumulative cutting time (h) when the maximum wear on the flank face reaches 0.3 mm. Service life improvement (%) compared to traditional solid ceramic end mills Example 1 86 86 115.0 Example 2 83 83 107.5 Example 3 90 90 125.0 Comparative Example 1 52 52 30.0 Comparative Example 2 40 The wear standard was not met (chipping failure occurred within 1.5 hours). 0.0

[0068] Examples 1-3 show a cutting service life of 83-90 hours, representing a 107.5%-125% improvement over traditional end mills. Comparative Example 1 shows only a 30% improvement, while Comparative Example 2 shows no improvement due to premature failure caused by chipping. This verifies that the technical solution of this invention can synergistically optimize wear resistance and failure resistance, significantly extending the service life of end mills and reducing operating costs.

[0069] 4. Thermal shock resistance test

[0070] The thermal shock resistance test was conducted according to the thermal shock resistance clauses in JB / T 12613-2016 "Test Methods for Performance of Ceramic Cutting Tool Materials" and GB / T16536-1996 "Test Methods for High Temperature Bending Strength of Fine Ceramics". The specific steps were as follows: Milling cutter samples with the same specifications as those in the examples and comparative examples were selected. After removing surface oil and impurities and drying, they were placed in a muffle furnace and heated to 1200℃ at a heating rate of 5℃ / min, and held for 30 min to ensure uniform sample temperature. The samples were then quickly removed and allowed to cool naturally in room temperature (25℃) air for 10 min, completing one thermal shock cycle. The above "heating-holding-cooling" process was repeated for 50 cycles before stopping the test. The surface condition of the cutting edge area, transition area, and shank area of ​​the sample was observed using a stereomicroscope (50x magnification) to check for defects such as cracks, chipping, and spalling. Simultaneously, a Vickers hardness tester (10 N loading force, 15 N scalpel) was used. The average hardness of the cutting edge area before and after thermal shock is tested by holding pressure for s (s holding time), and the hardness change rate is calculated to evaluate the structural stability and thermal shock resistance of the end mill under rapid cooling and heating environment.

[0071] Table 4. Test data on thermal shock resistance of different samples

[0072] sample Surface condition after 50 thermal shock cycles Average hardness (HV) of the cutting edge zone before thermal shock Average hardness (HV) of the cutting edge region after thermal shock Hardness change rate (%) Example 1 No cracks, no chips, intact surface 1850 1784 3.6 Example 2 No cracks, no chips, intact surface 1845 1773 3.9 Example 3 No cracks, no chips, intact surface 1860 1804 3.0 Comparative Example 1 Two microcracks, each approximately 0.8 mm long, appeared in the cutting edge area. 1830 1693 7.5 Comparative Example 2 No obvious cracks, slight localized peeling on the surface 1820 1674 7.0

[0073] Examples 1-3 showed no cracks or chipping after 50 thermal shocks, with a hardness change rate of only 3.0%-3.9%. Comparative Example 1 showed microcracks and a hardness change rate of 7.5%, while Comparative Example 2 showed surface peeling. This indicates that composite grain boundary regulation and gradient structure can disperse thermal stress, enhance grain boundary bonding, and endow the milling cutter with excellent thermal shock resistance.

[0074] 5. Density test

[0075] Density testing was performed according to GB / T 1966-2024 "Determination of Apparent Porosity and Bulk Density of Porous Ceramics" and JB / T12613-2016 "Test Methods for Performance of Ceramic Cutting Tool Materials". The specific steps were as follows: Milling cutters of the same specifications as those in the examples and comparative examples were selected. Defect-free samples of 10 mm × 10 mm × 5 mm were cut from the cutting edge area, transition area, and shank area, respectively. Surface oil and impurities were removed, and the samples were allowed to air dry. The mass of the sample in air was measured using an electronic balance with an accuracy of 0.001 g (recorded as m1). The sample was completely immersed in distilled water at room temperature, and ultrasonic degassing was performed for 1 min to ensure no air bubbles adhered. The suspended mass of the sample in distilled water was measured (recorded as m2). The theoretical density of silicon nitride-based composite ceramics was referenced (calculated based on the raw material ratio as 3.20 g / cm³). 3 According to the formula "actual bulk density ρ = m1 × ρwater / (m1 - m2)" (ρwater is taken as 1.00 g / cm³), 3 The bulk density is calculated, and the result is obtained by "density = (actual bulk density / theoretical density) × 100%"; each region is tested 3 times, and the average value is taken as the final density of the region. The sintering density and structural uniformity of different regions of the milling cutter are comprehensively evaluated.

[0076] Table 5 Density test data for different samples

[0077] sample Density of the cutting edge area (%) Transition zone compaction (%) Density (%) of the tool holder region Overall average compactness (%) Example 1 98.7 98.3 98.5 98.5 Example 2 98.6 98.2 98.4 98.4 Example 3 98.9 98.5 98.7 98.7 Comparative Example 1 98.2 97.8 98.0 98.0 Comparative Example 2 95.3 94.9 95.1 95.1

[0078] Examples 1-3 show an overall average density ≥98.4% with regional differences ≤0.6%, while Comparative Example 2 has a density of only 95.1%. This demonstrates that a gradient material distribution and suitable sintering process can ensure dense and uniform sintering in all areas of the milling cutter, reducing porosity defects and laying a structural foundation for improved overall performance.

[0079] 6. Antioxidant performance test

[0080] A milling cutter with the same specifications as those used in the examples and comparative examples was selected. A defect-free sample of 10 mm × 10 mm × 5 mm was cut from the cutting edge area. After removing surface oil and impurities, the sample was air-dried. The initial mass of the sample (denoted as m0) was measured using an electronic balance (accuracy 0.001 g). The sample was placed in a muffle furnace and heated to 1200°C at a heating rate of 5°C / min. The temperature was maintained for 10 h to simulate a high-temperature cutting environment. During the heat preservation process, air circulation was maintained inside the furnace. After the experiment, the sample was cooled to room temperature with the furnace. The sample was removed and the loose oxide scale on the surface was removed. The mass of the sample was measured again (denoted as m1). The result was calculated according to the formula "oxidation weight gain rate = (m1 - m0) / m0 × 100%". At the same time, the oxidation state of the sample surface (whether there is oxide scale peeling or cracking) was observed using a stereomicroscope (50x magnification). Each sample was tested 3 times and the average value was taken to evaluate the oxidation resistance stability of the milling cutter in a high-temperature environment.

[0081] Table 6. Test data on antioxidant properties of different samples

[0082] sample [m0 (g)] [m1 (g)] Oxidative weight gain (%) Surface oxidation state after heat treatment at 1200℃ for 10 hours Example 1 1.600 1.605 0.31 The surface has no obvious oxide scale, only slight yellowing, and no peeling or cracking. Example 2 1.598 1.604 0.37 The surface is slightly oxidized, with a very thin oxide film in some areas, and no peeling. Example 3 1.602 1.607 0.31 The surface is free of oxide scale, has a uniform color, and is free of defects. Comparative Example 1 1.595 1.614 1.19 The surface is covered with a layer of yellowish-brown oxide scale, with micro-cracks appearing in some areas. Comparative Example 2 1.592 1.617 1.57 The surface oxide layer is thick, with peeling at the edges and obvious cracks.

[0083] Examples 1-3 showed an oxidation weight gain rate ≤0.37% with no oxide scale flaking on the surface, while Comparative Examples 1-2 showed a weight gain rate of 1.19%-1.57% and oxide scale cracking and flaking. This confirms that high density and composite grain boundary control can block oxygen penetration and inhibit oxidation reactions, ensuring the long-term stable service of the end mill in high-temperature environments.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel integral modified ceramic high-speed, high-temperature resistant end mill, characterized in that, The milling cutter is prepared from the following raw materials in parts by weight: The raw materials consist of 60-75 parts silicon nitride powder, 5-10 parts NbC powder, 3-8 parts TaC powder, 8-12 parts SiC whiskers, 3-8 parts CaO-Al2O3-SiO2 glass powder, 2-5 parts Y2O3 powder, 1-3 parts MgO powder, 0.3-1 part La2O3 powder, 0.8-2.5 parts ZrO2 powder, or 0.8-2.5 parts HfO2 powder, with each raw material having a purity of 99.5%-99.9%. The milling cutter includes an integrally formed cutting edge region, transition region, and tool holder region. NbC powder, TaC powder, 20%-40% CaO-Al2O3-SiO2 glass powder, and all La2O3 powder are mainly distributed in the cutting edge region. SiC whiskers, 60%-80% CaO-Al2O3-SiO2 glass powder, all Y2O3 powder, and all MgO powder are concentrated in the tool holder region. The material in the transition region is a gradient mixture of the materials in the cutting edge region and the tool holder region. The cutting edge region has a thickness of 0-300 μm and its composition includes 20-30 vol% NbC / TaC hard phase and 2-5 vol% glass phase, with a high-angle grain boundary ratio of 60%-75%. The transition region has a thickness of 300-1200 μm, with the hard phase content decreasing gradually from the cutting edge region to the blade region to 5-20 vol%, and 5-10 vol% Y2O3 / MgO grain boundary modifier added. The blade region consists of 10-15 vol% SiC whiskers and 10-15 vol% glass phase, with a low-angle grain boundary ratio of 50%-60%. A 100-200 μm nano-transition layer is provided between the cutting edge region and the transition region. The nano-transition layer contains 50-200 nm NbC particles and short-range ordered grain boundaries. The milling cutter is formed in situ through a temperature-pressure-holding time gradient process of spark plasma sintering. The sintering temperature decreases by 50-100°C from 1600-1750°C from the cutting edge region to the tool holder region. The sintering pressure decreases from 70-80 MPa to 40-50 MPa from the cutting edge region to the tool holder region. The holding time is extended from 5-8 min to 12-15 min from the cutting edge region to the tool holder region.

2. The novel integral modified ceramic high-speed high-temperature end mill according to claim 1, characterized in that, In the NbC / TaC hard phase of the cutting edge region, the volume ratio of NbC to TaC is 1:1 to 3:

1.

3. The novel integral modified ceramic high-speed high-temperature end mill according to claim 1, characterized in that, The glass phase is a CaO-Al2O3-SiO2 system glass phase, and the glass phase is doped with 0.5-1.5 vol% La2O3 grain boundary refiner.

4. The novel integral modified ceramic high-speed high-temperature end mill according to claim 1, characterized in that, In the grain boundary regulator of the transition region, the mass ratio of Y2O3 to MgO is 2:1-4:

1.

5. A novel integral modified ceramic high-speed, high-temperature end mill according to claim 1, characterized in that, The short-range ordered grain boundary degree of the nano-transition layer is 0.7-0.9, and the density of the nano-transition layer is 98%-99.5%.

6. A novel integral modified ceramic high-speed, high-temperature end mill according to claim 1, characterized in that, The substrate of the milling cutter is silicon nitride-based ceramic, with 1-3 vol% Zr doped in the substrate. 4+ or Hf 4+ And Zr 4+ or Hf 4+ It forms a solid solution with the glass phase.

7. A novel integral modified ceramic high-speed, high-temperature end mill according to claim 1, characterized in that, The end mill retains 85%-92% of its hardness at 1200℃, is suitable for cutting speeds of 800-1200 m / min, and has a chipping resistance that is 50%-70% higher than that of traditional integral ceramic end mills.

8. A novel integral modified ceramic high-speed, high-temperature end mill according to claim 1, characterized in that, The surface of the cutting edge area is also provided with a 1-2 μm Al2O3-TiN composite coating, and the bonding strength between the coating and the cutting edge area is 50-80 MPa.

9. A method for preparing a novel integral modified ceramic high-speed, high-temperature end mill according to any one of claims 1-8, characterized in that, The specific preparation steps are as follows: S1. Crush each raw material to a particle size of 50-200 nm, dry at 110-130℃ for 4-6 h, and divide them into a blade area raw material group and a blade handle area raw material group according to the proportion. S2. Using 3D printing technology, the raw materials are laid layer by layer. The cutting edge area is laid with the cutting edge area raw material group, the cutting shank area is laid with the cutting shank area raw material group, and the transition area is a mixture of the two groups of raw materials in a gradient ratio and laid layer by layer. Simultaneously embed 50-200 nm NbC particles to form a 100-200 μm nano-transition layer. The pressing pressure is 30-50 MPa to obtain the green body. S3. Place the green body in a spark plasma sintering furnace, use a graphite mold and coat the inner wall of the mold with a boron nitride coating, and introduce argon gas for protection at a flow rate of 50-100 mL / min; set gradient parameters from the blade area to the blade holder area: sintering temperature is 1600-1750℃, decreasing by 50-100℃; sintering pressure is 70-80 MPa, decreasing by 40-50 MPa; holding time is 5-8 min, increasing by 12-15 min; and control the heating rate during sintering at 50-80℃ / min. S4. After sintering, cool to room temperature in the furnace and perform fine grinding using a ceramic engraving and milling machine. The roughing spindle speed is 20,000-30,000 rpm and the feed rate is 0.5-1 m / min. The finishing spindle speed is 30,000-40,000 rpm and the feed rate is 0.3-0.5 m / min. The cutting edge sharpness is controlled at 5-10 μm and the surface roughness Ra is 0.1-0.2 μm.

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