An AlCrBSiN coating for high-speed dry cutting, a preparation method thereof and an application thereof

Abstract

The present invention relates to the technical field of high-speed dry cutting machining, and particularly relates to an AlCrBSiN coating for high-speed dry cutting, a preparation method thereof and an application thereof. In the AlCrBSiN composite coating, the B and Si elements can refine grains and improve the coating hardness. At the same time, the addition of the B element can inhibit the decomposition of the composite coating under high-temperature conditions and improve its high-temperature stability. Meanwhile, during the high-speed dry cutting process, the B element can preferentially generate a friction oxidation film, reduce the friction coefficient and friction force, reduce the wear of the rake face and flank face of the coated tool, and improve its high-speed dry cutting performance. The high-speed dry cutting life of an AlCrBSiN coating for high-speed dry cutting is the longest (12.5 min), which is increased by 31% compared with an AlCrN coating without B and Si (9.5 min), and the cutting force is reduced by 23%, having great application prospects in the fields of tool and surface protection.

Description

Technical Field

[0001] The present invention relates to the technical field of high-speed dry cutting machining, and particularly relates to an AlCrBSiN coating for high-speed dry cutting, a preparation method thereof, and an application thereof. Background Art

[0002] In the machinery manufacturing industry, although there are many different process forming methods, more than 90% of mechanical parts are still manufactured through cutting processes. With the highly intelligent, integrated, and efficient development of modern manufacturing, higher requirements are put forward for the performance of tooling dies, and the concepts of green environmental protection and high efficiency and energy conservation are constantly mentioned. Traditional cutting technologies require a large amount of cutting oil or cutting fluid during the machining process, which not only has a certain negative impact on human health and the rational utilization of resources, but also seriously damages the ecological environment. High-speed dry cutting technology requires no (or a small amount of) cutting oil or cutting fluid, and has the characteristics of high efficiency and low energy consumption, and is a green manufacturing process. However, high-speed dry cutting technology has problems such as large cutting forces, high temperatures, severe adhesion, and tool wear. Therefore, how to reduce tool wear and thermal shock and extend the service life of tools has become an important research topic in the development of high-speed dry cutting technology.

[0003] In recent decades, the emergence of coated tools has led to a major breakthrough in high-speed dry cutting performance. The combination of a tool substrate and a hard coating, while maintaining the good toughness and high strength of the substrate, the hard coating has the advantages of high hardness, wear resistance, friction reduction, and high-temperature oxidation resistance, greatly improving the performance of the tool. Thanks to the development of Physical Vapor Deposition (PVD) technology, a variety of nitride coatings have been successfully deposited on the surface of cemented carbide tools to improve their high-speed dry cutting performance. However, under the strong thermo-mechanical coupling action of high-speed dry cutting, the temperature at the cutting edge of the coated tool rises sharply, the coating undergoes a phase transformation, the hardness drops sharply, the cutting force and the friction coefficient increase, resulting in accelerated wear of the coated tool, and further leading to a reduction in the high-speed dry cutting life of the tool.

[0004] In view of the above defects, the creators of the present invention have finally obtained the present invention through long-term research and practice. Summary of the Invention

[0005] The purpose of the present invention is to provide a solution to the problems of low coating hardness, high cutting force and friction coefficient, and severe wear during high-speed dry cutting. The existing AlCrN composite coating has poor toughness, low high-temperature hardness, high cutting force and high-temperature friction coefficient, which easily causes excessive wear of the coating during high-speed dry cutting, and further leads to a reduction in the tool life during cutting. The present invention provides an AlCrBSiN coating for high-speed dry cutting, a preparation method thereof, and an application thereof.

[0006] To achieve the above object, the present invention discloses an AlCrBSiN coating for high-speed dry cutting. The AlCrBSiN coating comprises 34% - 36% of Al, 15% - 17% of Cr, 0% - 3% of B, 1% - 6% of Si, and 44% - 46% of N.

[0007] The B exists in the form of amorphous BN phase, and the Si exists in the form of amorphous SiN phase.

[0008] The thickness of the AlCrBSiN coating is 4 μm.

[0009] The present invention also discloses a preparation method of the above-mentioned AlCrBSiN coating for high-speed dry cutting, comprising the following steps:

[0010] S1, subject the polished cemented carbide specimen to ultrasonic cleaning, rinse it with deionized water, and dry it for standby;

[0011] S2, heat the dried cemented carbide specimen in step S1, evacuate to vacuum, introduce Ar gas, turn on the Ti target, ionize a large amount of Ti + and electrons in the furnace cavity, strike Ar, form high-energy and high-density Ar+ to perform ion bombardment on the substrate surface for ion etching and cleaning;

[0012] S3, after the ion etching in step S2 ends, keep the deposition temperature and the pressure in the furnace cavity unchanged, turn on the Cr target, and deposit the Cr first bonding layer;

[0013] S4, after the deposition of the Cr first bonding layer in step S3 is completed, keep the deposition temperature unchanged, close the Ar gas, introduce N2 gas, and deposit the CrN second bonding layer;

[0014] S5, after the deposition of the CrN second bonding layer in step S4 is completed, keep the deposition temperature unchanged, turn on the AlCr target, further increase the flow rate of N2 gas, and deposit the AlCrN transition layer;

[0015] S6, after the deposition of the AlCrN transition layer in step S5 is completed, keep the deposition temperature unchanged, turn on the AlCrSi target and the AlCrB target simultaneously, further increase the flow rate of N2 gas, and deposit the AlCrBSiN functional layer.

[0016] In step S2, the heating temperature is 480 °C, the vacuum degree after evacuation is 10 -4 Pa, the flow rate of Ar gas is 200 - 600 sccm, the negative bias voltage of ion etching is -200 V, and the etching time is 40 min.

[0017] In step S3, the substrate bias voltage is -60 - -80 V, the target current of the metal Cr target is 100 - 130 A, and the deposition time is 5 - 10 min.

[0018] In step S4, after introducing N2 gas, the pressure is 1 - 2 Pa, the N2 flow rate is 100 - 300 sccm, and the deposition time is 5 - 10 min.

[0019] In step S5, the atomic ratio of Al:Cr in the AlCr target is 67:33, the pressure for increasing the N2 gas introduction amount is 2 - 5 Pa, the N2 flow rate is 400 - 800 sccm, and the deposition time is 10 - 15 min.

[0020] In step S6, the atomic ratio of Al:Cr:Si in the AlCrSi target is 60:30:10, the atomic ratio of Al:Cr:B in the AlCrB target is 65:30:5 or 60:30:10, the pressure after increasing the N2 gas introduction amount is 3 - 6 Pa, the N2 flow rate is 500 - 800 sccm, and the deposition time is 50 - 60 min.

[0021] The present invention also discloses the application of the above - mentioned AlCrBSiN coating for high - speed dry cutting in improving the cutting life of tools.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. Compared with the existing coatings, the AlCrBSiN composite coating of the present invention can simultaneously form a structure with amorphous BN and SiN phases. The coating has a better grain refinement effect and has the advantages of high hardness, good toughness, stable high - temperature structure and high - temperature hardness.

[0024] 2. When using the AlCrBSiN coating of the present invention for high - speed dry cutting, a friction - oxidation film containing B, Al and Si with a low friction coefficient can be in - situ formed on the tool surface within a wide temperature range (600 °C - 1000 °C), reducing the friction coefficient and cutting force of the composite coating, and significantly improving the high - speed dry cutting performance of the coated tool. Brief Description of the Drawings

[0025] Figure 1 It is the XPS spectrum of the B10 coating;

[0026] Figure 2 It is the cross - sectional morphology of the coating: (a) B0 coating, (b) B5 coating, (c) B10 coating;

[0027] Figure 3 It is the XRD spectrum of the coating after vacuum annealing: (a) B0 coating, (b) B5 coating, (c) B10 coating;

[0028] Figure 4 It is the turning life curve of the coating, the cutting force F x curve and the friction coefficient μ: (a) cutting life, (b) cutting force change curve F x, (c) Cutting friction coefficient μ;

[0029] Figure 5 It is the flank wear morphology diagram of the coated tool during turning for 3.5 min and 8 min. Specific implementation manners

[0030] The following further elaborates on the above and additional technical features and advantages of the present invention in conjunction with the accompanying drawings.

[0031] Example 1

[0032] First step, ultrasonically clean the ground and polished cemented carbide for a certain period of time, rinse it with deionized water, and dry the sample for standby;

[0033] Second step, place the treated cemented carbide sample on the substrate turntable, heat it to 480 °C, evacuate to 10 - 4 Pa, introduce Ar gas, with an Ar gas flow rate of 300 sccm, turn on the Ti target, control the negative bias voltage to -200 V, ionize a large number of Ti+ and electrons in the furnace chamber, bombard Ar, form high-energy and high-density Ar+ to perform ion bombardment on the substrate surface, ion etching and cleaning, activating the substrate while cleaning the surface, improving the film-substrate adhesion of the coating, and the etching time is 40 min;

[0034] Third step, keep the deposition temperature and the pressure in the furnace chamber unchanged, turn on the Cr target, deposit the Cr first bonding layer; under the condition that the substrate bias voltage is -60 V and the target current of the metal Cr target is 130 A, the deposition is completed after 5 min.

[0035] Fourth step, keep the deposition temperature unchanged, turn off the Ar gas, introduce a small amount of N2 gas, change the pressure to 1 Pa, and the N2 flow rate is 100 sccm, deposit the CrN second bonding layer, and the deposition time is 7 min;

[0036] Fifth step, keep the deposition temperature unchanged, turn on the AlCr target (Al:Cr atomic ratio is 67:33), further increase the N2 gas, change the pressure to 2 Pa, and the N2 flow rate is 400 sccm, deposit the AlCrN transition layer, and the deposition time is 70 min. The coating is denoted as the B0 coating.

[0037] Example 2

[0038] First step, ultrasonically clean the ground and polished cemented carbide for a certain period of time, rinse it with deionized water, and dry the sample for standby;

[0039] Second step, place the treated cemented carbide sample on the substrate turntable, heat it to 480 °C, evacuate to 10 - 4Pa, introduce Ar gas with a flow rate of 300 sccm. Turn on the Ti target and control the negative bias voltage at -200 V. Ionize a large number of Ti⁺ and electrons in the furnace chamber, which collide with Ar to form high-energy and high-density Ar⁺ for ion bombardment of the substrate surface. Perform ion etching and cleaning, which not only cleans the surface but also activates the substrate, improving the film-substrate adhesion of the coating. The etching time is 40 min;

[0040] In the third step, keep the deposition temperature and the pressure in the furnace chamber unchanged. Turn on the Cr target to deposit the first Cr bonding layer. Under the conditions that the substrate bias voltage is -60 V and the target current of the metal Cr target is 130 A, the deposition is completed after 5 min;

[0041] In the fourth step, keep the deposition temperature unchanged. Turn off the Ar gas and introduce a small amount of N₂ gas. Change the pressure to 1 Pa and the N₂ flow rate to 100 sccm to deposit the second CrN bonding layer, and the deposition time is 7 min;

[0042] In the fifth step, keep the deposition temperature unchanged. Turn on the AlCr target (Al:Cr atomic ratio is 67:33), further increase the N₂ gas, change the pressure to 2 Pa, and the N₂ flow rate to 400 sccm to deposit the AlCrN transition layer, and the deposition time is 10 min;

[0043] In the sixth step, keep the deposition temperature unchanged. At the same time, turn on the AlCrSi target (Al:Cr:Si atomic ratio is 60:30:10) and the AlCrB target (Al:Cr:B atomic ratio is 65:30:5), further increase the N₂ gas, change the pressure to 5 Pa, and the N₂ flow rate to 800 sccm to deposit the AlCrBSiN functional layer, and the deposition time is 60 min. The coating is denoted as the B5 coating.

[0044] Example 3

[0045] In the first step, perform ultrasonic cleaning of the polished cemented carbide for a certain period of time, rinse it with deionized water, and dry the sample for standby;

[0046] In the second step, place the treated cemented carbide sample on the substrate turntable, heat it to 480 °C, and evacuate to 10 - 4 Pa, introduce Ar gas with a flow rate of 300 sccm. Turn on the Ti target and control the negative bias voltage at -200 V. Ionize a large number of Ti⁺ and electrons in the furnace chamber, which collide with Ar to form high-energy and high-density Ar⁺ for ion bombardment of the substrate surface. Perform ion etching and cleaning, which not only cleans the surface but also activates the substrate, improving the film-substrate adhesion of the coating. The etching time is 40 min;

[0047] In the third step, keep the deposition temperature and the pressure in the furnace chamber constant, turn on the Cr target, and deposit the first Cr bonding layer; under the conditions that the substrate bias voltage is -60 V and the target current of the metal Cr target is 130 A, the deposition is completed after 5 minutes.

[0048] In the fourth step, keep the deposition temperature constant, turn off the Ar gas, introduce a small amount of N2 gas, change the pressure to 1 Pa, the N2 flow rate is 100 sccm, deposit the second CrN bonding layer, and the deposition time is 7 minutes.

[0049] In the fifth step, keep the deposition temperature constant, turn on the AlCr target (Al:Cr atomic ratio is 67:33), further increase the N2 gas, change the pressure to 2 Pa, the N2 flow rate is 400 sccm, deposit the AlCrN transition layer, and the deposition time is 10 minutes.

[0050] In the sixth step, keep the deposition temperature constant, turn on the AlCrSi target (Al:Cr:Si atomic ratio is 60:30:10) and the AlCrB target (Al:Cr:B atomic ratio is 60:30:10) simultaneously, further increase the N2 gas, change the pressure to 5 Pa, the N2 flow rate is 800 sccm, deposit the AlCrBSiN functional layer, and the deposition time is 60 minutes. The coating is denoted as the B10 coating.

[0051] The chemical compositions in the coatings are listed in Table 1. It can be seen that the main elements in the AlCrN coating are Al, Cr, and N, while the B5 and B10 coatings contain B and Si.

[0052] Table 1 Chemical compositions (at.%) of as-prepared AlCrBSiN coatings

[0053]

[0054] Figure 1 It is the XPS spectrum of a typical B10 coating. It can be seen from the B1s spectrum that the characteristic peak at 190.6 eV conforms to the B-N bond of the amorphous BN phase. In the Si 2p spectrum, the Si element in the coating mainly exists in the form of Si-N bonds, and its binding energy is 101.6 eV, which is consistent with the Si-N bond binding energy in the amorphous Si3N4 phase. It can be found from the XPS energy spectrum of N1s that characteristic peaks appear at the binding energies of 396.4 eV, 396.6 eV, 397.2 eV, and 398.2 eV, which are consistent with the bond energies of Al-N, Cr-N, B-N, and Si-N respectively.

[0055] Figure 2It is the cross-sectional morphology of the coating. As can be seen from the figure, the coating has a good bonding with the substrate, and its thickness is about 4 μm. The coating can be divided into three parts: the lower layer is the Cr + CrN bonding layer; the middle layer is the AlCrN transition layer, and an obvious columnar crystal structure can be observed; the top layer is the working layer. Through careful observation of the working layer, it can be found that after adding Si and B elements, the original columnar crystal structure of AlCrN becomes denser, indicating that Si and B elements have a refinement effect on the microstructure.

[0056] Figure 3 It is the XRD pattern of the coating after vacuum annealing at 800 °C, 900 °C, and 1000 °C. When the annealing temperature is 800 °C, an obvious diffraction peak of h-AlN appears at 35.9° for the AlCrN coating, while both h-AlN and h-Cr2N phases appear in the B10 coating, indicating that the coating will undergo phase decomposition when annealed above 800 °C, decomposing into h-AlN and h-Cr2N, which shows that both the B0 and B10 coatings have undergone phase decomposition after vacuum annealing at 900 °C. When the annealing temperature is further increased to 1000 °C, diffraction peaks of h-AlN and h-Cr2N appear in all three coatings, indicating that at 1000 °C, the (Al,Cr)N phase in the coating has all decomposed, and the metastable h-Cr2N phase further decomposes into body-centered cubic Cr and N2. It should be noted that although the diffraction peak intensities of the AlCrN (111) and (200) crystal planes in the B5 coating have decreased compared to those at 800 °C, their intensities are still higher than those of other coatings, indicating that it has not completely decomposed; while the AlCrN diffraction peak in the B10 coating has almost disappeared, indicating a higher degree of decomposition. From the high-temperature XRD results, the B5 coating has better high-temperature stability.

[0057] Table 2 shows the Knoop hardness of the coating after high-temperature annealing. It can be seen that the hardness of the AlCrN coating in the unannealed coating is the lowest. When the coating is annealed at 800 °C, the hardness of all three coatings increases slightly. When the annealing temperature is increased to 900 °C, the hardness of all three coatings shows a certain degree of decrease, which is mainly related to the phase decomposition of the coating after annealing at 900 °C. When the annealing temperature reaches 1000 °C, softer h-AlN phase is formed in the coating, and the h-Cr2N phase further decomposes into N2 and metallic Cr phase, resulting in a sharp decrease in the coating hardness. It should be noted that the hardness of the B0 coating is as low as 1050 HK0.05 at 1200 °C, while the B5 coating shows a higher hardness (2450 HK0.05) at 1200 °C. This can ensure that the cutting edge tip of the coated tool can still maintain a high mechanical strength under high-speed dry cutting conditions.

[0058] Table 2 Microhardness (HK of the coating after high-temperature vacuum annealing 0.05 )

[0059] Coating As-deposited 800℃ 900℃ 1000℃ 1100℃ 1200℃ B0 3520 3050 2500 1500 1300 1050 B5 3630 3720 3100 2800 2600 2450 B10 3700 3750 3000 2100 1900 1750

[0060] Figure 4 (a) shows the high-speed dry turning life curve of the coating at a cutting speed of 250 m / min. It can be seen from Figure 4 (a) that the cutting life of the AlCrN coating is the shortest, which is 9.5 min. The lives of the B5 and B10 coatings are 12.5 min and 11 min respectively. Compared with the B0 coating, the lives of the B5 and B10 coatings with added B element have both increased. Among them, the turning life of the B5 coating has increased by 31%.

[0061] During turning, the cutting force was measured, and the results are shown in Figure 4 (b). The cutting force F borne by the coated tool during cutting x increases with the increase of the flank wear degree. Among them, in the later stage of cutting, the cutting force borne by the B5 coating is the lowest, which is 100 N. Compared with 130 N of AlCrN, it is reduced by about 23%. This shows that the B5 tool coating is more suitable for high-speed dry turning. From the above high-temperature results, it can be seen that the B5 coating has the best high-temperature hardness and high-temperature phase structure stability performance, resulting in the lowest flank wear degree and the best cutting edge integrity under the same turning conditions. Furthermore, it reduces the friction between the tool-chip contact area and decreases its cutting force. Figure 4 (c) shows the average friction coefficient (μ) during the turning of the AlCrBSiN coating. It can be found that the friction coefficients of the B0, B5, and B10 coatings are 0.940, 0.883, and 0.908 respectively. Among them, the friction coefficient of the B5 coating during cutting is the lowest, and the friction coefficients of the B5 and B10 coatings with B during turning are both lower than that of the AlCrN coating.

[0062] Figure 5 They are the flank wear morphologies of the coating after turning for 3.5 min and 8 min respectively. It can be seen that under the same cutting time, the flank wear width of the B5-coated turning tool is the smallest, while that of the AlCrN-coated turning tool is the largest. As the turning test progresses, the flank wear amount gradually increases, showing a mountain shape. Its wear morphology is also similar to that in the initial stage. As the cutting time (length) increases, the cutting temperature rises, the wear intensifies, the tool becomes dull, and the tool fails. At the same time, due to the lack of the protection of the coating, the carbide tool substrate is more likely to soften at high temperatures, further exacerbating the tool wear. Therefore, the wear width of the coated tool increases rapidly until it fails in the middle and late stages of cutting. Table 3 lists the energy spectrum results of the flank of the B5 coating after wear. It can be found that the elements Al, Si, B, and O appear, which can further prove that a friction oxide film containing Al, Si, and B with a low friction coefficient is formed in-situ during the cutting process, which can reduce the cutting force and cutting heat and further improve the cutting life of the coated tool.

[0063] Table 3 Energy spectrum analysis of the flank face of the B5 coated turning tool

[0064]

[0065] The above are only the preferred embodiments of the present invention, which are illustrative rather than restrictive to the present invention. Those skilled in the art understand that many changes, modifications or even equivalents can be made within the spirit and scope defined by the claims of the present invention, but all will fall within the protection scope of the present invention.

Claims

1. A preparation method of an AlCrBSiN coating for high-speed dry cutting, characterized in that, It includes the following steps: S1. Ultrasonically clean the polished cemented carbide specimen, rinse it with deionized water, and dry it for standby; S2. Heat the dried cemented carbide sample in step S1, evacuate the air, introduce Ar gas, turn on the Ti target, and ionize a large amount of Ti in the furnace cavity + and electrons, strike Ar, form high-energy and high-density Ar+ to perform ion bombardment on the surface of the substrate, and ion etching and cleaning are carried out; S3. After the ion etching in step S2 ends, keep the deposition temperature and the pressure in the furnace chamber unchanged, turn on the Cr target, and deposit the first Cr bonding layer; S4. After the deposition of the first Cr bonding layer in step S3 is completed, keep the deposition temperature unchanged, turn off the Ar gas, introduce N2 gas, and deposit the second CrN bonding layer; S5. After the deposition of the second CrN bonding layer in step S4 is completed, keep the deposition temperature unchanged, turn on the AlCr target, further increase the flow rate of N2 gas, and deposit the AlCrN transition layer; S6. After the deposition of the AlCrN transition layer in step S5 is completed, keep the deposition temperature unchanged, turn on the AlCrSi target and the AlCrB target simultaneously, further increase the flow rate of N2 gas, and deposit the AlCrBSiN functional layer; In step S6, the atomic ratio of Al:Cr:Si of the AlCrSi target is 60:30:10, the atomic ratio of Al:Cr:B of the AlCrB target is 65:30:5 or 60:30:10, the pressure after increasing the flow rate of N2 gas is 3 - 6 Pa, the N2 flow rate is 500 - 800 sccm, and the deposition time is 50 - 60 min.

2. The preparation method of an AlCrBSiN coating for high-speed dry cutting according to claim 1, characterized in that, The AlCrBSiN coating contains 34% - 36% of Al, 15% - 17% of Cr, 0% - 3% of B, 1% - 6% of Si, and 44% - 46% of N.

3. The preparation method of an AlCrBSiN coating for high-speed dry cutting according to claim 2, characterized in that, The B exists in the amorphous BN phase, and the Si exists in the amorphous SiN phase.

4. The preparation method of an AlCrBSiN coating for high-speed dry cutting according to claim 2, characterized in that, The thickness of the AlCrBSiN coating is 4 μm.

5. The preparation method of an AlCrBSiN coating for high-speed dry cutting according to claim 1, characterized in that, In the step S2, the heating temperature is 480 °C, and after evacuation, the vacuum degree is 10 -4 Pa, the Ar gas flow rate is 200 - 600 sccm, the negative bias voltage of ion etching is -200 V, and the etching time is 40 min.

6. The preparation method of an AlCrBSiN coating for high-speed dry cutting according to claim 1, characterized in that In step S3, the substrate bias voltage is -60 to -80 V, the target current of the metal Cr target is 100 - 130 A, and the deposition time is 5 - 10 min.

7. The preparation method of an AlCrBSiN coating for high-speed dry cutting according to claim 1, characterized in that, In step S4, the pressure after introducing N2 gas is 1 - 2 Pa, the N2 flow rate is 100 - 300 sccm, and the deposition time is 5 - 10 min.

8. The preparation method of an AlCrBSiN coating for high-speed dry cutting according to claim 1, characterized in that, In step S5, the atomic ratio of Al:Cr of the AlCr target is 67:33, the pressure for increasing the flow rate of N2 gas is 2 - 5 Pa, the N2 flow rate is 400 - 800 sccm, and the deposition time is 10 - 15 min.

9. Application of the AlCrBSiN coating for high-speed dry cutting prepared by the preparation method according to any one of claims 1 - 8 in improving the cutting life of the tool.

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