A coated tool fatigue performance testing device and method

Abstract

This invention relates to a device and method for testing the fatigue performance of coated cutting tools. The device includes a control system, a worktable, an ultrasonic vibration mechanism, a fixture, a heating mechanism, a force measuring mechanism, a first moving mechanism, and a second moving mechanism. The heating mechanism, the first moving mechanism, and the second moving mechanism are all mounted on the worktable. The ultrasonic vibration mechanism, the heating mechanism, the force measuring mechanism, the first moving mechanism, and the second moving mechanism are all connected to the control system. Compared to existing fatigue impact testing methods for coated cutting tools, this invention achieves the synergistic effect of high-frequency impact and high-temperature thermo-mechanical coupling, increasing the cycle frequency of impact fatigue. The temperature control is stable and has a wide range, accurately simulating the high-frequency impact and thermo-mechanical coupling conditions in actual cutting of coated cutting tools. This provides experimental support for the optimized design of coated cutting tools and can be used to evaluate the impact resistance and spalling resistance of coated cutting tools under high temperature and high frequency conditions.

Description

Technical Field

[0001] This invention relates to the field of cutting tool technology, and specifically to a device and method for testing the fatigue performance of coated cutting tools. Background Technology

[0002] Dynamic thermo-coated impact fatigue is a complex material failure mode involving fatigue failure caused by the combined effects of high temperature and impact load. Coated cutting tools, under high-speed cutting conditions, are subjected to rapid heating and cooling cycles during service, while simultaneously bearing mechanical stress, ultimately leading to crack initiation and propagation, fatigue cracking and delamination of the coating. Understanding dynamic thermo-coated impact fatigue is crucial for predicting and assessing the lifespan of coated cutting tools.

[0003] Most existing tests for coating impact fatigue performance focus on single mechanical impacts and coupled impacts at low temperatures and low frequencies. For example, patent CN119064124A discloses an ultra-low temperature fully automatic hammer impact fatigue testing device and method. However, this method, using a pendulum impact, cannot simulate the working environment at higher frequencies. Another example is patent CN107860668A, which discloses a coating impact fatigue testing device. A speed-regulating motor drives a fork on a turntable to press down a lever mounted on a rotating shaft support. The right end of the lever falls freely under the gravity of a weight, causing a carbide ball below to impact the surface of the coating sample. However, in this invention, the lever's swing trajectory depends on the turntable speed and the fork's position accuracy. Even small deviations can cause the impact point to shift, making it difficult to achieve strictly repeatable impacts at the same location. Furthermore, it fails to achieve fatigue performance testing at ultra-high frequencies. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a fatigue performance testing device and method for coated cutting tools, which can perform fatigue performance testing on coated cutting tools under extreme coupled conditions of high temperature and ultra-high frequency vibration, thereby accurately simulating the actual cutting conditions of coated cutting tools.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A fatigue performance testing device for coated cutting tools includes a control system, a worktable, an ultrasonic vibration mechanism, a fixture, a heating mechanism, a force measuring mechanism, a first moving mechanism, and a second moving mechanism. The heating mechanism, the first moving mechanism, and the second moving mechanism are all mounted on the worktable. The ultrasonic vibration mechanism, the heating mechanism, the force measuring mechanism, the first moving mechanism, and the second moving mechanism are all connected to the control system. The clamp is used to hold the coated cutting tool, and the ultrasonic vibration mechanism is connected to the clamp to provide high-frequency vibration; the first moving mechanism includes a first horizontal moving module, which drives the ultrasonic vibration mechanism and the clamp to move synchronously relative to the force measuring mechanism. The second moving mechanism includes a first lifting module and a second horizontal moving module. The second horizontal moving module drives the first lifting module to move relative to the clamp, and the first lifting module drives the force measuring mechanism to move up and down. The heating mechanism is located between the first moving mechanism and the second moving mechanism. The heating mechanism includes a heating furnace, a temperature detection element, and a cooling circulation assembly. The heating furnace has a through-hole heating chamber. The temperature detection element is used to detect the temperature inside the heating chamber. The cooling circulation assembly is connected to the heating furnace through a pipe and forms a water circulation loop for regulating the temperature inside the heating chamber. The force measuring mechanism is equipped with a pressure head for contacting the coating tool. The coating tool held by the fixture and the pressure head can both extend into the heating chamber.

[0006] The ultrasonic vibration mechanism includes an ultrasonic generator, an ultrasonic transducer, and an amplitude transformer. One end of the amplitude transformer is connected to the output end of the ultrasonic transducer, and the other end of the amplitude transformer is connected to a clamp. The first horizontal moving module drives the ultrasonic transducer to move. The ultrasonic generator is electrically connected to the ultrasonic transducer, and the ultrasonic generator moves synchronously with the ultrasonic transducer. Alternatively, the ultrasonic generator can be located on or outside the worktable.

[0007] The ultrasonic vibration mechanism also includes a first extension rod, and the clamp is connected to the amplitude transformer rod through the first extension rod.

[0008] The first horizontal moving module, the first lifting module, and the second horizontal moving module are all linear moving modules built based on motors; the first horizontal moving module, the first lifting module, and the second horizontal moving module are all equipped with linear gratings, and the control system, the first horizontal moving module, the first lifting module, the second horizontal moving module, and the linear gratings work together to form a closed-loop moving control system.

[0009] The force measuring mechanism also includes a force sensor and a second extension rod. The pressure head is detachably connected to one end of the second extension rod, and the other end of the second extension rod is connected to the force sensor. The force sensor is connected to a first lifting module, and the first lifting module drives the force sensor, the second extension rod, and the pressure head to move synchronously.

[0010] The indenter is made of cubic boron nitride and is conical, triangular, or square-sided, with the tip of the indenter rounded.

[0011] The heating furnace is equipped with heat insulation components on both the side closest to the first moving mechanism and the side closest to the second moving mechanism.

[0012] The walls of the heating chamber are coated with a zirconium oxide coating.

[0013] This invention also discloses a method for testing the fatigue performance of coated cutting tools, which is implemented using the aforementioned coated cutting tool performance testing device and includes the following steps: S1. Mount the coated tool sample onto the fixture; S2. The heating furnace is turned on and heats up to the target temperature, and maintains the temperature for the set time. S3. By controlling the first and second moving mechanisms through the control system, the coated tool sample and the indenter are made to extend into the heating chamber and the two are controlled to make critical contact. S4. Turn on the ultrasonic vibration mechanism and run it at the set frequency. The high-frequency vibration generated by the ultrasonic vibration mechanism is transmitted to the coated tool sample and acts on the indenter. The force measuring mechanism collects and records the impact force in real time. S5. After setting the number of impact cycles, turn off the ultrasonic vibration mechanism and allow the heating furnace to cool to room temperature.

[0014] In step S3, the contact state between the coated tool sample and the indenter is determined by the critical contact force value N0. N0 < 0.01N indicates that the two are in critical contact.

[0015] After adopting the above scheme, the control system controls the coated tool sample to make contact with the indenter, the heating furnace is fixed on the worktable to heat the coated tool sample to provide the test temperature, and the ultrasonic vibration mechanism implements ultra-high frequency vibration. The obtained force data is collected and recorded by the force measuring mechanism. Compared with the existing fatigue impact testing methods for coated tools, this invention realizes the synergistic effect of high-frequency impact and high-temperature thermo-mechanical coupling, improves the cycle frequency of impact fatigue, has stable and wide temperature control, and accurately simulates the high-frequency impact and thermo-mechanical coupling working conditions in actual cutting of coated tools. It provides experimental support for the optimized design of coated tools and can be used to evaluate the impact resistance and spalling resistance of coated tools under high temperature and high frequency conditions. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the device of the present invention; Figure 2 This is a schematic diagram of the device of the present invention from another perspective; Figure 3 for Figure 1 A schematic diagram showing the concealed heating furnace; Figure 4 This is a schematic diagram of a heating furnace; Figure 5 This is a schematic diagram of a force-measuring mechanism; Figure 6The microstructure and impact force of the impact zone of the TiAlCrN coated tool after 40,000 high-temperature and ultra-high-frequency impact cycles are shown. Figure 7 The microstructure and impact force of the impact zone of a TiAlCrN coated tool after 80,000 high-temperature ultra-high frequency impact cycles are shown.

[0017] Explanation of key figure labels: Data acquisition subsystem 1, temperature control subsystem 2, first horizontal movement module 3, first lifting module 4, second horizontal movement module 5, linear grating 6, ultrasonic generator 7, ultrasonic transducer 8, amplitude transformer 9, first extension rod 10, clamp 11, force sensor 12, second extension rod 13, pressure head 14, furnace body 15, heating chamber 16, heat insulation component 17, heating element 18, temperature detection element 19, cooling circulation assembly 20, worktable 21. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0019] This invention discloses a fatigue performance testing device for coated cutting tools, comprising a control system, a worktable 21, an ultrasonic vibration mechanism, a fixture 11, a heating mechanism, a force measuring mechanism, a first moving mechanism, and a second moving mechanism. The ultrasonic vibration mechanism, heating mechanism, force measuring mechanism, first moving mechanism, and second moving mechanism are all connected to the control system. In this invention, the control system can be decomposed into multiple independent subsystems, such as a motion control subsystem for controlling the movement of the first and second moving mechanisms, a data acquisition subsystem 1 for receiving and recording feedback data from the force measuring mechanism, and a temperature control subsystem 2 for controlling the heating mechanism. Alternatively, the aforementioned motion control subsystem, data acquisition subsystem 1, and temperature control subsystem 2 can be integrated into one unit, such as on a single PLC.

[0020] The heating mechanism, the first moving mechanism, and the second moving mechanism are all mounted and locked on the worktable 21. The first moving mechanism, the heating mechanism, and the second moving mechanism are preferably arranged sequentially on the X-axis, with a certain distance between each other, to prevent the high temperature emanating from the heating mechanism from affecting the normal operation of other mechanisms.

[0021] The first moving mechanism includes a first horizontal moving module 3, which drives the ultrasonic vibration mechanism and the clamp 11 to move along the X-axis. The second moving mechanism includes a first lifting module 4 and a second horizontal moving module 5. The second horizontal moving module 5 drives the first lifting module 4 to move along the X-axis, and the first lifting module 4 drives the force measuring mechanism to move up and down (Z-axis).

[0022] The first horizontal moving module 3, the first lifting module 4, and the second horizontal moving module 5 are all linear moving modules based on motors. Linear moving modules are existing technology and generally include guide rails, slides, and screws. The guide rails and screws are arranged parallel to each other, and the slides are slidably connected to the guide rails. The slides are also threadedly connected to the screws, and the motor drives the screws to rotate. When the motor is running, the slides slide along the length of the guide rails. The guide rails ensure the stability of the slides' movement direction.

[0023] In addition, the first horizontal moving module 3, the first lifting module 4, and the second horizontal moving module 5 are all equipped with linear gratings 6. The control system, the first horizontal moving module 3, the first lifting module 4, the second horizontal moving module 5, and the linear gratings 6 work together to form a closed-loop moving control system. This combination can achieve a repeatability accuracy of up to 0.5μm. Compared with pendulum, turntable, or lever transmission, this closed-loop moving control system can provide real-time feedback and correction of position errors, eliminating random offsets caused by mechanical backlash and inertia.

[0024] The ultrasonic vibration mechanism includes an ultrasonic generator 7, an ultrasonic transducer 8, an amplitude transformer 9, and a first extension rod 10. One end of the amplitude transformer 9 is connected to the output end of the ultrasonic transducer 8, and the other end of the amplitude transformer 9 is connected to a clamp 11 via the first extension rod 10. The clamp 11 is used to hold the coated tool sample to be tested. The ultrasonic transducer 8 is mounted and locked on the slide corresponding to the first horizontal moving module 3. The first horizontal moving module 3 drives the ultrasonic transducer 8 to move. The length direction of the first extension rod 10 is parallel to the length direction of the guide rail corresponding to the first horizontal moving module 3. The ultrasonic generator 7 is electrically connected to the ultrasonic transducer 8, thereby providing the ultrasonic transducer 8 with a high-frequency vibration signal, such as 20kHz. The ultrasonic transducer 8 then achieves axial vibration and, utilizing the amplitude amplification effect of the amplitude transformer 9, generates an ultrasonic amplitude of 10μm. This setup enables high-precision repetitive impact actions.

[0025] The ultrasonic generator 7 moves synchronously with the ultrasonic transducer 8, meaning that the ultrasonic generator 7 is also installed on the slide corresponding to the first horizontal moving module 3; alternatively, the ultrasonic generator 7 can be set on the worktable 21 or outside the worktable 21; the setting position of the ultrasonic generator 7 can be flexibly adjusted.

[0026] The force-measuring mechanism includes a force sensor 12, a second extension rod 13, and a pressure head 14. The pressure head 14 is detachably connected (e.g., threaded) to one end of the second extension rod 13, while the other end of the second extension rod 13 is fixedly connected to the force sensor 12. The force sensor 12 is fixed to the slide corresponding to the first lifting module 4. The length direction of the second extension rod 13 is parallel to the length direction of the guide rail corresponding to the first horizontal moving module 3. The pressure head 14 is made of cubic boron nitride and is conical, triangular, or square-sided, with a rounded tip. For example, a conical pressure head 14 could have a rounded corner radius of 0.05 mm and a cone angle of 120°. The force sensor 12 has a force measurement accuracy higher than 0.002 N and a natural frequency less than 5 kHz or greater than 50 kHz to avoid resonance frequencies, such as 100 kHz. The control system sets the sampling frequency of the force sensor 12 to 5MHz, and the control system can set a dedicated data acquisition card to collect the measurement data of the force sensor 12.

[0027] The heating mechanism is located between the first and second moving mechanisms. The heating mechanism includes a heating furnace, a temperature sensing element 19, and a cooling circulation assembly 20. The heating furnace generally includes a furnace body 15 and a heating element 18. The furnace body 15 is fixedly connected to the worktable 21 via a fixed base. A through heating chamber 16 is provided at the center of the furnace body 15, with its length along the X-axis. The heating element 18 (e.g., a silicon molybdenum rod) is built into the furnace body 15 and positioned near the reinforcing chamber to increase its temperature. The temperature sensing element 19 is used to detect the temperature inside the heating chamber 16. Preferably, its heating rate is 10℃ / s, its thermal response time is less than 2s, its temperature control accuracy is within ±1℃, and its temperature range is 25℃-1500℃. Heat insulation components 17 (e.g., polycrystalline mullite plates) are provided on both sides of the furnace body 15 (i.e., the side of the furnace body 15 closest to the first moving mechanism and the side closest to the second moving mechanism). Additionally, a zirconium oxide coating is provided on the cavity wall of the heating chamber 16 for protection.

[0028] The cooling circulation assembly 20 is connected to the furnace body 15 via pipes. Specifically, the furnace body 15 has cooling pipes inside and / or outside, and the cooling circulation assembly 20 is connected to these pipes, thus forming a water circulation loop for regulating the temperature inside the heating chamber 16. The cooling circulation assembly 20 can participate in the temperature regulation of the heating chamber 16, and also enables rapid cooling of the furnace after testing. The cooling circulation assembly 20 is existing technology and generally includes a water pump and a radiator. The water pump pumps cold water into the cooling pipes of the furnace body 15, while the hot water in the cooling pipes enters the radiator for cooling, and then is pumped back into the cooling pipes by the water pump, thus circulating the water.

[0029] The central axis of the heating chamber 16 should be aligned with the central axis of the first extension rod 10 to ensure that the coated tool sample held by the fixture 11 can extend into the heating chamber 16. In addition, the pressure head 14 should also be able to extend into the heating chamber 16.

[0030] This invention also discloses a method for testing the fatigue performance of coated cutting tools, which is implemented using the aforementioned coated cutting tool performance testing device and includes the following steps: S0. Before the test, the vibration frequency is measured by a laser displacement sensor. The voltage of the ultrasonic generator 7 is adjusted to control the output of different displacement amplitudes. The sampling frequency of the laser displacement sensor is 392kHz, the displacement repeatability measurement accuracy is 0.025μm, and the vibration time is set to 8s.

[0031] S1. Clamp the coated tool sample onto the fixture 11. The fixture 11 can be moved away from the heating furnace to facilitate the clamping of the coated tool sample. A starting position can be set for loading and unloading the coated tool sample, which is also conducive to automatic control.

[0032] S2. The heating furnace is turned on and heated until the target temperature (e.g., 500℃) is reached, and maintained for a set time, such as 5 minutes.

[0033] S3. The control system controls the first and second moving mechanisms to make the coated tool sample and the pressure head 14 extend into the heating chamber 16 and control them to reach critical contact. The contact state between the coated tool sample and the pressure head 14 is determined by the critical contact force value N0. N0 < 0.01N indicates that the two are in critical contact.

[0034] S4. Turn on the ultrasonic vibration mechanism and run it at the set frequency. The high-frequency vibration generated by the ultrasonic vibration mechanism is transmitted to the coated tool sample and acts on the pressure head 14. The force measuring mechanism collects and records the impact force in real time.

[0035] S5. After setting the number of impact cycles, turn off the ultrasonic vibration mechanism and allow the heating furnace to cool to room temperature.

[0036] Following the above method and using the above apparatus, the following experiments were conducted on TiAlCrN coated cutting tools: (1) At a temperature of 300℃, an ultrasonic shock amplitude of 10μm, and a frequency of 20KHz, the number of shock cycles was 40,000. The relevant experimental results are as follows: Figure 6 As shown.

[0037] (2) At a temperature of 300℃, an ultrasonic shock amplitude of 10μm, and a frequency of 20KHz, the number of shock cycles was 80,000. The relevant experimental results are as follows: Figure 7 As shown.

[0038] The following conclusions were drawn from the fatigue performance tests of the above-mentioned coated cutting tools under high temperature and ultra-high frequency conditions: 1. The cyclic fatigue failure modes under 40,000 cyclic impacts include: circumferential fatigue cracks and divergent fatigue cracks, and the force value remains stable during the impact process.

[0039] 2. The coating peels off after 80,000 cyclic impacts, which means that the coated tool has reached its fatigue life. The decrease in impact force also indicates that fatigue peeling has occurred on the surface of the coated tool sample.

[0040] The key to this invention lies in the control system that controls the contact between the coated tool sample and the indenter 14, while a heating furnace fixed on the worktable 21 heats the sample to provide the test temperature. An ultrasonic vibration mechanism implements ultra-high frequency vibration, and the obtained force data is collected and recorded by a force measuring mechanism. Compared to existing fatigue impact testing methods for coated tools, this invention achieves a synergistic effect of high-frequency impact and high-temperature thermo-mechanical coupling, increasing the cycle frequency of impact fatigue. It also enables high-precision repeated impacts, stable and wide-range temperature control, and accurately simulates the high-frequency impact and thermo-mechanical coupling effect in actual cutting of coated tools. This provides experimental support for the optimized design of coated tools and can be used to evaluate the impact resistance and spalling resistance of coated tools under high temperature and high frequency conditions.

[0041] The above description is merely an embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A coated tool fatigue performance testing apparatus, characterized by: It includes a control system, a worktable, an ultrasonic vibration mechanism, a fixture, a heating mechanism, a force measuring mechanism, a first moving mechanism, and a second moving mechanism. The heating mechanism, the first moving mechanism, and the second moving mechanism are all mounted on the worktable. The ultrasonic vibration mechanism, the heating mechanism, the force measuring mechanism, the first moving mechanism, and the second moving mechanism are all connected to the control system. The clamp is used to hold the coated cutting tool, and the ultrasonic vibration mechanism is connected to the clamp to provide high-frequency vibration; the first moving mechanism includes a first horizontal moving module, which drives the ultrasonic vibration mechanism and the clamp to move synchronously relative to the force measuring mechanism. The second moving mechanism includes a first lifting module and a second horizontal moving module. The second horizontal moving module drives the first lifting module to move relative to the clamp, and the first lifting module drives the force measuring mechanism to move up and down. The heating mechanism is located between the first moving mechanism and the second moving mechanism. The heating mechanism includes a heating furnace, a temperature detection element, and a cooling circulation assembly. The heating furnace has a through-hole heating chamber. The temperature detection element is used to detect the temperature inside the heating chamber. The cooling circulation assembly is connected to the heating furnace through a pipe and forms a water circulation loop for regulating the temperature inside the heating chamber. The force measuring mechanism is equipped with a pressure head for contacting the coating tool. The coating tool held by the fixture and the pressure head can both extend into the heating chamber.

2. The apparatus of claim 1, wherein: The ultrasonic vibration mechanism includes an ultrasonic generator, an ultrasonic transducer, and an amplitude transformer. One end of the amplitude transformer is connected to the output end of the ultrasonic transducer, and the other end of the amplitude transformer is connected to a clamp. The first horizontal moving module drives the ultrasonic transducer to move. The ultrasonic generator is electrically connected to the ultrasonic transducer, and the ultrasonic generator moves synchronously with the ultrasonic transducer. Alternatively, the ultrasonic generator can be located on or outside the worktable.

3. The fatigue performance testing device for coated cutting tools according to claim 2, characterized in that: The ultrasonic vibration mechanism also includes a first extension rod, and the clamp is connected to the amplitude transformer rod through the first extension rod.

4. The fatigue performance testing device for coated cutting tools according to claim 1, characterized in that: The first horizontal moving module, the first lifting module, and the second horizontal moving module are all linear moving modules built based on motors; The first horizontal movement module, the first lifting module, and the second horizontal movement module are all equipped with linear gratings. The control system, the first horizontal movement module, the first lifting module, the second horizontal movement module, and the linear gratings work together to form a closed-loop movement control system.

5. The fatigue performance testing device for coated cutting tools according to claim 1, characterized in that: The force measuring mechanism also includes a force sensor and a second extension rod. The pressure head is detachably connected to one end of the second extension rod, and the other end of the second extension rod is connected to the force sensor. The force sensor is connected to a first lifting module, and the first lifting module drives the force sensor, the second extension rod, and the pressure head to move synchronously.

6. A fatigue performance testing device for coated cutting tools according to claim 1 or 5, characterized in that: The indenter is made of cubic boron nitride and is conical, triangular, or square-sided, with the tip of the indenter rounded.

7. The fatigue performance testing device for coated cutting tools according to claim 1, characterized in that: The heating furnace is equipped with heat insulation components on both the side closest to the first moving mechanism and the side closest to the second moving mechanism.

8. A fatigue performance testing device for coated cutting tools according to claim 1 or 7, characterized in that: The walls of the heating chamber are coated with a zirconium oxide coating.

9. A method for testing the fatigue performance of coated cutting tools, characterized in that: The coating tool performance testing device according to any one of claims 1-8 is used, comprising the following steps: S1. Mount the coated tool sample onto the fixture; S2. The heating furnace is turned on and heats up to the target temperature, and maintains the temperature for the set time. S3. By controlling the first and second moving mechanisms through the control system, the coated tool sample and the indenter are made to extend into the heating chamber and the two are controlled to make critical contact. S4. Turn on the ultrasonic vibration mechanism and run it at the set frequency. The high-frequency vibration generated by the ultrasonic vibration mechanism is transmitted to the coated tool sample and acts on the indenter. The force measuring mechanism collects and records the impact force in real time. S5. After setting the number of impact cycles, turn off the ultrasonic vibration mechanism and allow the heating furnace to cool to room temperature.

10. A method for testing the fatigue performance of coated cutting tools according to claim 9, characterized in that: In step S3, the contact state between the coated tool sample and the indenter is determined by the critical contact force value N0. N0 < 0.01N indicates that the two are in critical contact.

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