Preparation method and application of superhard surface with martensite phase transformation synergistically induced by heat-force

Abstract

The invention discloses a preparation method and application of a superhard surface with martensite phase transformation induced through heat-force synergism, and belongs to the technical field of laser surface machining. According to the core process, continuous laser is used for heating the metal surface to the temperature above the phase transformation point, a large number of lattice defects such as dislocation and stacking faults are introduced into the surface layer of the material through the in-situ composite pulse laser shock technology, then more martensite phase transformation is induced through air cooling, and therefore the surface hardening layer high in hardness and large in depth is obtained. According to the method, more driving force is provided for martensite phase transformation through the heat-force synergistic effect, and the method can be used for manufacturing super-hard surfaces of stainless steel and titanium alloy materials.

Description

Technical Field

[0001] The invention relates to the technical field of laser surface processing, and more specifically to a method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation and its application. Background Art

[0002] Gears, bearings and other metal parts are prone to fatigue cracks after surface wear, and it is necessary to prepare a superhard surface to improve its wear resistance. At present, the quenching method is often used to induce martensitic phase transformation, thereby building a hardened layer on the metal surface. In the quenching process, the rapid cooling process is the main stage of martensitic phase transformation. For example, the invention patent with patent number CN110724890A uses water spraying to cool the surface, and the invention patent with patent number CN113373286A uses liquid nitrogen to accelerate the cooling rate.

[0003] However, these inventions do not process and control the high temperature area of ​​the material, especially do not make good use of the high temperature softening phenomenon of the material. If lattice defects such as dislocations and stacking faults are introduced into the surface of the material through the action of force at high temperature, more driving force will be provided for the martensitic phase transformation, which will greatly improve the efficiency of the martensitic phase transformation during the rapid cooling process.

[0004] Based on this, developing a method for efficiently inducing martensitic phase transformation of materials is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation and its application, aiming to improve the wear resistance of metal parts. The metal surface hardening process is completed by using a laser heating-laser shock-air cooling composite quenching process, which can be applied to the preparation of superhard surfaces of stainless steel and titanium alloy materials.

[0006] In order to achieve the above object, the present invention proposes a method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation, comprising the following steps:

[0007] (A) Using continuous laser scanning to heat the surface of the metal material to be hardened to above the phase transition point of the metal material;

[0008] (B) When the temperature is higher than the phase transition point, the material surface softens, and a pulsed laser is used to impact the metal material surface, which can introduce a large number of lattice defects such as dislocations and stacking faults into the high-temperature phase;

[0009] (C) Use air cooling to quickly cool the surface of the metal material to room temperature, inducing a martensite phase transformation.

[0010] Preferably, in step (A), the metal material is stainless steel or titanium alloy.

[0011] Preferably, in step (A), the surface of the metal material is heated to 20°C to 50°C above the phase transition point, in order to restore the low-temperature phase in the microstructure to the high-temperature phase and soften the surface of the material.

[0012] Preferably, step (A) further comprises measuring the temperature of the front area of ​​the continuous laser scanning using an infrared thermal imager.

[0013] Further preferably, the continuous laser can be replaced by other non-contact heat sources, such as electric arc, electron beam, electromagnetic induction heating, etc.

[0014] Preferably, in step (B), the spot of the pulsed laser is always in the front region of the continuous laser scanning, ensuring that the surface temperature of the metal material remains 20° C. to 50° C. above the phase transition point during the impact treatment.

[0015] Preferably, in step (B), the wavelength of the pulsed laser is 1064 nm, the energy is 2-10 J, the frequency is 2-10 Hz, the pulse width is 15 ns, and the spot diameter is 1-3 mm.

[0016] Preferably, in step (C), argon is used for air cooling. Under the effect of air cooling, the high-temperature phase containing lattice defects such as high-density dislocations and stacking faults rapidly undergoes martensitic phase transformation due to its high phase transformation driving force, forming a martensitic hardened layer and obtaining an ultra-hard surface.

[0017] It can be seen from the above technical solution that, compared with the prior art, the beneficial effects achieved by the present invention are:

[0018] The present invention effectively utilizes the high-temperature softening effect of metal materials above the phase transition point, introduces more lattice defects such as dislocations and stacking faults on the surface of the metal material by laser impact, increases the driving force of the phase transition, thereby accelerating the martensitic phase transition rate during the air cooling process, and generating more hard martensitic phases on the material surface. Compared with the single thermal action of the traditional quenching process, the present invention introduces the action of force above the phase transition point of the metal material, utilizes the synergistic effect of heat and force to induce the martensitic phase transition, and realizes the preparation of a superhard surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] Figure 1 Schematic diagram of the method for preparing a superhard surface provided in an embodiment.

[0021] Figure 2 Microhardness provided for Examples and Comparative Examples.

[0022] Figure 3 This is the microstructure diagram of QP980 steel.

[0023] Figure 4 This is the microstructure diagram of TC17 titanium alloy.

[0024] Figure 5 A device for preparing super-hard surfaces of gears.

[0025] Figure 6 Schematic diagram of single tooth surface processing.

[0026] The numbers mean: 1-substrate, 2-air-cooling nozzle, 3-pulse laser head, 4-continuous laser head, 5-infrared thermal imager, 6-front area of ​​continuous laser scanning path, 7-robotic arm, 8-gear. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The present invention provides a method for preparing a superhard surface by synergistically inducing martensitic phase transformation through heat and force, and completes the metal surface hardening process through a laser heating-laser shock-air cooling composite quenching process.

[0029] like Figure 1 As shown, the specific implementation process of the method includes the following components: a substrate 1, an air-cooled nozzle 2, a pulse laser head 3, a continuous laser head 4, and an infrared thermal imager 5.

[0030] The specific implementation includes the following steps:

[0031] (1) After cleaning and drying the substrate 1, select the area to be processed;

[0032] (2) Turn on the continuous laser head 4 and scan at a constant speed from one end of the area to be processed to the other end to heat the surface of the substrate 1;

[0033] (3) Using an infrared thermal imager 5 to monitor the temperature field distribution of the front region 6 of the continuous laser scanning path, adjust the continuous laser power parameters to ensure that the front region 6 is heated to 20° C. to 50° C. above the phase transition point.

[0034] (4) Turn on the pulse laser head 3, focus the pulse laser spot on the front region 6, and move it quickly along a zigzag path to cover the front region 6.

[0035] (5) The air-cooling nozzle 2 blows argon gas into the composite processing area of ​​the continuous laser and pulsed laser to accelerate the cooling rate and promote the martensitic phase transformation.

[0036] (6) The movement paths and movement speeds of the continuous laser head 4, the pulse laser head 3, and the air-cooling nozzle 2 are controlled in a coordinated manner until the area to be processed of the substrate 1 completes the laser heating-laser shock-air cooling composite quenching process.

[0037] Example 1

[0038] According to the above implementation, QP980 steel is used, the phase transition point is 950°C, and the initial microhardness is 407HV. It is heated to 980°C using a continuous laser, and laser shock treatment is performed using a pulsed laser with a wavelength of 1064nm, energy of 10J, frequency of 2Hz, pulse width of 15ns, and spot diameter of 2mm, followed by air cooling, and the microhardness value is 574HV. Figure 2 shown.

[0039] Comparative Example 1

[0040] Using QP980 steel, after traditional laser quenching treatment (laser heating to 980℃-air cooling), the microhardness value is only 478HV.

[0041] like Figure 3 As shown in the figure, after the QP980 steel was treated by laser heating-laser shock-air cooling composite quenching process, the island martensite content was significantly higher than that of the laser heating-air cooling treatment.

[0042] Example 2

[0043] According to the above implementation, TC17 titanium alloy is used, the phase transition point is 985°C, and the initial microhardness is 337HV. It is heated to 1010°C using a continuous laser, and laser shock treatment is performed using a pulsed laser with a wavelength of 1064nm, an energy of 10J, a frequency of 2Hz, a pulse width of 15ns, and a spot diameter of 2mm, followed by air cooling, and the microhardness value is 546HV. Figure 2 shown.

[0044] Comparative Example 2

[0045] Using TC17 titanium alloy, after traditional laser quenching treatment (laser heating to 1010℃-air cooling), the microhardness value is only 413HV.

[0046] like Figure 4 As shown in the figure, after the TC17 titanium alloy is treated by laser heating-laser shock-air cooling composite quenching process, the size of the needle-shaped martensite becomes smaller.

[0047] Furthermore, based on the above-mentioned method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation, the present invention also provides a device for preparing a superhard surface of a gear for the application scenario of preparing a superhard surface on the tooth surface of a steel gear.

[0048] like Figure 5 As shown, the device specifically includes the following components: a robotic arm 7, a gear 8, an air-cooled nozzle 2, a continuous laser head 4, an infrared thermal imager 5, and a pulse laser head 3.

[0049] The specific implementation includes the following steps:

[0050] (1) The gear 8 is mounted on the robot arm 7, and the tooth surface of the gear 8 to be processed is placed in the laser processing area under the movement of the robot arm 7;

[0051] (2) Turn on the continuous laser head 4, scan along the path from the tooth top to the tooth root, and heat a single tooth surface;

[0052] (3) using an infrared thermal imager 5 to monitor the temperature of the front region of the continuous laser scanning path, and adjusting the continuous laser power in real time through signal feedback, so that the front region of the scanning path is heated to 20° C. to 50° C. above the phase transition point of the material;

[0053] (4) Control the pulse laser head 3 so that the pulse laser spot is close to the front edge of the continuous laser scanning path ( Figure 6 );

[0054] (5) Control the scanning galvanometer assembly in the pulse laser head 3 so that the pulse laser spot covers the front edge of the scanning path of the continuous laser ( Figure 6 );

[0055] (6) Linking and controlling the scanning paths of the continuous laser and the pulsed laser until the tooth surface is heated by the laser and the laser shock composite processing is completed ( Figure 6 );

[0056] (7) Open the air cooling nozzle 2 to accelerate the cooling speed of the tooth surface and complete the laser heating-laser shock-air cooling composite quenching process;

[0057] (8) The gear 8 is rotated by the robot arm 7 so that the next tooth surface enters the position to be processed;

[0058] (9) Repeat steps (2) to (8) until all tooth surfaces are machined.

[0059] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation, characterized in that: The following steps are involved: (A) Using continuous laser scanning to heat the surface of the metal material to be hardened to above the phase transition point of the metal material; (B) Using pulsed laser to impact the surface of metal materials; (C) Use air cooling to quickly cool the surface of the metal material to room temperature.

2. The method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation according to claim 1, characterized in that: In step (A), the metal material is stainless steel or titanium alloy.

3. The method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation according to claim 1, characterized in that: In step (A), the surface of the metal material is heated to 20° C. to 50° C. above the phase transition point.

4. The method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation according to claim 3, characterized in that: Step (A) also includes measuring the temperature of the front area of ​​the continuous laser scanning using an infrared thermal imager.

5. The method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation according to claim 4, characterized in that: The continuous laser is replaced by a non-contact heat source.

6. The method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation according to claim 1, characterized in that: In step (B), the spot of the pulsed laser is always in the front region of the continuous laser scanning, ensuring that the surface temperature of the metal material remains 20° C. to 50° C. above the phase transition point during the impact treatment.

7. The method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation according to claim 1, characterized in that: In step (B), the wavelength of the pulsed laser is 1064 nm, the energy is 2-10 J, the frequency is 2-10 Hz, the pulse width is 15 ns, and the spot diameter is 1-3 mm.

8. The method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation according to claim 1, characterized in that: In step (C), the air cooling adopts argon gas.

9. Application of a method for preparing a superhard surface by heat-mechanical synergistically inducing martensitic phase transformation, a method for preparing a superhard surface of a gear is designed according to any one of claims 1 to 8, characterized in that: The following steps are involved: (a) mounting a gear (8) on a mechanical arm (7), and placing the tooth surface of the gear (8) to be processed in a laser processing area under the movement of the mechanical arm (7); (b) turning on the continuous laser head (4) to scan along the path from the tooth top to the tooth root to heat a single tooth surface; (c) using an infrared thermal imager (5) to monitor the temperature of the front region of the continuous laser scanning path, and adjusting the continuous laser power in real time through signal feedback, so that the front region of the scanning path is heated to 20° C. to 50° C. above the phase transition point of the material; (d) controlling the pulse laser head (3) so that the pulse laser spot is close to the front edge (6) of the continuous laser scanning path; (e) controlling the scanning galvanometer assembly in the pulse laser head (3) so that the pulse laser spot covers the front edge (6) of the scanning path of the continuous laser; (f) controlling the scanning paths of the continuous laser and the pulsed laser in a coordinated manner until the tooth surface is heated by the laser and the laser impact composite processing is completed; (g) opening the air cooling nozzle (2) to accelerate the cooling speed of the tooth surface and complete the laser heating-laser shock-air cooling composite quenching process; (h) rotating the gear (8) by means of the robot arm (7) so that the next tooth surface enters the position to be processed; (i) Repeat steps (b) to (h) until all tooth surfaces are machined.

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