A new gear strengthening method of laser shock and carburizing compound

Abstract

The application discloses a novel gear strengthening method combining laser impact and carburizing, and comprises the following steps: S1, pretreating a gear to be processed; S2, performing first laser impact treatment on the cleaned gear; S3, performing carburizing treatment on the gear after the laser impact treatment, so that a carburizing strengthened layer is formed on the surface of the gear; and S4, performing second laser impact treatment on the gear after the carburizing treatment. The gear is subjected to the composite strengthening method of first laser impact treatment, then carburizing treatment, and second laser impact treatment, so that a composite strengthened layer is formed on the surface of the gear, and the fatigue resistance and wear resistance of the surface of the gear are improved, and the service life of the gear is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface strengthening treatment, in particular to a novel laser shock and carburizing composite gear strengthening method. BACKGROUND

[0002] The progress of science and technology has led to an increasing demand for energy by mankind, and the extensive exploitation and utilization of non-renewable energy has led to global warming and energy problems becoming increasingly prominent. Mankind urgently needs renewable energy to replace traditional non-renewable energy.

[0003] Wind energy is a clean and renewable energy source, and China will vigorously develop non-fossil energy and comprehensively promote the large-scale development and high-quality development of wind power generation. Wind power gear is a key transmission component of a wind turbine, and the load during service is complex and variable, and the load distribution on the tooth surface is uneven, which can aggravate the contact fatigue failure of the gear; the tooth root is prone to impact load, leading to gear bending fatigue failure, thereby causing wind turbine failure. Therefore, improving the anti-severe working condition and fatigue resistance of wind power gear has important significance for promoting the development of wind power technology.

[0004] Wind power gears are usually made of carburizing steel, which refers to steel that needs to be carburized and quenched and then tempered at low temperature for use.

[0005] The existing laser shock strengthening process for carburizing steel gears has the following defects:

[0006] 1. Only the gear is subjected to laser shock treatment, and the strengthening effect is poor, which cannot meet the required strengthening effect.

[0007] 2. When the gear is subjected to laser shock treatment, the laser will interfere with each other when impacting adjacent two teeth of the gear, which will weaken the strengthening effect or cause deviation. SUMMARY

[0008] The purpose of the present application is to provide a novel laser shock and carburizing composite gear strengthening method, which forms a composite strengthening layer on the surface of the gear to improve the fatigue resistance, wear resistance and corrosion resistance of the surface of the wind power gear.

[0009] To achieve the above purpose, the solution of the present application is as follows: a novel laser shock and carburizing composite gear strengthening method, comprising the following steps:

[0010] S1 pretreating the gear to be processed;

[0011] S2 performing first laser shock treatment on the pretreated gear;

[0012] S3 performing carburizing treatment on the gear after laser shock treatment to form a carburizing strengthening layer on the surface thereof;

[0013] S4 carries out the second laser impact treatment on the carburized gear, so that a composite strengthening layer is formed on the surface of the gear.

[0014] Further, the machined gear is a carburized steel gear.

[0015] Further, in steps S2 and S4, the laser impact treatment is laser oblique impact, and the incidence angle of the laser is less than 43°.

[0016] Further, in step S2, the laser impact treatment parameters are as follows:

[0017] The laser wavelength is 1064 nm; the pulse energy is 6-9 J; the pulse width is 10-20 ns; the spot diameter is 3-5 mm; and the lap rate is 50%;

[0018] The laser impact angle is 0° for the tooth top surface and the tooth bottom surface, 20° for the tooth surface, and 40° for the tooth root.

[0019] Further, in step S3, the carburizing process is as follows: the gear is placed in a carburizing furnace, heated to 650℃, kept for 30 min, then heated to 930℃, kept for 5 h for strong carburizing at a carbon potential of 1.1%, then cooled to 910℃, kept for 3 h for diffusion at a carbon potential of 0.7%, furnace cooled to 850℃, kept for 1 h, then oil quenched at 850℃, and finally tempered at 160℃ for 2 h, and air cooled after taking out of the furnace.

[0020] Further, in step S4, the laser impact treatment parameters are as follows:

[0021] The laser wavelength is 1064 nm; the pulse energy is 10-12 J; the pulse width is 10-20 ns; the spot diameter is 3-5 mm; and the lap rate is 50%;

[0022] The laser impact angle is 0° for the tooth top surface and the tooth bottom surface, 20° for the tooth surface, and 40° for the tooth root.

[0023] Further, in steps S2 and S4, before the laser impact treatment, black glue or aluminum foil is covered on the surface of the gear as an absorption layer, and deionized water is used as a constraint layer.

[0024] Further, the pretreatment carried out on the gear in step S1 includes ultrasonic cleaning and drying treatment of the gear to be machined.

[0025] Further, the laser impact device used in the laser impact treatment includes an operation table, a ball screw mechanism arranged above the operation table, a sliding table mechanism, and a rotating motor, the rotating motor being used to drive the gear to be machined to rotate, and the device further includes a laser generator arranged towards the gear.

[0026] After the above scheme is adopted, the present application has the following advantages:

[0027] 1、In the carburizing before laser shock processing, the gear surface roughness can be increased, the carbon atom adsorption is beneficial, the gear surface microstructure dislocation density is increased, the grain is refined, more diffusion channels and adsorption centers are provided for carbon atoms, the carburizing efficiency and the carburizing effect can be effectively improved;

[0028] 2、The second laser shock processing is carried out after the carburizing treatment, and a composite strengthening layer is formed on the gear surface, so that the fatigue resistance, wear resistance and corrosion resistance of the gear surface of the wind power gear can be improved;

[0029] 3、The laser oblique impact method is adopted, the problem that direct laser impact strengthening is difficult due to the special structure of the gear can be effectively solved, the wind power gear is strengthened in different regions according to the strengthening requirements of different regions of the wind power gear, and the service life of the wind power gear is improved. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a novel laser shock and carburizing composite gear strengthening process flowchart of an embodiment of the application;

[0031] Figure 2 It is a laser shock device structure schematic diagram of an embodiment of the application;

[0032] Figure 3 It is a gear regionalization schematic diagram of an embodiment of the application;

[0033] Figure 4 It is a laser oblique incidence schematic diagram of an embodiment of the application;

[0034] Figure 5 It is a carburizing process curve diagram of an embodiment of the application.

[0035] Label explanation:

[0036] 1, laser generator; 2, gear; 21, tooth top surface; 22, tooth bottom surface; 23, tooth surface; 24, tooth root; 3, rotating motor; 4, sliding table mechanism; 5, ball screw mechanism; 6, operation table. DETAILED DESCRIPTION

[0037] The application will be described in detail below in combination with the drawings and specific embodiments.

[0038] The application provides a novel laser shock and carburizing composite gear strengthening method, as shown in the figure, including the following steps: Figures 1 to 5

[0039] S1, pretreating the gear to be processed, including ultrasonic cleaning and drying treatment of the gear to be processed.

[0040] ​S2 carries out the first laser shock processing on the pretreated gear, as shown in Figure 3 Fig. 2 is a schematic diagram of the gear divided into regions, wherein the gear 2 comprises a tooth top surface 21, a tooth bottom surface 22, a tooth surface 23 and a tooth root 24 region, Figure 4 Fig. 3 is a schematic diagram of laser oblique incidence, wherein θ is the laser incidence angle.

[0041] The constraint layer is a uniform water layer with a thickness of 2 mm, and the energy absorption layer is black glue with a thickness of 100 μm; the laser wavelength is set to 1064 nm, the pulse energy is 6-9 J, the pulse width is 10-20 ns, the spot diameter is 3-5 mm, the lap rate is 50%, and the laser shock angles of the regions are as follows: 0° for the tooth top surface and the tooth bottom surface, 20° for the tooth surface, and 40° for the tooth root.

[0042] S3 carries out carburizing treatment on the gear after laser shock processing, so as to form a carburizing strengthened layer on the surface of the gear.

[0043] Before the carburizing treatment, the gear after laser shock processing is subjected to ultrasonic cleaning, and then is placed in a carburizing furnace, as shown in Figure 5 Fig. 4, the temperature is raised to 650 ℃, and is kept for 30 min, then the temperature is raised to 930 ℃, and is kept for 5 h for strong carburizing with a carbon potential of 1.1%, then the temperature is lowered to 910 ℃, and is kept for 3 h for diffusion with a carbon potential of 0.7%, and is cooled in the furnace to 850 ℃, and is kept for 1 h, then is oil quenched at 850 ℃, and finally is tempered at 160 ℃ for 2 h, and is air cooled after being taken out of the furnace.

[0044] S4 carries out polishing and ultrasonic cleaning treatment on the gear after carburizing treatment, and then places the gear on a laser shock device to carry out the second laser shock processing, so as to form a composite strengthened layer on the surface of the gear. The constraint layer is a uniform water layer with a thickness of 2 mm, and the energy absorption layer is black glue with a thickness of 100 μm; the laser wavelength is set to 1064 nm, the pulse energy is 10-12 J, the pulse width is 10-20 ns, the spot diameter is 3-5 mm, the lap rate is 50%, and the laser shock angles of the regions are as follows: 0° for the tooth top surface and the tooth bottom surface, 20° for the tooth surface, and 40° for the tooth root.

[0045] In steps S2 and S4, before the laser shock processing, black glue or aluminum foil is covered on the surface of the carburizing steel wind power gear as an absorption layer, and deionized water is used as a constraint layer.

[0046] In steps S2 and S4, the laser shock processing is laser oblique impact, and the energy of the laser oblique impact acting on the surface of the material is:

[0047]

[0048] Wherein, E' is the energy of laser oblique impact on the material surface; E is the energy of laser vertical impact on the material surface; L is the thickness of water layer, taking 2mm; L0 is the theoretical decay length of laser wavelength, the decay length of 1064nm laser is 35mm.

[0049] The energy loss rate is:

[0050]

[0051] The energy loss rate should be controlled within 7.5%, so the laser incidence angle should be controlled within 43°.

[0052] The laser energy can be calculated according to the formula of shock wave pressure generated by laser oblique impact:

[0053]

[0054]

[0055] Wherein, P is the laser shock wave pressure, its value is between 2-2.5 times of the dynamic elastic limit of laser impact material; Alpha is the efficiency of laser-induced plasma and sample interaction, generally taking 0.3-0.5; Z is the complex acoustic impedance of the sample and the constraint medium; E is the energy of laser acting on the material surface; Tau is the laser pulse width; S θ is the laser oblique impact spot area; R is the laser spot radius; Theta is the laser incidence angle.

[0056] In the method, the device used for laser impact treatment of the gear is a laser impact device, as shown in Figure 3 The device includes an operation table 6, a ball screw mechanism 5 arranged above the operation table 6, a sliding table mechanism 4, and a rotating motor 3 for driving the gear to be machined to rotate, and the device further includes a laser generator 1 arranged towards the gear.

[0057] Example 1:

[0058] The novel laser impact and carburizing combined gear strengthening method of the embodiment includes the following steps:

[0059] (1) The carburizing steel used in the embodiment is 20CrNiMo steel, and the 20CrNiMo steel is processed into M5 gear type samples;

[0060] (2) The 20CrNiMo steel gear samples are polished and ultrasonically cleaned;

[0061] (3) The sample is placed on a laser impact device, the restraining layer is a uniform water layer of 2 mm, and the energy absorption layer is 100 μm black glue; the laser wavelength is set to 1064 nm, the pulse energy is 6 J, the pulse width is 10 ns, the spot diameter is 3 mm, the overlap rate is 50%, and the laser impact angles of each region are respectively 0° for the tooth top surface and the tooth bottom surface, 20° for the tooth surface, and 40° for the tooth root;

[0062] (4) The laser-impacted gear sample is polished and ultrasonically cleaned;

[0063] (5) The laser-impacted gear sample is subjected to carburizing treatment, the gear sample is placed in a carburizing furnace, heated to 650 ℃, kept for 30 min, then heated to 930 ℃, kept for 5 h of strong carburizing at a carbon potential of 1.1%, then cooled to 910 ℃, kept for 3 h of diffusion at a carbon potential of 0.7%, cooled to 850 ℃ in the furnace, kept for 1 h, then oil-quenched at 850 ℃, and finally tempered at 160 ℃ for 2 h, and then air-cooled out of the furnace;

[0064] (6) The carburized gear sample is polished and ultrasonically cleaned;

[0065] (7) The gear sample is placed on a laser impact device for a second laser impact strengthening treatment, the restraining layer is a uniform water layer of 2 mm, and the energy absorption layer is 100 μm black glue; the laser wavelength is set to 1064 nm, the pulse energy is 10 J, the pulse width is 10 ns, the spot diameter is 3 mm, the overlap rate is 50%, and the laser impact angles of each region are respectively 0° for the tooth top surface and the tooth bottom surface, 20° for the tooth surface, and 40° for the tooth root.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that, in the present comparative example, the first laser impact treatment is not performed before the gear is subjected to carburizing treatment.

[0068] In the present comparative example, the gear strengthening method comprises the following steps:

[0069] (1) The 20CrNiMo steel is processed into a M5 tooth type sample;

[0070] (2) The 20CrNiMo steel gear sample is polished and ultrasonically cleaned;

[0071] (3) The sample is subjected to carburizing treatment, the sample is placed in a carburizing furnace, heated to 650 ℃, kept for 30 min, then heated to 930 ℃, kept for 5 h of strong carburizing at a carbon potential of 1.1%, then cooled to 910 ℃, kept for 3 h of diffusion at a carbon potential of 0.7%, cooled to 850 ℃ in the furnace, kept for 1 h, then oil-quenched at 850 ℃, and finally tempered at 160 ℃ for 2 h, and then air-cooled out of the furnace (the gear is naturally cooled in air);

[0072] (4) Polishing and ultrasonic cleaning treatment of the carburized sample;

[0073] (5) Placing the carburized sample on a laser shock device, with a 2mm uniform water layer as the constraint layer and a 100pm black glue as the energy absorption layer; setting the laser wavelength to 1064nm, the pulse energy to 10J, the pulse width to 10ns, the spot diameter to 3mm, the overlap rate to 50%, and the laser shock angles of each region to 0° for the tooth top surface and the tooth bottom surface, 20° for the tooth surface, and 40° for the tooth root.

[0074] Comparative Example 2

[0075] The difference from Example 1 is that, in this comparative example, no laser shock strengthening is performed after carburizing the gear.

[0076] In this comparative example, the gear strengthening method specifically includes the following steps:

[0077] (1) Processing 20CrNiMo steel into a M5 gear type sample;

[0078] (2) Polishing and ultrasonic cleaning of the 20CrNiMo steel gear sample;

[0079] (3) Placing the gear sample on a laser shock device, with a 2mm uniform water layer as the constraint layer and a 100pm black glue as the energy absorption layer; setting the laser wavelength to 1064nm, the pulse energy to 6J, the pulse width to 10ns, the spot diameter to 3mm, the overlap rate to 50%, and the laser shock angles of each region to 0° for the tooth top surface and the tooth bottom surface, 20° for the tooth surface, and 40° for the tooth root.

[0080] (4) Polishing and ultrasonic cleaning treatment of the laser shocked gear sample;

[0081] (5) Carburizing the laser shocked gear sample, placing the gear sample into a carburizing furnace, heating to 650℃, maintaining for 30min, then heating to 930℃, maintaining for 5h for strong carburizing at a carbon potential of 1.1%, then cooling to 910℃, maintaining for 3h for diffusion at a carbon potential of 0.7%, furnace cooling to 850℃, maintaining for 1h, oil quenching at 850℃, and finally tempering at 160℃ for 2h, and air cooling after taking out of the furnace.

[0082] Hardness and residual stress tests were performed on the gear tooth surfaces in Example 1 and Comparative Examples 1 and 2, and the results are shown in Table 1.

[0083] Table 1

[0084] Test criteria Examples Comparative Example 1 Comparative Example 2 Surface hardness / HV 0.1 ]] 962 920 854 Surface residual stress / MPa -1176 -894 -812

[0085] The test results show that the composite strengthening of the first laser shock processing, the carburizing processing and the second laser shock processing has the most remarkable effect on the improvement of the hardness and the surface residual compressive stress of the sample.

[0086] The above merely describes preferred embodiments of the present application, and is not intended to limit the design of the application. Any equivalent changes made according to the key design of the application shall fall within the protection scope of the application.

Claims

1. A new method of gear strengthening by laser shock and carburizing, characterized in that: The method comprises the following steps: S1, pretreating the gear to be machined; S2, performing first laser impact treatment on the pretreated gear; S3, performing carburizing treatment on the gear after laser impact treatment, so as to form a carburizing strengthened layer on the surface of the gear; S4, performing second laser impact treatment on the gear after carburizing treatment, so as to form a composite strengthened layer on the surface of the gear; The gear to be machined is a 20CrNiMo carburizing steel gear. In step S2, the laser impact treatment parameters are as follows: The laser wavelength is 1064 nm, the pulse energy is 6-9 J, the pulse width is 10-20 ns, the spot diameter is 3-5 mm, and the overlap rate is 50%. In step S4, the laser impact treatment parameters are as follows: The laser wavelength is 1064 nm, the pulse energy is 10-12 J, the pulse width is 10-20 ns, the spot diameter is 3-5 mm, and the overlap rate is 50%.

2. A novel laser shock and carburizing combined gear strengthening method according to claim 1, characterized in that: In steps S2 and S4, the laser impact treatment is laser oblique impact, and the incident angle of the laser is less than 43°.

3. A novel laser shock and carburizing combined gear strengthening method according to claim 1, characterized in that: In step S2, the laser impact angle is 0° for the addendum surface and the dedendum surface, 20° for the tooth surface, and 40° for the tooth root.

4. A novel laser shock and carburizing combined gear strengthening method according to claim 1, characterized in that: In step S3, the carburizing treatment process is as follows: the gear is placed in a carburizing furnace, heated to 650℃, kept for 30 min, then heated to 930℃, kept for 5 h for strong carburizing with a carbon potential of 1.1%, then cooled to 910℃, kept for 3 h for diffusion with a carbon potential of 0.7%, furnace cooled to 850℃, kept for 1 h, then oil quenched at 850℃, and finally tempered at 160℃ for 2 h, and air cooled after taking out of the furnace.

5. A novel laser shock and carburizing combined gear strengthening method according to claim 1, characterized in that: In step S4, the laser impact angle is 0° for the addendum surface and the dedendum surface, 20° for the tooth surface, and 40° for the tooth root.

6. A novel laser shock and carburizing combined gear strengthening method according to claim 1, characterized in that: In steps S2 and S4, before performing laser impact treatment, black glue or aluminum foil is covered on the surface of the gear as an absorption layer, and deionized water is used as a constraint layer.

7. A novel laser shock and carburizing combined gear strengthening method according to claim 1, characterized in that: The pretreatment performed on the gear in step S1 includes ultrasonic cleaning and drying treatment of the gear to be machined.

8. A new method of laser shock and carburizing combined gear strengthening according to claim 1, characterized in that: The laser impact device used in the laser impact treatment comprises an operation table, a ball screw mechanism arranged above the operation table, a sliding table mechanism, and a rotating motor, which is used to drive the gear to be machined to rotate. The device further comprises a laser generator arranged towards the gear.

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