Preparation method of engineering machinery transmission gear

Abstract

The invention discloses a preparation method of an engineering machinery transmission gear, and belongs to the technical field of machinery manufacturing. According to the technical scheme, after an engineering mechanical transmission gear blank is subjected to quenching, high-temperature tempering, rough machining, semi-finish machining, stress relief tempering, finish machining, deburring and cleaning, the CrTi / CrTiSiO / CrTiSiC composite coating is prepared through a reactive sputtering and co-sputtering composite method, and during deposition, one Cr sputtering target, one Ti sputtering target, one Si sputtering target and one C sputtering target are adopted. According to the invention, the physical property mismatch between the coating and the matrix caused by factors such as thermal expansion coefficient difference can be effectively relieved, so that the overall hardness, strength and crack propagation resistance of the coating are enhanced, and the tribological property and high-temperature stability of the transmission gear of the engineering machinery can be remarkably improved; therefore, the service life under the extreme working condition is effectively prolonged, and the industrial application value is high.

Description

Technical Field

[0001] This invention belongs to the field of mechanical manufacturing technology, and specifically relates to a method for preparing transmission gears for engineering machinery. Background Technology

[0002] Construction machinery is core equipment in various large-scale construction sites, often facing extremely harsh working environments and drastically fluctuating load conditions. This causes its transmission system components, especially transmission gears, to endure severe frictional wear and impact loads, significantly shortening their service life. To improve the load-bearing capacity and operational reliability of transmission gears, conventional technical approaches mainly include two categories: one is to increase the gear size to reduce the stress per unit area on the tooth surface; the other is to use surface heat treatment processes to improve the hardness of the tooth surface. However, the former leads to an increase in the size and weight of the transmission system, which is not conducive to lightweight and compact design of equipment; the latter, such as traditional heat treatment methods like carburizing and quenching, can improve surface hardness to a certain extent, but the processing temperature is high (usually exceeding 800℃), which easily causes deformation of the workpiece. Subsequent straightening and finishing are required, making the process complex and time-consuming, and it is difficult to completely avoid early pitting, spalling, and other failure modes caused by uneven hardness distribution or insufficient core toughness.

[0003] Surface-strengthening coating technology has attracted widespread attention as an effective means to improve the wear resistance of gears. Among them, carbide and oxide-based coatings have become a research hotspot due to their high hardness, excellent chemical stability, and outstanding high-temperature resistance and wear resistance. In particular, multi-component composite coating systems have shown superior comprehensive performance. Currently, common preparation methods for this type of coating include thermal spraying, carburizing, and physical vapor deposition (PVD).

[0004] While thermal spraying boasts high deposition efficiency, the resulting coating generally exhibits low bonding strength with the substrate, leading to poor surface quality. This makes it difficult to meet the surface finish requirements of high-precision transmission gears, easily causing additional vibration and noise, and even accelerating wear. Carburizing, by infiltrating carbon atoms into the workpiece surface, can effectively improve surface hardness and wear resistance. However, its high processing temperature, long cycle time, and significant deformation necessitate multiple subsequent correction processes, resulting in high costs and insufficient efficiency.

[0005] Physical vapor deposition (PVD) technology, as a low-temperature film-forming process, typically operates at temperatures not exceeding 400°C. This effectively avoids thermal damage and dimensional deformation to the gear substrate, while producing coatings with extremely high hardness, good toughness, and excellent wear resistance and thermal stability. However, directly applying this technology to the surface of transmission gears still faces a key bottleneck: significant differences exist between the gear substrate material and the PVD ceramic coating (such as carbides, nitrides, oxides, etc.) in terms of hardness, elastic modulus, and coefficient of thermal expansion. This leads to insufficient interfacial bonding strength, easily causing stress concentration under high-speed, heavy-load, and thermal cycling conditions, which in turn induces crack initiation and coating peeling, severely affecting the service life of the gears. Chinese invention patent CN120719247A provides a method for preparing a hard nitride ceramic coating on a magnesium alloy surface by controlling the intermittent discharge of the cathode target during the PVD process to form an intermittent plasma flow. This method can reduce growth defects caused by differences in thermal expansion, but it may still not completely eliminate growth defects such as pores and cracks in the coating caused by differences in thermal expansion, thus affecting the microstructure and mechanical properties of the coating.

[0006] In summary, existing surface treatment technologies still have significant shortcomings in the application of transmission gears in engineering machinery. There is a lack of a method for preparing composite coatings on gear surfaces that possess high hardness, excellent wear resistance, and high-temperature resistance, while achieving good interfacial matching and high bonding strength with the substrate, and ensuring long-term stable service under high-speed, heavy-load, and thermal shock conditions. Therefore, developing a novel surface treatment process that can effectively coordinate the mechanical properties between the coating and the substrate, enhance interfacial bonding, and is suitable for transmission gears in engineering machinery has significant engineering application value for improving the overall reliability, durability, and comprehensive operating efficiency of the machine. Summary of the Invention

[0007] This invention provides a method for preparing transmission gears for engineering machinery, which can effectively improve the friction reduction and wear resistance characteristics of transmission gears for engineering machinery under high temperature and high load conditions, thereby significantly improving their overall performance and service durability.

[0008] The technical solution of this invention is as follows: The preparation method of transmission gears for engineering machinery involves quenching, high-temperature tempering, rough machining, semi-finishing, stress-relief tempering, finishing, deburring, and cleaning of the transmission gear blank. Then, a CrTi / CrTiSiO / CrTiSiC composite coating is prepared by a combination of reactive sputtering and co-sputtering. During deposition, one Cr sputtering target, one Ti sputtering target, one Si sputtering target, and one C sputtering target are used. Specifically, the following steps are included: (1) Machining of transmission gear parts: blank quenching → high temperature tempering → rough machining → semi-finishing → stress relief tempering → finish machining → deburring → cleaning to remove surface oil stains; (2) Surface treatment of transmission gear parts: The gear parts are ultrasonically cleaned in alcohol and acetone respectively to remove surface impurities and attachments, and then dried and installed in a PVD composite coating machine. (3) Ion cleaning of transmission gear parts: pulse bias voltage adjusted to 520V, duty cycle 0.25, Ar gas pressure 1.5-1.7Pa, temperature 300℃, Ar + Ion cleaning for 40-45 minutes; (4) Deposit CrTi layer: Ar gas pressure is adjusted to 0.7-0.75 Pa, flow rate is 50-55 sccm, pulse bias voltage is 275 V, Cr target power is turned on at 85 W, Ti target power is 70 W, and CrTi coating is deposited for 10-15 min. (5) Reactive sputtering of CrTiSiO layer: Ar flow rate is 100-105 sccm, pulse bias voltage is 245V, Cr target power is 90W, Ti target power is 75W, Si target power is 60W, O2 gas flow rate is 15-20 sccm, and reactive sputtering deposition of CrTiSiO coating is carried out for 10-15 min. (6) Co-sputtering CrTiSiC layer: O2 gas is turned off, Ar flow rate is 70-75 sccm, pulse bias voltage is 225V, Cr target power is 85W, Ti target power is 70W, Si target power is 50W, C target power is 80W, and CrTiSiC coating is deposited by co-sputtering for 10-15 min. (7) Post-treatment: Turn off the power supply and gas source of each target, let the room temperature drop to below 80°C, take out the sample, and the coating is finished.

[0009] Preferably, the base material of the part is one of the following: 20CrMo, 20CrMnTi, 20CrMnMo, 20CrNi2MoNb, 22CrNi2MoNb, 20NiCrMoH, 30CrMnSi, and 35SiMn medium and low carbon steels and their alloy steels.

[0010] Preferably, in step (2), the cleaning time in alcohol and acetone is 30-40 min, and the composite coating machine is evacuated to 4.0 × 10⁻⁶. -3 Heat Pa to 300℃ and hold for 30-40 minutes.

[0011] Preferably, the deposition temperature in step (4) is 260-265℃.

[0012] Preferably, the deposition temperature in step (5) is 255-265℃.

[0013] Preferably, the deposition temperature in step (6) is 220-230℃.

[0014] Preferably, the oxygen atom content introduced by the O2 gas reaction in step (5) accounts for 16-19 at.% of the total metal atoms in the entire CrTiSiO layer.

[0015] Preferably, the manufactured engineering machinery transmission gear part has the following structure, with a composite coating of CrTi layer, CrTiSiO layer and CrTiSiC layer sequentially outward from the surface of the part substrate.

[0016] Compared with the prior art, the present invention has the following advantages: By combining the advantages of reactive sputtering and co-sputtering deposition technologies, a multilayer composite coating system of CrTi / CrTiSiO / CrTiSiC with excellent comprehensive performance is constructed on the surface of the gear substrate.

[0017] First, a CrTi transition layer is deposited on the pretreated gear substrate surface using a non-reactive sputtering process. This transition layer effectively alleviates the internal stress caused by the mismatch in physical parameters such as the coefficient of thermal expansion and elastic modulus between the hard coating and the substrate, significantly enhancing the interfacial bonding strength between the coating and the substrate, and providing a stable support and ideal bonding interface for the preparation of the functional coating. Based on the transition layer, a CrTiSiO oxide coating is prepared using a radio frequency reactive sputtering process. This coating exhibits high hardness, excellent oxidation resistance, and wear resistance, improving the strength, stiffness, and high-temperature oxidation resistance of the gear surface. Subsequently, a CrTiSiC carbide coating is deposited using co-sputtering technology. This carbide coating not only possesses high hardness and good wear resistance but also effectively reduces the coefficient of friction, improving the friction reduction characteristics of the gear pair during meshing and further optimizing wear resistance. This composite structure effectively inhibits the growth of columnar crystal structures, blocks the propagation path of microcracks, and mitigates the impact of external loads, allowing the coating to maintain high hardness and strength while achieving significantly improved toughness and impact resistance.

[0018] In summary, the CrTi / CrTiSiO / CrTiSiC multilayer composite coating prepared by the present invention through a combined reactive sputtering and co-sputtering process can enhance the adhesion between the coating and the substrate by more than 100%, reduce friction and adhesion during the operation of transmission gears, and increase the surface hardness by more than 2 times. Compared with the traditional carburizing process, it shortens the processing time, extends the service life of transmission gears in engineering machinery by more than 2 times, and reduces the maintenance and upkeep costs of transmission gears. Furthermore, since the preparation process temperature can be controlled below 300℃, it will not cause degradation of the matrix microstructure of the transmission gear parts, and the surface dimensions and shape accuracy are unaffected. No grinding or reprocessing is required after treatment, making it a suitable final processing method for transmission gear parts in engineering machinery. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the surface structure of the transmission gear obtained in Embodiment 1 of the present invention.

[0020] In the figure: 1. Component substrate; 2. CrTi layer; 3. CrTiSiO layer; 4. CrTiSiC layer.

[0021] Figure 2 This is a morphological image of the CrTi / CrTiSiO / CrTiSiC composite coated part prepared in Example 1 of the present invention.

[0022] Figure 3 This is a scratch morphology diagram of the CrTi / CrTiSiO / CrTiSiC composite coated part prepared in Example 1 of the present invention.

[0023] Figure 4 This is a surface wear mark morphology image of a CrTi / CrTiSiO / CrTiSiC composite coated part prepared in Example 1 of this invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this invention.

[0025] Example 1 The preparation method of transmission gears for engineering machinery: The base material of the transmission gear part 1 is 30CrMnSi. After the transmission gear blank is quenched, high temperature tempered, roughed, semi-finished, stress-relief tempered, finished, deburred and cleaned, a CrTi / CrTiSiO / CrTiSiC composite coating is prepared by a combination of reactive sputtering and co-sputtering. During deposition, one Cr sputtering target, one Ti sputtering target, one Si sputtering target and one C sputtering target are used. Specifically, the following steps are included: (1) Machining of transmission gear parts: blank quenching (910℃, oil quenching) → high temperature tempering (560℃, air cooling) → rough machining → semi-finishing → stress relief tempering (500℃, oil cooling) → finish machining (surface roughness Ra1.6μm, machining dimensions: lower tolerance limit) → deburring → cleaning to remove surface oil stains; (2) Surface treatment of transmission gear parts: The gear parts were placed in alcohol and acetone respectively, and ultrasonically cleaned for 40 minutes each to remove surface impurities and other attachments. After drying, they were quickly loaded into a PVD composite coating machine and vacuumed to 4.0×10 - 3 Pa, heat to 300℃, and hold for 30 minutes; (3) Ion cleaning of transmission gear parts: pulse bias voltage adjusted to 520V, duty cycle 0.25, Ar gas pressure 1.7Pa, temperature 300℃, Ar + Ion cleaning for 45 minutes; (4) Deposition of CrTi layer 2: Ar gas pressure is adjusted to 0.75 Pa, flow rate is 55 sccm, pulse bias voltage is 275 V, deposition temperature is 265 °C, Cr target power is turned on at 85 W, Ti target power is 70 W, and CrTi coating is deposited for 14 min. (5) Reactive sputtering of CrTiSiO layer 3: Ar flow rate is 105 sccm, pulse bias voltage is 245 V, deposition temperature is 265 °C, Cr target power is 90 W, Ti target power is 75 W, Si target power is 60 W, O2 gas flow rate is 20 sccm, reactive sputtering deposition of CrTiSiO coating is 15 min; the oxygen atom content introduced by the O2 gas reaction accounts for 16 at. of the total metal atoms in the entire CrTiSiO layer.

[0026] (6) Co-sputtering CrTiSiC layer 4: O2 gas was turned off. Ar flow rate was 75 sccm, pulse bias voltage was 225 V, deposition temperature was 230 °C, Cr target power was 85 W, Ti target power was 70 W, Si target power was 50 W, C target power was 80 W, and CrTiSiC coating was co-sputtered for 15 min; (7) Post-treatment: Turn off the power supply and gas source of each target, let the room temperature drop to below 80°C, take out the sample, and the coating is finished.

[0027] A schematic diagram of the surface structure of the manufactured transmission gear is shown below. Figure 1 As shown, the CrTi / CrTiSiO / CrTiSiC composite coating prepared in this embodiment exhibits excellent comprehensive performance on the part surface. This coating system possesses superior mechanical and tribological properties, with a surface microhardness reaching HV2610, nearly three times higher than the surface hardness of traditional carburizing processes (approximately HV650). The coating thickness is approximately 1.14 μm, the surface roughness is maintained at Ra 52 nm, and the surface morphology is as follows. Figure 2 As shown.

[0028] In terms of interfacial bonding performance, the bonding strength of this composite coating is 81N-85N, which is more than double that of a single PVD oxide coating (33N-38N), significantly enhancing interfacial adhesion. Bonding force scratch test results ( Figure 3 This confirms that even in the scratch end area under high load, there is still significant coating residue, reflecting a significant enhancement in the adhesion between the coating and the substrate.

[0029] Under the established friction conditions (using an HRT multi-functional friction tester, reciprocating linear motion mode, with bearing steel of hardness HRC50-56 as the grinding ball, a load of 60 N, a sliding speed of 10 mm / s, and a test time of 30 min), the composite coating exhibited stable friction behavior with a friction coefficient of 0.33-0.39, which is approximately 80% lower than that of traditional carburized samples (friction coefficient 0.64-0.67). Simultaneously, the coating wear rate was 2.44 × 10⁻⁶. -6 mm 3 / (N•m)-2.49×10 -6 mm 3 / (N•m), compared with carburized parts, the wear rate is reduced by 70%-75%. Figure 4 As shown in the surface scratch morphology of the coating, the coating still maintains an intact residual structure after the friction test, which proves its excellent durability and structural stability.

[0030] Example 2 A method for preparing transmission gears for engineering machinery. The base material 1 of the transmission gear part is 22CrNi2MoNb. After the transmission gear blank is quenched, high-temperature tempered, roughed, semi-finished, stress-relief tempered, finished, deburred, and cleaned, a CrTi / CrTiSiO / CrTiSiC composite coating is prepared by a combination of reactive sputtering and co-sputtering. During deposition, one Cr sputtering target, one Ti sputtering target, one Si sputtering target, and one C sputtering target are used.

[0031] Specifically, the following steps are included: (1) Machining of transmission gear parts: part blank → quenching (860℃, water cooling) → high temperature tempering (530℃, water cooling) → rough machining → semi-finishing → stress relief tempering (520℃, air cooling) → finish machining (surface roughness Ra 1.6μm, machining dimensions: lower limit of tolerance) → deburring → cleaning to remove surface oil stains; (2) Surface treatment of transmission gear parts: Place the gear parts separately in alcohol and acetone, and ultrasonically clean each for 30 minutes to remove surface impurities and other attachments. After drying, quickly load them into a PVD composite coating machine and vacuum to 4.0×10 -3 Pa, heat to 300℃, and hold for 40 minutes; (3) Ion cleaning of transmission gear surface: pulse bias voltage adjusted to 520V, duty cycle 0.25, Ar gas pressure 1.5Pa, temperature 300℃, Ar + Ion cleaning for 40 minutes; (4) Deposition of CrTi layer 2: Ar gas pressure is adjusted to 0.7 Pa, flow rate is 50 sccm, pulse bias voltage is 275 V, deposition temperature is 260 °C, Cr target power is turned on at 85 W, Ti target power is 70 W, and CrTi coating is deposited for 12 min. (5) Reactive sputtering of CrTiSiO layer 3: Ar flow rate 100 sccm, pulse bias 245 V, deposition temperature 255 °C, Cr target power 90 W, Ti target power 75 W, Si target power 60 W, O2 gas flow rate 16 sccm, reactive sputtering deposition of CrTiSiO coating for 12 min; the oxygen atom content introduced by the O2 gas reaction accounts for 19 at.% of the total metal atoms in the entire CrTiSiO layer. (6) Co-sputtering CrTiSiC layer 4: O2 gas was turned off. Ar flow rate was 72 sccm, pulse bias voltage was 225 V, deposition temperature was 220 °C, Cr target power was 85 W, Ti target power was 70 W, Si target power was 50 W, C target power was 80 W, and CrTiSiC coating was co-sputtered for 11 min; (7) Post-treatment: Turn off the power supply and gas source of each target, let the room temperature drop to below 80°C, take out the sample, and the coating is finished.

[0032] The CrTi / CrTiSiO / CrTiSiC composite coating prepared in this embodiment exhibits excellent mechanical and tribological properties. The coating surface has a microhardness as high as HV2560, nearly three times higher than the surface hardness (HV650) of the conventional carburizing process alone. Simultaneously, the coating thickness is approximately 1.01 μm, and the surface roughness is Ra 49 nm. Regarding bonding strength, the composite coating exhibits a bonding force of 83 N-86 N, more than double that of a simple PVD oxide coating (33-38 N), demonstrating superior bonding performance.

[0033] Although the present invention has been described in detail by way of preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for manufacturing transmission gears for engineering machinery, characterized in that, After quenching, high-temperature tempering, rough machining, semi-finishing, stress-relief tempering, finishing, deburring, and cleaning, the engineering machinery transmission gear blank is used to prepare a CrTi / CrTiSiO / CrTiSiC composite coating by a combination of reactive sputtering and co-sputtering. During deposition, one Cr sputtering target, one Ti sputtering target, one Si sputtering target, and one C sputtering target are used. Specifically, the following steps are included: (1) Machining of transmission gear parts: blank quenching → high temperature tempering → rough machining → semi-finishing → stress relief tempering → finish machining → deburring → cleaning to remove surface oil stains; (2) Surface treatment of transmission gear parts: The gear parts are ultrasonically cleaned in alcohol and acetone respectively to remove surface impurities and attachments, and then dried and installed in a PVD composite coating machine. (3) Ion cleaning of transmission gear parts: pulse bias voltage adjusted to 520V, duty cycle 0.25, Ar gas pressure 1.5-1.7Pa, temperature 300℃, Ar + Ion cleaning for 40-45 minutes; (4) Deposit CrTi layer: Ar gas pressure is adjusted to 0.7-0.75 Pa, flow rate is 50-55 sccm, pulse bias voltage is 275 V, Cr target power is turned on at 85 W, Ti target power is 70 W, and CrTi coating is deposited for 10-15 min. (5) Reactive sputtering of CrTiSiO layer: Ar flow rate is 100-105 sccm, pulse bias voltage is 245V, Cr target power is 90W, Ti target power is 75W, Si target power is 60W, O2 gas flow rate is 15-20 sccm, and reactive sputtering deposition of CrTiSiO coating is carried out for 10-15 min. (6) Co-sputtering CrTiSiC layer: O2 gas is turned off, Ar flow rate is 70-75 sccm, pulse bias voltage is 225V, Cr target power is 85W, Ti target power is 70W, Si target power is 50W, C target power is 80W, and CrTiSiC coating is deposited by co-sputtering for 10-15 min. (7) Post-treatment: Turn off the power supply and gas source of each target, let the room temperature drop to below 80°C, take out the sample, and the coating is finished.

2. The method for preparing transmission gears for engineering machinery as described in claim 1, characterized in that, The base material of the part is one of the following: 20CrMo, 20CrMnTi, 20CrMnMo, 20CrNi2MoNb, 22CrNi2MoNb, 20NiCrMoH, 30CrMnSi, and 35SiMn medium and low carbon steels and their alloy steels.

3. The method for preparing transmission gears for engineering machinery as described in claim 1, characterized in that, In step (2), the cleaning time in alcohol and acetone is 30-40 minutes each, and the composite coating machine is evacuated to 4.0 × 10⁻⁶. -3 Heat Pa to 300℃ and hold for 30-40 minutes.

4. The method for preparing transmission gears for engineering machinery as described in claim 1, characterized in that, The deposition temperature in step (4) is 260-265℃.

5. The method for manufacturing transmission gears for engineering machinery as described in claim 1, characterized in that, The deposition temperature in step (5) is 255-265℃.

6. The method for preparing transmission gears for engineering machinery as described in claim 1, characterized in that, The deposition temperature in step (6) is 220-230℃.

7. The method for preparing transmission gears for engineering machinery as described in claim 1, characterized in that, In step (5), the oxygen atom content introduced by the O2 gas reaction accounts for 16-19 at.% of the total metal atoms in the entire CrTiSiO layer.

8. The method for preparing transmission gears for engineering machinery as described in claim 1, characterized in that, The manufactured engineering machinery transmission gear parts have the following structure: a composite coating consisting of a CrTi layer, a CrTiSiO layer, and a CrTiSiC layer, which are sequentially applied outward from the surface of the part substrate.

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