High-hardness and high-wear-resistance coating and preparation method thereof

Abstract

The invention relates to the technical field of metal material coating manufacturing, and discloses a preparation method of an ultrahigh-speed laser cladding high-hardness and high-wear-resistance coating. The method aims at solving the technical problems that when an ultra-high-speed wear-resistant coating is prepared in the prior art, due to a formed non-equilibrium solidification structure, the hardness of alloy powder is low, the hardness of the wear-resistant coating is low, the crack sensitivity of a cladding layer is increased, and even the risk of cracking and peeling occurs. The method comprises the following steps: S1, carrying out heat treatment on an alloy bar; s2, alloy powder is prepared, and the performance of the alloy powder is tested; and S3, preparing the ultra-high-speed wear-resistant coating and testing the performance of the ultra According to the method, effective conversion of the target phase from the metal bar to the metal powder to the metal coating is achieved, and the difficulty of heat treatment of the target phase is greatly reduced; and the wear-resisting property is excellent, the surface roughness of the cladding layer is low, and the subsequent machining difficulty is greatly reduced.

Description

[0001] This application is a divisional application. The original application was entitled "A Method for Preparing a High-Hardness and High-Wear-Resistant Coating by Ultra-High-Speed ​​Laser Cladding", with application number 202311141234.3 and application date of September 5, 2023. Technical Field

[0002] This invention relates to the field of metal material coating manufacturing technology, and in particular to a method for preparing a high-hardness and high-wear-resistant coating by ultra-high-speed laser cladding. Background Technology

[0003] With the rapid development of modernization, higher demands are being placed on the manufacturing industry, especially in industries with high requirements for wear resistance, such as coal and petroleum, chemical metallurgy, and automobile manufacturing. Currently, by preparing a coating with high wear resistance on the surface of key components, the effects of surface strengthening and local repair can be effectively achieved, extending their service life and reducing remanufacturing costs.

[0004] Laser cladding technology utilizes a high-energy-density laser beam to rapidly melt and solidify the cladding material and the substrate surface, achieving a metallurgical bond between the cladding layer and the substrate surface. This significantly improves the wear resistance and corrosion resistance of the substrate surface. The cladding layer prepared by laser cladding has advantages such as metallurgical bonding with the substrate, fine and dense structure, and high performance.

[0005] Ultra-high-speed laser cladding technology, based on traditional laser cladding technology, achieves optimal coupling between powder particles and laser beams by adjusting the laser beam, thereby shortening the irradiation time of a single laser point and greatly improving the cladding rate and powder utilization. It solves the bottleneck problem that currently limits the application of cladding technology due to low efficiency and high cost. The preparation of ultra-high-speed wear-resistant coatings using ultra-high-speed laser cladding technology has attracted increasing attention.

[0006] The composition ratio and phase composition of raw material powders are among the main factors affecting the wear resistance of coatings. The phase composition of metal powders varies greatly due to different powder preparation processes. Gas atomization powder preparation is one of the most widely used methods for preparing metal powders. During the production process, due to the extremely fast cooling rate of molten fine droplets, some hard alloy phases cannot precipitate in the powder matrix, resulting in a non-equilibrium solidification structure that leads to a lower hardness of the alloy powder.

[0007] Similar process characteristics exist when preparing ultra-high-speed wear-resistant coatings using ultra-high-speed laser cladding technology. During conventional coating preparation, under extremely rapid cooling conditions, the precipitation of alloy phases in the cladding layer is low, resulting in low hardness of the wear-resistant coating. To achieve ideal performance, subsequent heat treatment of the cladding layer and even the entire component is required. For some ultra-large, ultra-long, or structurally complex metal parts that are difficult to heat treat, the hardness and wear resistance of the cladding layer are often further improved by adding an external hard phase. However, adding an external hard phase increases the cladding layer's susceptibility to cracking and may even lead to cracking and peeling. Summary of the Invention

[0008] In view of the above technical problems, this disclosure provides a method for preparing a high-hardness and high-wear-resistant coating by ultra-high-speed laser cladding, which solves the technical problem in the prior art that the non-equilibrium solidification structure formed during the preparation of ultra-high-speed wear-resistant coatings leads to low hardness of alloy powder, low hardness of wear-resistant coating, increased crack sensitivity of cladding layer, and even the risk of cracking and peeling.

[0009] According to one aspect of this disclosure, a method for preparing a high-hardness, high-wear-resistant coating by ultra-high-speed laser cladding is provided, comprising the following steps:

[0010] S1, heat-treated alloy rod: The alloy rod rich in carbide-forming elements is placed in an air-isolated heat treatment furnace for heat treatment. The alloy rod is quenched 1 to 2 times to obtain a quenched part. Then the quenched part is tempered 1 to 3 times. After being taken out and cooled to room temperature, the alloy rod with carbide fully precipitated is obtained.

[0011] S2, Preparation of alloy powder and testing of its properties: The alloy rods heat-treated in S1 are precision machined to obtain alloy electrode rods of the required specifications. The alloy electrode rods are placed in a plasma rotating electrode device for vacuum treatment. The distance between the plasma gun and the electrode rod, the rotation speed of the electrode rod, the feed speed, and the power parameters of the plasma gun are set. After the protective gas is introduced, alloy powder is prepared. The flowability, particle size, oxygen content, and sphericity of the prepared alloy powder are tested, and the morphology and microstructure of the alloy powder are observed by scanning electron microscopy.

[0012] S3, Prepare an ultra-high speed wear-resistant coating and test its performance: Pre-treat the surface of the part to be clad by grinding and cleaning to remove oxide scale; prepare an ultra-high speed wear-resistant coating by ultra-high speed laser cladding of the alloy powder obtained in S2 onto the surface of the part to be clad by ultra-high speed laser cladding; sample, grind and polish the wear-resistant coating, and analyze the microstructure of the wear-resistant coating by optical microscope and scanning electron microscope, and measure the hardness of the wear-resistant coating by microhardness tester.

[0013] In some embodiments of this disclosure, in step S1, the carbide-forming elements and their contents include: C: 0.50–1.80%, Mo: 2.00–6.00%, Cr: 3.00–10.0%, V: 1.0–5.50%, and W: 5.00–11.0%.

[0014] In some embodiments of this disclosure, in S2, the distance between the plasma gun and the electrode rod is 20-90 mm, the electrode rod rotation speed is 25000-35000 r / min, the feed speed is 0.5-1.5 mm / s, and the plasma gun power is 150 kW-200 kW.

[0015] In some embodiments of this disclosure, the process parameters of the ultra-high-speed laser cladding in S3 are as follows: spot diameter is 1-4 mm, laser power is 1500-5000 W, scanning speed is 40-60 m / min, overlap rate is 30-60%, powder feeding rate is 20-50 g / min, and argon flow rate is 4-15 g / min.

[0016] In some embodiments of this disclosure, the flowability of the alloy powder in S3 is 10-30 s / 50 g, and a large amount of particulate carbide alloy phase is precipitated from the alloy powder. The particulate carbide alloy phase includes MC, M6C, M23C6, or M7C3.

[0017] In some embodiments of this disclosure, the hardness of the cladding layer in S3 is not less than 65 HRC.

[0018] In some embodiments of this disclosure, the holding temperature for the quenching treatment in S1 is 800–1200°C, the holding time is 5–60 min, and the cooling method is oil cooling.

[0019] In some embodiments of this disclosure, the holding temperature of the tempering treatment in S1 is 400-600°C, the holding time is 30-130 min, and the cooling method is air cooling.

[0020] In some embodiments of this disclosure, the heating rate of the alloy rod containing the carbide-forming element in S1 during heat treatment is not higher than 10°C / min.

[0021] In some embodiments of this disclosure, the alloy electrode rod in S2 has a diameter of 20-55 mm, a length of 130-160 mm, and a straightness deviation of no more than 0.01 mm.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. In this invention, after adopting the above preparation scheme, the substrate is subjected to heat treatment and phase transformation, so that the carbides are fully precipitated. By utilizing the extraordinary cooling characteristics of plasma rotating electrode powder preparation and ultra-high speed laser cladding, the target phase is effectively transformed from metal rod to metal powder to metal coating, which greatly reduces the difficulty of heat treatment of the target phase. Compared with the current technology of processing powder and then performing phase transformation, or atomizing the powder after phase transformation, the powder obtained by phase transformation and subsequent processing has significantly improved hardness and wear resistance of the coating.

[0024] 2. The high-performance metal powder prepared by the rotating electrode in this invention has the characteristics of sphericity ≥94%, oxygen content ≤630ppm, and few hollow powders; the metal powder itself precipitates a large amount of high-hardness phase, which has excellent physical and chemical properties, and is particularly suitable for surface modification processes such as ultra-high speed laser cladding.

[0025] 3. The present invention can obtain excellent wear resistance by preparing a coating through an appropriate ultra-high speed laser cladding process. No additional heat treatment is required for the surface-modified metal parts. The surface roughness of the cladding layer is low, which greatly reduces the difficulty of subsequent machining.

[0026] 4. In this application, the ratio of W and V in the carbide-forming elements can be appropriately increased, which can effectively reduce the phenomenon of coating cracking caused by excessive W and V content in traditional methods.

[0027] 5. The scanning speed is relatively fast, and it can achieve an extraordinary rapid cooling effect during the ultra-high speed laser cladding process, reducing the existence time of the molten pool and maximizing the inheritance of carbides in the powder. Attached Figure Description

[0028] Figure 1 The microstructure morphology of the metal powder prepared in Example 1 of this invention;

[0029] Figure 2 The microstructure morphology of the metal powder prepared in Comparative Example 1 of this invention is shown.

[0030] Figure 3 The microstructure morphology of the cladding layer prepared in Example 1 of this invention;

[0031] Figure 4 The microstructure morphology of the cladding layer prepared in Comparative Example 2 of this invention is shown. Detailed Implementation

[0032] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0033] Example 1

[0034] This example discloses a method for preparing a high-hardness, high-wear-resistant coating using ultra-high-speed laser cladding. (See also...) Figures 1 to 4 ,

[0035] S1. Alloy rods of high-speed steel enriched with carbide-synthetic elements such as C, W, V, Cr, and Mo were selected for experiments. Their chemical composition is shown in Table 1, with the remainder being Fe.

[0036] Table 1. Carbide synthesis elements and their contents in alloy rods.

[0037]

[0038] The heat treatment process of the alloy rod is as follows: one quenching treatment and three tempering treatments. First, the alloy rod is held at 850℃ for 1 hour, and then the temperature is raised to 1160℃ and held for 5 minutes for quenching. The quenching medium is cooling oil. Immediately after quenching, three tempering treatments are performed. The tempering temperature is 550℃ and the holding time is 1 hour. After being taken out, it is cooled to room temperature to obtain an alloy rod with carbide fully precipitated. The heating rate during the heat treatment process is not higher than 10℃ / min.

[0039] S2. The heat-treated alloy rod is precision machined to obtain an alloy electrode rod; the alloy electrode rod has a diameter of 49 mm, a length of 150 mm, and a straightness deviation of 0.006 mm.

[0040] S3. The alloy electrode rod obtained in S2 is loaded into the plasma rotating electrode device and a vacuum is drawn. When the vacuum degree of the powder preparation chamber reaches 0.8 × 10⁻⁶, the vacuum level is adjusted to 0.8 × 10⁻⁶. -3 Argon gas is then introduced into the equipment after Pa to make the pressure higher than 1 standard atmosphere. The argon gas has a purity of 99.9%. The atomization powder production parameters are as follows: the distance between the plasma gun and the electrode rod is 21 mm, the electrode rod rotation speed is 34000 r / min, the feed speed is 1.1 mm / s, and the plasma gun power is 170 KW.

[0041] S4. The atomized powder obtained in S3 is cooled and sieved, and then sealed under vacuum to obtain high-performance alloy powder.

[0042] S5. The prepared high-performance metal powder is applied in the field of surface modification. Taking ultra-high-speed laser cladding technology as an example, a high-hardness wear-resistant coating is prepared using the high-performance metal powder prepared in this invention. The detailed implementation example is as follows:

[0043] Using 45# steel rods with a diameter of 50mm as the substrate material for ultra-high-speed laser cladding, the surface of the substrate rods is ground and polished, and ethanol is used to wipe away surface grease and impurities before coating preparation.

[0044] The high-performance metal powder was prepared on the surface of the experimental substrate using ultra-high-speed laser cladding technology. The ultra-high-speed laser cladding process parameters were as follows: spot diameter of 2.3 mm, laser power of 2970 W, scanning speed of 45 mm / s, overlap rate of 50%, powder feeding rate of 30 g / min, and protective gas flow rate of 7 L / min. After cladding, the clad part was wrapped with asbestos cloth and cooled to room temperature.

[0045] In this application, the power of the plasma gun was increased and the rotation speed of the electrode rod was improved. The purpose is to atomize and produce powder when the electrode rod reaches a semi-molten state under the action of high-speed centrifugal force, so as to minimize the time of liquid phase existence.

[0046] Example 2

[0047] S1. An alloy rod rich in carbide-synthesizing elements such as C, W, V, Cr, and Mo was selected for the experiment. Its chemical composition is shown in Table 2. Other components are the materials of the alloy rod itself, such as iron.

[0048] Table 2. Carbide synthesis elements and their contents in alloy rods.

[0049]

[0050] The heat treatment process of the alloy rod is as follows: it undergoes one quenching treatment and two tempering treatments. First, it is heated to 1190℃ and held for 10 minutes for quenching. The quenching medium is cooling oil. Immediately after quenching, it undergoes two tempering treatments. The tempering holding temperature is 550℃ and the holding time is 1 hour. After being taken out, it is cooled to room temperature to obtain an alloy rod with carbide fully precipitated. The heating rate during the heat treatment process is not higher than 10℃ / min.

[0051] S2. The heat-treated alloy rod is precision machined to obtain an alloy electrode rod; the alloy electrode rod has a diameter of 49 mm, a length of 150 mm, and a straightness deviation of 0.005 mm.

[0052] S3. The alloy electrode rod obtained in S2 is loaded into the plasma rotating electrode device and a vacuum is drawn. When the vacuum degree of the powder preparation chamber reaches 0.7×10-3Pa, argon gas is introduced into the device to make the gas pressure higher than 1 standard atmosphere. The mass purity of the argon gas is 99.9%. The atomization powder preparation parameters are: the distance between the plasma gun and the electrode rod is 21mm, the electrode rod rotation speed is 36000r / min, the feed speed is 1.0mm / s, and the plasma gun power is 175KW.

[0053] S4. The atomized powder obtained in S3 is cooled and sieved, and then sealed under vacuum to obtain high-performance alloy powder.

[0054] S5. The prepared high-performance metal powder can be applied to the field of surface modification. Taking ultra-high-speed laser cladding technology as an example, a high-hardness wear-resistant coating is prepared using the high-performance metal powder prepared in this invention. The detailed implementation example is as follows:

[0055] Using 45# steel rods with a diameter of 50mm as the substrate material for ultra-high-speed laser cladding, the surface of the substrate rods is ground and polished, and ethanol is used to wipe away surface grease and impurities before coating preparation.

[0056] The high-performance metal powder was prepared on the surface of the experimental substrate using ultra-high-speed laser cladding technology. The ultra-high-speed laser cladding process parameters were as follows: spot diameter of 2.3 mm, laser power of 3300 W, scanning speed of 40 mm / s, overlap rate of 40%, powder feeding rate of 50 g / min, and protective gas flow rate of 7 L / min. After cladding, the clad part was wrapped with asbestos cloth and cooled to room temperature.

[0057] Example 3

[0058] S1. Alloy rods rich in carbide-synthesizing elements such as C, W, V, Cr, and Mo were selected for experiments. Their chemical compositions are shown in Table 3.

[0059] Table 3. Carbide synthesis elements and their contents in alloy rods.

[0060]

[0061] The heat treatment process for the alloy rod is as follows: quenching once and tempering twice. First, the temperature is raised to 1225℃ and held for 10 minutes for quenching, with cooling oil as the quenching medium. Immediately after quenching, tempering is performed twice, with a holding temperature of 350℃ and a holding time of 2 hours. After being removed and cooled to room temperature, an alloy rod with fully precipitated carbides is obtained. The heating rate during the heat treatment process is not higher than 10℃ / min.

[0062] S2. The heat-treated alloy rod is precision machined to obtain an alloy electrode rod; the alloy electrode rod has a diameter of 49 mm, a length of 150 mm, and a straightness deviation of 0.007 mm.

[0063] S3. The alloy electrode rod obtained in S2 is loaded into the plasma rotating electrode device and a vacuum is drawn. When the vacuum degree of the powder preparation chamber reaches 0.8×10-3Pa, argon gas is introduced into the device to make the gas pressure higher than 1 standard atmosphere. The mass purity of the argon gas is 99.9%. The atomization powder preparation parameters are: the distance between the plasma gun and the electrode rod is 21mm, the electrode rod rotation speed is 34000r / min, the feed speed is 1.2mm / s, and the plasma gun power is 170KW.

[0064] S4. The atomized powder obtained in S3 is cooled and sieved, and then sealed under vacuum to obtain high-performance alloy powder.

[0065] S5. The prepared high-performance metal powder can be applied to the field of surface modification. Taking ultra-high-speed laser cladding technology as an example, a high-hardness wear-resistant coating is prepared using the high-performance metal powder prepared in this invention. The detailed implementation example is as follows:

[0066] Using 45# steel rods with a diameter of 50mm as the substrate material for ultra-high-speed laser cladding, the surface of the substrate rods is ground and polished, and ethanol is used to wipe away surface grease and impurities before coating preparation.

[0067] The high-performance metal powder was prepared on the surface of the experimental substrate using ultra-high-speed laser cladding technology. The ultra-high-speed laser cladding process parameters were as follows: spot diameter of 2.3 mm, laser power of 2970 W, scanning speed of 50 mm / s, overlap rate of 40%, powder feeding rate of 45 g / min, and protective gas flow rate of 7 L / min. After cladding, the clad part was wrapped with asbestos cloth and cooled to room temperature.

[0068] Comparative Example 1

[0069] Compared with Example 1, the difference in this example is in S1, where the alloy rod is made of commercially available annealed high-speed steel of the same material, and is no longer subjected to quenching and tempering treatment before being powdered using a plasma rotating electrode.

[0070] The remaining parameters, conditions, and preparation process are the same as in Example 1.

[0071] Comparative Example 2

[0072] Compared with Example 1, the difference in this example is in S5, where the alloy powder is used for coating preparation by conventional laser cladding. The process parameters of the laser cladding are: spot diameter of 2.0 mm, laser power of 2000 W, scanning speed of 800 mm / min, overlap rate of 50%, powder feeding rate of 40 g / min, and argon flow rate of 8 g / min.

[0073] The remaining parameters, conditions, and preparation process are the same as in Example 1.

[0074] Related tests

[0075] The metal powders prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to relevant tests, and the results are shown in Table 4.

[0076] Table 4 Performance test results of metal powder

[0077]

[0078] The metal powders prepared in Example 1 and Comparative Example 1 were sampled, and after metallographic sample preparation and treatment, the microstructure results are as follows: Figure 1 and Figure 2 As shown.

[0079] The microhardness of the cladding layers prepared in Examples 1-3 and Comparative Examples 1-2 was measured, and the results are shown in Table 5.

[0080] Table 5 Hardness test results of the coating

[0081]

[0082] analyze:

[0083] As shown in Table 4, the metal powders prepared by plasma rotating electrodes in Examples 1-3 and Comparative Examples 1-2 have advantages such as high sphericity, good flowability, and low oxygen content.

[0084] As shown in Table 5, the microhardness test results of the cladding layer prepared by ultra-high speed laser cladding show that the microhardness of the cladding layer obtained in Example 1 can reach 65.4 HV. Compared with Comparative Example 1, under the same ultra-high speed laser cladding preparation process conditions, the metal powder obtained in Example 1 can increase the hardness of the cladding coating by 45.7%. Compared with Comparative Example 2, under the same cladding powder conditions, the hardness of the cladding layer prepared by ultra-high speed laser cladding technology is increased by 33.2% compared with the cladding layer prepared by conventional laser cladding.

[0085] Figure 1 The high-performance metal powder prepared in Example 1; Figure 2 The microstructure of metal powder prepared from an electrode rod without heat treatment is shown in Example 1. The comparison shows that a large number of granular carbide phases precipitate in the high-performance metal powder prepared in Example 1, indicating that the carbides are largely inherited during the powder preparation process.

[0086] The cladding layer in Comparative Example 1 still exhibits a network of carbides, such as Figure 4 As shown, the cladding layer in Example 1 presents as granular carbides, such as... Figure 3 As shown, this is mainly related to the large amount of carbides inherited in the metal powder, and the cladding layer inherits the microstructure of the metal powder during ultra-high-speed laser cladding.

[0087] In summary, this invention can prepare high-performance metal powder by heat-treating the electrode rod and using plasma rotating electrode technology. Applying the metal powder to ultra-high-speed laser cladding technology can significantly improve the performance of the prepared workpiece.

[0088] In the above embodiments, due to improvements in materials and processes, the spot diameter can be replaced with 1.2mm, resulting in higher forming accuracy.

[0089] Although some preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0090] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A high-hardness, high-wear-resistant coating, characterized in that, The components include, by weight, C: 0.50–1.80%, Mo: 2.00–6.00%, Cr: 3.00–10.0%, V: 1.0–5.50%, and W: 5.00–11.0%.

2. The method for preparing the high-hardness, high-wear-resistant coating as described in claim 1, characterized in that, Includes the following steps: S2, Preparation of alloy powder and testing of its properties: The alloy rods heat-treated in S1 are precision machined to obtain alloy electrode rods of the required specifications. The alloy electrode rods are placed in a plasma rotating electrode device for vacuum treatment. The distance between the plasma gun and the electrode rod, the rotation speed of the electrode rod, the feed speed, and the power parameters of the plasma gun are set. After the protective gas is introduced, alloy powder is prepared. The flowability, particle size, oxygen content, and sphericity of the prepared alloy powder are tested, and the morphology and microstructure of the alloy powder are observed by scanning electron microscopy. S3, Prepare ultra-high speed wear-resistant coating and test its performance: Pre-treat the surface of the part to be clad, and grind and clean to remove oxide scale; The alloy powder obtained in S2 is prepared on the surface of the part to be clad by ultra-high speed laser cladding to prepare an ultra-high speed wear-resistant coating; the wear-resistant coating is sampled, ground, and polished, and the microstructure of the wear-resistant coating is analyzed by optical microscope and scanning electron microscope, and the hardness of the wear-resistant coating is measured by microhardness tester.

3. The method according to claim 2, characterized in that, In step S2, the distance between the plasma gun and the electrode rod is 20-90 mm, the electrode rod rotation speed is 25000-35000 r / min, the feed speed is 0.5-1.5 mm / s, and the plasma gun power is 150 kW-200 kW.

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