Alloy composition for laser cladding remanufacturing and alloy coating preparation method

Abstract

To provide an alloy composition for laser cladding remanufacturing and an alloy coating preparation method.SOLUTION: A composition comprises the following components in percentage by mass: 0.8% to 1.2% of C, 5.0% to 7.0% of Cr, 9.0% to 10.0% of W, 4% to 5% of V, 4.0% to 5.0% of Co, 1.0% to 2.0% of Si, 3.0% to 4.0% of B and the balance of Fe. The preparation method comprises the steps of: obtaining by preparing alloy powder for laser cladding according to an alloy composition and mass percentages; placing the alloy powder on a pre-treated 45 # steel substrate; and subjecting the alloy powder on the 45 # steel substrate to laser cladding to form an alloy coating. Through a solid solution strengthening effect of multiple alloy elements, a fine grain strengthening effect due to particle size reduction, and an interaction between microstructures, the present invention makes the alloy coating have excellent wear and corrosion resistance, and provides a new alloy composition and preparation process for the repair and remanufacturing of wear and corrosion failed parts.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention belongs to the field of laser cladding remanufacturing, relates to a technology for fabricating alloy coatings, and specifically relates to an alloy composition for laser cladding remanufacturing and a method for manufacturing an alloy coating.

Background Art

[0002] The diesel engine is one of the three main components for providing the propulsion force of a ship and plays a decisive role in the normal operation and continuous navigation of the ship. As a core component of the diesel engine, the camshaft is prone to abnormal wear and corrosion during the navigation process, posing a significant safety risk to the normal navigation of the ship. At the same time, it causes a great economic loss due to the stoppage of the ship's operation. In addition, the old parts discarded by replacing them with new parts cause a waste of many resources and environmental pollution problems. Therefore, the repair and remanufacturing of faulty cam parts has become one of the core issues that are being focused on.

[0003] Laser remanufacturing technology is one of the mainstream green remanufacturing processes being vigorously developed in China, with advantages such as high manufacturing efficiency, less post-treatment, excellent mechanical properties, and small heat-affected parts. Laser cladding technology is a technology that uses a high-energy laser beam to rapidly melt and solidify alloy powder, and it is a non-equilibrium solidification process in which complex physical and chemical reactions occur in the molten pool. Due to the rapid cooling and rapid heating forming characteristics of laser cladding, conventional alloy compositions are prone to defects such as pores and slag inclusions after being formed by laser cladding, and as a result, it affects the service performance such as wear resistance and corrosion resistance of laser cladding remanufactured parts. High-speed steel has the advantages of high hardness and high wear resistance, but in high-speed steel, due to the high carbon content and other alloy element contents, problems such as severe cracking and segregation occur during the preparation process of the alloy coating by laser cladding, and as a result, it affects the service performance of laser cladding remanufactured parts. Therefore, according to the wear and corrosion failure mechanism of diesel engine camshafts, the remanufacturing performance requirements, and the non-equilibrium solidification forming characteristics of laser cladding, designing a special alloy composition for remanufacturing worn or corroded camshafts by laser cladding is the key to camshaft remanufacturing.

Summary of the Invention

[0004] The object of the present invention is to overcome the disadvantages of the prior art. Through the solid solution strengthening effect of various alloy elements, the fine grain strengthening effect due to particle size reduction, and the interaction between fine microstructures, the alloy coating has excellent wear resistance and corrosion resistance, and provides a new alloy composition and manufacturing process for the repair and remanufacture of components failed due to wear or corrosion, and has important practical significance in promoting the application of laser cladding technology in the remanufacturing field, to provide an alloy composition for laser cladding remanufacturing and a method for manufacturing an alloy coating.

[0005] As a technical solution, in order to achieve the above object, the present invention provides an alloy composition for laser cladding remanufacturing. The alloy composition contains, by mass percentage, C: 0.8% - 1.2%, Cr: 5.0% - 7.0%, W: 9.0% - 10.0%, V: 4% - 5%, Co: 4.0% - 5.0%, Si: 1.0% - 2.0%, B: 3.0% - 4.0%, and the balance is Fe.

[0006] Furthermore, the alloy composition is used for laser cladding repair and remanufacturing of components failed due to wear or corrosion.

[0007] The present invention further provides a method for preparing an alloy coating for laser cladding remanufacturing. The method includes the following steps.

[0008] S1: According to the alloy composition and mass percentage, prepare alloy powder for laser cladding.

[0009] S2: Place the alloy powder on a pretreated 45# steel substrate.

[0010] S3: Laser clad the alloy powder on the 45# steel substrate to form an alloy coating.

[0011] Furthermore, the alloy composition in step S1 contains, by mass percentage, C: 0.8% - 1.2%, Cr: 5.0% - 7.0%, W: 9.0% - 10.0%, V: 4% - 5%, Co: 4.0% - 5.0%, Si: 1.0% - 2.0%, B: 3.0% - 4.0%, and the balance is Fe.

[0012] Furthermore, the method for preparing the alloy powder for laser cladding in step S1 is to weigh different alloy element powders by mass percentage, use a ball mill to uniformly mix the mixed alloy element powders, and obtain the alloy powder for laser cladding.

[0013] Furthermore, the particle size of the alloy element powders in step S1 is 30 - 70 μm.

[0014] Furthermore, the pretreatment method of the 45# steel substrate in step S2 is to use an angle grinder to remove impurities such as oxide scale on the surface of the 45# steel substrate, expose the metallic luster, further polish the surface of the 45# steel substrate with sandpaper until it is smooth and shiny, and sequentially use acetone and absolute ethanol to wipe the surface of the substrate to remove the oil stains on the surface.

[0015] Furthermore, before placing the alloy powder on the 45# steel substrate in step S2, it is dried. Specifically, the alloy powder is placed in a blower drying box and dried at 80 - 100°C for 1 - 2 hours.

[0016] Furthermore, the process parameters of laser cladding in step S3 are: laser output 2000 - 2500W, scanning speed 4 - 6mm / s, powder layer thickness 0.5mm / layer, overlap rate 50%, spot diameter 3mm, argon gas as protective gas, and gas flow rate 2 - 5L / min.

[0017] Furthermore, the thickness of the alloy coating in step S3 is 1 - 2mm.

[0018] In the present invention, by using a pre-alloy powder manufacturing method that melts and solidifies alloy powder with a high-energy laser beam, the clad coating and the 45# steel substrate form a good metallurgical bond. The alloy clad coating has good formability and exhibits excellent wear resistance and corrosion resistance.

[0019] The innovative points of the present invention include the following aspects.

[0020] The alloy clad coating forms eutectic boron carbide compounds with high hardness at grain boundaries during the laser cladding forming process, and its formation principle is as follows. The alloy composition provided by the present invention, due to specific contents of B and C, has high contents of B and C, and the solubility of B in γ-Fe is only 0.02%. During the solidification process in the laser melting pool, after reaching the eutectic transition temperature, B is first concentrated at the austenite grain boundaries and combines with C to form eutectic boron carbide compounds with high hardness, which is achieved by the matching relationship between the specific content ratios of B and C in this application.

[0021] There is a solid solution strengthening effect, and its principle is as follows. The present invention, due to specific contents of elements such as C and Cr, has high contents of elements such as C and Cr. In addition to forming boron carbide compounds in the alloy, excess elements are solid-solved within the crystal lattice, causing lattice distortion and resulting in a strengthening effect.

[0022] The alloy clad coating has a small particle size and plays a role in particle strengthening, and its principle is as follows. 1) Laser cladding belongs to a non-equilibrium solidification forming method of rapid heating and rapid cooling. Since the cooling rate is very fast, the structure solidifies without time to grow, thereby forming a fine structure. 2) The eutectic boron carbide compounds precipitated at the grain boundaries during the solidification process of laser cladding prevent the growth of crystal grains, thereby forming a fine particle size.

[0023] The beneficial effects are as follows. The present invention has the following advantages compared with the prior art.

[0024] 1. The obtained alloy clad coating has high hardness and excellent wear resistance. The alloy clad coating obtained by the present invention forms high-hardness eutectic boron carbide compounds at grain boundaries during the laser cladding forming process. The microstructure of the clad layer is mainly high-hardness martensite, with a small amount of retained austenite present. The content of alloying elements such as solid solution C and Cr in the alloy structure is high, achieving a solid solution strengthening effect. The particle size of the alloy clad coating is small, achieving a fine grain strengthening effect. Due to the combined effects of microstructure strengthening, solid solution strengthening, and fine particle strengthening, the alloy clad coating achieves the effect of high hardness and excellent wear resistance. The average microhardness of the alloy clad coating reaches 840 HV 0.2 and is 5 times the hardness of the substrate. The wear rate of the clad layer is 1.72×10 -8 mm 3 / N·mm and is 3 times the wear resistance of the substrate.

[0025] 2. The obtained alloy clad coating has excellent corrosion resistance. According to the analysis of the electrochemical curve of the clad layer, the corrosion potential of the clad layer is significantly higher than that of the 45# steel substrate. After electrochemical corrosion, there are a small number of corrosion pits on the surface of the clad layer, thereby significantly improving the corrosion resistance of the failed member.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0027] The present invention will be further described below in combination with the drawings and specific examples. It should be understood that these examples are only for explaining the present invention and are not intended to limit the scope of the present invention. After reading the present invention, all modifications of the present invention by those skilled in the art to various equivalent forms are included within the scope limited by the appended claims of this application.

[0028] Example 1: This example provides an alloy composition for laser cladding remanufacturing. The alloy composition contains, by mass percentage, C: 0.8%, Cr: 5.0%, W: 9.0%, V: 4%, Co: 4.0%, Si: 1.0%, B: 3.0%, and Fe: 73.2%.

[0029] In this example, the alloy composition is used for laser cladding repair and remanufacturing of a camshaft that has failed due to wear and corrosion of a diesel engine, and a method for preparing an alloy coating for laser cladding remanufacturing is provided. The method includes the following steps.

[0030] 1) Weigh different alloy element powders by mass percentage. The particle size of the alloy element powders is 30 - 70 μm. Use a ball mill to uniformly mix the alloy element powders after mixing at a rotation speed of 300 r / min for a mixing time of 8 h to obtain alloy powders for laser cladding.

[0031] 2) Use an angle grinder to remove impurities such as oxide scale on the surface of a 45# steel substrate to expose the metallic luster. Use sandpaper to further polish the surface of the 45# steel substrate until it is smooth and shiny. Use acetone and anhydrous ethanol to wipe the surface of the substrate in sequence to remove the oil stains on the surface.

[0032] 3) Place the alloy powders in a blow-drying box and dry them at 100°C for 1 h.

[0033] 4) Use a powder spraying tool to pre-spray the dried alloy powders onto the pretreated 45# steel substrate.

[0034] 5) Laser clad the alloy powder on the 45# steel substrate to form an alloy coating.

[0035] The process parameters of laser cladding are: laser power 2000 W, scanning speed 4 mm / s, overlap rate 50%, spot diameter 3 mm, argon gas as protective gas, gas flow rate 2 L / min, powder layer thickness 0.5 mm / layer.

[0036] The thickness of the finally formed alloy coating is 1 mm.

[0037] Example 2: This example provides an alloy composition for laser cladding remanufacturing. The alloy composition contains, by mass percentage, C: 1.2%, Cr: 7.0%, W: 10.0%, V: 5.0%, Co: 5.0%, Si: 2.0%, B: 4.0%, Fe: 65.8%.

[0038] In this example, the alloy composition is used for laser cladding repair and remanufacturing of a camshaft failed due to wear and corrosion of a diesel engine, and a method for preparing an alloy coating for laser cladding remanufacturing is provided. The method includes the following steps.

[0039] 1) Weigh different alloy element powders by mass percentage. The particle size of the alloy element powders is 30 - 70 μm. Use a ball mill to uniformly mix the alloy element powders after mixing at a rotation speed of 300 r / min for a mixing time of 8 h to obtain alloy powder for laser cladding.

[0040] 2) Use an angle grinder to remove impurities such as oxide scale on the surface of the 45# steel substrate to expose the metallic luster. Use sandpaper to further polish the surface of the 45# steel substrate until it is smooth and shiny. Rub the surface of the substrate successively with acetone and absolute ethanol to remove the oil stain on the surface.

[0041] 3) Place the alloy powder in a blowing and drying box and dry it at 80°C for 2 h.

[0042] 4) Use a powder spraying tool to pre-spray the dried alloy powder onto the pretreated 45# steel substrate.

[0043] 5) Laser clad the alloy powder on the 45# steel substrate to form an alloy coating.

[0044] The process parameters of laser cladding are laser output 2500W, scanning speed 6mm / s, overlap rate 50%, spot diameter 3mm, argon gas as the shielding gas, gas flow rate 5L / min, and powder layer thickness 0.5mm / layer.

[0045] The thickness of the finally formed alloy coating is 2mm.

[0046] Example 3: This example provides an alloy composition for laser cladding remanufacturing. The alloy composition contains, by mass percentage, C: 1.0%, Cr: 6.0%, W: 9.5%, V: 4.5%, Co: 4.5%, Si: 1.5%, B: 3.6%, and Fe: 69.4%.

[0047] In this example, the alloy composition is used for laser cladding repair and remanufacturing of a camshaft that has failed due to wear and corrosion of a diesel engine, and a method for preparing an alloy coating for laser cladding remanufacturing is provided. The method includes the following steps.

[0048] 1) Weigh different alloy element powders by mass percentage. The particle size of the alloy element powders is 30 - 70μm. Use a ball mill to uniformly mix the alloy element powders after mixing at a rotation speed of 300r / min for a mixing time of 8h to obtain alloy powder for laser cladding.

[0049] 2) Use an angle grinder to remove impurities such as oxide scale on the surface of the 45# steel substrate, expose the metallic luster, further polish the surface of the 45# steel substrate with sandpaper until it is smooth and shiny, and then wipe the surface of the substrate successively with acetone and absolute ethanol to remove the oil stains on the surface.

[0050] 3) Place the alloy powder in a blower drying box and dry it at 90 °C for 1.5 h.

[0051] 4) Use a powder spraying tool to pre-spray the dried alloy powder onto the pretreated 45# steel substrate.

[0052] 5) Laser clad the alloy powder on the 45# steel substrate to form an alloy coating.

[0053] The process parameters of laser cladding are: laser output 2300 W, scanning speed 5 mm / s, overlap rate 50%, spot diameter 3 mm, argon gas as protective gas, gas flow rate 4 L / min, and powder layer thickness 0.5 mm / layer.

[0054] The thickness of the finally formed alloy coating is 1.5 mm.

[0055] To verify the effectiveness and actual effect of the solution of the present invention, in this example, the hardness, wear rate, and electrochemical corrosion performance of the alloy clad coatings prepared in Example 1, Example 2, and Example 3 were respectively tested, and the specific test results and analysis are as follows.

[0056] (1) Analysis of the formability of the alloy clad coating The alloy clad coatings of Examples 1 to 3 all show good laser formability, and there are no obvious defects such as cracks, pores, and slag inclusions in the alloy clad coatings. The macroscopic morphology and cross-sectional morphology of the clad layer are shown in Figure 1.

[0057] (2) Analysis of the microstructure of the alloy clad coating The microstructures of the alloy clad coatings in Examples 1 to 3 mainly consist of martensite, grain boundary boron carbide compounds, and a small amount of retained austenite. Since the cooling rates of the alloy clad coatings in different laser cladding processes are different, the contents of the microstructures in the alloy clad coatings of different examples vary slightly.

[0058] (3) Analysis of the microhardness of the alloy clad coating The microhardness curves of the alloy clad coatings in Examples 1 to 3 are shown in Figure 2. It can be seen from Figure 2 that the hardness curve is composed of the alloy clad coating, the heat affected zone, and the substrate. The average hardness of the alloy clad coating in Example 1 is 840HV 0.2 and the average hardness of the alloy clad coating in Example 2 is 880HV 0.2 and the average hardness of the alloy clad coating in Example 3 is 830HV 0.2 which is about 5 times higher than the hardness of the substrate (173HV).

[0059] (4) Analysis of the wear resistance of the alloy clad coating In the wear resistance tests of the alloy clad coatings in Examples 1 to 3, Al2O3 was used as the friction pair, the wear load was 10N, the friction mode adopted reciprocating friction and wear mode, the wear time was 60min, and a white light interferometer was used to measure the wear volume of the clad layer. The calculated wear rates of Examples 1 to 3 are successively 1.72×10 -8 mm 3 / N·mm, 2.38×10 -8 mm 3 / N·mm and 2.51×10 -8 mm 3 / N·mm, and the wear resistance ratio is 3 times higher than that of the 45# steel substrate (8.22×10 -8 mm 3 / N·mm). Through the analysis of the wear morphology of the alloy clad coating, it can be seen that the wear mechanisms of the alloy clad coatings in Examples 1 to 3 are all mixed wear mechanisms of abrasive wear, adhesive wear, and oxidative wear.

[0060] (5) Analysis of the Corrosion Resistance of the Clad Layer The electrochemical Tafel curves of the alloy clad coatings of Examples 1 to 3 are shown in Fig. 3. The corrosion potential and corrosion current density of the alloy clad coatings were analyzed using the epitaxial method. The corrosion potentials of the alloy clad coatings of Examples 1 to 3 were -520 mV, -506 mV, and -560 mV, respectively, and the corrosion current densities were 2.58E-5 A / cm 2 , 2.98E-5 A / cm 2 and 2.67E-5 A / cm 2 respectively. All the alloy clad coatings showed good corrosion resistance. Through the analysis of the corrosion morphology of the samples after the electrochemical test, there were a few pits on the surface of the alloy clad coatings, and the corrosion mechanism was pitting corrosion.

Claims

1. An alloy composition for laser cladding remanufacturing, comprising: by mass percentage, C: 0.8% - 1.2%, Cr: 5.0% - 7.0%, W: 9.0% - 10.0%, V: 4% - 5%, Co: 4.0% - 5.0%, Si: 1.0% - 2.0%, B: 3.0% - 4.0%, with the balance being Fe, characterized by the alloy composition.

2. The alloy composition according to claim 1, characterized in that it is used for laser cladding repair and remanufacturing of components failed due to wear or corrosion.

3. A method for preparing an alloy coating for laser cladding remanufacturing, comprising: step S1 of preparing alloy powder for laser cladding by obtaining it according to the alloy composition and mass percentage; step S2 of placing the alloy powder on a pre-treated 45# steel substrate; step S3 of laser cladding the alloy powder on the 45# steel substrate to form an alloy coating, characterized by the method for preparing an alloy coating for laser cladding remanufacturing.

4. The alloy composition in step S1 in the method for preparing an alloy coating for laser cladding remanufacturing according to claim 3, characterized by by mass percentage, C: 0.8% - 1.2%, Cr: 5.0% - 7.0%, W: 9.0% - 10.0%, V: 4% - 5%, Co: 4.0% - 5.0%, Si: 1.0% - 2.0%, B: 3.0% - 4.0%, with the balance being Fe.

5. The method for preparing alloy powder for laser cladding in step S1 in the method for preparing an alloy coating for laser cladding remanufacturing according to claim 4, characterized by weighing different alloy element powders by mass percentage, using a ball mill to uniformly mix the alloy element powders, and obtaining the alloy powder for laser cladding.

6. The particle size of the alloy composition in step S1 in the method for preparing an alloy coating for laser cladding remanufacturing according to claim 5, characterized by being 30 - 70 μm.

7. The pre-treatment method of the 45# steel substrate in step S2 is to remove impurities on the surface of the 45# steel substrate using an angle grinder to produce a metallic luster, further polish the surface of the 45# steel substrate to a smooth and shiny state using sandpaper, wipe the surface of the substrate sequentially with acetone and absolute ethanol, and remove oil stains on the surface. The method for producing an alloy coating for laser cladding remanufacturing according to claim 3, characterized in that.

8. Before placing the alloy powder on the 45# steel substrate in step S2, it is dried. Specifically, the alloy powder is placed in a blow-drying box for drying. The method for producing an alloy coating for laser cladding remanufacturing according to claim 3, characterized in that.

9. The process parameters of the laser cladding in step S3 are a laser output of 2000 - 2500 W, a scanning speed of 4 - 6 mm / s, an overlap rate of 50%, a spot diameter of 3 mm, argon gas as the shielding gas, a gas flow rate of 2 - 5 L / min, and a powder layer thickness of 0.5 mm / layer. The method for producing an alloy coating for laser cladding remanufacturing according to claim 3, characterized in that.

10. The thickness of the alloy coating in step S3 is 1 - 2 mm. The method for producing an alloy coating for laser cladding remanufacturing according to claim 3, characterized in that.

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