A method for preparing a titanium diboride reinforced Ni60AA alloy coating on the surface of a continuous casting crystallizer copper plate

Abstract

The application relates to a preparation method of a titanium diboride reinforced Ni60AA alloy coating on the surface of a continuous casting crystallizer copper plate, and belongs to the technical field of laser cladding. The method comprises the following steps: S1, pretreatment of the surface of a substrate; S2, preheating of the substrate; S3, preparation of a nickel-based cladding layer on the surface of the copper plate as a transition layer; S4, preparation of a reinforced deposition layer on the surface of the nickel-based transition layer; and S5, machining of the cladded workpiece to the required precision and size under working conditions. According to the application requirements of the application of the crystallizer copper plate under the challenges of high temperature, high wear and thermal cracking resistance, a functional gradient coating of titanium diboride reinforced Ni60AA composite material is designed. The coating realizes the gradual enhancement of the material performance from the substrate to the surface layer by regulating the laser directional energy deposition of the titanium diboride and nickel-based composite powder on the surface of the copper plate, so that the hardness, wear resistance and thermal cracking resistance of the deposition layer are significantly improved.

Description

Technical Field

[0001] The invention relates to a method for preparing a titanium diboride reinforced Ni60AA alloy coating on the surface of a continuous casting crystallizer copper plate, and belongs to the technical field of laser cladding. Background Art

[0002] The mold is a crucial piece of equipment in the continuous casting process, and copper plates serve as a core component of the mold cooling system. Under harsh operating conditions such as high temperatures, strong impacts, and severe wear, the mold copper plates often suffer from surface wear, high-temperature oxidation, and thermal cracking, leading to performance degradation and eventual failure. Therefore, it is necessary to strengthen the mold copper plates' surfaces to improve their wear resistance and resistance to thermal cracking, extend their service life, and reduce production costs.

[0003] Titanium diboride (TiB2) is an outstanding modern ceramic material, known for its low density, extremely high hardness (34GPa), high melting point (2900°C), and excellent chemical stability. Particularly unique is its excellent electrical conductivity, a property not found in traditional ceramic materials. This characteristic makes it stand out in a variety of high-tech applications, and thus holds great research and development prospects. Currently, researchers are experimenting with using Ni60AA powder as a base powder and adding an appropriate amount of titanium diboride ceramic powder as a reinforcing phase to enhance the bonding strength between the deposited layer and the substrate, and improve the hardness and wear resistance of the deposit.

[0004] Electroplating and thermal spraying are commonly used to strengthen mold copper plates, but the plating layer lacks sufficient hardness. It can soften easily under high temperatures and harsh operating environments. Voids can easily form within the plating layer, affecting strength and wear resistance. The electroplating industry also causes environmental pollution. Thermal spraying typically provides a mechanical bond between the coating and the substrate, and internal voids can affect overall performance.

[0005] Laser directed energy deposition (LDED) is an additive technology that uses a laser beam to simultaneously melt the metal powder and the matrix material on the surface of the substrate and deposit them on the substrate surface. The laser beam is used to locally melt the metal powder, and the molten metal powder is deposited on the surface of the substrate to form a deposition layer with excellent performance to achieve surface modification. At the same time, it has the advantages of a small heat-affected zone, little thermal damage to the substrate, and a metallurgical bond with the substrate. Compared with traditional surface modification technologies such as electroplating and thermal spraying, the LDED process is easier to automate, and the resulting coating quality is superior, which is more in line with the continuous casting process's demand for mold surface strengthening technology.

[0006] It is difficult to eliminate the tiny pores and cracks in the deposited layer by optimizing the process parameters, but preheating the substrate can improve the crack sensitivity of the nickel-based transition deposited layer prepared on the surface of chromium-zirconium-copper alloy. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention realizes the surface strengthening of the crystallizer copper plate through laser directed energy deposition technology and combines certain process optimization measures, and extends the service life of the crystallizer by preparing a strengthening deposition layer metallurgically bonded to the copper plate.

[0008] The present invention aims to solve the problems of low surface hardness and poor wear resistance of the copper plate of the crystallizer, and provides a functional gradient coating of titanium diboride reinforced Ni60AA composite material to achieve crystallizer surface strengthening.

[0009] To achieve the purpose of strengthening the crystallizer surface, the present invention proposes the following technical solution: a titanium diboride-reinforced Ni60AA alloy coating on the surface of a continuous casting crystallizer copper plate and a preparation method thereof, comprising the following steps:

[0010] S1, substrate surface pretreatment;

[0011] S2, substrate preheating;

[0012] S3, preparing a nickel-based cladding layer on the surface of the copper plate as a transition layer;

[0013] S4, preparing a strengthening deposition layer on the surface of the nickel-based transition layer;

[0014] S5, processing the cladding workpiece to the required accuracy and size of the working condition;

[0015] In the above step S1 , the base material is a Cu-Cr-Zr alloy, and the weight percentages of the components are Cu: 99.25%, Cr: 0.65%, and Zr: 0.1%.

[0016] In the above step S1, the substrate is first polished with sandpaper before processing to remove the oxide film and a large amount of copper rust. Since copper has a low laser absorption rate, after removing the surface oxide film and copper rust, the surface is roughened with 60-mesh sandpaper to increase the absorbance. Then, the surface of the substrate is cleaned with anhydrous ethanol to ensure a clean and flat surface and reduce experimental errors.

[0017] In the above step S2, the preheating temperature is 400°C.

[0018] In the above step S3, the deposited powder is Ni60AA powder with a particle size of 100-200 mesh.

[0019] In the above step S3, the process parameters suitable for LDED (Laser Directed Energy Deposition) of the nickel-based transition layer on the surface of the crystallizer are laser power 850W, scanning speed 480mm / min, powder feeding rate 0.5r / min, and overlap rate 40%.

[0020] In the above step S4, Ni60AA powder is used as a base powder, 3 wt.% (weight percentage) of titanium diboride ceramic powder is added to form a composite powder, and 0.5% of Y2O3 is added to refine the deposited layer structure.

[0021] In the above step S4, the process parameters for preparing the enhanced deposition layer are: laser power 850 W, scanning speed 480 mm / min, powder feeding rate 0.5 r / min, and overlap rate 40%.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] To address the challenges of high temperature, high wear, and thermal crack resistance in mold copper plates, this paper designs a functionally gradient coating (FGC) made of a titanium diboride-reinforced Ni60AA composite material. This coating achieves a gradual enhancement of material properties from the base to the surface by controlling the laser-directed energy deposition of titanium diboride and nickel-based composite powders on the copper plate surface, significantly improving the hardness, wear resistance, and thermal crack resistance of the deposited layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a process principle diagram for preparing alloy coating using laser cladding equipment in the present invention.

[0025] Figure 2 This is the metallographic structure diagram of the crystallizer copper plate of the present invention.

[0026] Figure 3 Figure 2 shows the Ni60AA powder particles used in the transition layer of the present invention.

[0027] Figure 4 This is a metallographic diagram of the cross section of the overlapping deposited layer of the present invention.

[0028] Figure 5 This is a comparison chart of the preheating simulation and experiment of the present invention.

[0029] Figure 6 This is a microhardness distribution diagram of the deposited layer with different titanium diboride addition amounts of the present invention.

[0030] Figure 7a-7d The three-dimensional wear morphology of the substrate and the reinforced deposited layer with different titanium diboride contents of the present invention is shown in FIG. Figure 7a-7d The upper long bar and the lower arc shape are a whole picture. The upper long bar is used to mark the wear depth. The wear depth mark shows Figure 7a-7d The corresponding wear depth of the arc shape in the lower middle part.

[0031] Figure 8 Graph showing the change of the friction coefficient over time according to the present invention.

[0032] Figure 9This is a columnar weight loss graph of the deposit layer with different titanium diboride addition amounts according to the present invention. DETAILED DESCRIPTION

[0033] The technical features and advantages of the present invention are described in detail below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, the technology used in the present invention is laser directed energy deposition technology. Laser directed energy deposition equipment is used to prepare the nickel-based coating.

[0035] like Figure 2 As shown, the copper plate of the present invention is a crystallizer copper plate, and the base material is a chromium-zirconium-copper alloy, with the weight percentages of Cu: 99.25%, Cr: 0.65%, and Zr: 0.1%.

[0036] like Figure 3 As shown, a nickel-based alloy is selected from the metal powder, which has a linear expansion coefficient closest to that of copper alloy. The nickel-based alloy can form a good metallurgical bond with the matrix to extend the service life of the crystallizer while also taking into account the economy of use. The deposition powder used is Ni60AA powder with a particle size of 100-200 mesh.

[0037] The relationship between LDED process parameters and the quality and morphology of the deposited layer is very close. Therefore, optimizing the process parameters is of great importance to improving the quality and morphology of the deposited layer. In this paper, an entropy-weighted TOPSIS-based LDED process parameter optimization method for the nickel-based transition layer on the mold surface is proposed. The calculation results determine the ideal process parameters for the nickel-based transition layer deposited on the surface of chromium-zirconium-copper alloy by laser directed energy deposition (LDED).

[0038] The width of a single deposition layer is limited, and it is necessary to use laser directed energy deposition technology to prepare large-area multi-pass overlapping deposition layers to meet the needs of actual crystallizer usage. Based on recent research, the present invention selects an overlap rate of 40%.

[0039] like Figure 4 The cross-sectional morphology of the deposited layer shown in the figure indicates that the optimized process parameters can improve the quality of the deposited layer to a certain extent, but some pores and cracks cannot be completely eliminated by adjusting the process parameters.

[0040] The present invention explores the crack suppression mechanism of Ni60AA deposited layer by substrate preheating, analyzes the theoretical basis of temperature field, selects Gaussian heat source model, uses JMatPro software to calculate the thermophysical properties of materials at different temperatures, creates and solves the adaptive temperature field model in ANSYS, and combines the experiments at different temperatures, the comparison of preheating simulation and experiment, and the results show that the thermal properties of materials at different temperatures are better than those at ANSYS. Figure 5As shown in the figure, it is proved that substrate preheating can reduce both cracks and pores in the deposited layer, and the optimal preheating temperature is 400℃.

[0041] The present invention uses Ni60AA powder as the base powder and adds an appropriate amount of titanium diboride ceramic powder as a reinforcing phase to improve the performance of the deposited layer. 0.5% Y2O3 is added to the composite powder to refine the deposited layer structure. Figure 6 As shown in the figure, with the increase of titanium diboride addition, the microhardness of the strengthened deposited layer gradually increases, the microhardness of the transition deposited layer is about 651.8HV0.1, and the average microhardness of the strengthened deposited layers with titanium diboride addition of 1%, 2%, and 3% are 729.96HV0.1, 838.94HV0.1, and 1225.3HV0.1, respectively, which are about 1.12 times, 1.29 times, and 1.68 times higher than that of the Ni-based transition layer, and about 5.40 times, 6.21 times, and 9.07 times higher than that of the matrix chromium-zirconium-copper alloy.

[0042] like Figure 7a-7d The three-dimensional wear morphologies of the substrate and reinforced deposits with varying titanium diboride content are shown. Compared to the substrate, the wear scar depth and width are significantly improved. This indicates that the ceramic-reinforced reinforced deposits have enhanced wear resistance and improved wear behavior.

[0043] from Figure 8 It can be seen that under the same friction speed and applied load, the friction coefficient of the matrix chromium-zirconium-copper alloy continues to rise and finally tends to fluctuate to a stable value. This is because the wear debris generated by the friction and wear experiment at the beginning will cause the friction coefficient to continue to increase. Under the continuous accumulation of wear debris, the friction coefficient rises very quickly; and the friction coefficient change trend of Ni60AA reinforced deposits with different titanium diboride content ratios is roughly the same.

[0044] like Figure 9 As shown in the figure, after 3600 seconds of reciprocating friction, the wear resistance of the strengthened deposit layer is relatively much improved compared with the chromium-zirconium-copper alloy substrate, which proves that the unmelted titanium diboride particles and the newly formed reinforcement phase in the strengthened deposit layer play an anti-wear role, effectively resisting the cutting effect of the ceramic on the grinding pair, thereby reducing the wear amount and improving the wear resistance.

[0045] The above description is only a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any equivalent adjustment or innovation made within the technical framework of the present invention and based on the principles and ideas of the present invention shall be deemed to fall within the scope of patent protection of the present invention.

Claims

1. A method for preparing a titanium diboride reinforced Ni60AA alloy coating on the surface of a continuous casting mold copper plate, characterized in that: The following steps are involved: S1: substrate surface pretreatment; S2: substrate preheating; S3: preparing a nickel-based cladding layer on the surface of the copper plate as a transition layer; S4: preparing a strengthening deposition layer on the surface of the nickel-based transition layer; S5: Process the cladding workpiece to the required accuracy and size. In step S1, the base material is a Cu-Cr-Zr alloy, with the weight percentages of Cu: 99.25%, Cr: 0.65%, and Zr: 0.1%. The deposition powder used in step S3 is Ni60AA powder with a particle size of 100-200 mesh. The process parameters suitable for laser directed energy deposition of nickel-based transition layer on the surface of the crystallizer in step S3 are laser power 850W, scanning speed 480mm / min, powder feeding rate 0.5r / min, overlap rate 40%, In step S4, Ni60AA powder is used as the base powder, 3% by weight of titanium diboride ceramic powder is added to form a composite powder, and 0.5% by weight of Y2O3 is added to refine the deposited layer structure. The process parameters for preparing the enhanced deposition layer in step S4 are: laser power 850 W, scanning speed 480 mm / min, powder feeding rate 0.5 r / min, and overlap rate 40%.

2. The method for preparing a titanium diboride reinforced Ni60AA alloy coating on the surface of a continuous casting mold copper plate according to claim 1, characterized in that: In step S1, the failed position of the substrate is derusted and roughened with sandpaper to achieve the surface smoothness requirement for crystallizer strengthening based on laser directed energy deposition, and the substrate surface is cleaned with anhydrous ethanol to meet the processing requirements.

3. The method for preparing a titanium diboride reinforced Ni60AA alloy coating on the surface of a continuous casting mold copper plate according to claim 2, characterized in that: In the step S2, the substrate is preheated to 400°C to suppress cracks in the transition layer.

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