A method of laser nickel-based mesh organization coating

Abstract

The application designs a method for laser nickel-based net organization coating, and belongs to the technical field of laser processing and material synthesis, and the steps are as follows: raw material powder includes solvent powder and reaction powder, the solvent powder is metal Ni powder, and the reaction powder is composed of metal Ti powder and NiWC40 powder; a steel base plate is selected, surface treatment is carried out, a smooth and clean metal base plate is obtained, and a sample bag is used for packaging to avoid surface oxidation; the prepared raw material powder is smashed into a paste by anhydrous ethanol, and is pre-prepared on the base plate, the base plate is placed into a preheating device after anhydrous ethanol volatilization for preheating; the preheated sample is placed on a workbench under a laser head, the laser spot size is set to 10*2 mm 2 , the power is 2000 W-2600 W, and the scanning speed is 2-5 mm / s, in-situ synthesis reaction occurs in the molten pool to generate W2C and TiC reinforcing phases, then the molten pool is cooled, the liquid phase is solidified, the reinforcing phases are discharged to the boundary to form a net shape.

Description

TECHNICAL FIELD

[0001] The application designs a method for laser nickel-based mesh structure coating, and belongs to the technical field of laser processing and material synthesis. BACKGROUND

[0002] Metal matrix composites often improve the mechanical strength of the material by directly adding or in-situ generating reinforcing phases. However, the uniformly distributed particles or fibers will cause the loss of plasticity while improving the strength of the material, which is commonly known as the "banana curve". In order to overcome this inverted relationship between strength and plasticity, more and more researchers use more sophisticated configuration strategies to construct composites, and researches have proved that the mesh distribution of reinforcing phases has more excellent ductility than the uniform distribution, that is, the heterogeneous structure of reinforcing phases.

[0003] Compared with traditional homogeneous materials, the heterogeneous structure of reinforcing phases also has the effect of heterogeneous deformation induced strengthening (HDI), that is, by constructing soft and hard zones with mechanical incompatibility, using the hardening effect caused by the difference in plastic deformation ability between zones, inducing the back stress strengthening of the soft phase and the front stress softening of the hard phase, and jointly activating multiple slip systems to coordinate plastic deformation. For the mesh distribution of reinforcing phases, it improves the interface strength by inhibiting grain boundary sliding and hindering dislocations, and the mesh structure and the matrix wrapped by the mesh jointly improve the toughness of the material by deflecting the crack and bearing the strain of the matrix.

[0004] Low-energy ball milling followed by solid-state sintering is the most common method to prepare network reinforced phase at present. The network graphene structure is prepared by adding graphene directly in Ti-6Al-4V through low-energy ball milling followed by spark plasma sintering. The short sintering time can effectively avoid the reaction of the added phase. The in-situ reaction prepared reinforcing phase has better combination with the matrix, so that the material has more excellent strength and the ability to inhibit crack initiation. The fine reinforcing phase is wrapped around the matrix particles to form a core-shell structure through ball milling, and the network structure is formed by in-situ reaction during hot-pressing sintering. The network distributed TiC / TiBw structure is prepared by hot-pressing sintering after mixing graphene / boron / titanium, so that the yield strength and ultimate tensile strength of the material are increased to 1.86 GPa and 2.18 GPa respectively. The two-stage network structure of TiBw and Ti5Si3 is successfully prepared by low-energy ball milling and two-step sintering method. Compared with the material prepared by one-step hot-pressing sintering method, the yield strength is increased by 8% and the elongation is increased to 6.6%. In addition, additive manufacturing technology has greater flexibility to meet more sophisticated structural design requirements. However, due to its high cooling rate and large supercooling degree, it is more prone to form dendritic microstructure, and the control of microstructure is still a difficult problem. The ultra-fine network of nano-TiBw embedded in titanium-based powder is prepared by gas atomization method, and the heterogeneous structure with network distributed reinforcing phase is successfully prepared by additive manufacturing technology. In addition, Ni-coated Ti and C powder is prepared by low-energy ball milling method, and a network structure coating is prepared by selective laser melting. However, the current research on network structure preparation is mainly focused on titanium and titanium alloys, and the types of generated phases are limited to TiC and TiBw. Therefore, this study provides a design strategy for preparing W2C / Ni heterogeneous structure with network reinforcing phase by laser cladding technology through the selection of in-situ reaction, which realizes the fine control of microstructure in laser cladding process. SUMMARY

[0005] The purpose of the present application is to provide a method for laser nickel-based network structure coating. The method combines laser cladding technology with in-situ synthesis, selects the in-situ reaction (WC+Ti=W2C+TiC), separates the generation processes of reinforcing phases W2C and TiC from the liquid phase Ni solidification process, and makes the reinforcing phases only generated at high temperature (>1200°C) in the molten pool. Then the liquid phase solidification occurs, and the mechanism of reinforcing phase being pushed to the grain boundary and the hindering effect of reinforcing phase on the solidification boundary together lead to the formation of network structure.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A method for laser nickel-based network structure coating, the steps are as follows:

[0008] (1) Preparation of raw material powder: including solvent powder and reaction powder, the solvent powder is metal Ni powder, and the reaction powder is composed of metal Ti powder and NiWC40 powder;

[0009] (2) Pretreatment of metal substrate: a steel substrate is selected, surface treatment is carried out, a smooth and clean metal substrate is obtained, and the sample bag is sealed to avoid surface oxidation;

[0010] (3) The raw material powder prepared in step (1) is pounded into a paste by anhydrous ethanol and is pre-prepared on the substrate in step (2), and after the anhydrous ethanol is volatilized, the substrate is placed into a preheating device for preheating;

[0011] (4) The sample preheated in step (3) is placed on a workbench under a laser head, the laser spot size is set to 10*2 mm 2 , the power is 2000 W~2600 W, and the scanning speed is 2~5 mm / s, in-situ synthesis reaction occurs in the molten pool to generate W2C and TiC reinforcing phases, and then the molten pool is cooled, the liquid phase is solidified to arrange the reinforcing phases to the boundary to form a network;

[0012] (5) After the laser processing is completed, the sample is air-cooled to room temperature.

[0013] Further improvement of the technical scheme of the application is that the preparation method of the raw material powder in step (1) is that the molar ratio of Ti to WC in the reaction powder in step (1) is Ti:WC=1:2, and the mass of the reaction powder accounts for 10~18 wt% of the mass of the raw material powder.

[0014] Further improvement of the technical scheme of the application is that the average particle size of the metal Ni powder in step (1) is 44~100 μm, the purity is 99.9%, the average particle size of the metal Ti powder is less than 154 μm, the purity is 99.5%, and the average particle size of the NiWC40 powder is 15~53 μm, and the purity is 99.9%.

[0015] Further improvement of the technical scheme of the application is that in step (1), the raw material powder is accurately weighed, and each powder is put into a V-shaped powder mixer at a rotating speed of 15 r / min for 4 h, and then is put into a drying oven for drying at 120°C for 30 min to remove the water in the powder.

[0016] Further improvement of the technical scheme of the application is that in step (2), a Q235 steel with a size of 50*15*5 mm 3 is selected as the substrate, the surface of the Q235 steel is first polished using an angle grinder to remove surface stains, an oxidized layer and the like, then the substrate surface is washed with clean water to prevent the introduction of impurities, then the substrate is washed with anhydrous ethanol, and the surface is quickly dried through evaporation.

[0017] Further improvement of the technical scheme of the present application is that the pre-prepared powder layer in step (3) has a thickness of 1.2 mm, and is heated to 750°C in an argon atmosphere in a pre-heating device.

[0018] With the above technical scheme, the present application has the following technical effects:

[0019] The in-situ synthesis reaction of the present application has few raw material powders, simple and efficient reaction process, and can prepare mixed powders with different contents according to needs. The W2C and TiC reinforcing phases prepared by the present application are distributed in a network around the grains, have complete structure and no defects, and have a diameter of about 500 nm. The content of W2C and TiC at the boundary and the size of the network can be controlled by adjusting the content of the reaction powder, or the size of the W2C and TiC reinforcing phase can be controlled by adjusting the laser processing parameters, and the in-situ synthesized W2C and TiC reinforcing phase is firmly combined with the metal matrix and is not easy to fall off. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The flow chart of laser cladding in the examples is shown in the figure;

[0021] Figure 2 The figure shows the relationship between the Gibbs free energy and the temperature of the in-situ reaction in the examples;

[0022] Figure 3 The macrograph of the (W2C+TiC) / Ni alloy coating in Example 2 is shown in the figure;

[0023] Figure 4 The XRD analysis of the surface of the 10, 13 and 18 wt% (W2C+TiC) / Ni alloy coating in Examples 1-3 is shown in the figure;

[0024] Figure 5 The SEM morphology of the (W2C+TiC) / Ni alloy coating in Example 2 is shown in the figure;

[0025] Figure 6 The EDS line scan of the (W2C+TiC) / Ni alloy coating in Example 2 is shown in the figure. DETAILED DESCRIPTION

[0026] The present application will be described in detail below with reference to the accompanying drawings and specific examples, it should be understood that the examples only relate to preferred embodiments of the present application, and various changes and improvements in components and contents are possible without departing from the spirit and scope of the present application.

[0027] Example 1:

[0028] A method for preparing a laser nickel-based network structure coating, the steps of which are as follows:

[0029] (1) Selecting the average particle size of 44-100 μm, purity of 99.9% of metal Ni powder as solvent powder, and selecting the average particle size of less than 154 μm, purity of 99.5% of metal Ti powder and the average particle size of 15-53 μm, purity of 99.9% of NiWC40 as reaction powder.

[0030] (2) The reaction powder is mixed according to the molar ratio of Ti to WC in NiWC40 as Ti:WC=1:2, and the reaction powder accounts for 10 wt% of the mass of the raw material powder. The powders are put into a V-shaped powder mixer at a speed of 15 r / min for 4 h, and then put into a drying oven at 120°C for 30 min to remove the moisture in the powder;

[0031] (3) Selecting the size of 50*15*5 mm 3 Q235 steel as the substrate, first using an angle grinder to polish the surface of the Q235 steel, removing the surface oxidation layer, etc., then using clean water to rinse the surface of the substrate to prevent the introduction of impurities, then using anhydrous ethanol to rinse the substrate, and quickly drying the surface by evaporation;

[0032] (4) The powder prepared in step (2) is pounded into a paste by anhydrous ethanol and pre-prepared on the substrate of step (3), the pre-prepared powder layer thickness is 1.2 mm, and after the anhydrous ethanol volatilizes, the substrate is put into a preheating device and heated to 750°C under an argon atmosphere;

[0033] (5) The preheated sample of step (4) is placed on the workbench under the laser head, the laser spot size is set to 10*2 mm 2 , the power is 2400 W, and the scanning speed is 4 mm / s. In-situ synthesis reaction occurs in the molten pool to generate W2C and TiC reinforcing phases, and then the molten pool cools down, the liquid phase solidifies to form a network at the boundary; the reaction equation is:

[0034] Ti+2WC=TiC+W2C

[0035] After laser processing, the sample is air-cooled to room temperature.

[0036] Using an electric spark cutting machine, the sample is cut to the required size.

[0037] In the coating obtained in this embodiment, W2C and TiC particles can be observed to be distributed in a network around the grains. Using this preparation method, W2C and TiC reinforcing phases in a network distribution can be prepared.

[0038] Example 2:

[0039] A method for preparing a laser nickel-based network structure coating, the steps are as follows:

[0040] (1) Selecting the average particle size of 44-100 μm, purity of 99.9% of metal Ni powder as solvent powder, and selecting the average particle size of less than 154 μm, purity of 99.5% of metal Ti powder and the average particle size of 15-53 μm, purity of 99.9% of NiWC40 as reaction powder.

[0041] (2) The reaction powder is mixed according to the molar ratio of Ti to WC in NiWC40 as Ti:WC=1:2, and the reaction powder accounts for 13 wt% of the mass of the raw material powder. The powders are put into a V-shaped powder mixer at a speed of 15 r / min for 4 h, and then put into a drying oven at 120 °C for 30 min to remove the water in the powder;

[0042] (3) Selecting the size of 50*15*5 mm 3 Q235 steel as the substrate, first using an angle grinder to polish the surface of the Q235 steel, removing the surface oxidation layer, etc., then using clean water to rinse the surface of the substrate to prevent the introduction of impurities, then using anhydrous ethanol to rinse the substrate, and quickly drying the surface by evaporation;

[0043] (4) The powder prepared in step (2) is crushed into a paste by anhydrous ethanol and pre-prepared on the substrate of step (3), the pre-prepared powder layer thickness is 1.2 mm, and after the anhydrous ethanol volatilizes, the substrate is placed in a preheating device and heated to 750 °C under an argon atmosphere;

[0044] (5) The preheated sample of step (4) is placed on the workbench under the laser head, the laser spot size is set to 10*2 mm 2 , the power is 2400 W, and the scanning speed is 4 mm / s. In-situ synthesis reaction occurs in the molten pool to generate W2C and TiC reinforcing phases, and then the molten pool cools down, the liquid phase solidifies and the reinforcing phases are arranged at the boundary to form a network; the reaction equation is:

[0045] Ti+2WC=TiC+W2C

[0046] After laser processing, the sample is air-cooled to room temperature.

[0047] Using an electric spark cutting machine, the sample is cut to the required size.

[0048] In the coating obtained in this embodiment, W2C and TiC particles can be observed to be distributed in a network around the grains. Using this preparation method, W2C and TiC reinforcing phases in a network distribution can be prepared. Figure 1 The experimental flowchart is shown in the figure. In the laser cladding process, argon protection is carried out to avoid oxidation of the coating. Figure 2The Gibbs free energy curve designed by HSC software shows that W2C and TiC phases are formed at high temperature, and the in-situ reaction is inhibited at below 1200°C, so the generation of W2C and TiC is terminated, and there is no distribution of the reinforcing phase in the grain. Figure 3 The surface macro-morphology of the coating after polishing of Example 2 is shown in the figure, and the coating surface is formed well without cracks. Figure 4 The XRD analysis of the coating surface of Examples 1-3 shows that the XRD peak characteristic peaks of W2C and TiC are more and more obvious with the increase of the content of the added reaction powder. Figure 5 The SEM micro-morphology of the laser cladding coating of Example 2 is shown in the figure, and it can be seen that the granular phase is distributed in a network around the grain. Figure 6 The element distribution map of the network-distributed granular phase of the cladding layer of Example 2 observed by EDS shows that the element position of the granular phase is mainly W, and there is Ti enrichment nearby. Combined with the XRD result analysis, the granular phase is W2C, and the Ti enrichment is TiC.

[0049] Example 3:

[0050] A method for preparing a laser nickel-based network structure coating, comprising the following steps:

[0051] (1) Selecting metal Ni powder with an average particle size of 44-100 μm and a purity of 99.9% as solvent powder, and selecting metal Ti powder with an average particle size of less than 154 μm and a purity of 99.5% and NiWC40 with an average particle size of 15-53 μm and a purity of 99.9% as reaction powder.

[0052] (2) The reaction powder is prepared according to the molar ratio of Ti to WC phase in NiWC40 as Ti:WC=1:2, and the reaction powder accounts for 18 wt% of the mass of the raw material powder. The powders are put into a V-type powder mixer at a speed of 15 r / min for 4 h, and then put into a drying oven at 120°C for 30 min to remove the water in the powders;

[0053] (3) Selecting a Q235 steel with a size of 50×15×5 mm 3 as the substrate. First, polish the surface of the Q235 steel using an angle grinder to remove the oxidation layer on the surface, etc. Then, rinse the surface of the substrate with water to prevent the introduction of impurities. Then, rinse the substrate with anhydrous ethanol and dry the surface quickly by evaporation;

[0054] (4) The powder prepared in step (2) is crushed into a paste with anhydrous ethanol and pre-prepared on the substrate of step (3), and the pre-prepared powder layer has a thickness of 1.2 mm. After the anhydrous ethanol evaporates, the substrate is placed in a preheating device and heated to 750°C under an argon atmosphere.

[0055] (5) Place the preheated sample from step (4) on the worktable under the laser head and set the laser spot size to 10*2mm. 2 The power was 2400W, the scanning speed was 4 mm / s, and an in-situ synthesis reaction occurred in the molten pool to generate W2C and TiC reinforcing phases. Subsequently, the molten pool cooled, and the liquid phase solidified, displacing the reinforcing phases to the boundary to form a network. The reaction equation is as follows:

[0056] Ti + 2WC = TiC + W₂C

[0057] After laser processing, the sample is air-cooled to room temperature.

[0058] Use an electrical discharge machine to cut the sample to the required size.

[0059] In the coating obtained in this embodiment, W2C and TiC particles can be observed to be distributed in a network around the grains.

[0060] This preparation method can produce a network-distributed W2C and TiC reinforcing phases. Using pure nickel as the solvent powder provides better cladding performance and ensures that the reaction proceeds without affecting the reaction process. The reacted W2C and TiC phases form a uniformly distributed network structure at the grain boundaries. The network structure improves the interfacial strength by inhibiting grain boundary sliding and hindering dislocation movement. The crack deflection effect of the network structure and the strain-bearing effect of the matrix encased in the network together enhance the toughness of the material.

[0061] Matters not covered in this invention are common knowledge.

[0062] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method of laser nickel-based mesh organization coating, characterized by The steps are as follows: (1) Preparation of raw material powder: including solvent powder and reaction powder, the solvent powder is metal Ni powder, and the reaction powder is composed of metal Ti powder and NiWC40 powder; (2) Pretreatment of metal substrate: selecting steel substrate, performing surface treatment, obtaining smooth and clean metal substrate, packaging with sample bag to avoid surface oxidation; (3) Preparing the raw material powder prepared in step (1) into paste by anhydrous ethanol, pre-preparing on the substrate of step (2), and placing the substrate into a preheating device after volatilization of anhydrous ethanol; (4) Put the preheated sample of step (3) on the workbench under the laser head, set the laser spot size to 10 2mm 2 , the power to 2000 W~2600 W, the scanning speed to 2~5 mm / s, so that the molten pool temperature is higher than 1200℃, in-situ synthesis reaction occurs in the molten pool to generate W2C and TiC reinforcing phase, then the molten pool cools down, the liquid phase solidification will expel the reinforcing phase to the boundary to form a network; (5) After laser processing, the sample is air-cooled to room temperature; The preparation method of the raw material powder in step (1) is that the molar ratio of Ti to WC phase in the reaction powder in step (1) is Ti: WC = 1: 2, and the mass of the reaction powder accounts for 10-18 wt% of the mass of the raw material powder; The average particle size of the metal Ni powder in step (1) is 44-100 μm, and the purity is 99.9%; the average particle size of the metal Ti powder is less than 154 μm, and the purity is 99.5%; the average particle size of the NiWC40 powder is 15-53 μm, and the purity is 99.9%.

2. The method of claim 1, wherein: In step (1), the raw material powder is accurately weighed, and each powder is put into a V-shaped powder mixer at a speed of 15 r / min for 4 h, and then put into a drying oven at 120°C for 30 min to remove the water in the powder.

3. The method of claim 1, wherein: In step (2), the surface treatment step is: selecting Q235 steel with a size of 50×15×5 mm3 as the substrate, first polishing the surface of the Q235 steel substrate surface using an angle grinder and sandpaper to remove surface stains and oxidation layer, washing the substrate surface with water to prevent the introduction of impurities, then washing the substrate with anhydrous ethanol and quickly drying the surface through evaporation.

4. The method of claim 1, wherein: The thickness of the pre-prepared powder layer in step (3) is 1.2 mm, and the temperature is raised to 750°C in an argon atmosphere in the preheating device.

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