Ni625 recycled powder composite laser cladding layer and preparation method thereof

Abstract

The invention relates to the technical field of laser cladding, in particular to a Ni625 recycled powder composite laser cladding layer and a preparation method thereof.The Ni625 recycled powder composite laser cladding layer comprises base metal, a transition layer and a surface cladding layer, 4145H steel is selected as the base metal, and the transition layer is located between the base metal and the surface cladding layer and is composed of a Ni625 recycled powder cladding layer; the surface cladding layer is composed of two mixture cladding layers of Ni625 recycled powder and WC powder in different proportions, so that according to the Ni625 recycled powder composite laser cladding layer and the preparation method thereof, the bonding performance, the abrasion resistance and the corrosion resistance of a coating are improved, defects generated in the preparation process are reduced to the maximum extent, and the service life of the coating is prolonged. And meanwhile, powder raw materials in the laser cladding production process are recycled, so that the application range and effect of the composite cladding layer in the industrial field are expanded.

Description

Technical Field

[0001] The invention relates to the technical field of laser cladding, and in particular to a Ni625 recycled powder composite laser cladding layer and a preparation method thereof. Background Art

[0002] In the development process of modern industry, laser cladding technology, as an advanced surface modification technology, is widely used in the field of improving metal surface performance and extending service life, especially in the aerospace, automobile, energy and mold industries. With the continuous expansion of industrial production scale, the consumption of powder raw materials in the laser cladding process is huge, which not only increases production costs, but also causes a certain degree of waste of resources. At the same time, the traditional laser cladding layer still has some shortcomings in performance. For example, the bonding between the coating and the base metal is not ideal, and it is easy to peel off during long-term use, which seriously affects the protective effect of the coating. In addition, the lack of wear resistance and corrosion resistance also limits its application in some complex and harsh working conditions. For example, in the fields of marine engineering, chemical equipment, etc., facing multiple tests such as seawater corrosion, chemical medium erosion and mechanical wear, the existing coating is difficult to meet the needs of long-term stable operation of equipment.

[0003] Moreover, in the process of laser cladding coating preparation, some defects such as pores and cracks often occur, which will further weaken the performance of the coating, reduce its service life, and even cause the failure of the entire equipment. Therefore, how to effectively utilize resources in the production process, reduce waste, and reduce defects in the preparation process while improving the performance of the coating has become an important issue that needs to be solved in the field of laser cladding technology.

[0004] In view of the above problems, the present invention proposes a Ni625 recycled powder composite laser cladding layer and a preparation method thereof, aiming to improve the bonding, wear resistance and corrosion resistance of the coating and minimize the defects generated in the preparation process, while realizing the recycling of powder raw materials in the laser cladding production process, thereby expanding the application scope and effect of the composite coating in the industrial field. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a Ni625 recycled powder composite laser cladding layer and a preparation method thereof. The technical solution of the present invention is as follows: A Ni625 recycled powder composite laser cladding layer, including the composition of the recycled powder composite laser cladding layer, which includes a base metal, a transition layer, and a surface cladding layer. The main raw material of the cladding layer is Ni625 powder recycled during the laser cladding production process; the composite laser cladding layer includes a base metal, a transition layer, and two Ni625-WC surface cladding layers. The base metal is selected as 4145H steel. The transition layer is located between the base metal and the Ni625 surface cladding layer, and the transition layer is composed of pure Ni625.

[0006] A preparation method of a Ni625 recycled powder composite laser cladding layer includes the following steps: S1. Determine the main structure of the cladding layer, prepare the base metal and perform surface pretreatment on it; S2. Screen Ni625 recycled powder and WC powder; S3. Determine the laser cladding process parameters; S4. Laser clad pure Ni625 recycled powder on the surface of the base metal to form a transition layer; S5. Laser clad a mixture of Ni625 recycled powder and WC powder on the transition layer to form a Ni625-WC surface cladding layer.

[0007] The specific operations in the steps are as follows: S1. Determine the main structure of the cladding layer, prepare the base metal and perform surface pretreatment on it: The composite laser cladding layer includes a base metal, a transition layer, and two surface cladding layers. The base metal is selected as 4145H steel. The transition layer is located between the base metal and the surface cladding layer. The transition layer is composed of a pure Ni625 recycled powder cladding layer, and the surface cladding layer is composed of two mixed cladding layers with compositions of 70% Ni625 recycled powder + 30% WC and 40% Ni625 recycled powder + 60% WC respectively; Before preparing the composite laser cladding layer, surface pretreatment is required, including grinding and cleaning: successively use 600-mesh, 800-mesh, and 1000-mesh SiC sandpapers to grind the surface of the substrate, roughen the surface while removing the oxide layer on the substrate surface to enhance the bonding of the cladding layer; after grinding, use anhydrous ethanol to clean the surface, remove impurities such as surface debris and oil stains, and then put it into a vacuum drying oven and dry it at 65 °C and -0.05 MPa for 45 minutes.

[0008] 2. Screen Ni625 recycled powder and WC powder; Control and screen the quality of NIi625 recycled powder and WC powder; in step S2, the purity of Ni625 and WC powder is greater than 99.9%, the transition layer uses pure Ni625 alloy powder, and the average sphericity Q of Ni625 recycled powder and WC powder avg is greater than 0.9.

[0009] 3. Determine the laser cladding process parameters To reduce the thermal stress between the base metal and the surface cladding layer, reduce the power and layer thickness of the transition layer and the first layer, and preheat before cladding.

[0010] The laser cladding process parameters in step S3 are as follows: When laser cladding the transition layer, the power is 1800 W, the scanning speed is 400 mm / s, the spot diameter is 4 mm, the preheating temperature is 110 °C, and the layer thickness is 1 mm; When laser cladding the first layer of the surface cladding layer, the laser power is 2000 W, the scanning speed is 400 mm / s, the powder feeding rate is 0.8 r / min, the spot diameter is 4 mm, the preheating temperature is 250 °C, and the layer thickness is 1 mm; When laser cladding the second layer of the surface cladding layer, the laser power is 2200 W, the scanning speed is 400 mm / s, the powder feeding rate is 1 r / min, the spot diameter is 4 mm, no preheating is required, and the layer thickness is 1.8 mm.

[0011] 4. Preparation of the cladding layer Using a high-power laser (P6000) device, the pure Ni625 recycled powder or the mixed powder of Ni625 recycled powder and WC is cladded in a synchronous powder feeding manner; according to the process shown in Table 3, the 4145H stainless steel substrate is preheated at 110 °C for 10 minutes before cladding the transition layer, and a single layer of pure Ni625 recycled powder is cladded on the base metal by the synchronous powder feeding method to form a transition layer. Subsequently, the cladded Ni625 transition layer is preheated at 250 °C for 10 minutes, and a 70% Ni625 recycled powder + 30% WC mixed powder is cladded on its surface to form the first layer of the surface cladding layer. Subsequently, a 40% Ni625 recycled powder + 60% WC mixed powder is cladded on the surface of the first layer of the Ni625-WC surface cladding layer to form the second layer of the surface cladding layer. In this embodiment, a Ni625 recycled powder composite laser cladding layer composed of three cladding layers is finally prepared.

[0012] In summary, the present solution has the following beneficial effects: The Ni625 recycled powder composite laser cladding layer and its preparation method realize the recycling of powder raw materials in the laser cladding production process, comprehensively improve the bonding property, wear resistance and corrosion resistance of the cladding layer, and minimize the defects generated during the preparation process, thereby expanding the application scope and effect of the composite coating in the industrial field; the transition layer can enhance the bonding property between the cladding layer and the base metal; the coating has excellent wear resistance, corrosion resistance and high-temperature performance; and the preparation process of the present solution is simple and the cost is low; the surface of the coating is smooth and there are no defects such as pores and cracks. Description of the Drawings

[0013] Figure 1 It is a flowchart of the method for preparing the cladding layer of the present application Figure 2 It is a schematic diagram of preparing a specimen by laser cladding manufacturing of the present application; Figure 3 It is the microscopic morphology of the nickel-based alloy powder of the present application; Figure 4 It is a schematic diagram of the cross-section and surface of the Ni625 recycled powder composite laser cladding layer of the present application: (a) cross-section; (b, c) surface; Figure 5 It is the XRD pattern of the Ni625 recycled powder composite laser cladding layer of the present application; Figure 6 It is a schematic diagram of the Vickers hardness distribution of the cross-section of the cladding layer of the present application; Figure 7 It is a schematic diagram of the potentiodynamic polarization curve of the Ni625 recycled powder composite laser cladding layer of the present application. Detailed Embodiments

[0014] The following will describe in detail the embodiments of the present application with reference to the drawings.

[0015] Figure 1-7 As shown, a Ni625 recycled powder composite laser cladding layer includes a base metal, a transition layer, and a surface cladding layer. The main raw material is the Ni625 powder recycled during the laser cladding production process. The base metal is 4145H steel for oil drill collars. The transition layer is located between the base metal and the surface cladding layer and is composed of a Ni625 recycled powder cladding layer. The Ni625-WC surface cladding layer is composed of two cladding layers prepared from a mixed powder of 70% Ni625 recycled powder + 30% WC and a mixed powder of 40% Ni625 recycled powder + 60% WC respectively. The key flowchart of this Ni625 recycled powder composite laser cladding layer is as Figure 1 shown.

[0016] A method for preparing a Ni625 recycled powder composite laser cladding layer includes the following steps: S1. Determine the main structure of the composite laser cladding layer, prepare the base metal and pre-treat its surface; S2. Screen the Ni625 recycled powder and WC powder; S3. Determine the laser cladding process parameters; S4. Laser clad the pure Ni625 recycled powder on the surface of the base metal to form a transition layer; S5. Laser clad a mixed powder composed of Ni625 recycled powder and WC powder on the transition layer to form a Ni625-WC surface cladding layer.

[0017] The specific operations are as follows: 1. Determine the main structure of the cladding layer, prepare the base metal and pre-treat its surface; This composite laser cladding layer includes a base metal, a transition layer and two Ni625-WC surface cladding layers. The base metal is selected as 4145H steel. The transition layer is located between the base metal and the Ni625-WC surface cladding layer and is composed of pure Ni625 recycled powder. The Ni625-WC surface cladding layer is composed of two Ni625-WC surface cladding layers prepared from mixed powders with compositions of 70% Ni625 recycled powder + 30% WC and 40% Ni625 recycled powder + 60% WC respectively. Its structural and processing schematic diagrams are as Figure 2 shown.

[0018] Before preparing the cladding layer, the surface needs to be pre-treated, including grinding and cleaning: successively grind the surface of the substrate with 600-mesh, 800-mesh and 1000-mesh SiC sandpapers to roughen the surface and remove the oxide layer on the substrate surface, enhancing the bonding property of the cladding layer; after grinding, clean the surface with anhydrous ethanol to remove impurities such as surface debris and oil stains, and then put it into a vacuum drying oven for drying at 65 °C and -0.05 MPa for 45 minutes.

[0019] 2. Screen the Ni625 recycled powder and WC powder; Control and screen the quality of the NIi625 recycled powder and WC powder; the purity of the Ni625 recycled powder and WC powder is greater than 99.9%. The transition layer uses pure Ni625 alloy powder, the first layer of the surface cladding layer uses a mixed powder of 70% Ni625 recycled powder + 30% WC by mass fraction, and the second layer of the surface cladding layer uses a mixed powder of 40% Ni625 recycled powder + 60% WC by mass fraction; the average sphericity Q of the Ni625 recycled powder and WC powder avg is greater than 0.9; the chemical composition of Ni625 should conform to the composition range in Table 1.

[0020] Table 1 Standard Chemical Composition of Ni625 (wt.%)

[0021] Use a scanning electron microscope to take 100-fold morphology pictures of the Ni625 recycled powder and WC powder; calculate the sphericity Q of all particles in the picture, Q = ds / dc, where ds and dc are the area equivalent diameter and perimeter equivalent diameter of the particle cross-section respectively; calculate the average sphericity Q of all particles avg ; to ensure good flow performance of the powder during the cladding process and promote the formation of a well-bonded composite cladding layer.

[0022] Figure 3The particle size morphology of the mixed powder in the embodiment is shown. It can be seen that the sphericity of the particle size of the mixed powder is good. The average sphericity Q of the powder is calculated avg to be 0.98. The particle size distribution is uniform, the average particle size is 107 μm, and the particle size distribution range is 50 - 300 μm, meeting the usability requirements.

[0023] 3. Determine the laser cladding process parameters To reduce the thermal stress between the substrate and the coating, the present invention reduces the power and layer thickness of the transition layer and the first layer, and preheats before cladding. The detailed laser parameters are shown in Table 2: Table 2 Laser process parameters

[0024] According to the above table, in the present invention, when laser cladding the transition layer, the power is 1800 W, the scanning speed is 400 mm / s, the spot diameter is 4 mm, the preheating temperature is 110 °C, and the layer thickness is 1 mm.

[0025] When laser cladding the first layer of the Ni-WC coating, the laser power is 2000 W, the scanning speed is 400 mm / s, the powder feeding rate is 0.8 r / min, the spot diameter is 4 mm, the preheating temperature is 250 °C, and the layer thickness is 1 mm.

[0026] When laser cladding the second layer of the Ni-WC coating, the laser power is 2200 W, the scanning speed is 400 mm / s, the powder feeding rate is 1 r / min, the spot diameter is 4 mm, no preheating is required, and the layer thickness is 1.8 mm.

[0027] 4. Cladding layer preparation Using a high-power laser (P6000) device, the Ni625 and Ni625-WC mixed powder is transported by synchronous powder feeding onto the 4145H steel; the 4145H stainless steel substrate is preheated at 110 °C for 10 minutes before cladding the transition layer, and a single-layer pure Ni625 alloy transition layer is clad on the substrate by the synchronous powder feeding method. Subsequently, the clad Ni625 transition layer is preheated at 250 °C for 10 minutes, and a 70% Ni625 recycled powder + 30% WC mixed powder is clad on its surface to form the first layer of the Ni625-WC surface cladding layer. Subsequently, a 40% Ni625 recycled powder + 60% WC mixed powder is clad on the surface of the first layer of the Ni625-WC surface cladding layer to form the second layer of the Ni625-WC surface cladding layer.

[0028] 5. Cladding layer structure and microstructure After the surface of the Ni625 recycled powder composite laser cladding layer is treated with aqua regia corrosion, the morphology observed under the electron microscope is as Figure 4 shown.Figure 4 (a, b) are the cross-section and surface of the Ni625 recycled powder composite laser cladding layer. The bonding between each coating in the cross-section is good, and no cracks appear. On the surface, the WC particles are evenly distributed and can maintain a complete spherical particle shape during the laser cladding process. The WC particles are well bonded with Ni625, without obvious cracks, defects, or other inclusion substances ( Figure 4 (b, c). The surface microstructure of the Ni625 recycled powder composite laser cladding layer consists of WC particles, dendrites, and intergranular eutectic phases. There are a large number of irregular eutectic phases between the grains ( Figure 4 (b, c).

[0029] Figure 5 is the XRD pattern of the Ni625 recycled powder composite laser cladding layer. It can be seen from the figure that the phases on the surface of the Ni625 recycled powder composite laser cladding layer are composed of γ-Ni, W2C, and WC, and there are precipitation phases of CrC and MoC. Combining with the morphology, the dendritic phase is γ-Ni, and the intergranular eutectic phase is composed of a mixture of W2C and WC and solid-solves Mo and Cr.

[0030] 6. Properties of the cladding layer The change in microhardness at different positions from the cladding layer to the substrate is as Figure 6 shown. It can be observed from the figure that the microhardness of the three parts is different. The average Vickers hardness of the 4145H substrate is 358.1 HV 0.5 . The average microhardness of the transition layer is 304.5 HV 0.5 . The Ni-WC coating contains a large number of WC hard particles, which enhances the hardness of the cladding layer. The average surface microhardness of the cladding layer is 889 HV 0.2 .

[0031] The wear resistance of the cladding layer is usually quantified by the wear amount. The wear depth can reflect the wear degree of the cladding layer. When the local wear depth on the material surface increases, it will lead to an increase in the failure conditions such as peeling, spalling, and cracking of the cladding layer in this part. The corrosion resistance can be evaluated by the potentiodynamic polarization curve test. Under static conditions, the potentiodynamic polarization curve of the Ni625 recycled powder composite laser cladding layer measured in 3.5 wt.% NaCl solution is as Figure 6 shown. The results measured by the wear experiment and potentiodynamic polarization are shown in Table 4. The wear rate under a 20N load is 0.45 mm 3 ·N -1 ·m -1 . The wear rate is relatively low, effectively improving the wear resistance of the cladding layer. The self-corrosion current density is 9.20×10 -6 A·cm -2。The anodic polarization curve of the Ni625 recycled powder composite laser cladding layer shows passivation characteristics, indicating that a passive film is formed on the surface of the Ni625 recycled powder composite laser cladding layer, which has good corrosion resistance.

[0032] Table 4 Test results of surface wear and potentiodynamic polarization curves of Ni625 recycled powder composite laser cladding layer

[0033]

[0034] where V—the corrosion rate (g / m 2 · h) n—the valence of the metal F—Faraday's constant M—the gram atomic weight of the metal (g) Combined with the data in Table 4, the corrosion rate calculated according to the standard calculation of the corrosion rate is obtained. From Equation (1), it can be calculated that the corrosion rate under the condition of immersion in 3.5 wt.% NaCl solution at normal temperature and pressure is 0.11 mm / a, indicating that the composite cladding layer has excellent corrosion resistance.

[0035] Combined with the current actual needs, the above implementation methods adopted in this application, the protection scope is not limited to this. Within the scope of knowledge possessed by those skilled in the art, various changes made without departing from the concept of this application still fall within the protection scope of the present invention.

Claims

1. A Ni625 recycled powder composite laser cladding layer, characterized by: The main raw material of the cladding layer is Ni625 powder recycled in the laser cladding production process; the composite laser cladding layer includes a base metal, a transition layer and two Ni625-WC surface cladding layers. The base metal is 4145H steel. The transition layer is located between the base metal and the Ni625 surface cladding layer, and the transition layer is composed of pure Ni625.

2. The Ni625 recycled powder composite laser cladding layer according to claim 1 is characterized in that: The surface microstructure of the cladding layer is composed of WC particles, dendrites and intergranular eutectic phase.

3. The Ni625 recycled powder composite laser cladding layer according to claim 2 is characterized in that: The dendrite phase is γ-Ni, and the intergranular eutectic phase is composed of a mixture of W2C and WC and contains Mo and Cr in solid solution.

4. The Ni625 recycled powder composite laser cladding layer according to claim 1 is characterized in that: The average surface microhardness of the cladding layer is 889 HV 0.2 , the wear rate is 0.45 mm under 20N load 3 ·N -1 ·m -1 The corrosion rate is 0.11 mm / a when immersed in 3.5 wt.% NaCl solution at room temperature and pressure.

5. A method for preparing a Ni625 recycled powder composite laser cladding layer, comprising the following steps: S1. Determine the main structure of the cladding layer, prepare the base metal and pre-treat its surface; S2. Screening Ni625 recycled powder and WC powder; S3, determining laser cladding process parameters; S4, laser cladding pure Ni625 recycled powder on the surface of the base metal to form a transition layer; S5. Laser cladding Ni625 recycled powder and WC mixed powder on the transition layer to form a Ni625-WC surface cladding layer.

6. The method for preparing a Ni625 recycled powder composite laser cladding layer according to claim 5, characterized in that: The surface pretreatment in step S1 includes grinding and cleaning: the substrate surface is grinded with 600 mesh, 800 mesh and 1000 mesh SiC sandpaper in sequence to roughen the surface and remove the oxide layer on the substrate surface to enhance the bonding of the cladding layer; after grinding, the surface is cleaned with anhydrous ethanol to remove impurities such as surface debris and oil, and then placed in a vacuum drying oven and dried for 45 minutes at 65°C and -0.05 MPa.

7. The method for preparing a Ni625 recycled powder composite laser cladding layer according to claim 5, characterized in that: In step S2, the purity of Ni625 and WC powder is greater than 99.9%, the transition layer is made of pure Ni625 alloy powder, the first layer of Ni625-WC surface cladding layer is made of 70% Ni625+30% WC mixed powder by mass, and the second layer of Ni625-WC surface cladding layer is made of 40% Ni625+60% WC mixed powder by mass; the average sphericity Q of Ni625 and WC powder is avg Greater than 0.

9.

8. The method for preparing a Ni625 recycled powder composite laser cladding layer according to claim 5, characterized in that: In the step S3, a high-power laser (P6000) device is used to convey Ni625 and Ni625-WC mixed powders onto 4145H steel by synchronous powder feeding; before cladding the transition layer, the 4145H stainless steel substrate is preheated at 110°C for 10 minutes, and a single-layer pure Ni625 alloy transition layer is clad on the substrate by synchronous powder feeding method, and then the clad Ni625 transition layer is preheated at 250°C for 10 minutes, and 70% Ni625+30% WC composite powder is clad on its surface to form a first layer of Ni625-WC surface cladding layer, and then 40% Ni625+60% WC powder is clad on the surface of the first layer of Ni625-WC surface cladding layer to form a second layer of Ni625-WC surface cladding layer.

9. The method for preparing a Ni625 recycled powder composite laser cladding layer according to claim 5, characterized in that: The laser cladding process parameters in step S3 are as follows: the power for laser cladding of the transition layer is 1800 W, the scanning speed is 400 mm / s, the spot diameter is 4 mm, the preheating temperature is 110°C, and the layer thickness is 1 mm. The laser power for laser cladding of the first layer of the Ni-WC coating is 2000 W, the scanning speed is 400 mm / s, the powder feeding rate is 0.8 r / min, the spot diameter is 4 mm, the preheating temperature is 250°C, and the layer thickness is 1 mm. The laser power for laser cladding of the second layer of the Ni-WC coating is 2200 W, the scanning speed is 400 mm / s, the powder feeding rate is 1 r / min, the spot diameter is 4 mm, no preheating is required, and the layer thickness is 1.8 mm.

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