A method of inhibiting the settling of tungsten carbide particles and a wear-resistant composite coating

Abstract

The present application relates to a kind of wear-resistant composite coating and preparation method for inhibiting tungsten carbide particle settlement, comprising the following steps: 1) the surface of substrate is treated, and oxide layer and dirt are removed;2) respectively weigh Ni40A powder and Nickel-WC powder, uniformly mix powder, and dry;3) preheating of surfacing substrate, preheating temperature is 360~420 DEG C, and preheating time is 5~7h;4) using plasma transferred arc powder surfacing, transition layer and hard layer are formed on the surface of substrate;5) after welding, it is wrapped and cooled to room temperature.The advantages are: coating surface is smooth and even, and the density is high, the hard layer structure is dense and small, can effectively alleviate the settlement phenomenon of WC particle, increases the uniformity of WC particle distribution;And can effectively prevent pore, loose structure and crack occur, can significantly improve the wear resistance of roller, can effectively prolong the service life of roller.

Description

Technical Field

[0001] This invention belongs to the field of surface modification technology for metallurgical rollers, and particularly relates to a wear-resistant composite coating for inhibiting the sedimentation of tungsten carbide particles and its preparation method. Background Technology

[0002] Rolls require good overall mechanical properties, as well as excellent surface wear resistance. A composite manufacturing technique involving welding overlay is typically used to improve this surface wear resistance. Therefore, simulation experiments are needed to find better roll repair methods.

[0003] Ceramic materials possess excellent wear resistance and can be used as wear-resistant materials for weld overlay coatings. However, their properties differ significantly from the substrate, resulting in poor fusion and a tendency to crack. To prevent coating cracking and mitigate the material property differences between the weld overlay coating and the substrate, a gradient coating approach is employed. A transition layer is prepared between the substrate and the hard layer, with the transition layer made of a nickel-based alloy and the hard layer made of nickel-based alloy doped with WC particles. However, the settling of ceramic particles leads to porosity in the hard layer, resulting in a decrease in hardness and wear resistance. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a wear-resistant composite coating and its preparation method for inhibiting the sedimentation of tungsten carbide particles. The coating uses a composite of a base layer and a hard layer to reduce the sedimentation of ceramic particles and enhance hardness and wear resistance.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for suppressing the sedimentation of tungsten carbide particles includes the following steps:

[0007] 1) Grind the substrate surface to remove the oxide layer, and clean it with alcohol to remove oil stains from the substrate surface;

[0008] 2) Weigh Ni40A powder and Nickel-WC powder separately, wherein Ni40A powder is 40wt%~45wt% and the remainder is Nickel-WC powder; mix them evenly with a powder mixer for 8~12 hours and then dry them.

[0009] 3) Preheat the substrate for welding. The substrate is preheated in a heating furnace at a heating rate of 1~10℃ / min to the preheating temperature of 360~420℃ for 5~7h.

[0010] 4) Plasma-transferred arc powder surfacing is used to form a transition layer on the substrate surface by Ni40A powder surfacing. After the transition layer solidifies, a hard layer is formed on the transition layer by Nickel-WC powder surfacing.

[0011] The welding current parameters for the transition layer and hard layer are 110~140A, the oscillation width is 20~25mm, the corresponding oscillation time is 0.3~0.4s, the overlap rate is 30~50%, and the powder feeding speed is 38~45r / min;

[0012] 5) After welding, wrap the product with insulating cotton and let it cool to room temperature.

[0013] The Ni40A powder and Nickel-WC powder mentioned in step 2) are accurately weighed using an electronic balance.

[0014] In step 1), coarse sandpaper is used to polish the surface of the substrate.

[0015] The particle size of both the Ni40A powder and the Nickel-WC powder mentioned in step 2) is 50~300μm.

[0016] A wear-resistant composite coating for inhibiting the sedimentation of tungsten carbide particles, the composite coating being a wear-resistant composite coating formed on the surface of a metallurgical roller-like substrate, the composite coating comprising a transition layer welded to the substrate surface and a hard layer overlaid on the transition layer, wherein the transition layer is a nickel-based alloy transition layer; and the hard layer is a WC ceramic-reinforced nickel-based alloy hard layer.

[0017] The transition layer is formed by Ni40A powder overlay welding. The composition of Ni40A powder, by mass percentage, is as follows:

[0018] C∶Cr∶B∶Si∶Fe∶Ni∶Cu=(0.05~0.08)∶(11.07~11.10)∶(1.20~1.24)∶(3.44~3.48)∶(3.00~3.03)∶(77.38~77.60)∶(3.64~3.69).

[0019] The hard layer is formed by Nickel-WC powder overlay, and the composition of Nickel-WC powder by mass percentage is: C∶Cr∶B∶Si∶Fe∶W∶Ni=(1.81~1.83)∶(0.08~0.12)∶(1.22~1.26)∶(1.75~1.78)∶(1.42~1.48)∶(43.10~43.50)∶(50.03~50.62).

[0020] The thickness of the transition layer is 1.6–2.5 mm, and the thickness of the WC ceramic particle reinforced nickel-based alloy hard layer is 1.6–2.5 mm.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The wear-resistant composite coating obtained by this invention has high bonding strength with the roll substrate, a smooth and flat coating surface, high density, and a dense and fine hard layer structure, which can effectively alleviate the sedimentation phenomenon of WC particles. At the same time, a large number of flocculent secondary carbides formed by the decomposition of WC particles are evenly distributed between the WC particles, which increases the uniformity of WC particle distribution. It can also effectively prevent the occurrence of pores, loose structure and cracks, which can significantly improve the wear resistance of the roll and effectively extend the service life of the roll.

[0023] The present invention provides a wear-resistant composite coating that can suppress the sedimentation of tungsten carbide particles. It also has the advantages of being environmentally friendly, having good process repeatability, simple preparation steps for the composite coating, controllable composition, being economical and practical, and being easy to industrialize. Attached Figure Description

[0024] Figure 1 The image shows the XRD results of the matrix.

[0025] Figure 2 This is an XRD result diagram of the composite coating of the present invention.

[0026] Figure 3 The image shows the XRD results of the coating in the comparative example.

[0027] Figure 4 This is an optical morphology diagram of the composite coating of the present invention.

[0028] Figure 5 This is an optical morphology image of the coating in the comparative embodiment.

[0029] Figure 6 SEM images of the side surface and corresponding surface of the coating in the comparative embodiment are shown.

[0030] Figure 7 These are SEM images of the side surface and corresponding surface of the coating of the present invention.

[0031] Figure 8 This is a state diagram of the WC particles in the coating of the comparative embodiment.

[0032] Figure 9 This is a state diagram of WC particles in the coating of the present invention.

[0033] Figure 10 This is a diagram showing the wear and tear quality loss. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0035] Example

[0036] The substrate was 42CrMo steel, and the sample size was 200mm×200mm×40mm. The main components were γ-Fe / Ni and Fe-Cr phases. (See attached image.) Figure 1 A composite coating was prepared on the sample surface using plasma-transferred arc powder surfacing technology. Specifically, the method for preparing the wear-resistant composite coating that inhibits tungsten carbide particle sedimentation includes the following steps:

[0037] 1) Use 80# coarse sandpaper to grind the surface of the substrate (42CrMo steel) to remove the surface oxide layer and make the surface smooth and flat. Use alcohol to clean the surface of the substrate to remove oil stains.

[0038] 2) Ni40A powder and Nickel-WC powder were accurately weighed using an electronic balance, then mixed uniformly using a powder mixer for 8-12 hours, and then dried.

[0039] 3) Preheat the substrate for welding at a temperature of 360~420℃ (preferably 390℃, 400℃, 405℃, 410℃) for 5~7h (preferably 6h) to ensure that the substrate reaches the target preheating temperature (360~420℃) both inside and outside.

[0040] 4) The coating is prepared using plasma-transferred arc powder surfacing technology. The welding current parameters for the transition layer and hard layer are 110~140A, the oscillation width is 20~25mm, the corresponding oscillation time is 0.3~0.4s, the overlap rate is 30~50%, and the powder feeding speed is 38~45r / min.

[0041] The use of plasma-transferred arc powder cladding reduces the temperature gradient between the hard layer and the substrate, thus extending the molten pool time. Under the action of thermal energy input, WC particles decompose and form irregularly shaped precipitates. These precipitates hinder the descent of WC particles, impeding their traction and slowing down the occurrence of most WC particles settling to the bottom.

[0042] 5) After welding, wrap the product with insulating cotton and let it cool to room temperature.

[0043] The composite coating comprises a nickel-based alloy transition layer and a WC ceramic-reinforced nickel-based alloy hard layer. The nickel-based alloy transition layer is constructed using Ni40A powder, with the following composition by mass percentage: C:Cr:B:Si:Fe:Ni:Cu = 0.07:11.09:1.23:3.46:3.01:77.48:3.66; alternatively, it can be C:Cr:B:Si:Fe:Ni:Cu = 0.06:11.08:1.32:3.45:3.02:77.4:3.67. The addition of copper to the nickel-based alloy helps improve its resistance to corrosion from hydrofluoric acid, phosphoric acid, and sulfuric acid. Adding trace amounts of Cu to the Ni-based alloy refines its grain structure, generating copper-nickel and copper-chromium compounds that are securely embedded in the matrix, providing lubrication and improving the wear resistance of the nickel-based alloy.

[0044] The WC ceramic particle reinforced nickel-based alloy hard layer is welded using Nickel-WC powder. The Nickel-WC powder composition, by mass percentage, is: C:Cr:B:Si:Fe:W:Ni = 1.83:0.10:1.24:1.76:1.44:43.20:50.43; it can also be C:Cr:B:Si:Fe:W:Ni = 1.83:0.10:1.24:1.76:1.44:43.20:50.43.

[0045] The wear-resistant composite coating prepared in this embodiment, which can inhibit the sedimentation of tungsten carbide particles, has a smooth and flat surface, uniform color, and no obvious defects.

[0046] The XRD test results of the wear-resistant composite coating in this embodiment, which can suppress the sedimentation of tungsten carbide particles, are shown in the figure. Figure 2 .Depend on Figure 2 It can be seen that, in addition to γ-Fe / Ni, the mineral phases of the coating also include M7C3 and M... 23 C6, WC, W2C, and Cr3C2 phases. M7C3, M... 23 The presence of C6 and W2C indicates that element diffusion and precipitation processes are occurring in the molten pool. When WC particles added to a nickel-based alloy are heated, some dissolved W and C elements diffuse into the liquid phase, combining with Cr in the liquid phase to form M7C3 and M... 23Other carbides such as C6, when present in appropriate amounts and distributions, can enhance the wear resistance of the coating due to the presence of secondary phases. Phase characterization results for Fe3C, Ni2W4C, and Ni3Fe also show that WC particles and secondary hard phases together constitute the coating framework. WC particles and secondary carbides can act as hard phases to enhance the coating's hardness and anti-friction properties. The intensity of the highest peak γ-Ni / Fe in the composite coating of this invention is lower than that of the coating in the comparative example because the presence of WC particles on the coating surface reduces the diffraction peak intensity. The lower diffraction peak intensity of the coating of this invention compared to the coating in the comparative example indicates that preheating temperature and time alter the content of each phase deposited during the solidification process in the molten pool.

[0047] Depend on Figure 4 It can be seen that, Figure 4 The image, from bottom to top, corresponds to the substrate-transition layer-hard layer from lower to top. The coating structure of this invention is much denser than that of the comparative embodiment because preheating before welding reduces the temperature gradient, minimizes heat loss, facilitates the full development of the molten pool, provides time for gases and impurities to rise, and improves porosity and loose structure. The increase in preheating temperature improves the overall coating structure. A bright band exists between the substrate and the transition layer, indicating a metallurgical bond between them. The metallurgical bond region between the substrate and the transition layer consists of very narrow planar crystals, followed by cellular crystals, and then columnar crystals. The entire transition layer is almost entirely composed of columnar crystals. Furthermore, because the hard layer is deposited after the transition layer solidifies, the hard layer reheats the transition layer, and the remelting process further promotes the growth of the columnar crystals in the transition layer, forming coarse columnar crystals. Because WC particles have a high melting point, they remain entirely granular even when the nickel-based alloy is in the liquid phase. Therefore, the growth of columnar crystals is hindered by the WC particles. In regions where WC particles are distributed at or above a certain height, equiaxed crystal regions are formed, resulting in a dense and fine microstructure. According to alloy solidification theory, where G represents the temperature gradient and R represents the solidification rate, higher G / R ratios tend to form coarse microstructures, including planar, cellular, and columnar crystals. As G / R decreases, the microstructure gradually evolves from planar to cellular, columnar, and finally equiaxed crystals. Lower G / R ratios result in even finer planar crystal structures.

[0048] Depend on Figure 7It can be seen that when the preheating conditions are 360~420℃ / 5~7h, the WC particle sedimentation phenomenon is significantly improved. At the bottom of the hard layer, the WC particles are uniformly distributed without obvious concentrated distribution. Meanwhile, WC particles are found at the top of the hard layer, and between the WC particles and within the nickel-based alloy, many substances of the same color as the WC particles, resembling flocculent material, can be found. This is due to the decomposition of the WC particles, increasing the uniformity of their distribution. The surface image shows that the coating surface has a large number of WC particles, with numerous white secondary carbides formed by the decomposition of WC particles evenly distributed between them, a significantly increased quantity compared to the coating of the comparative example. Increasing the preheating temperature effectively alleviates the WC particle sedimentation phenomenon and promotes the formation of secondary carbides.

[0049] Because WC particles have a higher density than nickel-based alloys, they tend to settle to the bottom. However, under the influence of thermal energy, elemental dissolution and diffusion occur between the edges of WC particles and the nickel-based alloy, resulting in the appearance of white precipitates. More importantly, the elemental dissolution and diffusion between the edges of WC particles and the nickel-based alloys causes the edges of WC particles to become irregular, no longer the original smooth spherical boundaries. At the same time, the density of the WC retained after dissolution and solidification is lower than the density of the originally added WC particles. The irregular edges and the smaller density of WC particles will alleviate the settling tendency of WC particles.

[0050] Depend on Figure 9 It can be seen that the coating of the present invention has more white precipitates, and the size of WC particles in the hard layer is significantly smaller than that in the comparative embodiment. The edge integrity of WC particles in the coating of the comparative embodiment is better than that in the coating of the present invention, indicating that when the preheating regime is 360~420℃ / 5~7h, the degree of dissolution of WC particle edges is higher than that in the comparative embodiment. Figure 9 In the high-magnification images, WC particles exhibit three typical states: A, B, and C. State A is similar to... Figure 8 The consistency in state A, B, and C indicates partial edge dissolution of WC particles; state B shows that the WC particles have undergone a more severe edge dissolution effect and have not completely dissolved, with the edges and cores of the WC particles still differing, and the width of the dissolution zone is approximately 20 μm; state C shows stratification of the WC particles, with the dissolved edge separating from the parent WC particles, and nickel-based alloy filling the gap between the WC particles and the dissolution layer. These three WC particle states correspond to different degrees of WC dissolution in the molten pool, revealing a relatively mild edge dissolution process when the WC addition is 40-45%.

[0051] WC particles have a higher density than nickel-based alloys, thus exhibiting a tendency to settle. Under thermal energy, elemental dissolution and diffusion occur between the edges of WC particles and the nickel-based alloy, leading to the formation of white precipitates. Higher preheating temperatures reduce the temperature gradient between the hard layer and the matrix, prolonging the molten pool's existence time. Under thermal energy input, WC particles may decompose, forming irregularly shaped precipitates. These precipitates hinder the descent of WC particles, impeding their drag and slowing down settling. The elemental dissolution and diffusion between the edges of WC particles and the nickel-based alloys cause the WC particle edges to become irregular, no longer the initially smooth spherical boundaries. After dissolution and solidification, the density of WC decreases; these irregular edges and the reduced WC particle density alleviate the settling tendency.

[0052] In addition, the forces that play a major role in the weld pool include buoyancy, gravity, and Marangoni force. Under the combined action of various forces, the rough edges, the smaller WC particles, and the smaller remaining WC particles are less likely to settle, resulting in no significant settling of WC particles.

[0053] Depend on Figure 10 It can be seen that the influence of different processes on the wear resistance of the coating is determined by friction and wear testing. The parameters for coating friction and wear testing are as follows: grinding ball: Si3N4; rotation speed: 300 r / min; friction radius: 5 mm; load: 20 N; test time: 60 min.

[0054] The wear mass of the substrate was 3.9 mg, while the wear masses of the coating in the comparative example and the coating of the present invention were 2.7 mg and 1.3 mg, respectively, representing reductions of 30% and 66% compared to the substrate. The wear mass of the composite coating of the present invention was also reduced by 51% compared to the coating in the comparative example. This is because, as can be seen from the side and surface views, the WC particles in the coating of the comparative example are mainly concentrated at the bottom of the coating, with fewer WC particles at the top. Therefore, during the friction and wear process, the main component in contact with the grinding ball is the nickel-based alloy. However, when the preheating regime is 360~420℃ / 5~7h, the WC particle settling phenomenon can be effectively alleviated. Under this preheating regime, the WC particles are more uniformly distributed in the hard layer, and the degree of decomposition is more severe than that of the coating in the comparative example, forming secondary carbides. During the friction and wear process, the WC particles protect the nickel-based alloy, effectively reducing the wear amount and improving the wear resistance of the coating.

[0055] As can be seen, the hard layer of the coating in this embodiment has a dense and fine structure. The WC particles partially dissolve and diffuse to form a secondary hard phase, and the WC particle sedimentation phenomenon is significantly improved. WC particles are present at the top, and at the bottom of the hard layer, the WC particles are evenly distributed, which significantly improves the wear resistance.

[0056] Comparative Examples

[0057] The substrate composition, Ni40A powder, and Nickel-WC powder are the same as in the examples, but the difference between them lies in the preparation method. The specific preparation method in this comparative example is as follows:

[0058] 1) Use 80# coarse sandpaper to grind the surface of the base material (42CrMo steel) to remove the surface oxide layer and make the surface smooth and flat. Use alcohol to clean the surface of the base material to remove oil stains.

[0059] 2) Ni40A powder and Nickel-WC powder were accurately weighed using an electronic balance, then mixed uniformly using a powder mixer for 8-12 hours, and then dried.

[0060] 3) Preheat the substrate for welding at a temperature of 150~220℃ for 30~60 minutes.

[0061] 4) The coating is prepared by plasma-transferred arc powder surfacing technology. A transition layer is formed on the substrate surface by Ni40A powder surfacing. After the transition layer solidifies, a hard layer is formed on the transition layer by Nickel-WC powder surfacing.

[0062] The welding current parameters for the transition layer and hard layer are 110~140A, the oscillation width is 20~25mm, the corresponding oscillation time is 0.3~0.4s, the overlap rate is 30%~50%, and the powder feeding speed is 38~45r / min;

[0063] 5) After welding, wrap the coating with insulating cotton and allow it to cool to room temperature. Perform XRD analysis on the resulting composite coating. The results are shown in [Figure number missing]. Figure 3 The morphology of the solidified coating under a light microscope is shown below. Figure 5 , Figure 5 The images, from bottom to top, correspond to the substrate-transition layer-hard layer from lower to top. The comparative example coating clearly shows a small number of pores. The SEM morphology of the coating's side surface and corresponding surface is shown in [image missing]. Figure 6 The morphology of the hard coating layer was observed under high magnification using SEM. Figure 8 Electron microscopy images at 1500x magnification revealed internal cracks in the WC particles of the comparative example coating. These internal cracks may further propagate during coating service. Coating wear quality loss is shown in [reference needed]. Figure 10 It is evident that the WC particles in the composite coating of this comparative embodiment did not show significant dissolution and diffusion, exhibiting obvious WC particle sedimentation and a small amount of pores. Furthermore, the WC particles in the coating contained internal cracks, resulting in limited improvement in wear resistance.

Claims

1. A method for suppressing the sedimentation of tungsten carbide particles, characterized in that, Includes the following steps: 1) Grind the substrate surface to remove the oxide layer, and clean it with alcohol to remove oil stains from the substrate surface; 2) Weigh Ni40A powder and Nickel-WC powder separately; mix them evenly with a powder mixer for 8-12 hours, and then dry them; 3) Preheat the substrate for welding. The substrate is preheated in a heating furnace at a heating rate of 1~10℃ / min to the preheating temperature of 360~420℃ for 5~7h. 4) Plasma-transferred arc powder surfacing is used to form a transition layer on the substrate surface by Ni40A powder surfacing. After the transition layer solidifies, a hard layer is formed on the transition layer by Nickel-WC powder surfacing. The welding current parameters for the transition layer and hard layer are 110~140A, the oscillation width is 20~25mm, the corresponding oscillation time is 0.3~0.4s, the overlap rate is 30~50%, and the powder feeding speed is 38~45r / min; 5) After welding, wrap the product with insulating cotton and let it cool to room temperature.

2. The method for suppressing the sedimentation of tungsten carbide particles according to claim 1, characterized in that, The Ni40A powder and Nickel-WC powder mentioned in step 2) are accurately weighed using an electronic balance.

3. The method for suppressing the sedimentation of tungsten carbide particles according to claim 1, characterized in that, In step 1), coarse sandpaper is used to polish the surface of the substrate.

4. The method for suppressing the sedimentation of tungsten carbide particles according to claim 1, characterized in that, The particle size of both Ni40A powder and Nickel-WC powder mentioned in step 2) is 50~300μm.

5. A wear-resistant composite coating for inhibiting tungsten carbide particle sedimentation obtained by the method according to any one of claims 1-4, characterized in that, The composite coating is a wear-resistant composite coating formed on the surface of a metallurgical roller substrate. The composite coating includes a transition layer welded to the substrate surface and a hard layer welded to the transition layer. The transition layer is a nickel-based alloy transition layer; the hard layer is a WC ceramic-reinforced nickel-based alloy hard layer.

6. The wear-resistant composite coating for inhibiting tungsten carbide particle sedimentation according to claim 5, characterized in that, The transition layer is formed by Ni40A powder overlay welding. The composition of Ni40A powder, by mass percentage, is as follows: C∶Cr∶B∶Si∶Fe∶Ni∶Cu=(0.05~0.08)∶(11.07~11.10)∶(1.20~1.24)∶(3.44~3.48)∶(3.00~3.03)∶(77.38~77.60)∶(3.64~3.69).

7. The wear-resistant composite coating for inhibiting tungsten carbide particle sedimentation according to claim 5, characterized in that, The hard layer is formed by Nickel-WC powder overlay, and the composition of Nickel-WC powder by mass percentage is: C∶Cr∶B∶Si∶Fe∶W∶Ni = (1.81~1.83)∶(0.08~0.12)∶(1.22~1.26)∶(1.75~1.78)∶(1.42~1.48)∶(43.10~43.50)∶(50.03~50.62).

8. The wear-resistant composite coating for inhibiting tungsten carbide particle sedimentation according to claim 5, characterized in that, The thickness of the transition layer is 1.6–2.5 mm, and the thickness of the WC ceramic particle reinforced nickel-based alloy hard layer is 1.6–2.5 mm.

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