Tungsten carbide composite coating as well as preparation method and application thereof

Abstract

The invention provides a tungsten carbide composite coating as well as a preparation method and application thereof, and belongs to the technical field of surface protection. The preparation method of the tungsten carbide composite coating comprises the following steps that tungsten powder, chromium carbide powder and high-entropy alloy powder are mixed, and mixed raw material powder is obtained; and the mixed raw material powder is laid on the surface of a metal substrate material to form a preset coating, then laser cladding treatment is conducted, and the tungsten carbide composite coating is formed on the surface of the metal substrate material. Tungsten carbide is generated through an in-situ reaction in the laser cladding treatment process, so that the comprehensive performance (such as hardness, frictional wear resistance and corrosion resistance) of the coating is improved by adding the tungsten carbide.

Description

Technical Field

[0001] The present invention relates to the technical field of surface protection, and in particular to a tungsten carbide composite coating, a preparation method thereof, and an application thereof. Background Art

[0002] The laser cladding technology has almost no limitation on the types of metal plates and alloy powders, and has high working efficiency, simple operation, strong adaptability, and can also realize outdoor operation, with extremely high application value.

[0003] Currently, in order to make the metal plate have higher hardness, a certain content of ceramic materials, such as tungsten carbide (WC) ceramic materials, is usually added to the alloy powder. Its hardness can reach more than 800 HV, which can effectively improve the hardness of the metal plate. However, the thermal expansion coefficient of tungsten carbide ceramic particles is small, and there is a large difference from the thermal expansion coefficients of many metals. During the rapid cooling process of laser cladding, due to the difference in thermal expansion coefficients, the solidification shrinkage of each component is inconsistent, which easily forms pores and cracking defects, affecting the performance of the coating. Summary of the Invention

[0004] The purpose of the present invention is to provide a tungsten carbide composite coating, a preparation method thereof, and an application thereof. The tungsten carbide composite coating prepared by the method of the present invention has excellent comprehensive performance.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a tungsten carbide composite coating, including the following steps:

[0007] Mix tungsten powder, chromium carbide powder and high-entropy alloy powder to obtain a mixed raw material powder;

[0008] Lay the mixed raw material powder on the surface of a metal substrate material to form a pre-coated layer, and then perform laser cladding treatment to form a tungsten carbide composite coating on the surface of the metal substrate material.

[0009] Preferably, the high-entropy alloy powder includes AlCoCrFeNi high-entropy alloy powder, CoCrFeNi high-entropy alloy powder or CoCrFeNiMo high-entropy alloy powder.

[0010] Preferably, the mass ratio of the tungsten powder to the chromium carbide powder is 1:0.9 - 1.1; the mass ratio of the tungsten powder to the high-entropy alloy powder is 1:7.8 - 8.2.

[0011] Preferably, the method of laying the mixed raw material powder on the surface of the metal base material to form a pre-coating comprises the following steps: mixing the mixed raw material powder with a dispersant and coating the mixture on the surface of the metal base material, followed by drying to obtain the pre-coating.

[0012] Preferably, the thickness of the pre-coating layer is 0.9-1.1 mm.

[0013] Preferably, the conditions of the laser cladding treatment include: laser power of 1100-1300 W, laser scanning speed of 450-550 mm / min, overlap rate of 38-42%, and defocus of +5 mm.

[0014] Preferably, the metal substrate material is a steel material, and the steel material includes Q235 stainless steel, 304 stainless steel, 316L stainless steel or E690 steel.

[0015] The present invention provides a tungsten carbide composite coating prepared by the preparation method described in the above technical solution, comprising a high entropy alloy matrix and tungsten carbide particles, chromium carbide and chromium element distributed in the high entropy alloy matrix.

[0016] Preferably, the thickness of the tungsten carbide composite coating is 0.9-1.1 mm.

[0017] The present invention provides application of the tungsten carbide composite coating described in the above technical solution in ship steel or dock steel.

[0018] The present invention provides a method for preparing a tungsten carbide composite coating, comprising the following steps: mixing tungsten powder, chromium carbide powder and high entropy alloy powder to obtain a mixed raw material powder; laying the mixed raw material powder on the surface of a metal base material to form a pre-coating, and then performing a laser cladding process to form a tungsten carbide composite coating on the surface of the metal base material. In the laser cladding process, the present invention generates tungsten carbide by an in-situ reaction, thereby realizing the addition of tungsten carbide to improve the comprehensive performance of the coating (such as hardness, friction and wear resistance, and corrosion resistance). DETAILED DESCRIPTION

[0019] The present invention provides a method for preparing a tungsten carbide composite coating, comprising the following steps:

[0020] Mixing tungsten powder, chromium carbide powder and high entropy alloy powder to obtain mixed raw material powder;

[0021] The mixed raw material powder is laid on the surface of the metal base material to form a pre-coating, and then laser cladding treatment is performed to form a tungsten carbide composite coating on the surface of the metal base material.

[0022] In the present invention, unless otherwise specified, the raw materials used are commercially available products well-known to those skilled in the art or prepared by methods well-known to those skilled in the art.

[0023] In the present invention, tungsten powder, chromium carbide powder and high-entropy alloy powder are mixed to obtain a mixed raw material powder. As an embodiment of the present invention, the high-entropy alloy powder may include AlCoCrFeNi high-entropy alloy powder, CoCrFeNi high-entropy alloy powder or CoCrFeNiMo high-entropy alloy powder, specifically, it may be AlCoCrFeNi high-entropy alloy powder; the atomic percentages of the elements in the high-entropy alloy powder may be the same. As an embodiment of the present invention, the mass ratio of the tungsten powder to the chromium carbide powder may be 1:0.9 - 1.1, specifically 1:1; the mass ratio of the tungsten powder to the high-entropy alloy powder may be 1:7.8 - 8.2, specifically 1:8. The present invention uses chromium carbide powder as a carbon source, which is beneficial to ensuring the formation of free carbon during the laser cladding process and in-situ reaction with tungsten to form tungsten carbide ceramic particles. In the examples of the present invention, limiting the mass ratio of the tungsten powder, chromium carbide powder and high-entropy alloy powder within the above range is beneficial to ensuring that the final composite coating has excellent comprehensive properties (such as hardness, friction and wear resistance, and corrosion resistance). As an embodiment of the present invention, the particle sizes of the tungsten powder, chromium carbide powder and high-entropy alloy powder may independently be 15 - 53 μm. As an embodiment of the present invention, the mixing may be ball milling, the rotation speed of the ball milling may be 500 - 700 rpm, specifically 600 rpm; the ball milling time may be 2 - 4 h, further 2 - 3 h.

[0024] After obtaining the mixed raw material powder, the present invention lays the mixed raw material powder on the surface of a metal substrate material to form a pre-coated layer, and then performs laser cladding treatment to form a tungsten carbide composite coating on the surface of the metal substrate material. As an embodiment of the present invention, the metal substrate material may be a steel material, and the steel material may include Q235 stainless steel, 304 stainless steel, 316L stainless steel or E690 steel, specifically Q235 stainless steel. As an embodiment of the present invention, the metal substrate material may be pretreated before use, and the pretreatment may include grinding, washing and drying in sequence; in the examples of the present invention, specifically, an angle grinder is used to remove the rust and oil on the surface of the metal substrate material, and it is polished bright with sandpaper, then washed with acetone and alcohol respectively, and then dried with a hair dryer to obtain a metal substrate material with a clean surface for standby.

[0025] As an embodiment of the present invention, the method of laying the mixed raw material powder on the surface of the metal base material to form a pre-coating may include the following steps: mixing the mixed raw material powder with a dispersant and applying it on the surface of the metal base material, and then drying to obtain the pre-coating. As an embodiment of the present invention, the dispersant may include ethanol, specifically anhydrous ethanol; the present invention has no special limitation on the amount of the dispersant, as long as it can ensure smooth coating; the drying temperature may be 175-185°C, specifically 180°C, and the present invention has no special limitation on the drying time, as long as it is fully dried. As an embodiment of the present invention, the thickness of the pre-coating may be 0.9-1.1mm, specifically 1mm.

[0026] After the mixed raw material powder is laid on the surface of the metal base material to form a pre-coating, the present invention performs laser cladding treatment to form a tungsten carbide composite coating on the surface of the metal base material. During the laser cladding treatment, on the one hand, since W is a single substance, W in a molten state is very active in a high-temperature molten pool and is easy to form W compounds; on the other hand, in a high-temperature molten pool, part of Cr 3 C 2 Decomposed into highly active free Cr and free C, molten W combined with free C to form WC, and preserved in the form of WC ceramic particles during the solidification process. The addition of WC ceramic particles is achieved through the in-situ synthesis method, thereby achieving the purpose of adding WC ceramic particles to enhance the hardness and other comprehensive properties of the composite coating; the remaining Cr 3 C 2 And the generated Cr and WC ceramic particles play a synergistic enhancement role. As an embodiment of the present invention, the conditions of the laser cladding treatment may include: the laser power is 1100-1300W, specifically 1200W; the laser scanning speed is 450-550mm / min, specifically 500mm / min; the overlap rate can be 38-42%, specifically 40%; the defocus amount is +5mm. In the embodiment of the present invention, laser cladding treatment is carried out under the above conditions, which is conducive to ensuring that the final composite coating has excellent hardness, corrosion resistance and other comprehensive properties, and the composite coating has good bonding with the metal substrate material. In the embodiment of the present invention, if the laser power is lower than 1100W, the pre-coating will not be completely melted, resulting in a weak bonding between the composite coating and the metal substrate material; if the laser power is higher than 1300W, the forming effect of the composite coating is not good, the cladding depth is too large, and the composite coating has signs of burning.

[0027] The present invention generates tungsten carbide by in-situ reaction during the laser cladding process, thereby realizing the addition of tungsten carbide to improve the comprehensive performance of the coating (such as hardness, friction and wear resistance, and corrosion resistance), avoiding the problem that the direct addition of tungsten carbide ceramic particles is prone to cause pores and cracking defects in the coating due to inconsistent solidification shrinkage of each component. In addition, tungsten carbide has the brittleness of ceramic materials and is prone to brittle fracture. If tungsten carbide ceramic particles are directly added, the performance of the coating will be affected by the brittleness of tungsten carbide; moreover, during the laser cladding process, under high-temperature laser irradiation, the temperature of the molten pool will reach 2500 Kelvin or even higher. If tungsten carbide ceramic particles are directly added, the high temperature will cause part of the tungsten carbide ceramic particles to liquefy and melt, thereby generating other brittle intermetallic compounds, affecting the performance of the coating. The present invention does not directly add tungsten carbide ceramic particles, but generates tungsten carbide ceramic particles in the laser cladding process through in-situ reaction, utilizes high-energy density laser irradiation to melt high-entropy alloy powder, and generates a layer of coating with good metallurgical bonding on the surface of the metal base material, so that the original metal base material has the properties of the high-entropy alloy powder metal while utilizing the generated tungsten carbide ceramic particles to play a reinforcing role, thereby preparing a composite coating with excellent comprehensive performance, thereby realizing surface modification of the metal base material.

[0028] The present invention provides a tungsten carbide composite coating prepared by the preparation method described in the above technical solution, comprising a high entropy alloy matrix and tungsten carbide particles, chromium carbide and chromium element distributed in the high entropy alloy matrix. As an embodiment of the present invention, the thickness of the tungsten carbide composite coating can be 0.9 to 1.1 mm, specifically 1 mm.

[0029] The present invention provides the application of the tungsten carbide composite coating in the above technical solution in ship steel or dock steel. The present invention has no special limitation on the specific application of the tungsten carbide composite coating, and the application method familiar to those skilled in the art can be adopted.

[0030] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The tungsten (W) powder and chromium carbide (Cr 3 C 2 ) powder and AlCoCrFeNi high entropy alloy powder have a particle size of 15 to 53 μm.

[0032] Example 1

[0033] Use an angle grinder to remove rust and oil on the surface of the metal substrate material (specific type is Q235 stainless steel), polish it bright with sandpaper, then clean it with acetone and alcohol respectively, and dry it with a hair dryer to obtain a metal substrate material with a clean surface for standby;

[0034] Mix tungsten (W) powder, chromium carbide (Cr 3 C 2 ) powder and AlCoCrFeNi high-entropy alloy powder in a mass ratio of 1:1:8, place them in a ball mill, and ball mill for 2 h under the condition of a rotation speed of 600 rpm. Stir and mix the obtained mixed powder with a dispersant (specifically anhydrous ethanol) to obtain a paste-like mixture; coat the paste-like mixture on the surface of the metal substrate material with a clean surface, and dry it at 180 °C to obtain a preplaced coating; then use a laser to perform laser cladding treatment on the preplaced coating to form a tungsten carbide composite coating (thickness is 1 mm) on the surface of the metal substrate material; among them, the conditions of the laser cladding treatment include: laser power is 1200 W, laser scanning speed is 500 mm / min, overlap rate is 40%, and defocus amount is +5 mm.

[0035] Comparative Example 1

[0036] Operate according to the method of Example 1, the difference is that chromium carbide powder is replaced with carbon powder.

[0037] Comparative Example 2

[0038] Operate according to the method of Example 1, the difference is that chromium carbide powder is replaced with carbon powder and chromium powder, and the molar ratio of the carbon powder to the chromium powder is 2:3.

[0039] Comparative Example 3

[0040] Operate according to the method of Example 1, the difference is that tungsten powder and chromium carbide powder are replaced with tungsten carbide powder, and the mass ratio of tungsten in the tungsten carbide powder to AlCoCrFeNi high-entropy alloy powder is 1:1.

[0041] Test Example 1

[0042] After the laser cladding treatment in Example 1, the obtained specimens were characterized and performance tested as follows:

[0043] The specimens were detected by XRD. The results showed that WC was contained in the composition of the composite coating, proving that the W powder and Cr 3 C 2 powder did undergo an in-situ reaction to form WC.

[0044] The hardness of the specimen was tested, and the results showed that the Vickers hardness of the composite coating was 1250 HV, indicating that it had a high hardness, while the hardness of the Q235 stainless steel material was only 200 HV.

[0045] The friction and wear properties of the specimen were tested. Specifically, under room temperature conditions, a 6 mm GCr steel ball was used, and the test was carried out under the conditions of a pressure of 15 N, a rotation radius of 2 mm, and a rotation speed of 200 r / min for a duration of 1 h. The results showed that the friction coefficient of the composite coating was 0.45, which was significantly lower than that of the Q235 stainless steel material (friction coefficient of 0.7), indicating that it had excellent friction and wear resistance.

[0046] The specimen was cut along the direction perpendicular to the laser cladding treatment to obtain a specimen with dimensions of 10 mm × 5 mm × 5 mm. Then, grinding and polishing treatments were carried out. Next, the specimen was corroded for 15 s at room temperature using a 4 wt% nitric acid alcohol solution (prepared from nitric acid and alcohol), and then the electrochemical properties were tested. The results showed that the corrosion current of the composite coating was 1.28×10 -8 A, and the corrosion voltage was -0.4 V, which had excellent electrochemical properties compared with the Q235 stainless steel material (corrosion current of 4.29×10 -7 A and corrosion voltage of -0.934 V).

[0047] Referring to the above method, the specimens obtained after laser cladding treatment in each comparative example were tested for performance. The results showed that the hardness, friction and wear properties, and corrosion resistance of the specimens in Example 1 of the present invention were all superior to those of the specimens in Comparative Examples 1-3.

[0048] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a tungsten carbide composite coating, comprising the following steps: Mixing tungsten powder, chromium carbide powder and high entropy alloy powder to obtain mixed raw material powder; The mixed raw material powder is laid on the surface of the metal base material to form a pre-coating, and then laser cladding treatment is performed to form a tungsten carbide composite coating on the surface of the metal base material.

2. The preparation method according to claim 1, characterized in that: The high entropy alloy powder includes AlCoCrFeNi high entropy alloy powder, CoCrFeNi high entropy alloy powder or CoCrFeNiMo high entropy alloy powder.

3. The preparation method according to claim 1 or 2, characterized in that: The mass ratio of the tungsten powder to the chromium carbide powder is 1:0.9-1.1; the mass ratio of the tungsten powder to the high entropy alloy powder is 1:7.8-8.

2.

4. The preparation method according to claim 1, characterized in that: The method of laying the mixed raw material powder on the surface of a metal base material to form a pre-coating layer comprises the following steps: mixing the mixed raw material powder with a dispersant and then coating the mixed raw material powder on the surface of the metal base material, followed by drying to obtain the pre-coating layer.

5. The preparation method according to claim 1 or 4, characterized in that: The thickness of the pre-coating layer is 0.9-1.1 mm.

6. The preparation method according to claim 1, characterized in that: The conditions of the laser cladding treatment include: laser power of 1100-1300W, laser scanning speed of 450-550mm / min, overlap rate of 38-42%, and defocus amount of +5mm.

7. The preparation method according to claim 1, characterized in that: The metal substrate material is a steel material, and the steel material includes Q235 stainless steel, 304 stainless steel, 316L stainless steel or E690 steel.

8. The tungsten carbide composite coating prepared by the preparation method according to any one of claims 1 to 7 comprises a high entropy alloy matrix and tungsten carbide particles, chromium carbide and chromium element distributed in the high entropy alloy matrix.

9. The tungsten carbide composite coating according to claim 8, characterized in that: The thickness of the tungsten carbide composite coating is 0.9-1.1 mm.

10. Use of the tungsten carbide composite coating according to claim 8 or 9 in ship steel or dock steel.