CN113755835A

CN113755835A - Wear-resistant coating and preparation method thereof

Info

Publication number: CN113755835A
Application number: CN202110864518.XA
Authority: CN
Inventors: 刘照云; 陈宇秋; 王灜川; 肖双; 彭梦琪
Original assignee: Shenzhen Aerospace Technology & Innovation Industrial Co ltd
Current assignee: Shenzhen Aerospace Technology & Innovation Industrial Co ltd; Aerospace Science and Industry Shenzhen Group Co Ltd
Priority date: 2021-07-29
Filing date: 2021-07-29
Publication date: 2021-12-07

Abstract

The invention relates to the technical field of alloy material processing, in particular to a wear-resistant coating and a preparation method thereof. The preparation method comprises the following steps: using WC-Co alloy as a main raw material, and preparing WC-Co powder by adopting an arc micro-explosion powder preparation method; mixing the WC-Co powder, the Ni powder and a fluxing agent to prepare mixed powder; covering the mixed powder on the surface of a substrate, and processing the mixed powder by adopting a heat source cladding method to prepare the wear-resistant coating. According to the invention, firstly, alloy elements are designed, alloy element combination beneficial to increasing the wear resistance of the coating is obtained, then WC-Co powder is prepared by arc micro-explosion according to the related alloy elements, and compared with the method of independently adding WC powder and Co powder, the coating has higher hardness and better wear resistance.

Description

Wear-resistant coating and preparation method thereof

Technical Field

The invention relates to the technical field of alloy material processing, in particular to a wear-resistant coating and a preparation method thereof.

Background

The wear-resistant coating is prepared on the surface of the mechanical part, so that the wear resistance of the part can be improved, and the service life and reliability of mechanical equipment can be improved. Meanwhile, the alloy is a solid product with metal property, which is obtained by mixing and melting one metal and another metal or nonmetal powder, cooling and solidifying. The final performance of the wear-resistant alloy is determined by the combined action of various elements, and the wear resistance of the alloy can be better by designing the combination of various elements and components, so that the formation of the wear-resistant alloy coating on the surface of a part is a popular research subject.

At present, the method for forming the wear-resistant alloy coating on the surface of the part, which is commonly used in the market, mainly comprises the following steps: physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), thermal spraying, bead welding, and the like. Particularly, the application of the thermal spraying method is the most extensive, the thermal spraying method can be used for coating, strengthening and repairing various universal mechanical parts in various industrial fields, such as various shafts, valves, fans and the like, and remarkable social and economic benefits are obtained. With the technological progress, new thermal spraying means such as supersonic flame spraying, supersonic plasma spraying and other methods are continuously developed, and the application fields are necessarily wider, and the method is further developed in various fields such as steel, petroleum, chemical engineering, automobiles, machinery, printing, food machinery and the like.

However, the thermal spraying method has certain disadvantages, and the requirement of the technique on alloy powder is high, and if the powder quality is poor and hollow balls are formed, holes appear after spray welding. Furthermore, painting machinery is of a wide variety, and some components typically undergo different forms of mechanical movement during their operation. Some relative motion occurs during the spraying process to generate friction, which not only consumes energy but also generates a large amount of heat, and causes parts of the spraying equipment to be worn to different degrees, even leading to premature failure.

The heat source cladding is a surface modification method different from thermal spraying, alloy powder is cladded on the surface of a substrate by utilizing a heat source with high energy density, and the heat source cladding can be used for preparing a wear-resistant alloy coating. However, when a heat source cladding method is adopted to process a material containing WC alloy powder, the WC alloy powder needs to be mixed with other powder, and the mixed powder containing WC alloy powder has the problem of uneven component distribution in the cladding process; meanwhile, because the melting point of the WC alloy powder is high, the WC alloy powder is generally prepared by a chemical method, the self sphericity of the WC alloy powder is poor, the thickness of mixed powder laying is uneven in the cladding process, and the two uneven phenomena can generate adverse effects on the wear resistance and hardness of a final product.

Disclosure of Invention

Based on the method, the invention provides a preparation method of a wear-resistant coating, which solves the problems of uneven component distribution and uneven powder laying thickness when mixed powder containing WC alloy powder is subjected to cladding processing by adopting a heat source, and the prepared coating has better wear resistance and hardness.

The technical scheme is as follows:

a preparation method of a wear-resistant coating comprises the following steps:

using WC-Co alloy as a main raw material, and preparing WC-Co powder by adopting an arc micro-explosion powder preparation method;

mixing the WC-Co powder, the Ni powder and a fluxing agent to prepare mixed powder;

covering the mixed powder on the surface of a substrate, and processing the mixed powder by adopting a heat source cladding method to prepare the wear-resistant coating.

In one embodiment, the mass ratio of the WC-Co powder to the Ni powder to the fluxing agent is (10-45): (40-80): (2-10).

In one embodiment, the mass ratio of the WC-Co powder to the Ni powder to the fluxing agent is (15-35): (50-70): (4-8).

In one embodiment, the method for preparing WC-Co powder by adopting electric arc micro-explosion powder preparation comprises the following steps:

electrically connecting an electrode and the WC-Co alloy with two poles of a power supply respectively, generating arc plasma in a discharge gap of the electrode and the WC-Co alloy, enabling the surface of the WC-Co alloy to be partially melted by the arc plasma to form a melting zone, simultaneously causing the working form of the arc plasma to be changed, enabling the melting zone to generate micro explosion, crushing and throwing away materials in the melting zone, and collecting WC-Co powder.

In one embodiment, the WC-Co powder has a particle size of 100 mesh to 400 mesh.

In one embodiment, the WC-Co alloy has a WC to Co mass ratio of (5-10): 1.

In one embodiment, the flux is Si powder and/or B powder.

In one embodiment, the heat source in the heat source cladding is laser, plasma or electron beam.

In one embodiment, the step of coating the mixed powder on the surface of the substrate includes:

forming a nickel layer on the surface of the substrate;

covering the mixed powder on the nickel layer.

The invention also provides a wear-resistant coating prepared by the preparation method.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, firstly, alloy elements are designed to obtain alloy element combination beneficial to increasing the wear resistance of a coating, then, according to the related alloy elements, WC-Co powder is prepared through arc micro-explosion, compared with the WC powder and Co powder which are independently added, the WC-CO alloy powder prepared through arc micro-explosion is prepared through single spherical powder, the single spherical powder is pre-alloyed powder, and after the pre-alloyed powder is mixed with Ni powder and a fluxing agent, all components of the mixed powder are uniformly distributed in the hot melting and cladding process, and no segregation is generated. Moreover, the WC-CO alloy powder prepared by the electric arc micro-explosion is spherical and has high sphericity, and when the mixed powder is spread, the spreading thickness is uniform, so that the coating with good wear resistance and high hardness is finally prepared.

Detailed Description

The present invention will be described in further detail with reference to specific examples. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Term(s) for

Unless otherwise stated or contradicted, terms or phrases used herein have the following meanings:

as used herein, the term "and/or", "and/or" includes any one of two or more of the associated listed items, as well as any and all combinations of the associated listed items, including any two of the associated listed items, any more of the associated listed items, or all combinations of the associated listed items.

As used herein, "one or more" means any one, any two, or any two or more of the listed items. Wherein, the 'several' means any two or more than any two.

In the present invention, the terms "first", "second", "third", "fourth", "first type", "second type", "first segment", "second segment", etc. in the terms "first", "second", "third", "fourth", "first segment", "second segment", etc. are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity, nor is it to be construed as implying that importance or quantity is indicative of the technical features being indicated. Also, "first," "second," "third," "fourth," etc. are used for non-exhaustive enumeration of description purposes only and should not be construed as a closed limitation to the number.

Herein, "preferred" merely describes a more effective embodiment or example, and it should be understood that the scope of the present invention is not limited thereto.

In the present invention, the technical features described in the open type include a closed technical solution composed of the listed features, and also include an open technical solution including the listed features.

In the present invention, the numerical range is defined to include both end points of the numerical range unless otherwise specified.

The percentage contents referred to in the present invention mean, unless otherwise specified, mass percentages for solid-liquid mixing and solid-solid phase mixing, and volume percentages for liquid-liquid phase mixing.

The temperature parameter in the present invention is not particularly limited, and may be a constant temperature treatment or a treatment within a certain temperature range. The constant temperature process allows the temperature to fluctuate within the accuracy of the instrument control.

The heat source cladding is a surface modification method different from thermal spraying, alloy powder is cladded on the surface of a substrate by utilizing a heat source with high energy density, and the heat source cladding can be used for preparing a wear-resistant alloy coating. However, when a material containing tungsten-based alloy powder is processed by adopting a heat source cladding method, the tungsten-based alloy powder and other powder need to be mixed, and the mixed powder containing the tungsten-based alloy powder has the problem of uneven component distribution in the cladding process; meanwhile, because the tungsten-based alloy powder has a high melting point and is generally prepared by a chemical method, the tungsten-based alloy powder has poor self-sphericity, the thickness of mixed powder laying is uneven in the cladding process, and the two uneven phenomena can generate adverse effects on the wear resistance and hardness of a final product.

Based on the method, the invention provides a preparation method of the wear-resistant coating.

The technical scheme is as follows:

a preparation method of a wear-resistant coating comprises the following steps:

According to the invention, firstly, alloy elements are designed to obtain alloy element combination beneficial to increasing the wear resistance of a coating, then, according to the related alloy elements, WC-Co powder is prepared through arc micro-explosion, compared with the WC powder and Co powder which are independently added, the WC-CO alloy powder prepared through arc micro-explosion is prepared through single spherical powder, the single spherical powder is pre-alloyed powder, and after the pre-alloyed powder is mixed with Ni powder and a fluxing agent, all components of the mixed powder are uniformly distributed in the hot melting and cladding process, and no segregation is generated. Moreover, the WC-CO alloy powder prepared by the electric arc micro-explosion is spherical and has high sphericity, and when the mixed powder is spread, the spreading thickness is uniform, so that the coating with better wear resistance and higher hardness is finally prepared.

The content of each element in the wear-resistant coating is optimized, and the wear resistance of the coating is improved.

In a more preferred embodiment, the ratio of (15-35) of the WC-Co powder, the Ni powder and the flux is: (50-70): (4-8).

It is understood that the mass ratio of W, C to Co in the WC-Co powder is consistent with the mass ratio of W, C to Co in the WC-Co alloy.

In one embodiment, the WC-Co powder has a particle size of 100 mesh to 400 mesh. The WC-Co powder has good sphericity.

In one embodiment, the WC-Co alloy has a WC to Co mass ratio of (5-10): 1.

In one embodiment, WC has W and C in a 1:1 molar ratio.

The electrodes and the WC-Co alloy are electrically connected to the two poles of a power source, respectively, it being understood that the electrodes are connected to the anode of the power source and the WC-Co alloy is connected to the cathode of the power source. It is also understood that the electrode is connected to the cathode of the power source and the WC-Co alloy is connected to the anode of the power source.

When the electrode is connected to the anode of a power source, the power source drives the electrode to rotate. At this time, the electrode is provided with a hollow cavity. Some or all of the fluid medium is introduced from within the hollow cavity of the electrode. That is, the fluid medium may be introduced entirely from the hollow cavity of the electrode, or may be introduced partially from the hollow cavity of the electrode and partially from outside the hollow cavity of the electrode, including flowing along the outer surface of the electrode toward the WC-Co alloy, thereby being introduced into the discharge gap between the electrode and the WC-Co alloy, and including being introduced into the gap between the electrode and the alloy ingot by other means.

It will be appreciated that the fluid media flowing from within the hollow cavity and from outside the hollow cavity may be the same fluid media or different fluid media.

In a preferred embodiment, the fluid medium is a water-based medium and/or an inert gas, the inert gas comprising nitrogen.

In a preferred embodiment, the water-based medium is distilled water.

It is understood that the electrode provided with a hollow cavity is an electrode provided with a single tube, multiple tubes and hollow nests.

When the WC-Co alloy is connected to the anode of a power source, the power source drives the WC-Co alloy to rotate. At this time, the WC — Co alloy was provided with a hollow cavity. Some or all of the fluid medium is introduced from within the hollow cavity of the WC-Co alloy. That is, the fluid medium may be introduced entirely from the hollow cavity of the WC-Co alloy, or may be introduced partially from the hollow cavity of the WC-Co alloy and the remainder from outside the hollow cavity of the WC-Co alloy, including flowing along the outer surface of the WC-Co alloy toward the electrode, thereby being introduced into the discharge gap between the WC-Co alloy and the electrode, and including being introduced into the gap between the WC-Co alloy and the electrode by other means.

In a preferred embodiment, the water-based medium is distilled water.

Preferably, the electrode is a single element electrode, the element of which is W, C or Co.

Preferably, the electrode is an alloy electrode, the elements of which are W, C and Co.

It will be appreciated that the power supply is a pulsed power supply, with a pulse width of 2 mus-200000 mus and a pulse interval of 2 mus-200000 mus. Adjusting the gap between the electrode and the WC-Co alloy to generate arc plasma, wherein the discharge gap, namely the distance between the discharge end of the electrode and the surface of the WC-Co alloy is preferably 0.1mm-100 mm. This distance allows the arc plasma to act on the electrode and the WC — Co alloy and ensures a high pressure when the fluid medium passes through. The central temperature of the arc plasma is as high as 10000K, most of alloy can be melted, the WC-Co alloy surface is melted under the action of the arc plasma, a tiny melting pit with the radius range of 0.5mm-2mm, namely a melting area is formed, and at the moment, the electrode does high-speed rotation mechanical motion relative to the WC-Co alloy.

Preferably, the power supply parameters of the power supply further include: the gap voltage is 10-160V, and the discharge current is 5A-1000A.

When the electrode is connected with the anode of the power supply, the electrode is preferably controlled to rotate at a speed of 100r/min-6000 r/min.

When the WC-Co alloy is connected to the anode of the power source, the electrode is preferably controlled to rotate at a speed of 100r/min to 6000 r/min.

A fluid medium is introduced between the electrode and the WC-Co alloy while the power source is activated. The working state of the arc plasma can be changed by controlling the relative rotating speed of the electrode or the WC-Co alloy and the flow rate of the fluid medium, micro explosion is generated in a melting zone, the material in the melting zone is crushed and thrown away, and then the material is rapidly condensed into spherical WC-Co powder in the fluid medium.

Preferably, the flow rate at which the fluid medium is initially introduced is 0.5L/min to 500L/min.

The heat source cladding is to coat the alloy powder to be clad on the surface of a matrix in advance, then to scan the surface of the alloy precoat by adopting a heat source, and the surface of the precoat absorbs energy, and the temperature rises and is melted. Meanwhile, surface heat is transferred to the inside through heat conduction, so that the whole alloy pre-coating layer and a part of the matrix are melted, and after a heat source is separated, the melted metal is rapidly solidified on the surface of the matrix to form an alloy cladding layer, namely the wear-resistant alloy coating. The wear-resistant coating formed by the method has high bonding strength with the substrate, better compatibility and bonding property between the wear-resistant coating and the substrate, and high strength and wear resistance of the coating.

In one embodiment, the heat source in the heat source cladding is laser, plasma or electron beam. When the heat source is laser, the laser cladding is performed, and when the heat source is plasma, the plasma cladding is performed.

In one embodiment, the flux is Si powder and/or B powder.

Boron and silicon can lower the melting point of the alloy and act as slag-forming to avoid oxidation.

In one embodiment, the process parameters of heat source cladding include: welding current is 90A-120A, welding speed is 120mm/min-140mm/min, powder feeding amount is 30g/min-45g/min, and swing width is 11mm-17 mm.

The WC-Co powder, Ni powder and flux were mixed until the components were uniform.

In one embodiment, the thickness of the mixed powder coating is 2mm to 5 mm.

forming a nickel layer on the surface of the substrate;

covering the mixed powder on the nickel layer.

The nickel layer is formed in advance, so that the wettability between the surface of the substrate and the wear-resistant coating can be improved.

Alternatively, the nickel layer can be formed on the substrate by heat source cladding.

In one embodiment, Ni powder is covered on the surface of a substrate, and the nickel powder is processed by adopting a heat source cladding method to prepare a nickel layer.

In one embodiment, the Ni powder coating has a thickness of 1mm to 3 mm.

It is understood that the present invention also includes the conventional pre-treatment operations of cleaning, desmutting and blasting the substrate before covering the mixed powder or the Ni powder.

The invention also provides a wear-resistant coating prepared by the preparation method. The coating has excellent wear resistance.

The following examples and comparative examples are further described below, and the starting materials used in the following examples can be commercially available, unless otherwise specified, and the equipment used therein can be commercially available, unless otherwise specified.

Example 1

The embodiment provides a wear-resistant coating and a preparation method thereof, and the preparation method comprises the following steps:

1) preparation of WC-Co powder

A WC — Co alloy in which WC and Co are present in a mass ratio of 5:1 and W and C are present in a molar ratio of 1:1 was taken and electrically connected to the negative electrode of a power source. The graphite electrode provided with the single tube is electrically connected with the positive electrode of the power supply.

The power supply is a pulse power supply, and power supply parameters are set as follows: 60V, the discharge current is 600A, a power supply is started, an electrode rotates around a main shaft at the rotation speed of 4000r/min for 360 degrees, the distance between the electrode and the WC-Co alloy is adjusted to be 1mm through a motion control system, high-energy arc plasma is generated in a discharge gap between the electrode and the WC-Co alloy, the arc plasma acts on the WC-Co alloy, a part of the WC-Co alloy is melted by high energy to form a melting zone, meanwhile, distilled water is introduced from a hollow cavity of the electrode and flows to the WC-Co alloy, the flow rate is 50L/min when the distilled water is introduced, the working form of the arc plasma in the discharge gap is changed under the action of the rotating electrode and the distilled water flow field, the melting zone is observed to generate tiny explosion, materials in the melting zone are crushed and thrown away, and finally the materials in the melting zone are condensed into WC-Co powder in the distilled water.

2) Preparation of the Mixed powder

Weighing the following components in percentage by mass: 30% WC-Co powder, 65% Ni powder and 5% Si powder (Co-solvent).

Mixing the above powders for 2h to obtain mixed powder.

3) Preparation of wear-resistant coatings

Q235/45# steel is used as a matrix, and is subjected to pretreatment of cleaning, decontamination and sand blasting.

Covering Ni powder on the pre-processed substrate with the thickness of 3mm to form a first pre-coating layer, scanning the surface of the first pre-coating layer by using laser, wherein the welding current is changed within 100-110A, the welding speed is 120mm/min, the powder feeding amount is 30g/min, the swing width is 11mm, and the Ni powder of the first pre-coating layer absorbs energy, rises in temperature and is melted. Meanwhile, surface heat is transferred to the inside through heat conduction, so that the whole first pre-coating layer and a part of the substrate are melted, the laser is removed, and the melted Ni is rapidly solidified on the surface of the substrate to form a nickel layer.

Covering the mixed powder prepared in the step 2) on a nickel layer with the covering thickness of 2mm to form a second pre-coating layer, then scanning the surface of the second pre-coating layer by adopting laser, wherein the welding current is changed within 100-110A, the welding speed is 120mm/min, the powder feeding amount is 30g/min, the swing width is 11mm, and the temperature of the second pre-coating layer gold powder is increased and melted by absorbing energy. Meanwhile, surface heat is transferred to the inside through heat conduction, so that the whole second pre-coating layer and a part of the nickel layer are melted, the laser is removed, and the melted alloy is rapidly solidified on the surface of the nickel layer to form the wear-resistant coating.

Example 2

This example provides a wear-resistant coating and a method for producing the same, and is different from example 1 mainly in the mass ratio of each element of the mixed powder. The method comprises the following steps:

1) preparation of WC-Co powder

Taking a WC-Co alloy, wherein the mass ratio of WC to Co is 5:1, the molar ratio of W to C is 1:1, electrically connected to the negative pole of the power supply. The graphite electrode provided with the single tube is electrically connected with the positive electrode of the power supply.

2) Preparation of the Mixed powder

Weighing the following components in percentage by mass: 10% WC-Co powder, 80% Ni powder and 10% Si powder (Co-solvent).

Mixing the above powders for 2h to obtain mixed powder.

3) Preparation of wear-resistant coatings

And carrying out pretreatment of cleaning, decontaminating and sand blasting on the substrate.

Example 3

This example provides a wear-resistant coating and a method for preparing the same, which is mainly different from example 1 in that there is no nickel layer and the steps are as follows:

1) preparation of WC-Co powder

2) Preparation of the Mixed powder

Mixing the above powders for 2h to obtain mixed powder.

3) Preparation of wear-resistant coatings

Covering the mixed powder on the substrate after the pretreatment with the covering thickness of 3mm to form a pre-coating layer, scanning the surface of the pre-coating layer by adopting laser, changing the welding current in 100-110A, ensuring that the welding speed is 120mm/min, the powder feeding amount is 30g/min, the swing width is 11mm, and ensuring that the pre-coating layer gold powder absorbs energy and the temperature rises and is melted. Meanwhile, surface heat is transferred to the inside through heat conduction, so that the whole second pre-coating layer and a part of the substrate are melted, the laser is removed, and the melted alloy is rapidly solidified on the surface of the substrate to form the wear-resistant coating.

Comparative example 1

1) Preparation of the Mixed powder

Weighing the following components in percentage by mass: 25% WC powder, 5% Co powder, 65% Ni powder and 5% Si powder (Co-solvent).

Mixing the above powders for 2h to obtain mixed powder.

2) Preparation of wear-resistant coatings

The coatings of examples 1-3 and comparative example 1 were tested for hardness using a rockwell hardness tester and the results are shown: compared with the comparative example 1, the hardness value of the wear-resistant coating is improved by 10 percent in the example 1, the hardness value of the wear-resistant coating is improved by 15 percent in the example 2, the hardness value of the wear-resistant coating is improved by 12 percent in the example 3, and the hardness is increased, which indicates that the wear resistance of the wear-resistant coating is more excellent.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The preparation method of the wear-resistant coating is characterized by comprising the following steps:

2. The method for preparing the wear-resistant coating according to claim 1, wherein the mass ratio of the WC-Co powder to the Ni powder to the fluxing agent is (10-45): (40-80): (2-10).

3. The method for preparing the wear-resistant coating according to claim 1, wherein the mass ratio of the WC-Co powder to the Ni powder to the fluxing agent is (15-35): (50-70): (4-8).

4. The method for preparing the wear-resistant coating according to claim 1, wherein the WC-Co powder is prepared by an arc micro-explosion powder preparation method, and the method comprises the following steps:

5. The method of preparing a wear resistant coating according to claim 4, wherein the WC-Co powder has a particle size of 100 mesh to 400 mesh.

6. The method for preparing a wear-resistant coating according to claim 1, wherein the mass ratio of WC to Co in the WC-Co alloy is (5-10): 1.

7. The method of producing a wear resistant coating according to any of claims 1-6, characterized in that the fluxing agent is Si powder and/or B powder.

8. The method for preparing a wear resistant coating according to any one of claims 1-6, wherein the heat source in the heat source cladding is a laser, a plasma or an electron beam.

9. The method for preparing a wear resistant coating according to any of claims 1-6, wherein the step of covering the surface of the substrate with the mixed powder comprises:

forming a nickel layer on the surface of the substrate;

covering the mixed powder on the nickel layer.

10. An abrasion-resistant coating produced by the production method described in any one of claims 1 to 9.