Preparation and application of cold spraying wear-resistant copper-based coating

Abstract

The invention discloses a preparation method of a cold-sprayed wear-resistant copper-based coating. The preparation method comprises the following steps that firstly, pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder are mixed and sprayed on the surface of a steel substrate through supersonic speed cold spraying, and a braze coating prefabricated layer is obtained; wherein the mass of the WC-Co composite powder is m, the total mass of the powder forming the brazing coating prefabricated layer is M, and m / M is larger than or equal to 0.5; secondly, heating brazing is conducted, a wear-resistant coating is formed, and the wear-resistant coating comprises Cu-P-Sn brazing filler metal and WC-Co which is dispersed in the Cu-P-Sn brazing filler metal and serves as wear-resistant mass points; the invention further discloses application of the prepared copper-based coating, WC-Co composite powder and Cu3P eutectic powder are introduced to the surface of a steel substrate in a cold spraying mode to form a compact layer, then a wear-resistant layer with wear-resistant particles is formed in a brazing mode, and the wear resistance is enhanced while the steel substrate is prevented from being oxidized.

Description

Technical Field

[0001] The invention relates to the technical field of wear-resistant coatings, and in particular to the preparation and application of a cold-sprayed wear-resistant copper-based coating. Background Art

[0002] In modern industrial production, in order to improve the performance of parts, especially wear resistance, corrosion resistance, and fatigue resistance, it is necessary to use hard materials to coat certain parts of soft base parts into parts with wear-resistant surfaces, in order to achieve the goal of meeting various performance requirements, saving precious materials, and reducing production costs.

[0003] Wear-resistant coating parts are widely used in engineering machinery and equipment, loading and unloading machinery and equipment, construction machinery and equipment, metallurgical machinery and equipment, mining machinery and equipment and other machinery and equipment such as sand mill barrels, blades, various port machinery wear-resistant parts, bearing structures, etc., and have broad practical application prospects.

[0004] The Chinese invention patent application with publication number CN117403227A discloses a wear-resistant coating for a plowshare tip and a wear-resistant strengthening method thereof. The coating components include 7% to 11% diamond powder by mass and the rest is nickel-based solder. The wear-resistant strengthening method for the plowshare tip is grinding, pre-treatment, loading 14% to 22% diamond powder and nickel-based solder by mass into a mixer and mixing for 2.5 hours before taking them out, using a binder to prepare the two mixed powders into a paste, applying the paste in step S3 on the plowshare tip, the coating thickness is 0.6 to 1 mm, and the coated plowshare tip is dried, preheated, heat treated, and vacuum heat treated. The wear-resistant coating prepared by the present invention has high hardness and corrosion resistance, but the construction process is relatively complicated and is not suitable for coatings with larger thicknesses. Summary of the invention

[0005] The purpose of the present invention is to provide a cold-sprayed wear-resistant copper-based coating. The present invention uses cold spraying to introduce WC-Co composite powder and Cu3P eutectic powder into the surface of a steel substrate to form a dense layer, and then forms a wear-resistant layer with wear-resistant particles by brazing, thereby preventing oxidation of the steel substrate and enhancing the wear resistance.

[0006] To solve this technical problem, the technical solution of the present invention is: a method for preparing a cold spray wear-resistant copper-based coating, comprising the following steps:

[0007] Step 1: Pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder are mixed and sprayed on the surface of the steel substrate by supersonic cold spraying to obtain a brazing coating prefabricated layer;

[0008] Wherein, the mass of WC-Co composite powder is m, and the total mass of powder forming the brazing coating prefabricated layer is M, wherein m / M≥0.5;

[0009] Step 2: heating and brazing to form a wear-resistant coating, wherein the wear-resistant coating comprises a low-melting-point Cu-P-Sn brazing material and WC-Co dispersed in the Cu-P-Sn brazing material as wear-resistant particles.

[0010] Preferably, the total mass of the pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder in the brazing pre-layer formed by cold spraying is 100 parts, wherein the mass fraction of each component is as follows:

[0011]

[0012] The mass ratio of WC and Co in the preferred WC-Co composite powder is (8.5 to 9.5): 1. Pure Cu powder, Cu3P copper-phosphorus eutectic powder, Sn powder, and WC-Co composite powder are mixed uniformly in a mixer in proportion, canned in a mixed powder tank of a supersonic cold spraying device, and the corundum for sandblasting surface treatment is loaded into the sandblasting tank. First, the Q345 steel to be brazed is sandblasted, and at this time, a high-speed airflow flows through the sandblasting tank, and the corundum is blown out at a high speed to mechanically clean the surface of the Q345 steel. After cleaning, the high-speed gas is switched to a supersonic airflow, which flows through the mixed powder tank. The uniformly mixed brazing material powder and WC-Co composite powder flow out of the spray gun in the form of a high-speed airflow under the action of the high-speed airflow to impact the Q345 steel substrate, and finally a pre-set brazing coating with a certain bonding strength is formed on the surface of the Q345 steel substrate and the surface of the substrate. The supersonic cold spraying equipment successively combines the sandblasting surface treatment and the pre-set brazing coating.

[0013] Preferably, the mass ratio of WC to Co in the WC-Co composite powder is 9:1.

[0014] Another object of the present invention is to provide an application of a cold-sprayed wear-resistant copper-based coating brazed on the surface of a steel substrate to obtain a wear-resistant layer. The present invention uses cold spraying to introduce WC-Co composite powder and Cu3P eutectic powder into the surface of the steel substrate to form a dense layer, and then brazing is used to form a wear-resistant layer with wear-resistant particles, thereby preventing oxidation of the steel substrate and enhancing the wear resistance.

[0015] To solve this technical problem, the technical solution of the present invention is: an application of brazing the copper-based coating of the present invention on the surface of a steel substrate to obtain a wear-resistant layer, comprising the following steps:

[0016] S1. Surface sandblasting treatment of the steel substrate to be brazed;

[0017] S2, placing the cold sprayed wear-resistant copper-based coating brazing material on the surface of the steel substrate after S1 to form a brazing coating;

[0018] S3. Brazing to obtain a copper-based wear-resistant layer.

[0019] The optimal process parameters for cold spraying are as follows:

[0020]

[0021] The present invention controls the working pressure, powder feeding rate, spray distance and spray angle of supersonic compressed gas, accurately controls the thickness of the brazing material layer, and requires the brazing coating layer to have a density higher than 95%. The brazing material layer is free of oxidation, phase change and ablation. The cross section of the brazing material particle flow sprayed by cold spraying is small and narrow, and has good directivity, and can be sprayed on the brazing material layer on the local surface of the material to be welded.

[0022] Preferably, the brazing temperature in S3 is 695° C. to 705° C., and the brazing time is 8 min to 15 min.

[0023] The preferred thickness of the copper-based wear-resistant layer is 1 mm to 10 mm. The present invention can continuously control the thickness of the copper-based wear-resistant layer, which is tightly combined with the steel substrate, and the density of the brazing coating exceeds 95%.

[0024] Preferably, the steel matrix is ​​Q345 steel.

[0025] By adopting the above technical solution, the beneficial effects of the present invention are:

[0026] The present invention adopts pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder to form a brazing coating including low-melting-point Cu-P-Sn brazing filler metal and high-melting-point WC-Co wear-resistant particles. The Cu-based brazing filler metal has excellent plasticity, thermal conductivity, electrical conductivity and corrosion resistance, and is very suitable as a low-melting-point component of the brazing coating. Pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder are mixed and cold sprayed on the surface of a steel substrate to form a tight bond with the steel substrate. At the same time, the particle impact in the cold spraying enhances the diffusion of the brazing coating pre-layer and the Fe coating in the steel substrate, making it easy to form a diffusion bonding interface. P is added in the form of Cu3P eutectic powder, and with subsequent welding, while effectively ensuring safety, the melting characteristics and spreading performance of the Cu-P-Sn brazing filler metal are improved, and the microstructure performance of the brazing coating layer is improved. After welding, a brazing coating layer of low-melting-point Cu-P-Sn brazing filler metal and high-melting-point WC-Co wear-resistant particles are formed. The present invention uses a method in which the melting point of the Cu-P-Sn brazing filler metal is controlled below 670°C, and pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder are evenly mixed and supersonic sprayed onto a steel substrate to form a brazing coating layer, thereby solving the problem that Cu3P and WC-Co composite powders are not easy to be processed by traditional brazing coating. The present invention also utilizes the self-brazing effect of the P element to reduce the amount of brazing flux used in the subsequent furnace. The WC-Co composite powder takes into account the high hardness of WC and the toughness of Co, so that the wear resistance, corrosion resistance and interface bonding strength of the joint are further improved.

[0027] The cold spray powder of the present invention is added with P element in the form of Cu3P powder and WC in the form of WC-Co composite powder, which solves the problem that Cu3P and WC are brittle and difficult to be processed into brazing coating by traditional brazing coating. While improving the quality of brazing coating, it can also complete the automatic brazing coating of specific areas of complex workpieces.

[0028] The melting point of the pre-set solder layer of the present invention should be lower than 670°C, and the melting temperature range should be small; when the solder melts, it should have good fluidity, be able to timely wet and tightly combine the WC-Co wear-resistant particles, and the WC-Co wear-resistant particles in the wear-resistant coating and the Cu-P-Sn alloy achieve effective interface bonding, and the macroscopic performance is that the hardness of the obtained solder coating is higher than 1500HV, the bonding strength of the solder coating is higher than 260MPa, and the density is higher than 95%. Compared with the traditional coating layer, the solder coating thickness is larger and continuously controllable. DETAILED DESCRIPTION

[0029] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0030] Example 1

[0031] The invention discloses a method for preparing a cold spray wear-resistant copper-based coating, comprising the following steps:

[0032] Step 1: Pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder are mixed and sprayed on the surface of the steel substrate by supersonic cold spraying to obtain a brazing coating prefabricated layer;

[0033] Wherein, the mass of WC-Co composite powder is m, and the total mass of powder forming the brazing coating prefabricated layer is M, wherein m / M≥0.5;

[0034] Step 2: heating and brazing to form a wear-resistant coating, wherein the wear-resistant coating comprises a low-melting-point Cu-P-Sn brazing material and WC-Co dispersed in the Cu-P-Sn brazing material as wear-resistant particles.

[0035] In this embodiment, the total mass of the pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder in the brazing pre-layer formed by cold spraying is calculated as 100 parts, and the mass fraction of each component is shown in Table 1;

[0036] This embodiment also discloses an application of brazing the copper-based coating prepared by the present invention on the surface of a Q345 steel substrate to prepare a wear-resistant layer, comprising the following steps:

[0037] S1. Surface sandblasting treatment of the steel substrate to be brazed;

[0038] S2, placing the cold sprayed wear-resistant copper-based coating brazing material on the surface of the steel substrate after S1 to form a brazing coating. The specific process parameters are shown in Table 2;

[0039] S3. Brazing. The specific process parameters are shown in Table 2. A copper-based wear-resistant layer is obtained. The specific thickness is shown in Table 2.

[0040] The process parameters of cold spraying in this embodiment are shown in Table 2:

[0041] The brazing temperature in S3 is 695° C. to 705° C.; the brazing time is 8 min to 15 min.

[0042] Example 2

[0043] The main differences between this embodiment and embodiment 1 are shown in Table 1 and Table 2.

[0044] Example 3

[0045] The main differences between this embodiment and embodiment 1 are shown in Table 1 and Table 2.

[0046] Example 4

[0047] The main differences between this embodiment and embodiment 1 are shown in Table 1 and Table 2.

[0048] Comparative Example

[0049] This comparative example discloses that an equal amount of powder as in Example 3 is placed on the surface of a Q345 steel substrate that has been sandblasted in the same manner as in Example 3, and ethanol and paste are applied to the surface of a steel substrate in an area equal to that in Example 1 and then dried; the steel substrate pre-prepared with a brazing material coating is brazed at 695°C for 8 minutes, taken out and cooled to room temperature, to obtain a copper-based wear-resistant coating on the surface of the steel substrate.

[0050] Table 1 Composition and mass fraction of solder coating of Examples 1 to 4

[0051] project Cu powder <![CDATA[Cu3P]]> Sn WC-Co mWC:mCo Example 1 35 5 4 56 8.5:1 Example 2 38 8 2 52 9.0:1 Example 3 38 6 3 53 9.5:1 Example 4 40 7 3 50 9.0:1 Comparative Example 38 6 3 53 9.5:1

[0052] Table 2 Process parameters for preparing wear-resistant coatings in Examples 1 to 4

[0053] project Example 1 Example 2 Example 3 Example 4 Work Pressure 0.6Mpa 0.7Mpa 0.8Mpa 0.6Mpa Powder feeding rate 15g / min 22g / min 25g / min 20g / min Spray distance 15mm 20mm 20mm 30mm Spray Angle 30° 20° 30° 30° Density 96％ 98％ 97％ 96％ Brazing temperature 695℃ 700℃ 705℃ 705℃ Brazing time 8min 15min 10min 10min Coating thickness 3.2mm 9.5mm 7.6mm 5.8mm

[0054] Table 3 Performance indicators of wear-resistant coatings obtained in Examples 1 to 4 and Comparative Examples

[0055] project Coating hardness Bonding strength Pitting potential Example 1 1550HV 262MPa 329mV Example 2 1686HV 298MPa 346mV Example 3 1654HV 287MPa 340mV Example 4 1611HV 273MPa 333mV Comparative Example 526HV 201MPa 301mV

[0056] The invention uses Q345 steel as a base material, pre-sets a brazing material and a wear-resistant particle layer which are closely combined with the base by supersonic cold spraying on the Q345 steel coating layer after the surface treatment before welding, adopts a furnace heating brazing method under the condition that vacuum brazing equipment is not required, melts the brazing material part in the pre-set coating layer, realizes a brazing coating in which a low-melting-point copper-based brazing material and a high-melting-point WC-Co are dispersedly distributed and closely combined with the base, and meets the requirements of automatic and intelligent brazing coating preparation; through the ratio of copper-based brazing material components and wear-resistant WC-Co, and by utilizing the continuous and adjustable dispersion distribution effect of WC-Co in the brazing material, the wear resistance and corrosion resistance of the brazing coating are further improved.

[0057] In order to overcome the surface oxidation of Q345 steel before brazing coating, the present invention adopts surface sandblasting treatment, and then pre-sets the cold spraying process to block the brazing material and WC-Co powder particles from air to prevent the surface oxidation of Q345 steel; improves the brazing coating interface bonding strength, and the wear resistance and corrosion resistance of the brazing coating.

[0058] Supersonic cold spraying is a process in which a 20μm to 50μm mixed powder is shot onto a substrate by a supersonic gas-solid two-phase gas flow at room temperature to form a dense layer. Supersonic cold spraying equipment uses compressed gas to generate a supersonic gas flow through a zoom-in type Lava tube, and feeds the brazing powder and WC-Co composite powder that are proportioned and evenly mixed into the supersonic gas flow axially to form a gas-solid two-phase flow. After acceleration, it hits the Q345 steel substrate to be coated in a completely solid state, causing a large plastic deformation and depositing on the surface of the substrate to form a coating layer with a certain bonding strength. Therefore, there is no high-temperature heating in the cold spraying technology, and there is no high-temperature oxidation, gasification, melting, crystallization, and other effects that affect the performance of the brazing coating.

[0059] The thickness of the supersonic cold spray brazing coating can be effectively and accurately controlled. Unlike the high temperature of hot spraying, which produces high stress and thermal deformation, supersonic cold spraying has no oxidation, no phase change, and no ablation. The cross-section of the particle flow sprayed by cold spraying is small and narrow, and has good directionality. It can spray the brazing material layer locally on the surface, which is very suitable for pre-setting the brazing coating in the area to be brazed to eliminate waste. Because the pre-sprayed brazing coating can ensure the quantitative, uniform and stable addition of brazing material and wear-resistant phase, it has the characteristics of simple process, easy operation, no waste of each component and controllable dosage, which meets the needs of efficient, high-quality and clean production. While improving the quality of the brazing coating, it can complete the local automatic brazing coating of specific wear-resistant surfaces of complex workpieces.

[0060] Combined with the data in Table 3, it can be seen that compared with the comparative example, the melting point of the pre-set solder layer of the present invention should be lower than 670°C, and the melting temperature range is smaller; when the solder melts, it should have good fluidity, and be able to wet and tightly combine the WC-Co wear-resistant particles in time; the hardness of the solder coating is higher than 1500HV, the bonding strength of the solder coating is higher than 260MPa, and the solder coating has a density higher than 95%; compared with the traditional coating layer, the solder coating is thicker, continuously controllable and dense, and the corrosion resistance and wear resistance are simultaneously improved.

Claims

1. A method for preparing a cold spray wear-resistant copper-based coating, characterized in that: The following steps are involved: Step 1: Pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder are mixed and sprayed on the surface of the steel substrate by supersonic cold spraying to obtain a brazing coating prefabricated layer; Wherein, the mass of WC-Co composite powder is m, and the total mass of powder forming the brazing coating prefabricated layer is M, wherein m / M≥0.5; Step 2: heating and brazing to form a wear-resistant coating, wherein the wear-resistant coating includes Cu-P-Sn brazing material and WC-Co dispersed in the Cu-P-Sn brazing material as wear-resistant particles.

2. The method for preparing the cold sprayed wear-resistant copper-based coating according to claim 1, characterized in that: The total mass of the pure Cu powder, Cu3P eutectic powder, Sn powder and WC-Co composite powder in the brazing pre-layer formed by cold spraying is calculated as 100 parts, wherein the mass fraction of each component is as follows:

3. The method for preparing the cold sprayed wear-resistant copper-based coating according to claim 1, characterized in that: The mass ratio of WC to Co in the WC-Co composite powder is (8.5 to 9.5):

1.

4. The method for preparing the cold sprayed wear-resistant copper-based coating according to claim 3, characterized in that: The mass ratio of WC to Co in the WC-Co composite powder is 9:

1.

5. An application of brazing the copper-based coating obtained according to any one of claims 1 to 4 on the surface of a steel substrate to obtain a wear-resistant layer, characterized in that: The following steps are involved: S1. Surface sandblasting treatment of the steel substrate to be brazed; S2, placing the cold sprayed wear-resistant copper-based coating brazing material on the surface of the steel substrate after S1 to form a brazing coating; S3. Brazing to obtain a copper-based wear-resistant layer.

6. The use according to claim 5, characterized in that: The process parameters of cold spraying are as follows:

7. The use according to claim 5, characterized in that: The brazing temperature in S3 is 695° C. to 705° C.; the brazing time is 8 min to 15 min.

8. The use according to claim 5, characterized in that: The thickness of the copper-based wear-resistant layer is 1 mm to 10 mm.

9. The use according to claim 5, characterized in that: The steel matrix is ​​Q345 steel.

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