Wear-resistant coating with dispersed and distributed wear-resistant particles and preparation method of wear-resistant coating

Abstract

The invention discloses a method for preparing a wear-resistant coating with dispersively distributed wear-resistant particles, which comprises the following steps: S1, sand blasting to remove an oxide film on the surface of a steel substrate; s2, brazing filler metal mixed particles and wear-resistant particles are evenly mixed and then sprayed to the steel substrate treated in the S1 through supersonic speed cold spraying, the wear-resistant particles are evenly fixed between the brazing filler metal mixed particles, and a compact preset brazing coating is formed; the wear-resistant particles are WC particles; the brazing filler metal mixed particles comprise pure copper powder, a P element added through a compound carrier and Sn powder; s3, heating, melting and wetting the brazing filler metal mixed particles in the preset brazing coating and tightly combining the brazing filler metal mixed particles with the wear-resistant particles; cooling to obtain Cu-P-Sn on which wear-resistant particles are uniformly distributed as a wear-resistant coating; component particles used for preparing the coating are sprayed and compactly preset on the surface of the steel substrate through cold spraying after the oxidation film is removed from the surface of the steel substrate, then the steel substrate and the wear-resistant coating are stably connected in a matched welding mode, and the obtained wear-resistant coating is uniform and stable.

Description

Technical Field

[0001] The invention relates to the technical field of surface treatment, and in particular to a wear-resistant coating with wear-resistant particles dispersed therein and a preparation method thereof. Background Art

[0002] Most of them increase the service life of mechanical equipment by adding a high chromium wear-resistant layer at the key position of the machinery. However, as a common wear-resistant layer, the wear resistance of the high chromium wear-resistant layer needs to be improved, and it is still easy to wear during the construction process. In recent years, tungsten carbide has begun to be used to form a wear-resistant layer on many mechanical equipment. The tungsten carbide wear-resistant layer formed on the working surface of the mechanical equipment can well protect the mechanical equipment and extend the service life of the mechanical equipment by utilizing the high wear resistance of tungsten carbide.

[0003] There are also certain limitations in applying cemented carbide WC to wear-resistant layers. For example, the mechanical properties, especially hardness, of the brazing filler alloy are very different from those of cemented carbide. During work, the brazing seam is often damaged first, and then the entire cemented carbide tool begins to be damaged, and finally it is broken and cannot be used again; secondly, there are great differences in the physical and chemical properties of the brazing filler and cemented carbide. It is easy to generate large stress during the brazing process, so the welding problem of high-quality and large-size cemented carbide has been difficult to solve. The Chinese invention patent application with publication number CN2015101748137 discloses a cemented carbide reinforced with WC particles in situ. By using the perturbation effect of ultrasound, after the brazing filler dissolves the Co matrix in the cemented carbide, the WC particles without Co matrix bonding migrate to the brazing seam to form a brazing seam reinforced with WC particles, thereby greatly improving the mechanical properties of the joint. The invention uses ultrasonic cavitation to remove the oxide film on the surface of cemented carbide and steel, and does not require the use of brazing agents, and can be welded in the atmosphere. However, as a wear-resistant coating with a large area, the addition of WC is not easy to achieve. The Chinese invention patent application with publication number CN111118436A records a Co-based-WC / TiN / TiCN composite coating, which uses supersonic flame spraying and ion source assisted unbalanced magnetron sputtering technology to prepare a Co-based-WC / TiN / TiCN composite coating with low friction coefficient, wear resistance, hardness and impact resistance, which greatly improves the service life of the stamping die. During the spraying process, the molten spray powder hits the die surface, and the exothermic reaction is continuously maintained so that the surface reaches a molten state to form a metallurgical bond, which improves the bonding force between the die and the Co-based-WC coating, but the preparation process is complicated, and the metal substrate may be further oxidized during the preparation process. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a wear-resistant coating with dispersed WC-Co particles. After removing the oxide film from the surface of the steel substrate, the component particles for preparing the coating are sprayed and densely pre-placed on the surface of the steel substrate by cold spraying, and then the steel substrate and the wear-resistant coating are stably connected by welding, so that the obtained wear-resistant coating is uniform and stable.

[0005] To solve this technical problem, the technical solution of the present invention is: a method for preparing a wear-resistant coating with dispersed wear-resistant particles, comprising the following steps:

[0006] S1, sandblasting, to remove the oxide film on the surface of the steel substrate;

[0007] S2, after the mixed solder particles and the wear-resistant particles are evenly mixed, they are supersonic cold sprayed on the steel substrate after S1, and the wear-resistant particles are evenly fixed between the mixed solder particles to form a dense pre-set solder coating;

[0008] The wear-resistant particles are WC particles;

[0009] The solder mixed particles include pure copper powder, P element added through a compound carrier, and Sn powder;

[0010] S3, heating, the brazing material mixed particles in the pre-brazing coating melt, wet and tightly combine with the wear-resistant particles; cooling to obtain Cu-P-Sn with evenly distributed wear-resistant particles as the wear-resistant coating.

[0011] Preferably, P as the self-fluxing agent is Cu 3 P eutectic powder is added, and in traditional brazing, due to Cu 3 P eutectic powder is a brittle compound that is difficult to make into foil and is not suitable for use in brazing.

[0012] Preferably, WC is added in the form of WC-Co composite powder;

[0013] The mass ratio of WC to Co in the WC-Co composite powder is (8.5 to 9.5):1.

[0014] The WC-Co composite powder of the present invention takes into account both the high hardness of WC and the toughness of Co, so that the wear resistance, corrosion resistance and interface bonding strength of the wear-resistant coating are further improved.

[0015] Preferably, the total mass of the pre-formed brazing coating is calculated as 100 parts, and the mass fractions of each component are as follows:

[0016]

[0017] The present invention effectively controls the amount of each substance to ensure the formation of Cu-P-Sn on the one hand, and on the other hand, the Cu as the P introduction carrier in the present invention 3As a brittle compound, P eutectic powder can only be introduced into copper-phosphorus brazing material by extrusion in hot state or by use in rolling state. The present invention utilizes the deformation of two relatively soft metal powders, pure copper powder and tin powder, which are matched by cold spraying, to introduce Cu 3 The P eutectic powder and wear-resistant particles are evenly fixed on the surface of the steel substrate, which avoids the oxidation of the steel substrate and also 3 P eutectic powder and wear-resistant particles are stably introduced into the pre-brazing coating, and with the subsequent welding film formation, the pre-brazing coating is formed as a fixed phase with wear-resistant particles evenly distributed in the layer; at the same time, the pre-brazing coating has a tighter and more concave-convex fit with the steel matrix under the action of cold spraying and high-hardness WC particles, which increases the interfacial force.

[0018] Preferably, the mass of the wear-resistant particles in the pre-coated brazing coating is m 1 The mass of the solder mixture particles is m 2 , where m 1 ≥m 2 In order to ensure the wear resistance of the obtained coating, the present invention needs to ensure that the amount of wear-resistant particles is greater than or equal to the mass of the brazing coating mixed particles.

[0019] The process parameters of supersonic cold spraying in step S2 are preferably as follows:

[0020]

[0021]

[0022] Preferably, the brazing temperature in S3 is 695° C. to 705° C., and the brazing time is 8 min to 15 min. In the present invention, the wear-resistant coating is formed in situ when the surface of the pre-brazing coating is covered on the steel substrate, and the damage to the steel substrate is small.

[0023] The thickness of the wear-resistant coating is preferably 1 mm to 10 mm. The present invention can prepare a wear-resistant coating with different wear-resistant particle distribution amounts by adjusting the amount of wear-resistant particles, and control the proportion of wear-resistant particles during cold spraying to construct a wear-resistant coating with a step-wise concentration change of wear-resistant particles.

[0024] Preferably, the steel substrate surface sandblasting treatment in S1 and the pre-brazing coating in S2 are completed in the same supersonic cold spraying equipment. 3P eutectic powder, Sn powder, and WC-Co composite powder are mixed evenly in proportion in the mixer and canned in the mixed powder tank of the supersonic cold spray equipment. The corundum for sandblasting surface treatment is loaded into the sandblasting tank. First, the steel substrate to be brazed is sandblasted. At this time, the high-speed airflow flows through the sandblasting tank, and the corundum is blown out at high speed to mechanically clean the surface of the steel substrate. After cleaning, the high-speed gas is switched to supersonic airflow and flows through the mixed powder tank. Under the action of the high-speed airflow, the evenly mixed brazing powder and WC-Co composite powder flow out of the spray gun in the form of high-speed airflow to impact the steel substrate, and finally a pre-brazing coating with a certain bonding strength is formed on the surface of the steel substrate and the surface of the substrate. The supersonic cold spray equipment combines the sandblasting surface treatment and the pre-brazing coating work in succession.

[0025] The wear-resistant coating with dispersed wear-resistant particles prepared by the present invention is suitable for wear-resistant parts in screw compressors, for example, because the wear-resistant coating is prepared by cold spraying combined with heating welding, and the film thickness can be more accurately controlled. It can maintain wear resistance and good corrosion resistance.

[0026] By adopting the above technical solution, the beneficial effects of the present invention are:

[0027] The present invention cold-sprays a pre-set brazing coating on the surface of a steel substrate from which an oxide film has been removed. The pre-set brazing coating includes brazing material mixed particles and wear-resistant particles uniformly distributed among the brazing material mixed particles to form a dense pre-set brazing coating. Before solidification, the hard wear-resistant particles are ejected and stacked to form a controllable pre-positioning of the wear-resistant particles. Subsequently, as welding proceeds, the brazing material mixed particles in the pre-set brazing coating melt, wet and tightly combine with the wear-resistant particles. The wear-resistant coating having the wear-resistant particles uniformly distributed thereon is cooled, and the wear-resistant particles can be effectively fixed on the surface of the steel substrate by controlling the mass proportion of the wear-resistant particles. In the process of welding, P as a self-brazing agent forms Cu-P-Sn with pure copper powder and tin powder, and the wear-resistant particles are infiltrated and combined with the molten metal to form a wear-resistant coating as it is cooled and solidified. The wear-resistant coating has high density, high coating hardness, high bonding strength with the steel substrate, and improved corrosion resistance. DETAILED DESCRIPTION

[0028] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0029] Example 1

[0030] This embodiment discloses a method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles, comprising the following steps:

[0031] S1, sandblasting, to remove the oxide film on the surface of the steel substrate;

[0032] S2, after the mixed solder particles and the wear-resistant particles are evenly mixed, they are supersonic cold sprayed on the steel substrate after S1, and the wear-resistant particles are evenly fixed between the mixed solder particles to form a dense pre-set solder coating;

[0033] The wear-resistant particles are WC particles;

[0034] The solder mixed particles include pure copper powder, P element added through a compound carrier, and Sn powder;

[0035] S3, heating, the brazing material mixed particles in the pre-brazing coating melt, wet and tightly combine with the wear-resistant particles; cooling to obtain Cu-P-Sn with evenly distributed wear-resistant particles as the wear-resistant coating.

[0036] Among them, P as a self-fluxing flux is Cu 3 P eutectic powder is added, and in traditional brazing, due to Cu 3 P eutectic powder is a brittle compound that is difficult to make into foil and is not suitable for use in brazing.

[0037] In this embodiment, WC is added in the form of WC-Co composite powder;

[0038] The mass ratio of WC to Co in the WC-Co composite powder is shown in Table 1.

[0039] The total mass of the pre-brazing coating layer formed in this embodiment is calculated as 100 parts, and the mass fractions of each component are shown in Table 1.

[0040] The present invention effectively controls the amount of each substance to ensure the formation of Cu-P-Sn on the one hand, and on the other hand, the Cu as the P introduction carrier in the present invention 3 As a brittle compound, P eutectic powder can only be introduced into copper-phosphorus brazing material by extrusion in hot state or by use in rolling state. The present invention utilizes the deformation of two relatively soft metal powders, pure copper powder and tin powder, which are matched by cold spraying, to introduce Cu 3 The P eutectic powder and wear-resistant particles are evenly fixed on the surface of the steel substrate, which not only avoids the oxidation of the steel substrate, but also 3 P eutectic powder and wear-resistant particles are stably introduced into the pre-brazing coating, and with the subsequent welding film formation, the pre-brazing coating is formed as a fixed phase with wear-resistant particles evenly distributed in the layer; at the same time, the pre-brazing coating forms a tighter and more concave-convex fit with the steel matrix under the action of cold spraying and high-hardness WC particles, thereby increasing the interfacial force.

[0041] The mass of the wear-resistant particles in the pre-plated brazing coating in this embodiment is m 1 The mass of the solder mixture particles is m 2 , where m 1 ≥m 2In order to ensure the wear resistance of the obtained coating, the present invention needs to ensure that the amount of wear-resistant particles is greater than or equal to the mass of the brazing coating mixed particles.

[0042] The process parameters of supersonic cold spraying in step S2 of this embodiment are shown in Table 2

[0043] The brazing temperature and brazing time in this embodiment S3 are shown in Table 2. The steel substrate of the present invention ensures the in-situ formation of the wear-resistant coating when the surface of the pre-brazing coating is covered, and the damage to the steel substrate is small.

[0044] The thickness of the wear-resistant coating in this embodiment is 1 mm to 10 mm. The present invention can prepare a wear-resistant coating with different wear-resistant particle distribution amounts by adjusting the amount of wear-resistant particles, and control the proportion of wear-resistant particles during cold spraying to construct a wear-resistant coating with a step-wise concentration change of wear-resistant particles.

[0045] The steel substrate surface sandblasting treatment in S1 and the pre-brazing coating in S2 are completed in the same supersonic cold spraying equipment. 3 P eutectic powder, Sn powder, and WC-Co composite powder are mixed evenly in proportion in the mixer and canned in the mixed powder tank of the supersonic cold spray equipment. The corundum for sandblasting surface treatment is loaded into the sandblasting tank. First, the steel substrate to be brazed is sandblasted. At this time, the high-speed airflow flows through the sandblasting tank, and the corundum is blown out at high speed to mechanically clean the surface of the steel substrate. After cleaning, the high-speed gas is switched to supersonic airflow and flows through the mixed powder tank. Under the action of the high-speed airflow, the evenly mixed brazing powder and WC-Co composite powder flow out of the spray gun in the form of high-speed airflow to impact the steel substrate, and finally a pre-brazing coating with a certain bonding strength is formed on the surface of the steel substrate and the surface of the substrate. The supersonic cold spray equipment combines the sandblasting surface treatment and the pre-brazing coating work in succession.

[0046] In this embodiment, the steel substrate is Q345, which is a low-alloy high-strength steel whose main components include iron (Fe), carbon (C), manganese (Mn), silicon (Si), phosphorus (P) and sulfur (S). The wear-resistant coating with dispersed wear-resistant particles prepared on the surface of the Q345 steel substrate of the present invention.

[0047] Example 2

[0048] The main differences between this embodiment and embodiment 1 are shown in Table 1 and Table 2.

[0049] Example 3

[0050] The main differences between this embodiment and embodiment 1 are shown in Table 1 and Table 2.

[0051] Example 4

[0052] The main differences between this embodiment and embodiment 1 are shown in Table 1 and Table 2.

[0053] Example 5

[0054] The main differences between this embodiment and embodiment 1 are shown in Table 1 and Table 2.

[0055] Comparative Example

[0056] This comparative example discloses a method for preparing a wear-resistant coating having dispersed wear-resistant particles, wherein pure copper powder, Cu 3 P eutectic powder, Sn powder and wear-resistant particles WC are mixed evenly according to the amount of Example 3, and then ethanol and paste are used, and coated on an area of ​​the same area as Example 3. After drying, the thickness of the pre-deposited layer is about 3.5 mm;

[0057] In this comparative example, the oxide film on the surface of the Q345 steel substrate was removed by sandblasting as in Example 3 before coating;

[0058] The steel substrate coated with the dried brazing material coating was brazed at 695° C. for 8 minutes, taken out and cooled to room temperature, thereby obtaining a copper-based wear-resistant coating on the surface of the steel substrate.

[0059] Table 1 Mass fractions of the pre-set solder layers in Examples 1 to 5 (total amount calculated as 100 parts)

[0060] Components Pure Cu powder <![CDATA[Cu 3 P]]> Sn powder Wear-resistant particles WC:Co Example 1 35 5 4 56 Does not contain Co Example 2 38 5 4 53 8.5:1 Example 3 40 6 2 52 9.0:1 Example 4 35 7 2 56 9.5:1 Example 5 38 8 2 52 9.0:1

[0061] Table 2 Process parameters for preparing wear-resistant coatings in Examples 1 to 5

[0062] project Example 1 Example 2 Example 3 Example 4 Example 5 Airflow working pressure 0.6MPa 0.7MPa 0.8MPa 0.7MPa 0.6MPa Powder feeding rate 15g / min 15g / min 20g / min 20g / min 25g / min Spray distance 15mm 20mm 30mm 30mm 30mm Spray Angle 20° 20° 30° 30° 30° Preset braze coating thickness 3.2mm 3.5mm 3.1mm 7.6mm 8.3mm Brazing temperature 695℃ 700℃ 705℃ 705℃ 700℃ Brazing time 8min 8min 8min 15min 15min

[0063] The density, coating hardness, bonding strength and pitting potential of the wear-resistant coatings obtained in Examples 1 to 5 and the comparative example were respectively tested. The specific data are shown in Table 3.

[0064] Table 3 Performance indicators of wear-resistant coatings obtained in Examples 1 to 5 and Comparative Examples

[0065] project Density Coating hardness Bonding strength Pitting potential Example 1 91％ 1026HV 210MPa 308mV Example 2 95％ 1679HV 292MPa 345mV Example 3 96％ 1657HV 288MPa 334mV Example 4 96％ 1685HV 295MPa 343mV Example 5 97％ 1675HV 293MPa 336mV Comparative Example 73％ 531HV 203MPa 299mV

[0066] Combining Table 1, Table 2 and Table 3, it can be seen that in the comparative example, the pre-coated brazing coating is arranged on the surface of the steel substrate by applying and drying. Before welding, the bonding between the pre-coating and the surface of the steel substrate is not dense. As the welding process progresses, the pure Cu powder and Cu 3P eutectic powder and Sn powder melt and infiltrate WC-Co wear-resistant particles to form a wear-resistant coating; further comparing the wear-resistant coatings obtained in Examples 1 to 5, since the present invention cold-sprays a pre-set brazing coating on the surface of the steel substrate from which the oxide film is removed, especially the pure Cu powder and Sn powder in the present invention are relatively soft, the Cu 3 The P eutectic powder and WC-Co particles are densely fixed on the surface of the steel matrix. Before solidification, the hard wear-resistant particles are ejected and stacked with the brazing material mixed particles to form controllable pre-positioning of the wear-resistant particles. Then, as welding proceeds, the brazing material mixed particles in the pre-brazing coating melt, wet and tightly combine with the wear-resistant particles. The wear-resistant coating is cooled to form a uniform distribution of wear-resistant particles. The wear-resistant particles can be effectively fixed on the surface of the steel matrix by controlling the mass ratio of the wear-resistant particles. In the welding process, the addition of P as a self-brazing flux forms Cu-P-Sn, and the wear-resistant particles are infiltrated and combined with the molten metal to form a wear-resistant coating as it cools and solidifies. Since the Q345 steel matrix also contains P and Fe, the P element in the steel matrix can also participate in the formation of Cu-P-Sn. With the addition of pure Cu powder, Cu 3 The P eutectic powder and Sn powder collide with the WC-Co particles on the surface of the steel substrate together, exposing more of the surface of the steel substrate due to their own high hardness. Under welding conditions, Cu-P-Sn is formed on the surface of the steel substrate and the WC-Co wear-resistant particles are evenly dispersed in the layer.

Claims

1. A method for preparing a wear-resistant coating having dispersed wear-resistant particles, characterized in that: The following steps are involved: S1, sandblasting, to remove the oxide film on the surface of the steel substrate; S2, after the mixed solder particles and the wear-resistant particles are evenly mixed, they are supersonic cold sprayed on the steel substrate after S1, and the wear-resistant particles are evenly fixed between the mixed solder particles to form a dense pre-set solder coating; The wear-resistant particles are WC particles; The solder mixed particles include pure copper powder, P element added through a compound carrier, and Sn powder; S3, heating, the brazing material mixed particles in the pre-brazing coating melt, wet and tightly combine with the wear-resistant particles; cooling to obtain Cu-P-Sn with evenly distributed wear-resistant particles as the wear-resistant coating.

2. The method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles according to claim 1, characterized in that: P as a self-fluxing agent is added in the form of Cu3P eutectic powder.

3. The method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles according to claim 2, characterized in that: WC is added in the form of WC-Co composite powder; 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 a wear-resistant coating having dispersedly distributed wear-resistant particles according to claim 3, characterized in that: The total mass of the pre-brazing coating is calculated as 100 parts, and the mass fractions of each component are as follows:

5. The method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles according to claim 1, characterized in that: The mass of the wear-resistant particles in the pre-solder coating is m1, and the mass of the solder mixed particles is m2, wherein m1≥m2.

6. The method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles according to claim 1, characterized in that: The process parameters of supersonic cold spraying in step S2 are as follows:

7. The method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles according to claim 1, 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 method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles according to claim 1, characterized in that: The wear-resistant coating has a thickness of 1 mm to 10 mm.

9. The method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles according to claim 1, characterized in that: The steel substrate surface sandblasting in S1 and the pre-brazing coating in S2 were completed in the same supersonic cold spraying equipment.

10. A wear-resistant coating having dispersedly distributed wear-resistant particles obtained by the method for preparing a wear-resistant coating having dispersedly distributed wear-resistant particles according to any one of claims 1 to 9.

Images