Alloy coating, preparation method thereof and metal part

Abstract

The invention belongs to the technical field of coatings, and particularly discloses an alloy coating, a preparation method thereof and a metal part. The alloy powder is heated and then cooled to the room temperature through the laser cladding technology, the alloy powder can be attached to the surface of the metal base material, and a composite coating used for protecting the base material is formed; the alloy powder comprises, by mass, 10%-15% of Mo, 5%-10% of B4C and the balance Ti. The alloy formula design is combined with the laser cladding process, the defect that hardness and corrosion resistance of an existing alloy coating are difficult to combine is overcome, the alloy coating which is high in hardness, good in abrasion resistance and high in corrosion resistance and does not generate cold cracks is obtained, and the service life of a metal part can be effectively prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating, in particular to an alloy coating, a preparation method thereof and a metal part. BACKGROUND

[0002] At present, laser cladding method is usually used to make alloy powder cladding on the surface of metal substrate and combined with the surface of metal substrate to form a protective coating of metal substrate to improve the wear resistance and corrosion resistance of metal substrate. However, the hardness and corrosion resistance of the alloy coating enhanced by adding the second phase (ceramic reinforcing phase) cannot be considered at the same time. The alloy coating prepared by laser cladding method has high hardness and strong wear resistance, but there is a potential difference between the coating metal and the ceramic reinforcing phase, which will lead to the reduction of corrosion resistance. In addition, high-hardness coating is prone to cold cracking, which affects the quality and service life of the coating. SUMMARY

[0003] To solve the above problems, the present application provides an alloy coating, a preparation method thereof and a metal part, which can realize the preparation of an alloy coating with high hardness, good corrosion resistance and no cracks, thereby prolonging the service life of the metal material.

[0004] To achieve the above purpose, the specific technical solutions adopted by the present application are as follows:

[0005] In a first aspect, the present application provides an alloy coating, the raw material of which is an alloy powder, and the alloy powder comprises Mo: 10-15%, B4C: 5-10%, and the balance is Ti, by mass percentage.

[0006] In this formula, B4C and Ti will generate TiB and TiC, and the potential difference between TiB and TiC and titanium is relatively small compared with other ceramic reinforcing phases, so the reduction of corrosion resistance will be relatively smaller. The purpose of adding Mo is to compensate for the reduction of corrosion resistance caused by the potential difference on the basis of increasing the hardness and wear resistance of the ceramic reinforcing phase, and further enhance the hardness, wear resistance and corrosion resistance. The hardness of the alloy coating of this formula is greater than 500 HV 0.2 and not more than 600 HV 0.2 ; if the hardness is more than 600 HV 0.2 , more reinforcing phases (i.e. adding more B4C in the mixed powder) are needed, which will lead to further reduction of corrosion resistance, which does not meet the requirements of improving both hardness and corrosion resistance.

[0007] Secondly, this invention provides a method for preparing the aforementioned alloy coating. This method uses coaxial powder-feeding laser cladding technology to form a composite coating (composed of a ceramic phase and a solid solution matrix) on the surface of a metal substrate from alloy powder. The steps are as follows: alloy powder is fed onto the surface of the metal substrate, melted under laser heating, and then rapidly cooled to room temperature to form a composite coating for protecting the substrate. Laser cladding offers a fast heating rate, enabling rapid formation of the composite titanium alloy coating and improving the efficiency of alloy coating preparation.

[0008] Preferably, the alloy powder is heated to a temperature of not less than 2700°C to ensure that the alloy powder melts and reacts to form a titanium alloy composite coating.

[0009] Preferably, the rapid cooling rate is 10. 3 ~10 5 At ℃ / s, a large degree of supercooling can be created without causing problems such as cracks and oxidation, thereby allowing the strengthening phase to react and precipitate, and the alloy powder to form a titanium alloy composite coating.

[0010] Preferably, the laser power used in the laser cladding is 1600~1800W, which can ensure that the alloy powder melts and reacts to form a titanium alloy composite coating.

[0011] Preferably, before the alloy powder is fed onto the surface of the metal substrate, a step of drying the alloy powder is included to avoid the problem of a large number of pores and water-induced oxidation inside the coating after laser cladding.

[0012] Furthermore, the drying temperature is 80~120℃, and the drying time is 3~6h.

[0013] Thirdly, the present invention provides a metal part comprising a metal substrate, wherein an alloy coating is attached to the surface of the metal substrate, the alloy coating being the aforementioned alloy coating or an alloy coating prepared according to the aforementioned preparation method.

[0014] The present invention has the following beneficial effects:

[0015] 1. This invention overcomes the shortcomings of existing alloy coatings in achieving both hardness and corrosion resistance by using a formula design of "Mo: 10-15%, B4C: 5-10%, with the balance being Ti" combined with laser cladding technology.

[0016] 2. The alloy coating of the present invention has high hardness, good wear resistance, strong corrosion resistance, and no cold cracks, which can effectively extend the service life of metal parts.

[0017] 3. This invention provides a method for preparing alloy coatings by laser cladding, which is simple in process, easy to operate, has high preparation efficiency, and is convenient for production application. Attached Figure Description

[0018] Figure 1 This is a photograph showing the appearance of the titanium alloy composite coating in Example 1.

[0019] Figure 2 This is a backscattered electron micrograph of the titanium alloy composite coating of Example 1.

[0020] Figure 3 This is a backscattered electron micrograph of the titanium alloy composite coating in Comparative Example 1.

[0021] Figure 4 The figures show the wear amount from friction and wear tests of Example 1 and Comparative Examples 1 and 2.

[0022] Figure 5 The images show Tafel curves of electrochemical polarization tests for Example 1 and Comparative Examples 1 and 2. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Unless otherwise specified in the embodiments, conditions are performed according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0024] The preparation method of the metal parts and alloy coatings of the present invention will be described in detail below.

[0025] An embodiment of the present invention provides a metal part comprising a metal substrate, wherein an alloy coating is attached to the surface of the metal substrate, and the preparation method of the alloy coating is as follows:

[0026] (1) Prepare alloy powder and dry it. The constituent elements of the alloy powder include, by mass percentage: Mo: 10-15%, B4C: 5-10%, and the balance is Ti. Mix and dry the alloy powder.

[0027] Mixing and drying processes are beneficial for the subsequent formation of a titanium alloy composite coating on the alloy powder. During the mixing process, the alloy powder can be mixed at 200-250 rpm for 8-12 hours. For example, the alloy powder can be mixed at 200 rpm for 8, 9, or 12 hours, or at 250 rpm for 8, 9, or 12 hours. As an example, the alloy powder can be mixed at 240 rpm for 10 hours. During the drying process, the alloy powder can be dried at 80-120°C for 3-6 hours. For example, the alloy powder can be dried at 80°C for 3, 4, or 6 hours, or at 120°C for 3, 5, or 6 hours. As an example, the alloy powder can be dried at 100°C for 3 hours.

[0028] It should be noted that in this embodiment of the invention, the alloy powder refers to a mixture of Ti particles with a particle size of 53-150 micrometers and B4C and Mo particles with a particle size of 15-53 micrometers.

[0029] (2) Then, the dried alloy powder is coated onto the surface of the metal substrate, heated to above 2700°C, and then applied at 10°C. 3 ~10 5 Rapid cooling at a rate of ℃ / s melts the alloy powder and causes it to adhere to the surface of the metal substrate, forming a titanium alloy composite coating. Furthermore, the resulting titanium alloy composite coating has a hardness exceeding 500 HV. 0.2 .

[0030] In addition, in this embodiment of the invention, the alloy powder is heated to above 2700°C, and then subjected to 10... 3 ~10 5 Rapid cooling at a rate of ℃ / s is to ensure that the alloy powder can form a titanium alloy composite coating through reaction.

[0031] Furthermore, to enable the alloy powder to form a titanium alloy composite coating more quickly, this invention, by way of example, employs laser cladding to process the alloy powder. Laser cladding is a method that uses a high-energy-density laser beam to melt and solidify the alloy powder together with a thin layer on the surface of the substrate. Laser cladding has high heating temperatures, typically exceeding 2700°C, and exhibits rapid heating and cooling rates, reaching up to 10... 3 ~10 5 The temperature (℃ / s) is sufficient to meet the formation conditions for titanium alloy composites. Of course, in other embodiments, composite coatings can also be prepared by other methods, such as vacuum plasma cladding followed by cooling to form the titanium alloy composite coating; this invention does not impose strict limitations on these methods.

[0032] In specific embodiments of the present invention, the laser power is generally adjusted to 1600~1800W to ensure that the heating temperature is sufficient for the alloy powder to form a titanium alloy composite coating, and also to ensure that the area of ​​the titanium alloy composite coating is appropriate to meet the requirements of metal parts.

[0033] It should be noted that since titanium alloy composite coatings require the alloy powder to be heated and then rapidly cooled to be produced, and the alloy powder is fused onto the surface of the metal substrate, the titanium alloy composite coating itself can adhere to the surface of the metal substrate after the alloy powder is heated to form the titanium alloy composite coating, regardless of the method used to prepare the titanium alloy composite coating.

[0034] In addition, in this embodiment of the invention, the room temperature is generally 20~30℃. As an example, the alloy powder is typically rapidly cooled to room temperature (25℃) to form the titanium alloy composite coating. In the alloy powder, the TiC and TiB formed by the reaction of B4C with Ti at high temperature ensure that the formed titanium alloy composite coating has a hardness exceeding 500 HV without cold cracking. 0.2 .

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] This embodiment provides an alloy coating and a metal part. The metal part includes a metal substrate (specifically, TC4 alloy in this embodiment) and an alloy coating attached to the surface of the metal substrate. The alloy coating serves as a protective layer, and its preparation method is as follows:

[0038] (1) Select alloy powder

[0039] First, prepare an alloy powder whose constituent elements, by mass percentage, include Mo: 13%, B4C: 5%, and the balance Ti. Then, place the alloy powder in an oven and dry it at 100°C for 3 hours.

[0040] (2) Formation of titanium alloy composite coating

[0041] Coaxial powder feeding technology is used to deliver alloy powder to the surface of a metal substrate, and a titanium alloy composite coating is formed by laser cladding. The alloy powder is melted and adheres to the surface of the metal substrate as a protective layer.

[0042] In this embodiment, a fiber laser (Laserline LDF-8000) with a maximum power of 8kW was used to heat and melt the alloy powder. The laser power was adjusted to 1600W, and a 1.2mm diameter spot was used to heat the surface of the metal substrate, forming a molten pool on the surface of the metal substrate. Argon gas was used as a carrier to feed the alloy powder into the molten pool, and high-purity argon gas was also used as a protective gas during the cladding process. The remaining parameters of the fiber laser are shown in Table 1 below. The alloy powder was heated to ≥2700℃ under laser action and then molten, and then... 5 Rapidly cooled to room temperature at a cooling rate of ℃ / s, forming a titanium alloy composite coating.

[0043] Table 1 Parameters of fiber lasers

[0044]

[0045] In this embodiment, the appearance of the alloy coating is as follows: Figure 1 As shown, the surface is smooth and free of cracks; the microscopic morphology image is as follows. Figure 2As shown, the left side is the overall view, where matrix refers to the overall morphology of the alloy coating, and the right side is a magnified view, where reinforcement is the reinforcing phase in the alloy coating.

[0046] Comparative Example 1

[0047] This comparative example is basically the same as Example 1, except that the Mo component was not added. That is, in step (1), the powder composition was replaced with B4C: 5%, and the remainder was Ti.

[0048] In this comparative example, the microstructure of the alloy coating is shown in the following image. Figure 3 As shown, the left side is the overall view, where matrix refers to the overall morphology of the alloy coating, and the right side is a magnified view of a part, where reinforcement is the reinforcing phase in the alloy coating. Figure 3 The interior of the display coating exhibits a black and gray reinforcing phase, compared to Figure 2 Larger sizes of reinforcing phases make them more prone to detachment during friction and wear, leading to increased wear.

[0049] Comparative Example 2

[0050] This comparative example provides a metal part, which, compared to Example 1 and Comparative Example 1, is a metal substrate without coating.

[0051] The following performance tests were performed on the alloy coatings of the metal parts in Example 1 and Comparative Example 1, and on the metal parts (metal substrate) in Comparative Example 2:

[0052] I. Hardness Testing

[0053] The alloy coatings of the metal parts in Example 1 and Comparative Example 1, and the metal substrates of the metal parts in Comparative Example 2 were tested for hardness using GB / T 4340.1-1999, the Vickers hardness test method for metals. The results are shown in Table 2 below. The coating hardness of Example 1 exceeded 500 HV. 0.2 And it is higher than that of comparative examples 1 and 2.

[0054] Table 2: Hardness of Example 1 and Comparative Examples 1-2

[0055]

[0056] II. Friction and Wear Test

[0057] A friction and wear test was conducted using an alumina grinding ball with a diameter of 5 mm on a friction and wear testing machine at room temperature. The friction radius was 10 mm, the rotational speed was 200 rpm, the load was 30 N, and the test time was 1 hour. Wear data of the alloy coating of the metal part in Example 1 and the metal substrate of the metal part in Comparative Example 2 are compared. Figure 4As shown in the figure, the wear amount of Example 1 and Comparative Example 1 is lower than that of Comparative Example 2, and the wear amount of Example 1 is lower than that of Comparative Example 1, indicating that Example 1 has better wear resistance.

[0058] III. Electrochemical Testing

[0059] Electrochemical polarization was performed using a Princeton Versastat 4 in a 3.5% wt sodium chloride solution at room temperature. Samples were prepared in a flat-plate electrolytic cell, with an SCE as the reference electrode and a platinum sheet as the auxiliary electrode. The Tafel onset and termination potentials were -1 to 1 V, and the Tafel scan rate was 5 mV / s. A comparison of the Tafel curves of the alloy coating on the metal part in Example 1 and the metal substrate on the metal part in Comparative Example 2 is provided. Figure 5 As shown in Table 3, the corrosion potential and corrosion current density of the alloy coatings of the metal parts in Example 1, Comparative Example 1, and the metal substrate of the metal parts in Comparative Example 2, derived from the Tafel curves, are shown below. It can be concluded that the alloy coating of Example 1 exhibits better corrosion resistance than Comparative Examples 1 and 2.

[0060] Table 3: Corrosion potential and corrosion current density of Example 1 and Comparative Examples 1-2

[0061]

[0062] In summary, the alloy coating prepared using the alloy powder and preparation method of the present invention has excellent hardness, good wear resistance and corrosion resistance, and no surface cracks.

[0063] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. Any changes made by those skilled in the art after reading the specification of the present invention, as long as they are within the scope of the claims of the present invention, will be protected by patent law.

Claims

1. An alloy coating, characterized in that, Its raw material is alloy powder, which includes, by mass percentage: Mo: 10-15%, B4C: 5-10%, and the balance is Ti.

2. The alloy coating according to claim 1, characterized in that, The coating has a hardness greater than 500 HV. 0.2 and not greater than 600 HV 0.2 .

3. The method for preparing the alloy coating according to claim 1 or 2, characterized in that, This method uses coaxial powder feeding laser cladding technology to form a composite coating on the surface of a metal substrate by alloy powder. The steps are as follows: the alloy powder is fed to the surface of the metal substrate, melted under laser heating, and then rapidly cooled to room temperature to form a composite coating for protecting the substrate.

4. The preparation method according to claim 3, characterized in that, The alloy powder is heated to a temperature of not less than 2700°C.

5. The preparation method according to claim 3, characterized in that, The rapid cooling rate is 10. 3 ~10 5 ℃ / s.

6. The preparation method according to claim 3, characterized in that, The laser power used in the laser cladding is 1600~1800W.

7. The preparation method according to claim 3, characterized in that, Before the alloy powder is fed onto the surface of the metal substrate, the process also includes a step of drying the alloy powder.

8. The preparation method according to claim 7, characterized in that, The drying temperature is 80~120℃, and the drying time is 3~6h.

9. A metal part, characterized in that, It includes a metal substrate, the surface of which is coated with an alloy coating, the alloy coating being the alloy coating according to any one of claims 1 to 2, or an alloy coating prepared according to the preparation method according to any one of claims 3 to 8.

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