A strong corrosion-resistant CoCrNi-based medium-entropy alloy coating and a preparation method thereof

Abstract

The application provides a strong corrosion-resistant CoCrNi-based medium-entropy alloy coating and a preparation method thereof.The preparation method comprises the following steps: step 1, proportioning according to the mass ratio of components; step 2, preparation of CoCrNi-Y2O3 composite powder; step 3, pretreatment and sand blasting; and step 4, preparation of a Y2O3 ceramic phase reinforced CoCrNi-based medium-entropy alloy coating.The strong corrosion-resistant CoCrNi-based medium-entropy alloy coating prepared by the method has good mechanical properties and excellent corrosion resistance due to the synergistic strengthening effect of the ceramic phase Y2O3 particles.

Description

Technical Field

[0001] This invention belongs to the field of medium-entropy alloys and relates to a highly corrosion-resistant CoCrNi-based medium-entropy alloy coating and its preparation method. Background Technology

[0002] The marine environment contains abundant oil, natural gas, and mineral resources, making it a strategic high ground for economic and military development worldwide. Therefore, accelerating the development of marine resources is imperative. However, the complex natural environment of marine areas, including constant salt spray and waves, easily causes severe corrosion to marine engineering equipment. Traditional metal alloys have limited properties, and their matrix structure is prone to instability under marine conditions, leading to material failure. This fails to meet the ever-increasing demands of users, necessitating a novel alloying strategy to break free from the constraints of traditional methods and extend the service life of marine engineering equipment.

[0003] The concept of medium / high entropy alloys (or multi-principal element alloys) was proposed in 2004. Compared to traditional metallic materials, medium / high entropy alloys exhibit superior performance due to their thermodynamic high entropy effect, kinetic slow diffusion effect, structural lattice distortion effect, and "cocktail" effect in terms of properties. Among the many medium / high entropy alloys, CoCrNi medium-entropy alloy has attracted widespread attention due to its relatively good corrosion resistance and excellent plasticity. Currently, medium-entropy alloys are mostly in bulk form, requiring high-level post-processing, making the fabrication of large parts difficult and costly, and thus unsuitable for the diverse and complex structural shapes of marine engineering equipment.

[0004] Medium-entropy alloy coatings are developed based on medium-entropy alloy theory and combined with material surface technology. Compared with medium-entropy alloy blocks, medium-entropy alloy coatings have lower production costs and achieve integrated preparation and molding, resulting in better economic benefits and adaptability to extreme environments in actual production, meeting the surface protection requirements of polar and marine engineering equipment. However, compared with alloy blocks, coatings have more surface defects and reduced corrosion resistance, making them unsuitable for long-term service in marine environments and causing damage to marine engineering equipment.

[0005] Therefore, developing a CoCrNi-based medium-entropy alloy coating with strong corrosion resistance has become an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a method for preparing a highly corrosion-resistant CoCrNi-based medium-entropy alloy coating. This method can improve the corrosion resistance of the CoCrNi-based medium-entropy alloy coating, enabling it to meet the surface protection requirements of marine engineering equipment.

[0007] Another object of the present invention is to provide a highly corrosion-resistant CoCrNi-based medium-entropy alloy coating.

[0008] To achieve the above objectives, the present invention provides a method for preparing a highly corrosion-resistant CoCrNi-based medium-entropy alloy coating, comprising the following steps:

[0009] Step 1: Proportion the ingredients according to the mass ratio.

[0010] Weigh out CoCrNi alloy powder with a particle size between 15-53μm, and weigh out Y2O3 powder with a particle size of 50nm according to 1wt.% to 3wt.% of CoCrNi alloy powder. Then put the CoCrNi powder and Y2O3 powder into a vacuum drying oven and dry them at 60℃ for 12h.

[0011] Step 2: Preparation of CoCrNi-Y2O3 composite powder

[0012] The dried CoCrNi powder and Y2O3 powder were placed together into the container inside the acoustic resonance mixer, and argon gas was introduced into the container to remove excess air. Then, the mixture was vibrated three times, each time for three minutes, with a one-minute interval between vibrations. The vibrated mixed powder was then sieved using 300-mesh and 600-mesh sieves to collect CoCrNi-Y2O3 composite powder with a particle size of 23-53μm.

[0013] Step 3: Pretreatment and sandblasting

[0014] The substrate surface is pretreated, and then the substrate is hot-blasted twice and cold-blasted once.

[0015] Step 4: Preparation of Y2O3 ceramic phase reinforced CoCrNi-based medium-entropy alloy coating

[0016] The CoCrNi-Y2O3 composite powder was sprayed onto the substrate surface as a coating using a supersonic flame spraying device. The spraying process parameters were set as follows: air pressure 0.648MPa, fuel pressure 0.614MPa, spraying distance 240mm, powder feeding rate 3rpm, and spray gun moving speed 1000mm / s.

[0017] As described above, the CoCrNi alloy powder with equal atomic ratio is spherical or near-spherical, the particle size of the CoCrNi alloy powder is 15-53 μm, and the purity of the CoCrNi alloy powder is ≥99.95%.

[0018] As described above, the purity of the Y2O3 powder is ≥99.95%, and the particle size of the Y2O3 powder is 50 nm.

[0019] As described above, the substrate is made of carbon steel; the method for pretreating the surface of the substrate is as follows: the substrate is polished to remove surface rust, and then the surface of the substrate is cleaned with acetone to remove surface oil.

[0020] As described above, the material used for sandblasting is 80-mesh white corundum.

[0021] The present invention also provides a highly corrosion-resistant CoCrNi-based medium-entropy alloy coating prepared by the above-described preparation method.

[0022] This invention also provides the application of CoCrNi-based medium-entropy alloy coatings in the surface protection of marine engineering equipment.

[0023] The preparation method provided by this invention employs acoustic resonance technology combined with supersonic flame spraying technology, resulting in a dense coating structure with good mechanical stability. During preparation, nano-sized Y₂O₃ ceramic powder is uniformly distributed on the surface of CoCrNi powder particles, maintaining powder flowability and inhibiting the oxidation of the CoCrNi powder. This method introduces ceramic phases to disperse and strengthen the CoCrNi medium-entropy alloy, giving it excellent hardness and superior corrosion resistance. The supersonic flame spraying technology makes the coating more adaptable to the diverse and complex structural shapes of marine engineering equipment and reduces resource consumption.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention provides a highly corrosion-resistant CoCrNi-based medium-entropy alloy coating and its preparation method. The CoCrNi-based medium-entropy alloy coating prepared by this method has a dense structure, good mechanical stability, and excellent corrosion resistance. The preparation method is reasonable and simple, with high repeatability, enabling industrial-scale mass production. The prepared coating is more adaptable to the diversity and complexity of marine engineering equipment structures and reduces resource consumption. Attached Figure Description

[0026] Figure 1 SEM images of the powders as shown in Comparative Example 1 (without Y2O3 powder), as shown in Example 1 (mixed after adding 1 wt.% Y2O3 for acoustic resonance), and as shown in Example 2 (mixed after adding 3 wt.% Y2O3 for acoustic resonance).

[0027] Figure 2 The images show cross-sectional SEM images of the CoCrNi-based medium-entropy alloy coatings prepared using the preparation method of the present invention, specifically Examples 1, 2, and Comparative Example 1.

[0028] Figure 3 The X-ray diffraction patterns are for the coatings of Comparative Example 1 and Examples 1 and 2.

[0029] Figure 4 The image shows a bar chart of Vickers hardness for the coatings of Comparative Example 1 and Examples 1 and 2.

[0030] Figure 5 The potentiodynamic polarization curves of the coatings in Comparative Example 1 and Examples 1 and 2 in 3.5 wt.% NaCl solution are shown. Detailed Implementation

[0031] The embodiments of the present invention will now be described in detail and comprehensively so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0032] Material:

[0033] CoCrNi alloy powder was purchased from Shandong Lianhong New Material Technology Co., Ltd., with a particle size of 15-53μm and a purity of ≥99.95wt.%.

[0034] Y2O3 ceramic phase particles were purchased from Zhongke Yannuo (Beijing) Technology Co., Ltd., with a powder particle size of 50nm and a powder purity of ≥99.95wt.%.

[0035] equipment:

[0036] Acoustic Resonance Mixing Machine: The acoustic resonance mixing machine mainly consists of a mixing container and a vibration platform. The mixing container is a sealed, cylindrical plastic container with a diameter of 10cm and a height of 20cm. The opening at the top of the container is used to connect argon gas. The vibration platform is manufactured by Suzhou Dongling Vibration Testing Instrument Co., Ltd., and the machine model is ES-35WLS3Y0-340.

[0037] Vacuum drying oven: The vacuum drying oven was purchased from Beijing Hengnuolixing Technology Co., Ltd., and the machine model is DZF-6020AB.

[0038] Supersonic flame spraying equipment: The supersonic flame spraying equipment was purchased from Kermetico, San Francisco, California, USA. The HVAF C7 spraying system (Kermetico, USA) was used to prepare the coating, and the spray gun model was AK-07.

[0039] CoCrNi powder and Y2O3 powder are mixed using an acoustic resonance mixer, allowing the Y2O3 powder to embed into the surface of the CoCrNi powder, forming a unified structure that is not sieved out during subsequent sieving. The nano-sized Y2O3 powder, with its small particle size, can be better embedded in the micron-sized CoCrNi powder surface. This embedding of Y2O3 powder also improves powder flowability during spraying, preventing agglomeration and providing dispersion reinforcement within the structure, resulting in a denser coating. Furthermore, at high temperatures, the nano-sized ceramic particles embedded in the CoCrNi surface reduce CoCrNi oxidation, further improving coating quality.

[0040] Example 1

[0041] Step 1:

[0042] Weigh 1000g of equiatomic CoCrNi powder (powder purity ≥99.95%, particle size 23μm-53μm), and weigh 10g of Y2O3 powder according to the Y2O3 addition amount (1wt.%Y2O3), Y2O3 powder purity ≥99.95%, particle size 50nm. Then place the CoCrNi powder and Y2O3 powder separately into a vacuum drying oven and dry at 60℃ for 12h.

[0043] Step 2:

[0044] The dried CoCrNi powder and Y2O3 powder were placed together in the container inside an acoustic resonance mixer, and argon gas was introduced into the container to purge excess air. The acoustic resonance mixer was set to the optimal frequency of 120Hz. After each three-minute vibration, the machine was stopped for one minute to allow for heat dissipation, and this process was repeated three times. The mixed powder was then sieved using 600-mesh and 300-mesh screens to collect CoCrNi-Y2O3 composite powder with a particle size of 23-53μm.

[0045] Step 3:

[0046] Pretreatment of carbon steel substrate surface: Grind the carbon steel substrate to remove surface rust, then clean the carbon steel substrate surface with acetone to remove surface oil, and perform hot sandblasting twice and cold sandblasting once. The sandblasting material is 80-mesh white corundum.

[0047] Step 4:

[0048] The HVAF technology was used to spray CoCrNi-Y2O3 composite powder onto the substrate surface as a coating using a supersonic flame spraying device. The spraying process parameters were set as follows: air pressure 0.648MPa, fuel pressure 0.614MPa, spraying distance 240mm, powder feeding rate 3rpm, and spray gun moving speed 1000mm / s.

[0049] Example 2

[0050] Step 1:

[0051] Weigh 1000g of CoCrNi powder with an atomic ratio (powder purity ≥99.95%, particle size 23um-53um), and weigh 30g of Y2O3 powder according to the amount of Y2O3 added (3wt.%Y2O3), Y2O3 powder purity ≥99.95%, particle size 50nm.

[0052] Step 2:

[0053] The dried CoCrNi powder and Y2O3 powder were placed together in a container inside an acoustic resonance mixer, and argon gas was introduced into the container to purge excess air. The optimal frequency was set for the acoustic resonance machine, and after each three-minute vibration, the machine was stopped for one minute to allow for heat dissipation, for a total of three vibrations. The mixed powder was then sieved using 600-mesh and 300-mesh screens to collect CoCrNi-Y2O3 composite powder with a particle size of 23-53 μm.

[0054] Step 3:

[0055] Pretreatment of carbon steel substrate surface: Grind the carbon steel substrate to remove surface rust, then clean the carbon steel substrate surface with acetone to remove surface oil, and perform hot sandblasting twice and cold sandblasting once. The sandblasting material is 80-mesh white corundum.

[0056] Step 4:

[0057] The HVAF technology was used to spray CoCrNi-Y2O3 composite powder onto the substrate surface as a coating using a supersonic flame spraying device. The spraying process parameters were set as follows: air pressure 0.648MPa, fuel pressure 0.614MPa, spraying distance 240mm, powder feeding rate 3rpm, and spray gun moving speed 1000mm / s.

[0058] Comparative Example 1

[0059] Step 1:

[0060] In this specific embodiment, 1000g of atomically equivalent CoCrNi powder (powder purity ≥99.95%, particle size 23um-53um) was weighed.

[0061] Step 2:

[0062] Pretreatment of carbon steel substrate surface: Grind the carbon steel substrate to remove surface rust, then clean the carbon steel substrate surface with acetone to remove surface oil, and perform hot sandblasting twice and cold sandblasting once. The sandblasting material is 80-mesh white corundum.

[0063] Step 3:

[0064] HVAF technology was used to spray the substrate surface. The spraying process parameters were set as follows: air pressure 0.648MPa, fuel pressure 0.614MPa, spraying distance 240mm, powder feeding rate 3rpm, and spray gun moving speed 1000mm / s.

[0065] The CoCrNi-Y2O3 composite powder after acoustic resonance mixing in step 2 of Examples 1 and 2, and the CoCrNi powder in Comparative Example 1 were subjected to scanning electron microscopy (SEM) imaging. The results are as follows: Figure 1 As shown. From Figure 1 It can be seen that the composite powders in Examples 1 and 2 have good sphericity, with no obvious satellite-shaped spherical particles or irregular spherical particles.

[0066] The coatings prepared in Examples 1, 2, and the comparative examples were imaged using a scanning electron microscope (SEM). The results are as follows: Figure 2 As shown. From Figure 2 It can be seen that the coatings of Comparative Example 1 and Example 1 have good adhesion to the carbon steel substrate, with a coating thickness of approximately 400 μm and a dense coating structure. The coating of Example 1 has better density and smaller pores. In Example 2, the addition of too many Y2O3 ceramic phase particles led to a decrease in coating density and the appearance of a large number of pores.

[0067] The coatings prepared in Examples 1, 2, and Comparative Example 1 were subjected to XRD diffraction imaging. The XRD diffraction patterns are shown below. Figure 3 As shown. From Figure 3 It can be seen that the crystal structures in Examples 1, 2 and Comparative Example 1 are all FCC crystal structures, indicating that adding the Y2O3 phase does not significantly change the structure.

[0068] The hardness of the coatings prepared in Examples 1, 2, and Comparative Example 1 was measured using a Vickers hardness tester, and the results are as follows: Figure 4 As shown. From Figure 4 It can be seen that the hardness of Example 1 is 505 HV. 0.1 The hardness of Example 2 is 550 HV. 0.1 The hardness of Comparative Example 1 is only 404 HV. 0.1 The mechanical properties of the CoCrNi coating were greatly improved after adding 1 wt.% Y2O3 ceramic phase. However, the hardness of the coating was only slightly improved after adding 3 wt.% Y2O3. This is attributed to the fact that the addition of too many Y2O3 ceramic phase particles caused pores in the coating. However, the Y2O3 ceramic phase particles can still improve the hardness of the coating within a certain range through heterogeneous strengthening.

[0069] The potentiodynamic polarization curves of Examples 1, 2, and Comparative Example 1 in 3.5 wt.% NaCl solution were measured using an electrochemical workstation, as shown below. Figure 5 As shown. From Figure 5 It can be seen that the cathodic and anodic polarization curves of Example 1 are wider than those of Comparative Example 1 and Example 2, showing a more obvious passivation region. The passivation range is greater than 1000mV, indicating that the coating of Example 1 can form a stable and dense passivation film on the coating surface during anodic corrosion, exhibiting better corrosion resistance. The self-corrosion current densities of Comparative Example 1 and Examples 1 and 2 are 8.9 × 10⁻⁶. -7 A / cm 2 4.59×10 -7 A / cm 2 27.8×10 -7 A / cm 2 The lower the self-corrosion current density, the better the corrosion resistance of the coating. In summary, Example 1 has better corrosion resistance than Example 2 and Comparative Example 1.

[0070] As can be seen from the above embodiments, the highly corrosion-resistant CoCrNi-based medium-entropy alloy coating and its preparation method provided by the present invention exhibit a dense structure, good mechanical stability, and excellent corrosion resistance in the prepared CoCrNi-based medium-entropy alloy coating. Due to the strengthening effect of Y2O3, the corrosion resistance and mechanical properties of the Y2O3 ceramic phase-reinforced CoCrNi coating obtained by the present invention are comprehensively improved.

[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. The application of a highly corrosion-resistant CoCrNi-based medium-entropy alloy coating in the surface protection of marine engineering equipment, characterized in that: The preparation method of this highly corrosion-resistant CoCrNi-based medium-entropy alloy coating includes the following steps: Step 1: Proportion the ingredients according to the mass ratio. Weigh out CoCrNi alloy powder with a particle size between 15-53μm, and weigh out Y2O3 powder with a particle size of 50nm at a ratio of 1 wt.% to 3 wt.% of the CoCrNi alloy powder. Then, place the CoCrNi powder and Y2O3 powder into a vacuum drying oven and dry them at 60℃ for 12h. Step 2: Preparation of CoCrNi-Y2O3 composite powder The dried CoCrNi powder and Y2O3 powder were placed together into the container inside the acoustic resonance mixing machine, and argon gas was introduced into the container to remove excess air. Then vibrate three times, each time for three minutes, with a one-minute interval between vibrations; sieve the vibrated mixed powder using 300-mesh and 600-mesh screens to collect CoCrNi-Y2O3 composite powder with a particle size of 23-53μm. Step 3: Pretreatment and sandblasting The substrate surface is pretreated, and then the substrate is hot-blasted twice and cold-blasted once. Step 4: Preparation of Y2O3 ceramic phase reinforced CoCrNi-based medium-entropy alloy coating The CoCrNi-Y2O3 composite powder was sprayed onto the substrate surface as a coating using a supersonic flame spraying device. The spraying process parameters were set as follows: air pressure 0.648 MPa, fuel pressure 0.614 MPa, spraying distance 240 mm, powder feeding rate 3 rpm, and spray gun moving speed 1000 mm / s.

2. The application as described in claim 1, characterized in that: The CoCrNi alloy powder is spherical or near-spherical, with a particle size of 15~53 μm and a purity of ≥ 99.95%.

3. The application as described in claim 1, characterized in that: The purity of the Y2O3 powder is ≥99.95%, and the particle size of the Y2O3 powder is 50 nm.

4. The application as described in claim 1, characterized in that: The substrate is made of carbon steel. The method for pre-treating the surface of the substrate is as follows: the substrate is polished to remove surface rust, and then the surface of the substrate is cleaned with acetone to remove surface oil.

5. The application as described in claim 1, characterized in that: The material used for sandblasting is 80-mesh white corundum.

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