A high-temperature stable multi-element nanocomposite coating with a gradient structure and a preparation method thereof

Abstract

The present application relates to a kind of high-temperature stable multi-element nanocomposite coating with gradient structure and its preparation method, belong to metal material surface engineering technical field.It includes metal bonding layer, transition layer and working layer from inside to outside in turn, the metal bonding layer is located on the surface of matrix, for improving the binding force of coating and matrix.Transition layer is composed of metal matrix and first composite additive phase, for relieving the internal stress generated due to mismatch of thermal expansion coefficient.Working layer is composed of metal matrix, second composite additive phase and third additive phase, for providing excellent wear resistance and friction reduction performance.First composite additive phase is the mixed particles of nanometer silicon carbide and nanometer aluminum oxide, second composite additive phase is the mixed particles of nanometer silicon carbide and nanometer zirconium oxide, and third additive phase is rare earth oxide nanoparticles.The present application realizes the ultra-uniform dispersion of nanoparticles in nanocomposite coating and long-term stability under high temperature.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology of metallic materials, and relates to a high-temperature stable multi-component nanocomposite coating with a gradient structure for use under high-temperature and heavy-load conditions and its preparation method. Background Technology

[0002] In industries such as metallurgy, machinery, and energy, friction and wear of metal equipment under high temperature and heavy load conditions are among the main causes of failure. Metal-based nanocomposite coating technology, by adding nano-ceramic particles to a metal matrix and utilizing mechanisms such as fine grain strengthening and dispersion strengthening, significantly improves the hardness and wear resistance of the coating, showing broad application prospects.

[0003] However, existing technologies (such as nickel-based nano-SiC-Al2O3 composite electroplating) still have the following technical bottlenecks: 1) Nanoparticles are prone to agglomeration: High surface energy nanoparticles are difficult to achieve monodispersity in metal matrices and tend to form micron-sized agglomerates. Not only can they not exert the nano effect, but they also become stress concentration sources, leading to the deterioration of coating performance.

[0004] 2) High-temperature performance degradation: Under long-term high-temperature service environment, the elements inside the coating undergo interdiffusion, the nanoparticles coarsen or react with the matrix at the interface, resulting in a sharp decline in the fine grain strengthening and dispersion strengthening effects, and the coating hardness and wear resistance are significantly reduced, making it difficult to meet the requirements of high-temperature and long-life working conditions.

[0005] 3) Simple structure: Traditional composite coatings are mostly homogeneous structures, which make it difficult to balance the bonding strength between the coating and the substrate, the toughness inside the coating, and the ultra-high hardness of the surface. Under heavy load conditions, they are prone to peeling failure.

[0006] Therefore, developing a metal-based nanocomposite coating that can effectively suppress nanoparticle aggregation and has excellent structural stability and mechanical properties at high temperatures remains a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a high-temperature stable multi-component nanocomposite coating with a gradient structure and its preparation method. By introducing a third component, rare earth oxide, and constructing a composition and structural gradient, ultra-uniform dispersion of nanoparticles and long-term stability at high temperatures are achieved, solving the problems of easy agglomeration of nanoparticles, high-temperature performance degradation, and simple structure in the prior art.

[0008] To achieve the above objectives, the present invention provides a high-temperature stable multi-element nanocomposite coating with a gradient structure, which includes a metal bonding layer, a transition layer and a working layer from the inside to the outside. The metal bonding layer is located on the surface of the substrate and has a thickness of 5~20 μm, which is used to improve the adhesion between the coating and the substrate.

[0009] The transition layer, consisting of a metal matrix and a first composite additive phase, has a thickness of 20–50 μm and is used to alleviate internal stress caused by the mismatch in thermal expansion coefficients. The working layer, consisting of a metal matrix, a second composite additive phase, and a third additive phase, has a thickness of 50–200 μm and is used to provide excellent wear resistance and friction reduction properties.

[0010] Furthermore, the metal matrix is ​​nickel or a nickel-cobalt alloy.

[0011] The first composite additive phase is a mixture of nano-silicon carbide and nano-alumina particles, the second composite additive phase is a mixture of nano-silicon carbide and nano-zirconia particles, and the third additive phase is rare earth oxide nanoparticles. Preferably, the third additive phase is nano-lanthanum oxide or nano-cerium oxide particles.

[0012] Furthermore, the diameter of the rare earth oxide nanoparticles is smaller than the diameter of the nanoparticles in the second composite additive phase.

[0013] Furthermore, in the transition layer, the volume ratio of the first composite additive phase to the metal matrix is ​​5:100, and the particle diameter in the first composite additive phase is 50~80 nm.

[0014] Furthermore, in the working layer, the volume ratio of the second composite additive phase to the metal matrix is ​​10:100 to 15:100, and the particle diameter in the second composite additive phase is 50~80 nm; the amount of the third additive phase added is 1%~5% of the total mass of the second composite additive phase, and the particle diameter in the third additive phase is 10~30 nm.

[0015] Another aspect of the present invention provides a method for preparing a high-temperature stable multi-component nanocomposite coating with a gradient structure, the method comprising: Pretreatment of the matrix; A pure nickel or nickel-cobalt alloy layer with a thickness of 5-20 μm is deposited on the pretreated substrate surface using electroplating or chemical plating methods to form a metal bonding layer; A base plating solution is prepared, and then a first composite plating solution and a second composite plating solution are prepared based on the base plating solution; wherein, the first composite plating solution is obtained by adding a first composite additive phase that has been pre-ultrasonically dispersed to the base plating solution; the second composite plating solution is obtained by adding a second composite additive phase and a third additive phase that have been pre-ultrasonically dispersed to the base plating solution; The substrate with the deposited metal binder layer is placed in the first composite plating solution, and a transition layer with a thickness of 20~50 μm is deposited on the surface of the metal binder layer using DC electroplating or pulse electroplating. The electroplating process parameters are: current density 1~5 A / dm², temperature 40~60℃, pH 3.5~5.0. The substrate with the transition layer is transferred to the second composite plating solution, and a working layer with a thickness of 50~200 μm is deposited on the surface of the transition layer using the same electroplating process.

[0016] After the coating sample has been deposited, it is cleaned and dried to obtain a high-temperature stable multi-component nanocomposite coating with a gradient structure.

[0017] Furthermore, the base plating solution includes nickel salts, cobalt salts, complexing agents, buffers, and surfactants.

[0018] Furthermore, the volume fraction of the first composite additive phase in the first composite plating solution is 5%; the volume fraction of the second composite additive phase in the second composite plating solution is 10-15%; and the amount of the third additive phase added is 1%-5% of the mass of the second composite additive phase.

[0019] The beneficial effects of this invention are as follows: (1) Achieving ultra-uniform dispersion of nanoparticles: This invention introduces a third phase of rare earth oxide nanoparticles (La2O3 / CeO2) with a large difference in dielectric constant from the main nanoparticles (SiC, ZrO2). The presence of the third phase can regulate the Hamek constant of the system, making its negative absolute value larger, thereby generating stronger repulsive force between the main nanoparticles, effectively suppressing the agglomeration of SiC and ZrO2 particles, and achieving a dispersion effect far superior to the prior art.

[0020] (2) Excellent high-temperature stability of the coating: Due to their high surface energy and unique electronic structure, rare earth oxide nanoparticles preferentially segregate at the grain boundaries of the metal matrix during electrodeposition. During high-temperature service, these nanoparticles generate a strong drag force on grain boundary migration through the Zener pinning effect, effectively inhibiting the growth of metal matrix grains and the Ostwald ripening of second-phase particles, thus solving the industry problem of rapid degradation of the high-temperature performance of traditional nanocomposite coatings.

[0021] (3) A strong and tough integrated gradient structure was constructed: By designing a gradient structure from a pure metal bonding layer, a transition layer with low particle content to a working layer with high particle content, the difference in thermal expansion coefficient and stress concentration between the coating and the substrate were effectively alleviated. This ensured both the high bonding strength between the coating and the substrate (bonding layer) and gave the coating surface ultra-high hardness and wear resistance (working layer), avoiding the defect of easy peeling of traditional single-layer coatings under heavy load conditions.

[0022] (4) Experiments show that the wear of the gradient composite coating prepared by the present invention at 800℃ is only 1 / 5 of that of the prior art, and after 100 hours of heat treatment at 800℃, its hardness retention rate is as high as 90%, while the hardness of the coating of the prior art decreases by more than 40% under the same conditions, thus achieving long-term stability at high temperature.

[0023] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a cross-sectional structural diagram of a high-temperature stable multi-element nanocomposite coating with a gradient structure provided in Embodiment 1 of the present invention.

[0025] Figure 2 This is a schematic diagram of the mechanism of rare earth oxide-assisted nanoparticle dispersion in the working layer, where (a) shows the state of easy particle agglomeration in the prior art without rare earth addition, and (b) shows the state of ultra-uniform particle dispersion after adding rare earth in this invention.

[0026] Figure 3 This is a comparative schematic diagram of the grain structure of the coating of the present invention and the coating of the prior art after long-term heat treatment at 800°C. (a) shows the grain growth and coarsening of the coating of the prior art, and (b) shows the grains of the coating of the present invention being pinned by rare earth particles and kept small.

[0027] Figure 4 The process flow diagram for preparing the high-temperature stable multi-component nanocomposite coating with gradient structure provided by the present invention is shown.

[0028] Reference numerals: 100-substrate, 101-metallic adhesive layer, 102-transition layer, 103-working layer. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0031] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0032] Example 1 This embodiment provides a high-temperature stable multi-element nanocomposite coating with a gradient structure. From the inside out, the coating consists of a metal bonding layer 101, a transition layer 102, and a working layer 103. Figure 1 As shown.

[0033] The metal bonding layer 101 is located on the surface of the substrate 100 and has a thickness of 5 μm, which is used to improve the adhesion between the coating and the substrate 100.

[0034] The transition layer 102 is located above the metal bonding layer 101, with a thickness of 20 μm, and is composed of a metal matrix and a first composite additive phase, used to alleviate the internal stress caused by the mismatch of thermal expansion coefficients. The working layer 103 is located above the transition layer and has a thickness of 50 μm. It consists of a metal matrix, a second composite additive phase, and a third additive phase, and is used to provide excellent wear resistance and friction reduction properties.

[0035] In this embodiment, the metal matrix is ​​nickel.

[0036] The first composite additive phase is a mixture of nano-silicon carbide (SiC) and nano-alumina (Al2O3) particles with a volume ratio of 5:100 to the metal matrix and a particle diameter of 50 nm.

[0037] The second composite additive phase is a mixture of nano-silicon carbide (SiC) and nano-zirconia (ZrO2) particles, with a volume ratio of 10~15:100 to the metal matrix and a particle diameter of 50 nm.

[0038] The third additive phase is rare earth oxide nanoparticles, specifically nano-lanthanum oxide (La2O3), and its addition amount is 5% of the total mass of the second composite additive phase.

[0039] In the working layer, the Hamelin constant of the nanocomposite coating system is negative and its absolute value is greater than that of the Hamelin constant of the single composite additive phase system through doping modification of rare earth oxide nanoparticles, thereby achieving ultra-uniform dispersion of the second composite additive phase (e.g., Figure 2 As shown), and at high temperatures, it pins grain boundaries, inhibits grain growth and grain coarsening (e.g. Figure 3 (As shown).

[0040] Example 2 This embodiment provides a method for preparing a high-temperature stable multi-element nanocomposite coating with a gradient structure, such as... Figure 4 As shown, it includes the following steps: (1) Material selection: Nano SiC and nano Al2O3 with a diameter of 60 nm were selected as the first composite additive phase; nano SiC and nano ZrO2 with a diameter of 60 nm were selected as the second composite additive phase; nano La2O3 with a diameter of 20 nm was selected as the third additive phase; the metal matrix was nickel.

[0041] (2) Pretreatment of the substrate: The 45# steel substrate is degreased, pickled and activated.

[0042] (3) Preparation of metal bonding layer: A pure nickel layer with a thickness of 10 μm is deposited on the pretreated substrate surface by electroplating to form a metal bonding layer.

[0043] (4) Preparation of electroplating solution: Base plating solution: Nickel sulfamate 300 g / L, nickel chloride 10 g / L, boric acid 30 g / L, sodium dodecyl sulfate 0.1 g / L; First composite plating solution: Pre-ultrasonically dispersed nano-SiC and Al2O3 (volume ratio 1:1) are added to the base plating solution to achieve a volume fraction of 5% in the plating solution; Second composite plating solution: Pre-ultrasonically dispersed nano-SiC and ZrO2 (volume ratio 1:1) and nano-La2O3 are added to the base plating solution, wherein the volume fraction of the second composite added phase is 12% and the amount of nano-La2O3 added is 3% of the total mass of the second composite added phase.

[0044] (5) Electrodeposition of gradient coatings: First, the substrate was placed in the first composite plating solution and electroplated using direct current (current density 2 A / dm², temperature 50℃, pH 4.0) for 30 minutes to obtain a transition layer with a thickness of about 30 μm. Then, the substrate with the transition layer is transferred to the second composite plating solution, and the same electroplating process is used to deposit it for 90 minutes to obtain a working layer with a thickness of about 100 μm.

[0045] (6) Post-treatment: The deposited coating sample is washed with deionized water and dried to obtain the high-temperature stable multi-element nanocomposite coating with gradient structure.

[0046] Example 3 The process is basically the same as in Example 2, except that: the third additive phase is nano CeO2, and the amount added is 5% of the total mass of the second composite additive phase; the working layer deposition time is 120 minutes, and the thickness is about 150 μm.

[0047] Example 4 It is basically the same as Example 1, except that: the metal substrate is a nickel-cobalt alloy (cobalt content 10%); the thickness of the transition layer is 20 μm and the thickness of the working layer is 80 μm.

[0048] The performance of the composite coating prepared in Example 2 was tested and compared with that of the prior art (nickel-based nano SiC-Al2O3 composite coating).

[0049] Hardness test: A microhardness tester was used, with a load of 50 g and a loading time of 10 s. The test results showed that the surface hardness of the coating of this invention was HV0.05 495, while that of the prior art coating was HV0.05 200.

[0050] Wear test: A reciprocating friction and wear tester was used, with Si3N4 ceramic balls as the friction component, a load of 15 N, a time of 60 min, and a high temperature of 800℃. The test results showed that the wear amount of the coating of the present invention was 0.045 mm³, while the wear amount of the coating of the prior art was 0.225 mm³ (approximately 5 times that of the present invention).

[0051] High-temperature stability test: After the coating was subjected to vacuum heat treatment at 800℃ for 100 hours, the hardness was tested again. The test results showed that the hardness retention rate of the coating of the present invention was 92%, while the hardness retention rate of the coating of the prior art was 58%.

[0052] According to the test results, the coating of the present invention has achieved significantly better results than the prior art in terms of hardness, wear resistance and high temperature stability.

[0053] In summary, this invention can effectively suppress the agglomeration of SiC and ZrO2 particles, achieving a dispersion effect far superior to existing technologies; it can effectively suppress the growth of metal matrix grains and the Ostwald ripening of second-phase particles, solving the industry problem of rapid degradation of the high-temperature performance of traditional nanocomposite coatings; it can effectively alleviate the difference in thermal expansion coefficients and stress concentration between the coating and the substrate, ensuring both high bonding strength between the coating and the substrate (adhesive layer) and endowing the coating surface with ultra-high hardness and wear resistance (working layer), avoiding the defect of easy peeling of traditional single-layer coatings under heavy load conditions.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-temperature stable multi-element nanocomposite coating with a gradient structure, characterized in that, From the inside out, it includes a metal bonding layer, a transition layer, and a working layer, wherein the metal bonding layer is located on the surface of the substrate; The transition layer is composed of a metal matrix and a first composite additive phase; the working layer is composed of a metal matrix, a second composite additive phase, and a third additive phase.

2. The coating according to claim 1, characterized in that, The metal matrix is ​​nickel or a nickel-cobalt alloy.

3. The coating according to claim 1, characterized in that, The first composite additive phase is a mixture of nano-silicon carbide and nano-alumina particles, the second composite additive phase is a mixture of nano-silicon carbide and nano-zirconia particles, and the third additive phase is rare earth oxide nanoparticles.

4. The coating according to claim 3, characterized in that, The third additive phase is nano-lanthanum oxide or nano-cerium oxide particles.

5. The coating according to claim 4, characterized in that, The diameter of the rare earth oxide nanoparticles is smaller than that of the nanoparticles in the second composite additive phase.

6. The coating according to claim 3, characterized in that, In the transition layer, the volume ratio of the first composite additive phase to the metal matrix is ​​5:100, and the particle diameter of the first composite additive phase is 50~80 nm.

7. The coating according to claim 3, characterized in that, In the working layer, the volume ratio of the second composite additive phase to the metal matrix is ​​10:100 to 15:100, and the particle diameter in the second composite additive phase is 50~80 nm; the amount of the third additive phase added is 1%~5% of the total mass of the second composite additive phase.

8. A method for preparing a high-temperature stable multi-component nanocomposite coating with a gradient structure, characterized in that, Pretreatment of the matrix; A metal bonding layer is deposited on the pretreated substrate surface; A base plating solution is prepared, and then a first composite plating solution and a second composite plating solution are prepared based on the base plating solution; wherein, the first composite plating solution is obtained by adding a first composite additive phase that has been pre-ultrasonically dispersed to the base plating solution; The second composite plating solution is obtained by adding a pre-ultrasonically dispersed second composite additive phase and a third additive phase to a base plating solution. The substrate with the deposited metal bonding layer is placed in the first composite plating solution, and a transition layer is deposited on the surface of the metal bonding layer. The substrate with the transition layer is transferred to the second composite plating solution, and the working layer is deposited on the surface of the transition layer. The coated sample was cleaned and dried after deposition.

9. The preparation method according to claim 8, characterized in that, The base plating solution includes nickel salt, cobalt salt, complexing agent, buffer, and surfactant; the first composite additive phase is a mixture of nano-silicon carbide and nano-alumina particles, the second composite additive phase is a mixture of nano-silicon carbide and nano-zirconia particles, and the third additive phase is rare earth oxide nanoparticles.

10. The preparation method according to claim 9, characterized in that, The first composite additive phase has a volume fraction of 5% in the first composite plating solution; the second composite additive phase has a volume fraction of 10-15% in the second composite plating solution; and the third additive phase has an addition amount of 1%-5% of the mass of the second composite additive phase.

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