CN-121976144-A - Preparation method of high-entropy alloy gradient coating based on layer-by-layer solid-phase densification

CN121976144ACN 121976144 ACN121976144 ACN 121976144ACN-121976144-A

Abstract

The invention belongs to the technical field of preparation of high-entropy alloy gradient coatings, and in particular relates to a preparation method of a high-entropy alloy gradient coating based on layer-by-layer solid-phase densification, comprising the following steps of S1, selecting a metal material as a matrix, and cleaning and roughening the surface of the matrix; S2, quantitatively calculating gradient coating components and determining the number of layers, wherein the total number of layers n of the coating is more than or equal to 3, S3, performing layer-by-layer spray deposition-solid phase densification cyclic manufacturing, and S4, performing final surface treatment. The plasma spraying process and the friction stir processing process are combined and alternately circulated, and the interlayer defects are effectively eliminated layer by layer and the component gradient is constructed in a circulating construction mode of layer by layer spraying and layer by layer solid phase densification, so that the densification degree is high, the bonding strength is high, and the thickness is controllable.

Inventors

WANG WENQUAN
JIANG FAN
ZHANG XINGE
ZUO JIALONG
Ge Lianhong
ZHANG DANDAN
HE ZIQI
Sun Zhuobin
Han Tuanjie

Assignees

吉林大学

Dates

Publication Date: 20260505
Application Date: 20260113

Claims (10)

1. The preparation method of the high-entropy alloy gradient coating based on layer-by-layer solid phase densification is characterized by comprising the following steps of: S1, selecting a metal material as a matrix, and cleaning and roughening the surface of the matrix; S2, quantitatively calculating gradient coating components and determining the number of layers, wherein the total number of layers of the coating ≥3; S3, layer-by-layer spray deposition-solid phase densification cycle manufacturing: (I) The following two processes are sequentially performed for each layer: step A, performing coating deposition treatment by plasma spraying; Step B, performing coating densification treatment through friction stir processing; (II) circulating operation and interlayer treatment, namely checking the forming quality of a processing area after finishing the process B of the current layer, and repeatedly executing the process A and the process B until finishing the preparation of the n-th layer coating under the condition that the forming quality meets the requirement; s4, final surface treatment.
2. The method for preparing a gradient coating of high-entropy alloy based on layer-by-layer solid phase densification according to claim 1, wherein in step S2, the mass percentage of the high-entropy alloy powder is adjusted according to the level by adopting a mode that the high-entropy alloy powder is mixed with the homogeneous powder of the matrix, and the mass percentage of the high-entropy alloy powder of the i-th layer is adjusted according to the level The calculation is performed according to the following formula: ; wherein: The number of the current layers is 1 to less than or equal to ≤ ; Is the total number of layers of the coating; Is the current first High-entropy alloy powder mass percent of the layer; The mass percentage of the high-entropy alloy powder as the bottom layer is 10% -30%; The high-entropy alloy powder is a surface layer, and the value range is 80% -100%; is a fixed increment of high entropy alloy content between coatings.
3. The method for preparing a gradient coating of high-entropy alloy based on layer-by-layer solid phase densification according to claim 2, wherein in the step S3, the current layer of coating is deposited by using an atmospheric plasma spraying device, and the thickness is deposited by single-layer spraying The value range of (2) is 0.1 mm-1.0 mm.
4. The method for preparing a gradient coating of high-entropy alloy based on layer-by-layer solid phase densification according to claim 3, wherein the spraying process parameters in the procedure a of the step S3 are as follows: the spraying current is 450A-550A; The spraying voltage is 40V-55V; The flow rate of the main gas Ar is 35L/min-45L/min; the flow rate of the auxiliary gas H2 is 5L/min-10L/min; The powder feeding rate is 20 g/min-30 g/min; the spraying distance is 90 mm-110 mm; And (3) cooling the coating, namely after the spraying is finished, cooling the surface of the coating by compressed air or naturally cooling, and after the temperature of the coating is reduced to below 100 ℃, performing the operation of the step B.
5. The preparation method of the high-entropy alloy gradient coating based on layer-by-layer solid phase densification according to claim 4, wherein in the step B of the step S3, a needleless stirring head made of hard alloy WC-Co or polycrystalline cubic boron nitride is adopted to carry out friction stir processing, the diameter of a shaft shoulder of the needleless stirring head is 10 mm-15 mm, the end face of the shaft shoulder of the needleless stirring head is of a concave structure, and the concave angle is 3-8 degrees.
6. The method for preparing a gradient coating of high-entropy alloy based on layer-by-layer solid phase densification according to claim 5, wherein the densification of the coating in step S3 is performed in the following manner: And (3) cooling the surface of the coating, and after the temperature of the surface of the coating is reduced to below 100 ℃, adopting a needleless stirring head to stir and rub the current layer, introducing local inert gas for protection in the stirring and rubbing processing process, wherein the flow of the protective gas is 15L/min-25L/min, and the protection area of the inert gas is a stirring and rubbing processing area.
7. The method for preparing the high-entropy alloy gradient coating based on layer-by-layer solid phase densification according to claim 6, wherein the shoulder pressing depth of the needleless stirring head is as follows According to the thickness of single-layer spray deposition The dynamic setting is carried out, and the specific calculation formula is as follows: ; wherein: ; the thickness of the single-layer spray coating deposition is the thickness; The value range of the densification coefficient is 0.25-0.5.
8. The preparation method of the high-entropy alloy gradient coating based on layer-by-layer solid phase densification, which is characterized in that the rotation speed of the needleless stirring head is 1000 rpm-1500 rpm, the advancing speed is 60 mm/min-100 mm/min, and the inclination angle of the shaft shoulder of the needleless stirring head is 2-2.5 degrees.
9. The method for preparing the high-entropy alloy gradient coating based on layer-by-layer solid phase densification according to claim 8, wherein the method comprises the steps of, The method for checking the forming quality of the processing area after the step B of the current layer is completed in the step S3 is as follows: (1) The edge treatment of the friction stir processing area, namely removing the edge flash by using a mechanical or manual polishing mode if the flash generated by stirring and extrusion exists at the edge of the coating; (2) The surface state of the friction stir processing area is reserved, and the microscopic arc concave-convex texture of the surface is reserved; The final surface treatment in step S4 is as follows: and after the preset total number of layers is reached, carrying out mechanical grinding or polishing treatment on the surface of the outermost layer according to the final dimensional accuracy and surface quality requirements of the product, and obtaining the high-entropy alloy gradient coating with compact inside and gradient distribution of components.
10. The method for preparing a high-entropy alloy gradient coating based on layer-by-layer solid phase densification according to claim 9, wherein the step S1 is to clean and roughen the surface of the substrate by: (1) Carrying out sand blasting roughening treatment on the surface of the matrix by adopting corundum sand with the granularity of 24-60 meshes, and controlling the sand blasting air pressure to be 0.5-0.7 MPa; (2) And ultrasonically cleaning the matrix for 10-15 min by using acetone or absolute ethyl alcohol, and drying for later use after cleaning.

Description

Preparation method of high-entropy alloy gradient coating based on layer-by-layer solid-phase densification Technical Field The invention belongs to the technical field of preparation of high-entropy alloy gradient coatings, and particularly relates to a preparation method of a high-entropy alloy gradient coating based on layer-by-layer solid-phase densification. Background Gradient coating is a form of functionally structured integrated coating characterized by a continuous or quasi-continuous variation of the composition, organization and properties of the coating in a certain dimension. Compared with the traditional coating with uniform components, the gradient design can effectively relieve the interface stress concentration between the coating and the matrix caused by the abrupt change of the performance, and realize the smooth transition from the matrix to the surface, thereby remarkably improving the bonding strength, the toughness and the overall service reliability of the coating. Therefore, developing a high-performance gradient coating has important significance for meeting the use requirements of aerospace, energy equipment and other extreme working conditions. In recent years, with the continuous emergence of new materials, high-entropy alloy provides brand new possibility for the design and preparation of gradient coatings. The high-entropy alloy is a novel alloy material composed of five or more metal elements in equal proportion or nearly equal proportion. Since the high entropy alloy has a higher mixed entropy, it makes it easier to form a solid solution structure, rather than brittle intermetallic compounds. Therefore, the high-entropy alloy has excellent comprehensive properties of high strength, high hardness, excellent high-temperature stability, wear resistance, corrosion resistance and the like, so that the high-entropy alloy becomes an ideal material for preparing high-performance gradient coatings. Plasma spraying is a common method for preparing high-entropy alloy coating due to the advantages of low substrate temperature rise, wide range of sprayable materials, high deposition efficiency and the like. However, during the spraying process, the spray powder is in a molten or semi-molten state under the high temperature of the plasma flame stream and impinges on the spray substrate at a high velocity. These molten or semi-molten spray powders spread, solidify and stack layer-by-layer on the substrate surface to form a lamellar structure, ultimately forming a coating. It is these characteristics that lead to defects such as unavoidable pores, oxide inclusions, and microcracks inside the coating. These defects seriously affect the compactness of the coating and impair its mechanical properties. In order to solve the inherent defects of continuous oxide film, high porosity, low bonding strength between sheets and the like formed by oxidizing the surfaces of spray powder particles due to higher spray flame flow temperature in the traditional plasma spraying process, researchers try to introduce a friction stir processing technology to carry out aftertreatment. The friction stir processing is a solid phase material surface modification technology developed based on the friction stir welding principle, and utilizes a rotating stirring head to generate friction heat and severe plastic deformation on the surface of the material, so that a continuous oxide film is crushed and dispersed into fine reinforced particles, and meanwhile, pore closure and tissue refinement and densification of the material can be realized. Because the processing temperature is lower than the melting point of the material, the friction stir processing can effectively avoid secondary defects caused by melting and solidification, and has great potential in improving the quality of the sprayed coating. However, in terms of preparing a high-performance high-thickness high-entropy alloy coating with an accurate gradient structure, a certain technical bottleneck still exists in the above technical means, for example, a preparation method for preparing a high-entropy alloy coating and in-situ generation thereof is disclosed in Chinese patent application with application publication number of CN118932328A, and the method comprises the steps of firstly cold spraying a first high-entropy alloy coating on the surface of a metal substrate such as aluminum, magnesium, copper, titanium and the like, then carrying out one-time penetrating friction stir processing (the stirring depth is greater than the coating thickness), so that the first high-entropy alloy and the substrate metal are subjected to in-situ alloying to form a second high-entropy alloy coating, and the bonding strength, plasticity and compactness of the coating are obviously improved. The design initially and the application range of the method are limited to in-situ modification of a single layer or a thin coating, and the plastic deformation and densification effec