Gradient wear-resistant coating based on superfine high-temperature alloy waste powder and preparation method of gradient wear-resistant coating

Abstract

The invention provides a gradient wear-resistant coating based on superfine high-temperature alloy waste powder and a preparation method thereof.The superfine high-temperature alloy waste powder with the particle size smaller than 15 microns generated by gas atomization powder preparation is used as a main raw material, the superfine high-temperature alloy waste powder, WC powder and Co powder are subjected to ball-milling compounding according to a preset proportion, then spray granulation and radio frequency plasma spheroidizing treatment are conducted, and the gradient wear-resistant coating based on the superfine high-temperature alloy waste powder is obtained. A series of gradient composite powder with controllable components and sphericity greater than 0.92 is prepared; and then a thermal spraying process is adopted for sequentially spraying the powder on the surface of a base body, a gradient coating structure from a bonding layer, a transition layer to a wear-resistant surface layer is formed, and the microhardness of the gradient coating structure is stably transited from 280-400 HV at the interface of the base body to 1250-1450 HV of the surface layer. According to the method, high value-added utilization (the utilization rate gt is 95%) of the superfine waste powder is achieved, the bonding strength of the prepared coating reaches 65-85 MPa, the wear resistance is improved by 150%-300% compared with a pure alloy coating, the process is stable, and the cost benefit is remarkable.

Description

Technical Field

[0001] This invention relates to the field of metal powder recycling and surface engineering technology, specifically to a method for preparing a wear-resistant coating with a gradient structure of composition and performance from ultrafine high-temperature alloy waste powder generated during the gas atomization powder preparation process through specific material design and powder remanufacturing technology, and the resulting coating product. Background Technology

[0002] High-temperature alloys, due to their excellent high-temperature strength, corrosion resistance, and fatigue resistance, are widely used in core components in aerospace, energy, and other fields. In recent years, additive manufacturing technologies such as selective laser melting (SLM) have become important methods for preparing complex high-temperature alloy components. However, during the gas atomization process of preparing high-temperature alloy powder, a certain amount of ultrafine powder with a particle size of less than 15 μm is inevitably generated. This powder, especially because its particle size distribution does not meet the 15–53 μm particle size range typically required by additive manufacturing processes such as SLM, is prone to problems such as poor flowability, satellite powder, and high oxygen content. Therefore, it is usually treated as waste powder, resulting in a serious waste of resources and loss of high-value materials.

[0003] On the other hand, equipment components operating under harsh wear conditions often require wear-resistant coatings to extend their service life. WC-Co based cemented carbide coatings are widely used due to their high hardness and excellent wear resistance. Traditional methods typically involve spraying with commercially available WC-Co composite powders or mechanically mixed powders. However, coatings prepared directly from these powders exhibit significant differences in physical (e.g., coefficient of thermal expansion) and chemical properties with the high-temperature alloy substrate, leading to high internal stress, low bonding strength, and susceptibility to cracking and peeling under alternating loads or thermal shock. To alleviate this problem, researchers have proposed the concept of functionally graded coatings, which involve designing an intermediate layer between the coating and the substrate with a continuous transition in composition, microstructure, and properties to improve stress distribution and enhance bonding strength.

[0004] Currently, there are two main conventional technical approaches to achieve gradient coatings: one is to mix powders of different proportions in real time through multiple powder feeders during the spraying process, but this method involves complex equipment, difficult process control, and poor reproducibility; the other is to prepare several composite powders with fixed components in advance for layered spraying, but there are still interfaces with abrupt changes in composition between the layers, which is not an ideal continuous gradient, and the powders used are mostly commercially available powders, which are costly.

[0005] Therefore, how to transform the ultrafine high-temperature alloy waste powder generated by additive manufacturing, which is difficult to recycle directly, into high-value-added products, and innovatively use it as a matrix phase to design and prepare a series of gradient composite powders with precise controllable composition and good physical properties, thereby efficiently preparing gradient wear-resistant coatings with high bonding strength, excellent wear resistance, and controllable cost, has become a technical problem that urgently needs to be solved in this field. This invention is proposed to address the above-mentioned problems. Summary of the Invention

[0006] The present invention aims to solve the following problems existing in the prior art: resource waste and coating adhesion and performance issues.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a gradient wear-resistant coating based on ultrafine high-temperature alloy waste powder is disclosed. The method uses one or more of the following powder raw materials: ultrafine high-temperature alloy waste powder with a particle size less than 15 μm, WC powder, and Co powder. Through mechanical mixing and ball milling, followed by spray granulation and radio frequency plasma spheroidization treatment, a binder layer powder, a gradient transition layer powder, and a wear-resistant surface layer powder are obtained. Finally, the binder layer powder, gradient transition layer powder, and wear-resistant surface layer powder are sequentially sprayed onto a substrate using a thermal spraying process to form a gradient wear-resistant coating. From the bonding layer to the wear-resistant surface layer, the content of the ultrafine high-temperature alloy waste powder decreases, while the sum of the contents of the WC powder and Co powder increases.

[0008] Furthermore, the method for preparing the gradient wear-resistant coating of the present invention specifically includes the following steps: Step 1: Pretreatment of ultrafine high-temperature alloy waste powder and system design of gradient composite powder: a) Collect ultrafine high-temperature alloy waste powder with a particle size of less than 15 μm; b) The design includes a gradient composition system comprising a binder layer powder, at least two gradient transition layer powders, and a wear-resistant surface powder; wherein the powder raw material of the gradient transition layer powder includes the ultrafine high-temperature alloy waste powder; Step 2: Preparation of gradient composite powder: A) Based on the gradient composition system designed in step one (b), the ultrafine high-temperature alloy waste powder is mechanically mixed and ball-milled with WC powder and Co powder in a preset ratio to obtain composite powder precursors with different compositions. B) The composite powder precursor is spray-granulated to obtain composite powder, and the composite powder is spheroidized by radio frequency plasma to prepare gradient composite powder with sphericity greater than 0.92 and flowability <35 s / 50g. The gradient composite powder includes a gradient transition layer powder and a wear-resistant surface layer powder: The gradient transition layer powder is composed of 20-75 parts by weight of ultrafine high-temperature alloy waste powder, 10-35 parts by weight of Co powder, and 10-70 parts by weight of WC powder. The wear-resistant surface powder is composed of 0-20 parts by weight of ultrafine high-temperature alloy waste powder, 10-20 parts by weight of Co powder, and 70-85 parts by weight of WC powder.

[0009] Specifically, ultrafine high-temperature alloy waste powder with a particle size of less than 15 μm was selected as the main matrix phase for the transition layer and wear-resistant surface layer in the gradient coating. A complete coating system from the substrate to the surface was designed, which includes at least: an adhesive layer, at least two gradient transition layers, and a wear-resistant surface layer.

[0010] The preparation of gradient composite powders is a key innovative step: Composition Design and Mixing: Precise composition ratios were designed based on the performance requirements of each layer of the gradient coating. The ultrafine high-temperature alloy waste powder was mixed with different proportions of tungsten carbide (WC) powder and cobalt (Co) powder. A typical gradient composition design from the transition layer to the wear-resistant surface layer is as follows: from the transition layer near the substrate to the surface layer, the content of ultrafine high-temperature alloy waste powder decreases from 55-75 parts by mass to 0-20 parts by mass, while the content of the hard reinforcing phase WC powder increases from 10-30 parts by mass to 70-85 parts by mass, and the content of the metallic binder phase Co powder decreases from 15-35 parts by mass to 10-20 parts by mass.

[0011] Powder compounding and spheroidization: The prepared mixture is subjected to mechanical compounding treatment such as high-energy ball milling to uniformly coat or embed high-temperature alloy waste powder particles with WC powder and Co powder, forming a composite powder precursor with uniform composition. Subsequently, the precursor is spray-granulated to obtain composite powder, which is then subjected to radio frequency plasma spheroidization treatment to finally obtain a series of gradient composite powders with a sphericity greater than 0.92, flowability <35 s / 50g, and precise controllable composition.

[0012] The gradient coating is constructed using thermal spraying processes such as high-velocity oxygen fuel (HVOF) spraying or atmospheric plasma spraying (APS). In particular, because HVOF spraying possesses the characteristics of low temperature and high speed, it can minimize overheating and burn-off of the powder during flight, better preserving the designed composition and microstructure of the composite powder. Therefore, it is the preferred process for preparing the high-performance gradient coating of this invention. Using a single powder feeder, the corresponding powders prepared in step two are sequentially sprayed onto the pretreated substrate surface in the order of adhesive layer → gradient transition layer (from inside to outside) → wear-resistant surface layer. By controlling the thickness of each layer and the spraying parameters, a wear-resistant coating with controllable total thickness, no obvious interlayer interfaces, and a continuous gradient variation in composition and properties is finally formed.

[0013] Furthermore, the spraying distance of the supersonic flame spraying is 100~200 mm, and the powder feeding rate is 10~40 g / min.

[0014] To further improve the density and interlayer adhesion of the coating, a diffusion heat treatment can be performed on the gradient coating after spraying. This heat treatment is carried out at a temperature below the harmful phase transformation point of the substrate material, aiming to strengthen metallurgical bonding and eliminate microscopic defects by promoting atomic interdiffusion within and between the coating layers, while ensuring that the mechanical properties of the substrate are not compromised.

[0015] Furthermore, in the method for preparing the gradient wear-resistant coating of the present invention, the gradient transition layer powder includes at least a first transition layer powder and a second transition layer powder. The first transition layer powder consists of 55-75 parts by weight of ultrafine high-temperature alloy waste powder, 15-35 parts by weight of Co powder, and 10-30 parts by weight of WC powder. The second transition layer powder consists of 20-45 parts by weight of ultrafine high-temperature alloy waste powder, 10-35 parts by weight of Co powder, and 45-70 parts by weight of WC powder.

[0016] Furthermore, in the method for preparing the gradient wear-resistant coating of the present invention, the adhesive layer powder is a normal spherical high-temperature alloy powder with a particle size of 15~53μm or a Co-containing composite powder prepared from the ultrafine high-temperature alloy waste powder.

[0017] Furthermore, in the method for preparing the gradient wear-resistant coating of the present invention, the ball milling composite treatment time is 4~12 h.

[0018] Furthermore, in the method for preparing the gradient wear-resistant coating of the present invention, the thermal spraying process is supersonic flame spraying or atmospheric plasma spraying.

[0019] Furthermore, the method for preparing the gradient wear-resistant coating of the present invention further includes heat-treating the gradient wear-resistant coating in a vacuum or protective atmosphere, holding it at 700°C to 850°C for 1 to 4 hours, and then cooling it to below 200°C before removing it from the furnace.

[0020] According to the above method, the present invention also provides a gradient wear-resistant coating, wherein the gradient wear-resistant coating comprises, from the substrate to the surface, the following layers in sequence: an adhesive layer, at least two gradient transition layers, and a wear-resistant surface layer; The adhesive layer is formed by thermal spraying of adhesive layer powder, which is a normal spherical high-temperature alloy powder with a particle size of 15~53 μm or a Co-containing composite powder prepared from the ultrafine high-temperature alloy waste powder. The gradient transition layer is formed by thermal spraying of gradient transition layer powder, which consists of 20-75 parts by weight of ultrafine high-temperature alloy waste powder, 10-35 parts by weight of Co powder, and 10-70 parts by weight of WC powder. The wear-resistant surface layer is formed by thermal spraying of wear-resistant surface layer powder, which consists of 0-20 parts by weight of ultrafine high-temperature alloy waste powder, 10-20 parts by weight of Co powder, and 70-85 parts by weight of WC powder.

[0021] Furthermore, the gradient transition layer of the gradient wear-resistant coating of the present invention has 2 to 4 layers.

[0022] Furthermore, the gradient wear-resistant coating of the present invention exhibits increasing hardness and wear resistance from the adhesive layer to the wear-resistant surface layer.

[0023] This coating enables efficient utilization of ultrafine waste powder and exhibits excellent overall wear resistance.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: This method achieves high-value-added resource utilization of waste powder: transforming previously unusable and low-value ultrafine high-temperature alloy waste powder into a key raw material for high-performance coatings, thus "turning waste into treasure." The utilization rate of ultrafine waste powder can reach over 95%, resulting in significant economic and social benefits.

[0025] An innovative design and preparation path for gradient coating materials has been developed: through an integrated process of "composition design - mechanical compounding - spray granulation - plasma spheroidization," a series of gradient composite powders with controllable composition, good sphericity, and excellent flowability have been successfully prepared. This powder can be directly used in standard thermal spraying equipment, avoiding the complex and unstable real-time mixing and powder feeding process.

[0026] A gradient coating with high bonding strength and excellent wear resistance was obtained: a gradient transition layer designed with waste powder as the matrix has good physical compatibility with the metal substrate, effectively alleviating thermal stress; at the same time, the continuous change of its composition ensures a steady increase in coating hardness from the inside to the outside, eliminating abrupt performance interfaces. The prepared gradient wear-resistant coating is firmly bonded to the substrate, and its wear resistance can be improved by 150% to 300% compared with pure high-temperature alloy coatings.

[0027] Excellent process compatibility and significant cost advantages: This invention requires minimal modification to existing thermal spraying production lines, eliminating the need for complex devices such as additional powder feeders. By using low-cost waste powder to replace most commercial alloy powder as the base material, it significantly reduces the raw material cost of high-end gradient wear-resistant coatings, giving it strong market competitiveness. Attached Figure Description

[0028] Figure 1This is a scanning electron microscope image of the waste powder of the high-temperature alloy ultrafine powder described in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the Co powder described in Embodiment 1 of the present invention; Figure 3 This is a scanning electron microscope image of the WC powder described in Embodiment 1 of the present invention; Figure 4 The image shows the microstructure of the composite powder after spray granulation. Figure 5 The image shows the microstructure of the gradient composite powder after plasma spheroidization. Detailed Implementation

[0029] This invention proposes a gradient wear-resistant coating based on ultrafine high-temperature alloy waste powder and its preparation method. The invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings, not all of them. Example 1

[0030] In this embodiment, an ultrafine powder with a particle size of less than 15 μm, generated during the production of GH4169 alloy powder by selective laser melting (SLM) using gas atomization, is used as raw material to prepare a WC-Co-based gradient wear-resistant coating for the surface of a high-temperature alloy substrate.

[0031] Step 1: Raw material preparation and system design: Collect GH4169 ultrafine waste powder with a D90 of approximately 9 μm that is sieved out during the gas atomization powder production process.

[0032] The design incorporates a five-layer coating system: an adhesive layer, a first transition layer, a second transition layer, a third transition layer, and a wear-resistant surface layer.

[0033] The target composition of each powder layer is determined as shown in the table below: Table 1. Five-layer design components

[0034] like Figures 1-3 As shown, our unit produces GH4169 high-temperature alloy powder ultrafine waste powder through gas atomization, as well as commercial Zhuzhou cemented carbide Co powder and Xingrongyuan WC powder.

[0035] Step 2: Preparation of gradient composite powder: Mixing and ball milling: Weigh out GH4169 ultrafine waste powder, Co powder, and WC powder with a particle size ≤15 μm according to the proportions in the table above. Place each mixture in a high-energy ball mill under argon protection, with a ball-to-material ratio of 2:1, a rotation speed of 300 rpm, and ball mill for 4 hours. This process ensures that WC and Co powders are uniformly coated on the surface of GH4169 particles, forming a composite powder.

[0036] Spray granulation and spheroidization: The ball-milled composite powder precursor is mixed with an appropriate amount of polyvinyl alcohol solution as an organic binder to form a slurry, which is then spray-dried and granulated to obtain a composite powder that has initially agglomerated into spherical particles, such as... Figure 4 As shown. Subsequently, the composite powder was fed into a radio frequency plasma spheroidizing furnace, where the particles were instantaneously melted and spheroidized using a high-temperature plasma torch under an argon atmosphere. This resulted in a series of gradient composite powders with a sphericity >0.92 and a flowability (Hall flowmeter) <35 s / 50g, as shown. Figure 5 As shown, its particle size distribution is mainly concentrated in the range of 15~53 μm, which meets the requirements of thermal spraying.

[0037] Step 3: Substrate pretreatment and coating application: The substrate was a GH4169 nickel-based superalloy that had been conventionally forged and subjected to standard heat treatment. The substrate surface was sandblasted (using 24-mesh brown corundum sand), followed by ultrasonic cleaning with acetone and drying.

[0038] The coating was carried out using a supersonic flame spraying system. The main process parameters were: powder feed rate 35 g / min, powder carrier gas (N2) pressure 0.7 MPa, spraying distance 150 mm, and spray gun moving speed 500 mm / s.

[0039] Sequential spraying: Using a single powder feeder, sequentially replace and spray the bonding layer (approximately 50 μm thick), three transition layer composite powders (80~100 μm thick / layer), and the final wear-resistant surface layer (approximately 150 μm thick). The total coating thickness is approximately 450 μm.

[0040] Step 4: Post-coating treatment: The coated workpiece is placed in a vacuum heat treatment furnace and held at 800°C for 2 hours, then cooled in the furnace to below 200°C before being removed. This heat treatment aims to further diffuse alloying elements, eliminate interlayer micro-interfaces, and improve the density and bonding strength of the coating.

[0041] This embodiment 1 achieves an excellent combination of high strength, high toughness, and high wear resistance in the gradient wear-resistant coating: The gradient wear-resistant coating is firmly bonded to the substrate, with an average bonding strength higher than 70 MPa (range 70~85 MPa). The gradient wear-resistant coating is dense, with an overall porosity of less than 1.5% (the wear-resistant surface layer can reach ≤1%). The microhardness of the cross section exhibits a continuous gradient distribution from the interface to the surface. It starts at approximately 350 MPa at the matrix / binder interface, then smoothly and continuously rises through three transition layers to approximately 520 HV, 830 HV, and 1125 HV, reaching approximately 1330 HV on the wear-resistant surface. This achieves an excellent transition from tough to hard, effectively eliminating stress concentration and preventing abrupt changes in performance at the interface.

[0042] In abrasive wear tests, the coating's wear resistance was improved by approximately 240% compared to the pure GH4169 high-temperature alloy coating, with volumetric wear at (1.0±0.15)×10⁻⁶. -4 mm 3 / (N×m).

[0043] Example 2 This Example 2 aims to illustrate the flexibility of the gradient coating system design and post-processing in this invention. Unless otherwise specified, the content of this Example 2 is the same as or similar to that of Example 1. The main difference between Example 2 and Example 1 is that a three-layer gradient transition layer design is adopted, and the adhesive selection and post-processing method are optimized. In this embodiment 2, an ultrafine powder with a particle size of less than 15 μm, generated during the production process of GH4169 alloy powder by selective laser melting (SLM) using gas atomization, was used as raw material to prepare a WC-Co-based gradient wear-resistant coating for the surface of a high-temperature alloy substrate.

[0044] Step 1: Raw material preparation and system design: Collect GH4169 ultrafine waste powder with a D90 of approximately 10 μm that is sieved out during the gas atomization powder production process.

[0045] The design incorporates a four-layer coating system: an adhesive layer, a first transition layer, a second transition layer, and a wear-resistant surface layer.

[0046] The target composition of each powder layer is determined as shown in the table below: Table 2 Four-layer design components

[0047] Step 2: Preparation of gradient composite powder: Mixing and ball milling: Weigh out GH4169 ultrafine waste powder, Co powder, and WC powder with a particle size ≤15 μm according to the proportions in the table above. Place the mixture of the transition layer and the wear-resistant surface layer in a high-energy ball mill under argon protection, with a ball-to-material ratio of 4:1 and a rotation speed of 250 rpm for 8 h to obtain a composite powder precursor with uniform composition.

[0048] Spray granulation and spheroidization: The ball-milled composite powder precursor is mixed with an appropriate amount of polyvinyl alcohol and polyethylene glycol composite organic binder to form a slurry, which is then spray-dried and granulated to obtain pre-agglomerated spherical particles. Subsequently, the granulated powder is fed into an radio frequency plasma spheroidization furnace.

[0049] Step 3: Substrate pretreatment and coating application: GH4169 nickel-based superalloy, formed by selective laser melting, was used as the substrate. The substrate surface was subjected to sandblasting and ultrasonic cleaning with acetone.

[0050] The coating was carried out using a supersonic flame spraying system. The process parameters were: powder feed rate 32 g / min, spraying distance 145 mm.

[0051] Sequential spraying: Using a single powder feeder, sequentially replace and spray the bonding layer (approximately 60 μm thick), two transition layer composite powders (120 μm thick / layer), and the final wear-resistant surface layer (approximately 200 μm thick). The total coating thickness is approximately 500 μm.

[0052] Step 4: Post-coating treatment: The coated workpiece is placed in a vacuum heat treatment furnace and held at 750°C for 4 hours, then cooled in the furnace to below 200°C before being removed. This heat treatment aims to further diffuse alloying elements, eliminate interlayer micro-interfaces, and improve the density and bonding strength of the coating.

[0053] This embodiment 2 achieves an excellent combination of high strength, high toughness, and high wear resistance in a gradient wear-resistant coating using fewer layers: Its bonding strength with the substrate is higher than 68 MPa (range 68~80 MPa), and the gradient wear-resistant coating is dense with a porosity of <1.5% (the wear-resistant surface layer can reach ≤1%). The cross-sectional microhardness gradually transitions from approximately 340 HV in the adhesive layer, through approximately 580 HV in the first transition layer, and approximately 950 HV in the second transition layer, before smoothly transitioning to approximately 1400 HV in the wear-resistant surface layer. In abrasive wear tests, the wear resistance was improved by 183% compared to the pure GH4169 high-temperature alloy coating, and the volumetric wear was (1.2±0.15)×10. -4 mm 3 / (N×m).

[0054] In addition, the utilization rate of ultrafine waste powder is high: the utilization rate of ultrafine high-temperature alloy waste powder in raw materials reaches more than 95%.

[0055] Comparative Example 1 On the same GH4169 substrate, using the same HVOF process and parameters as in Example 1, commercial GH4169 powder (particle size 15~53 μm) was sprayed to prepare a pure high-temperature alloy coating with a thickness of about 500 μm.

[0056] Results: The coating had an average hardness of ~350 HV and a volumetric wear rate of 3.4 × 10⁻⁶ in the abrasive wear test. -4 mm 3 / (N×m), set as the baseline value of 100%.

[0057] Comparative Example 2 Comparative Example 2 aims to compare the differences in technical effects between directly using raw waste powder and the present invention's material design and powder reprocessing of waste powder.

[0058] GH4169 ultrafine waste powder with a particle size of less than 15 μm, which has not undergone any ball milling or spheroidizing treatment, was directly mixed with commercially available WC-10Co powder (particle size 15~53 μm) using a simple mechanical-physical mixing process to simulate the gradient components in Example 1.

[0059] Using the same HVOF process and parameters as in Example 1, a commercial adhesive layer, a transition layer, and a wear-resistant surface layer were sequentially sprayed onto the same substrate.

[0060] Results: The mixed powder exhibited extremely poor flowability, unstable powder feeding, and generated significant dust during the spraying process. The coating bonding strength was only ~35 MPa. In the abrasion resistance test, due to the uneven distribution of the hard phase and weak bonding force, the coating experienced early particle peeling, and its abrasion resistance was only about 50% higher than that of the pure GH4169 coating, far lower than that of the embodiments of this invention.

[0061] Comparative Example 3 Comparative Example 3 aims to compare the differences in cost and overall performance between conventional non-gradient coatings prepared using expensive commercial powders and gradient coatings prepared using waste powders according to the present invention.

[0062] All powders used are commercially available. The bonding layer is GH4169 powder with a specification of 15~53 μm produced by our company, and the wear-resistant layer is WC-10Co powder from Zhuzhou Sanli.

[0063] On the same substrate, after directly spraying a GH4169 adhesive layer of about 150 μm thickness, a WC-10Co wear-resistant layer of about 350 μm thickness is sprayed, forming a typical "hard coating / adhesive layer" double-layer structure.

[0064] Results: A significant abrupt change in performance exists between the WC-10Co layer with a hardness of up to 1200 HV and the softer GH4169 adhesive layer. Although the initial bond strength is acceptable (approximately 55 MPa), cracks easily initiate and propagate at the hard / soft interface during high-load reciprocating sliding wear tests, leading to large-scale coating peeling and failure.

[0065] Performance and cost: Its service life under high-stress wear conditions is far shorter than that of the gradient coating of this invention. More importantly, it uses all commercial powders, and the raw material cost is about 3 to 4 times that of the embodiments of this invention (using waste powder as the main raw material).

Claims

1. A method for preparing a gradient wear-resistant coating based on ultrafine high-temperature alloy waste powder, characterized in that, One or more of ultrafine high-temperature alloy waste powder, WC powder, and Co powder with a particle size of less than 15 μm are used as powder raw materials; after mechanical mixing and ball milling, spray granulation and radio frequency plasma spheroidization treatment are performed to obtain binder layer powder, gradient transition layer powder and wear-resistant surface layer powder; finally, the binder layer powder, gradient transition layer powder and wear-resistant surface layer powder are sequentially sprayed onto the substrate through a thermal spraying process to form a gradient wear-resistant coating. From the bonding layer to the wear-resistant surface layer, the content of the ultrafine high-temperature alloy waste powder decreases, while the sum of the contents of the WC powder and Co powder increases.

2. The preparation method according to claim 1, characterized in that, Specifically, the following steps are included: Step 1: Pretreatment of ultrafine high-temperature alloy waste powder and system design of gradient composite powder: a) Collect ultrafine high-temperature alloy waste powder with a particle size of less than 15 μm; b) The design includes a gradient composition system comprising a binder layer powder, at least two gradient transition layer powders, and a wear-resistant surface powder; wherein the powder raw material of the gradient transition layer powder includes the ultrafine high-temperature alloy waste powder; Step 2: Preparation of gradient composite powder: A) Based on the gradient composition system designed in step one (b), the ultrafine high-temperature alloy waste powder is mechanically mixed and ball-milled with WC powder and Co powder in a preset ratio to obtain composite powder precursors with different compositions. B) The composite powder precursor is spray-granulated to obtain composite powder, and the composite powder is spheroidized by radio frequency plasma to prepare gradient composite powder with sphericity greater than 0.92 and flowability <35 s / 50g. The gradient composite powder includes a gradient transition layer powder and a wear-resistant surface layer powder: The gradient transition layer powder is composed of 20-75 parts by weight of ultrafine high-temperature alloy waste powder, 10-35 parts by weight of Co powder, and 10-70 parts by weight of WC powder. The wear-resistant surface powder is composed of 0-20 parts by weight of ultrafine high-temperature alloy waste powder, 10-20 parts by weight of Co powder, and 70-85 parts by weight of WC powder.

3. The preparation method according to claim 2, characterized in that, In step two (B), the gradient transition layer powder includes at least a first transition layer powder and a second transition layer powder. The first transition layer powder consists of 55-75 parts by weight of ultrafine high-temperature alloy waste powder, 15-35 parts by weight of Co powder, and 10-30 parts by weight of WC powder. The second transition layer powder consists of 20-45 parts by weight of ultrafine high-temperature alloy waste powder, 10-35 parts by weight of Co powder, and 45-70 parts by weight of WC powder.

4. The preparation method according to claim 2, characterized in that, In step one (b), the adhesive layer powder is a normal spherical high-temperature alloy powder with a particle size of 15~53 μm or a Co-containing composite powder prepared from the ultrafine high-temperature alloy waste powder.

5. The preparation method according to claim 2, characterized in that, In step two (A), the ball milling composite treatment takes 4 to 12 hours.

6. The preparation method according to claim 1, characterized in that, The thermal spraying process is either supersonic flame spraying or atmospheric plasma spraying.

7. The preparation method according to claim 1, characterized in that, It also includes heat-treating the gradient wear-resistant coating in a vacuum or protective atmosphere, holding it at 700°C to 850°C for 1 to 4 hours, and then cooling it to below 200°C before removing it from the furnace.

8. A gradient wear-resistant coating prepared according to the preparation method of any one of claims 1 to 7, characterized in that, The gradient wear-resistant coating comprises, from the substrate to the surface, an adhesive layer, at least two gradient transition layers, and a wear-resistant surface layer. The adhesive layer is formed by thermal spraying of adhesive layer powder, which is a normal spherical high-temperature alloy powder with a particle size of 15~53 μm or a composite powder containing Co (0~10 parts by mass) prepared from the ultrafine high-temperature alloy waste powder. The gradient transition layer is formed by thermal spraying of gradient transition layer powder, which consists of 20-75 parts by weight of ultrafine high-temperature alloy waste powder, 10-35 parts by weight of Co powder, and 10-70 parts by weight of WC powder. The wear-resistant surface layer is formed by thermal spraying of wear-resistant surface layer powder, which consists of 0-20 parts by weight of ultrafine high-temperature alloy waste powder, 10-20 parts by weight of Co powder, and 70-85 parts by weight of WC powder.

9. The gradient wear-resistant coating according to claim 8, characterized in that, The gradient transition layer has 2 to 4 layers.

10. The gradient wear-resistant coating according to claim 8, characterized in that, From the adhesive layer to the wear-resistant surface layer, hardness and wear resistance increase progressively.

Images