Powder metallurgy element with gradient composite coating and preparation method of powder metallurgy element

Abstract

The invention discloses a preparation method of a powder metallurgy element with a gradient composite coating, the prepared powder metallurgy element takes an HIP powder base material as a base body layer, and a metallurgical bonding layer is firstly used on the outer surface of the HIP powder base material as primary transition and has the effects of relieving thermal mismatch and enhancing interface bonding force; the function transition layer is used for secondary transition, and the used gradient coincidence mode not only further enhances the bonding force between the interfaces, but also has the effect of enhancing the hardness of the element; and the outermost surface protection layer adopts a sandwich structure combination mode of the CrN / DLC layer, the AlCrSiN layer and the WC-DLC nano layer, so that not only is the friction coefficient of the element reduced, but also an excellent corrosion-resistant effect is achieved. According to the preparation method of the metallurgical element, a three-stage gradient system of a nanometer protective layer, a hard transition layer and a metallurgical bonding layer is established, a special interface structure which deforms synergistically with an HIP substrate is also developed, and continuous gradient change of coating components / tissues is achieved.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy material surface strengthening technology, and specifically to a method for preparing powder metallurgy components with gradient composite coatings. Background Technology

[0002] Hot isostatic pressing (HIP) is a process that combines powder sintering and isostatic pressing into a single step by applying isostatic pressure to powder or compact at high temperatures. The HIP apparatus mainly consists of a water-cooled pressure vessel, a furnace insulated from the pressure vessel, and auxiliary facilities for control, safety, and operation. The core of the apparatus includes the water-cooled pressure vessel, the furnace, and the control system. Pressure vessels have two sealing methods: threaded and frame-type. Threaded seals can only be opened, closed, and loaded from the top; frame-type seals can be opened and closed simultaneously from the top and bottom. HIP has become an advanced process in modern powder metallurgy for producing large, complex-shaped products and high-performance materials, and is widely used in the forming and sintering of cemented carbides, cermets, powder metallurgy high-temperature alloys, powder metallurgy high-speed steel, powder metallurgy stainless steel, powder titanium alloys, radioactive materials, nuclear fuel, and powder metallurgy beryllium. The basic operating steps of HIP (High-Intensity Processing) are as follows: Powder or powder compact is loaded into a casing; gases adsorbed on the powder surface, in the gaps between powder particles, and inside the casing are removed; the casing is vacuum-sealed and placed in a pressure vessel with a heating furnace; after sealing the pressure vessel, an inert gas (i.e., the pressure-transmitting medium) is pumped in to a certain pressure; then the temperature is raised to the required level, and due to gas expansion, the pressure inside the vessel also rises to the required level. Forming and sintering are completed under the combined action of high temperature and high pressure. Afterwards, the casing is removed mechanically or by acid leaching to obtain the finished product.

[0003] As mentioned above, the greatest advantage of HIP (High-Intensity Interlayer) is that the pressed material exhibits excellent viscous flow under high temperature and pressure. Furthermore, due to its uniform pressure in all directions, it can produce products with fine grains, excellent microstructure, near-theoretical density, and superior performance at relatively low temperatures (generally 50%-70% of the material's melting point) and pressures. However, traditional HIP metallurgical parts, such as titanium alloys and high-temperature alloys, are prone to pitting corrosion and wear failure under acid etching or high-temperature friction conditions. To address these issues, coating treatments are commonly used. However, single-coating technologies, such as CrN and DLC, offer limited performance and are insufficient for complex operating conditions. Moreover, traditional coating technologies (such as thermal spraying and CVD / PVD) suffer from poor interfacial adhesion, high thermal stress, and the problem of interfacial delamination during multi-layer surface treatment. Furthermore, current coating technologies often have limited composition, leading to a trade-off between wear resistance and corrosion resistance. The preparation of gradient materials using existing functional coating materials also faces challenges due to complex processes and high costs.

[0004] More importantly, the application of hot isostatic pressing (HIP) technology in the preparation of gradient materials has not been fully developed. Therefore, it is necessary to disclose a powder metallurgy component with a gradient composite coating and its preparation method. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a powder metallurgy component with a gradient composite coating, disclosing a powder metallurgy surface strengthening technology, wherein the wear-resistant and corrosion-resistant coating and the hot isostatic pressing substrate have a synergistic strengthening effect.

[0006] To achieve the above objectives, the present invention proposes the following technical solution:

[0007] A powder metallurgical component with a gradient composite coating includes a powder metallurgical substrate layer.

[0008] The outer surface of the powder metallurgy matrix layer is sequentially provided with a bonding layer, a transition layer and a surface protective layer;

[0009] The powder metallurgy matrix layer is prepared by hot isostatic pressing of powder substrate; the bonding layer is a metallurgical bonding layer, and the transition layer is a functional transition layer; the surface protective layer is a sandwich structure coating, which includes a CrN / DLC coating, an AlCrSiN layer and a WC-DLC nanolayer sequentially from the transition layer.

[0010] Furthermore, the powder metallurgy matrix layer is one or more of the following: HIP-molded WC-Co cemented carbide, 316L stainless steel, titanium-based alloy mixture, and titanium-aluminum-based composite material.

[0011] Furthermore, the metallurgical bonding layer is composed of NiCrAlY and SiC, wherein SiC accounts for 15-25 vol% of the total volume of the metallurgical bonding layer material, and the thickness of the metallurgical bonding layer is 0.5-2 μm; wherein the elemental content of NiCrAlY is: 60 at% Ni, 10-30 at% Cr, 10-20 at% Al, 0.5-1.0 at% Y, with the balance being impurities. NiCrAlY exhibits a γ+β dual-phase structure with fine grains and uniform microstructure, which can significantly improve the hot corrosion resistance and service life of the matrix material.

[0012] Furthermore, the thickness of the functional transition layer is 3-8 μm.

[0013] Furthermore, the thickness of the CrN / DLC coating in the surface protective layer is 2.85-3.05 μm, the thickness of the AlCrSiN layer is 3.27-5.67 μm, and the thickness of the WC-DLC nanolayer is 6.48-6.68 μm.

[0014] Furthermore, the elemental composition of the AlCrSiN layer is: 41-49 at% Al, 23-27 at% Cr, 7-9 at% Si, 21-23 at% N, with the balance being impurities. The AlCrSiN layer not only enhances the interfacial bonding between the AlCr / DLC coating and the WC-DLC nanolayer, but also facilitates the formation of a sandwich structure of CrN / DLC, AlCrSiN, and WC-DLC. In addition, the progressive thickness design of each coating layer ensures both a stable surface protective layer and a progressive mechanical strengthening effect, resulting in good mechanical weather resistance. Generally, DLC coating is a diamond-like carbon surface coating process, which involves coating a layer of amorphous carbon film with diamond-like properties onto the material surface using physical or chemical methods, enabling it to withstand high-temperature environments to a certain extent. The outermost WC-DLC nanolayer utilizes tungsten added to the DLC to facilitate the formation of sp... 2 Bonding enhances the mechanical and weather resistance of the coating.

[0015] Furthermore, the WC-DLC nanolayer comprises a diamond-like matrix and a WC nanocrystalline dispersed phase, and the thickness of the WC nanocrystalline dispersed phase is 10-30 nm.

[0016] Furthermore, the method for preparing the powder metallurgy component with the gradient composite coating includes the following steps:

[0017] S1. Material pretreatment and preparation

[0018] Select a 100-500 mesh sieve to sieve the alloy powder, use metal or gold powder with uniform particle size distribution, and perform pretreatment of the material by ball milling or pre-alloying.

[0019] S2, Molding and Pre-densification

[0020] The pre-treated material is loaded into a flexible mold and formed into a green material by cold isostatic pressing. Then the casing is removed to obtain the green material.

[0021] S3, Packaging and HIP Molding

[0022] The green blank is directly loaded into a homogeneous sheath of the alloy blank, and a vacuum is drawn to 10. -3 After degassing for 2-24 hours following Pa, the material is sealed. After sealing, the parameters are adjusted for HIP molding, and the encapsulation is removed by acid washing to obtain the HIP matrix, i.e., the powder metallurgy matrix layer. The oxygen content inside the encapsulation is ≤480ppm.

[0023] S4, Post-processing

[0024] The HIP substrate from step S3 was subjected to solution treatment by water quenching at 1050℃ to optimize corrosion resistance. After cooling and drying, it was roughened by sandblasting to control the surface roughness Ra of the HIP substrate to 1.5-3.0μm, thus obtaining a roughened HIP substrate.

[0025] S5, Preparation of the bonding layer

[0026] The rough surface HIP substrate is placed on the rotary table of the processing chamber. NiCrAlY and SiC materials are prepared and mixed. The mixture is ball-milled under Ar gas protection, ball-to-material ratio of (9-11):1, and rotation speed of 300-500 rpm for 2-4 hours to obtain the bonding layer material. Then, the bonding layer material is sprayed onto the rough surface HIP substrate using a supersonic flame spraying process to form a dense coating, i.e., the bonding layer.

[0027] S6, Transition Layer Preparation

[0028] Based on step S5, turn on the TiAl target arc source with a current of 60A, select a Cr target and use magnetron sputtering process to prepare a Cr / CrN gradient layer, i.e., a transition layer, by controlling the N2 flow rate in a stepped flow rate of "50sccm-150sccm-250sccm-300sccm".

[0029] S7. Preparation of Surface Protective Layer

[0030] Based on step S6, a CrN / DLC layer is deposited on the surface of the transition layer using physical vapor deposition (PVD). Then, an AlCrSiN layer and a DLC-W coating are sequentially deposited on the surface of the CrN / DLC layer using plasma-enhanced chemical vapor deposition (PECVD). After standing for 2-8 hours, the metallurgical component is obtained for the next step.

[0031] S8, Package

[0032] Remove the metallurgical component from the rotating table in step S7, clean it with deionized water using ultrasonic cleaning, then dry it with N2 inert gas, and vacuum dry it at 50-80°C for 1-2 hours to completely remove moisture. Finally, encapsulate it with anti-scratch material to obtain the metallurgical component of the present invention.

[0033] Furthermore, the cold isostatic pressing process parameters in step S2 are as follows:

[0034] The flexible mold material is polyurethane or rubber;

[0035] Temperature: Room temperature, 20-25℃;

[0036] Pressure range: 200-400MPa;

[0037] Pressure holding time: 1-10 minutes;

[0038] Pressure transmission medium: Glycerin;

[0039] In step S3, the HIP molding process parameters are as follows:

[0040] Heating rate: 5℃ / min;

[0041] Temperature: 1200-1450℃;

[0042] Pressure: 100-200 MPa;

[0043] Keep the furnace under heat and pressure for 1-2 hours, and then cool it to room temperature with the furnace.

[0044] The supersonic flame spraying process parameters in step S5 are as follows:

[0045] Substrate preheating: 250±10℃;

[0046] Particle velocity: ≥600m / s;

[0047] Fuel: kerosene + oxygen, with a flow ratio of 1:(3.2-3.8).

[0048] Furthermore, the alloy billet dimensions are Φ65×150mm.

[0049] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0050] This invention discloses a method for preparing powder metallurgy components with gradient composite coatings. The prepared powder metallurgy components use HIP powder substrate as the base layer, and a metallurgical bonding layer is first used on its outer surface as an initial transition, which can alleviate thermal mismatch and enhance interfacial adhesion. Next, a functional transition layer is used for a secondary transition. The gradient conformation mode used not only further enhances the interfacial adhesion but also increases the component's hardness. The outermost surface protective layer adopts a sandwich structure combination of CrN / DLC layer, AlCrSiN layer, and WC-DLC nanolayer, which not only reduces the component's friction coefficient but also provides excellent corrosion resistance. This invention's method for preparing metallurgical components not only establishes a three-level gradient system of "nanoprotective layer - hard transition layer - metallurgical bonding layer" but also develops a special interfacial structure that deforms synergistically with the HIP substrate, achieving a continuous gradient change in coating composition / structure.

[0051] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the subject matter disclosure of the present invention, provided that such concepts do not contradict each other.

[0052] The foregoing and other aspects, embodiments, and features of the teachings of this invention will be more fully understood from the following description. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of this invention. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is a schematic cross-sectional view of the metallurgical component of the present invention.

[0055] In the figure, 1 is the powder metallurgy substrate layer; 2 is the bonding layer; 3 is the transition layer; and 4 is the surface protective layer. Detailed Implementation

[0056] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples, but these should not be construed as limiting the present patent.

[0057] Unless otherwise specified, the test methods or experimental methods described in the following examples / comparative examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0058] In this invention, a powder metallurgy component with a gradient composite coating includes a powder metallurgy substrate layer. The outer surface of the powder metallurgy substrate layer 1 is sequentially provided with a bonding layer 2, a transition layer 3, and a surface protective layer 4. The powder metallurgy substrate layer 1 is prepared from a powder substrate through a hot isostatic pressing process. The bonding layer 2 is a metallurgical bonding layer, and the transition layer 3 is a functional transition layer. The surface protective layer 4 is a sandwich structure coating, comprising, from the transition layer 3 in sequence, a CrN / DLC coating, an AlCrSiN layer, and a WC-DLC nanolayer.

[0059] Furthermore, the powder metallurgy matrix layer 1 is one or more of the following: HIP-molded WC-Co cemented carbide, 316L stainless steel, titanium-based alloy mixture, and titanium-aluminum-based composite material. Through testing, the titanium-based alloy mixture used has a wider range of applications and a better service life compared to other matrix materials. Therefore, this invention uses a titanium-based alloy mixture as the preferred material for the HIP substrate of the powder metallurgy matrix layer 1.

[0060] Furthermore, with the titanium-based alloy mixture as the matrix material of powder metallurgy matrix layer 1, a metallurgical bonding layer composed of NiCrAlY and SiC is used as bonding layer 2. Firstly, the rare earth element composition in the constituent elements can alleviate thermal mismatch; secondly, the aluminum element is the same as the main element composition in the titanium-based alloy mixture, which can enhance the interfacial bonding; and thirdly, the addition of SiC helps alloying, optimizes the microstructure, and improves the product yield.

[0061] Furthermore, a transition layer 3 is obtained by applying a stepped flow rate control Cr / CrN gradient layer on the basis of bonding layer 2. This allows both layers to have the same Cr element content, resulting in a gradually hardening bonding coating that further enhances the mechanical weather resistance of the component. If bonding layer 3 is designed directly on the surface of powder metallurgy matrix layer 1, not only will the interface stabilization effect not be achieved, but also, due to the phase transformation control after HIP (from the α2+β two-phase region to the α2 / β phase equilibrium), directly using bonding layer 3 will cause two-phase imbalance due to the environmental influence of the Cr target magnetron sputtering process. It should be noted that the CrN / DLC coating in the surface protective layer 4 requires Cr as a transition bond; therefore, the outermost layer of bonding layer 3 is Cr, followed by a CrN reinforcing layer, and finally a DLC layer.

[0062] Of course, replacing surface protective layer 4 will also cause the same problems, eventually leading to failure phenomena such as cracks, peeling, or even structural delamination between the substrate and the coating. There is also an increasing hardness relationship between transition layer 3 and surface protective layer 4, so the layer structure cannot be changed. Moreover, the outermost WC-DLC nanolayer in surface protective layer 4 has excellent corrosion resistance, which helps to extend the service life of the component.

[0063] The use of composite coatings in the fabrication of metallurgical components aims to address issues such as interfacial cracking caused by the mismatch in thermal expansion coefficients between traditional coatings and the HIP substrate, and the difficulty for single-function coatings to simultaneously meet requirements for corrosion resistance, wear resistance, and impact resistance. Furthermore, our designed gradient coating structure can resolve stress concentration issues caused by abrupt changes in performance between layers of multi-layer coatings, resulting in components with better interfacial adhesion, friction coefficient, and operational stability.

[0064] Preferably, this invention uses a titanium-based alloy mixture as the powder metallurgy matrix layer, providing a foundation for the development of subsequent coating structures and the special interface structure for synergistic deformation of the HIP matrix. Furthermore, the bonding layer is a metallurgical bonding layer, specifically comprising NiCrAlY and SiC, which can alleviate thermal mismatch problems in the preparation process and enhance interfacial adhesion. Even further, the functional transition layer is prepared using a Cr target and a magnetron sputtering process, controlling the N2 flow rate to create a Cr / CrN gradient layer, forming a Cr→CrN transition layer. xThe gradient transition layer structure causes a gradual change in the hardness of its layer structure. It should be noted that, after numerous experiments, the Cr / CrN gradient layer of this invention exhibits a gradual change in hardness. x The value of x ranges from 0.3 to 0.9, and the hardness of this layer of coating is tested separately using a micro / nano mechanical property testing system (Antonpah, Austria, NHT). 3 Its hardness value is 200-1800HV.

[0065] Furthermore, the surface protective layer 4 is a sandwich-structured coating, consisting of a CrN / DLC coating, an AlCrSiN layer, and a WC-DLC nanolayer, sequentially arranged from near the transition layer 3. Testing showed that the component of this invention has a friction coefficient ≤0.1 and exhibits resistance to Cl... - Advantages of corrosion.

[0066] Performance testing

[0067] The component materials are subjected to corrosion resistance tests, bonding strength tests, friction coefficient tests, and fretting wear rate tests, among which the corrosion resistance test includes a neutral salt spray test.

[0068] Neutral salt spray test

[0069] The neutral salt spray test was conducted according to the method described in the national standard GB6458-86: a 5% sodium chloride aqueous solution (pH 6.8±0.3) was prepared at a temperature of 35℃±2℃ and a relative humidity greater than 95%, with a certain mist reduction rate [1.5mL / (80cm²)]. 2 The solution is sprayed onto the surface of the component using a continuous spraying method, with each cycle lasting 24 hours.

[0070] Combined with strength performance test

[0071] The bonding strength of the material will be tested according to the standard test method of ASTM C633-24 for adhesion or bond strength of thermal spray coatings, and the unit is N.

[0072] Friction coefficient test

[0073] The friction coefficient test standard for powder metallurgy components is mainly based on ASTM G99, and the friction coefficient is usually required to be ≤0.25.

[0074] Fretting wear rate test

[0075] The fretting wear rate test standard for powder metallurgy components is mainly based on GB / T 12444, with the unit being mm³ / N·m.

[0076] Example 1

[0077] A powder metallurgical component with a gradient composite coating includes a powder metallurgical substrate layer. A bonding layer, a transition layer, and a surface protective layer are sequentially disposed on the outer surface of the powder metallurgical substrate layer. The powder metallurgical substrate layer is prepared from powder substrate through a hot isostatic pressing process. The bonding layer is a metallurgical bonding layer, the transition layer is a functional transition layer, and the surface protective layer is a sandwich structure coating, comprising, from the transition layer upwards, a CrN / DLC coating, an AlCrSiN layer, and a WC-DLC nanolayer.

[0078] Furthermore, the powder metallurgy matrix layer is a titanium-based alloy mixture, comprising a first titanium-based alloy and a second titanium-based alloy. The first titanium-based alloy is Ti4522XD pre-alloyed powder obtained by gas atomization from the Institute of Metal Research, Chinese Academy of Sciences. The second titanium-based alloy is Ti-6Al-4V titanium alloy with titanium alloy grade TC4, and the mass ratio of the first titanium-based alloy to the second titanium-based alloy is 2:1. The elemental composition of the powder metallurgy matrix layer is shown in Table 1 below.

[0079] Table 1. Composition of Powder Metallurgy Matrix Layer Elemental composition content Al (at.%) 6.8 V (at.%) 4.2 Fe (at.%) 0.27 C (at.%) 0.01 H (at.%) 0.02 O (at.%) 0.1 N (at.%) 0.01 Nb (at.%) 0.04 Mn (at.%) 0.04 <![CDATA[TiB 2 (vol.%)]]> 0.16 Ti (at.%) margin

[0080] Furthermore, the metallurgical bonding layer is composed of NiCrAlY and SiC, wherein SiC accounts for 15 vol% of the total volume percentage of the metallurgical bonding layer material, and the thickness of the metallurgical bonding layer is 1.5 μm. Further, the thickness of the functional transition layer is 5 μm. Still further, the elemental content of NiCrAlY is: 60 at% Ni, 20 at% Cr, 15 at% Al, 0.7 at% Y, with the balance being impurities.

[0081] Furthermore, the thickness of the functional transition layer is 6 μm. Even further, the thickness of the CrN / DLC coating in the surface protective layer is 2.95 μm, the thickness of the AlCrSiN layer is 4.47 μm, and the thickness of the WC-DLC nanolayer is 6.58 μm. The elemental composition of the AlCrSiN layer is: 45 at% Al, 25 at% Cr, 8 at% Si, 22 at% N, with the balance being impurities.

[0082] Furthermore, the method for preparing the powder metallurgy component with the gradient composite coating includes the following steps:

[0083] S1. Material pretreatment and preparation

[0084] The titanium-based alloy and aluminum-based alloy mixed powder is sieved using a sieve, and the material is pre-treated by using metal or gold powder with uniform particle size distribution and pre-alloying.

[0085] S2, Molding and Pre-densification

[0086] The pre-treated material is loaded into a flexible mold and formed into a green material by cold isostatic pressing. Then the casing is removed to obtain the green material.

[0087] S3, Packaging and HIP Molding

[0088] The green blank is directly loaded into a homogeneous sheath of the alloy blank, and a vacuum is drawn to 10. -3 After degassing for 2-24 hours following Pa, the material is sealed. After sealing, the parameters are adjusted for HIP molding, and the encapsulation is removed by acid washing to obtain the HIP matrix, i.e., the powder metallurgy matrix layer. The oxygen content inside the encapsulation is ≤480ppm.

[0089] S4, Post-processing

[0090] The HIP substrate from step S3 was subjected to solution treatment by water quenching at 1050℃ to optimize corrosion resistance. After cooling and drying, it was roughened by sandblasting to control the surface roughness Ra of the HIP substrate to 2.0 μm, thus obtaining a surface roughened HIP substrate.

[0091] S5, Preparation of the bonding layer

[0092] The roughened HIP substrate is placed on the rotary table of the processing chamber. NiCrAlY and SiC materials are prepared and mixed. The mixture is ball-milled under Ar gas protection, with a ball-to-material ratio of 10:1 and a rotation speed of 400 rpm for 2-4 hours to obtain the bonding layer material. Then, the bonding layer material is sprayed onto the roughened HIP substrate using a supersonic flame spraying process to form a dense coating, i.e., the bonding layer.

[0093] S6, Transition Layer Preparation

[0094] Based on step S5, turn on the TiAl target arc source with a current of 60A, select a Cr target and use magnetron sputtering process to prepare a Cr / CrN gradient layer, i.e., a transition layer, by controlling the N2 flow rate in a stepped flow rate of "50sccm-150sccm-250sccm-300sccm".

[0095] S7. Preparation of Surface Protective Layer

[0096] Based on step S6, a CrN / DLC layer is deposited on the surface of the transition layer using physical vapor deposition (PVD). Then, an AlCrSiN layer and a DLC-W coating are sequentially deposited on the surface of the CrN / DLC layer using plasma-enhanced chemical vapor deposition (PECVD). After standing for 2-8 hours, the metallurgical component is obtained for the next step.

[0097] Specifically, the formation of the CrN / DLC coating involves first introducing Ar gas into the processing chamber at a bias voltage of -50 to -200V and a power of 1-5kW for 5-15 minutes; then introducing an N2 / Ar mixed gas with a N2 to Ar ratio of 1:1 at a bias voltage of -50 to -150V and a target current of 60-100A for 15-30 minutes; finally, in an Ar / C2H2 atmosphere, using C2H2 as the carbon source and a graphite target as the cathode arc at a bias voltage of -500 to -1000V, and ensuring the ambient temperature is below 200℃, for 30-45 minutes of deposition.

[0098] Secondly, the deposition of the AlCrSiN layer involves bombarding the surface of the object with Ar or H2 plasma; then, the AlCrSiN layer is deposited using an AlCrSi alloy target or an AlCrSi composite target as the target material, N2 as the reactive gas, and Ar as the sputtering gas under a pressure of 0.2-0.5 Pa.

[0099] Finally, the formation of the WC-DLC nanolayer is achieved by introducing an Ar / C2H2 mixed gas at a pressure of 0.5-1.0 Pa into the processing chamber on the basis of the AlCrSiN layer deposition, and then applying a pulsed bias voltage to introduce the WC target material to generate the nanocomposite WC-DLC layer. After deposition and stacking, the WC-DLC nanolayer is then stacked on the AlCrSiN layer to form a surface protective layer. After standing for 2-8 hours, the next step is carried out.

[0100] S8, Package

[0101] The metallurgical component from step S7 is removed from the rotating table, ultrasonically cleaned with deionized water, then dried with N2 inert gas, and vacuum dried at 60°C for 2 hours to completely remove moisture. Finally, it is encapsulated with scratch-resistant material to obtain the metallurgical component of the present invention.

[0102] Furthermore, the cold isostatic pressing process parameters in step S1 are as follows:

[0103] The flexible mold material is polyurethane or rubber;

[0104] Temperature: Room temperature, 22℃;

[0105] Pressure range: 300MPa;

[0106] Pressure holding time: 5 minutes;

[0107] Pressure transmission medium: Glycerin;

[0108] In step S3, the HIP molding process parameters are as follows:

[0109] Heating rate: 5℃ / min;

[0110] Temperature: 1350℃;

[0111] Pressure: 150 MPa;

[0112] Keep the furnace under heat and pressure for 2 hours, and then cool it to room temperature with the furnace.

[0113] The supersonic flame spraying process parameters in step S5 are as follows:

[0114] Substrate preheating: 260℃;

[0115] Particle velocity: ≥600m / s;

[0116] Fuel: kerosene + oxygen, with a flow ratio of 1:3.5.

[0117] Furthermore, the alloy billet dimensions are Φ65×150mm.

[0118] Example 2

[0119] Unlike Embodiment 1 above, the structural parameters of each layer of the powder metallurgy component are as follows:

[0120] Substrate: Powder substrate prepared by HIP, same as in Example 1;

[0121] Coating system:

[0122] Bonding layer: 0.5µm thickness, NiCrAlY+20vol%SiC, applied by plasma spraying + diffusion annealing (800℃ / 2h).

[0123] Transition layer: 3µm total thickness, Cr / CrN (20nm period), interlayer nanoscale interlocking achieved by magnetron sputtering;

[0124] Surface protective layer: CrN / DLC coating thickness is 2.85um, AlCrSiN layer thickness is 3.27um, WC-DLC nanolayer thickness is 6.48um.

[0125] Other operations are the same as in Example 1.

[0126] Example 3

[0127] Unlike Embodiment 1 above, the structural parameters of each layer of the powder metallurgy component are as follows:

[0128] Substrate: Powder substrate prepared by HIP, same as in Example 1;

[0129] Coating system:

[0130] Bonding layer: 2µm thickness, NiCrAlY+20vol%SiC, applied by plasma spraying + diffusion annealing (800℃ / 2h).

[0131] Transition layer: 8µm total thickness, Cr / CrN (50nm period), interlayer nanoscale interlocking achieved by magnetron sputtering;

[0132] Surface protective layers: CrN / DLC coating thickness is 3.05um, AlCrSiN layer thickness is 5.67um, and WC-DLC nanolayer thickness is 6.68um.

[0133] Other operations are the same as in Example 1.

[0134] Comparative Example 1

[0135] Unlike Example 1, the outer surface of the powder metallurgy matrix layer is provided with only one bonding layer.

[0136] Other operations are the same as in Example 1.

[0137] Comparative Example 2

[0138] Unlike Embodiment 1 above, the outer surface of the powder metallurgy matrix layer is provided with only one transition layer.

[0139] Other operations are the same as in Example 1.

[0140] Comparative Example 3

[0141] Unlike Embodiment 1 above, the outer surface of the powder metallurgy substrate layer is provided with only one layer of the aforementioned surface protective layer.

[0142] Other operations are the same as in Example 1.

[0143] Comparative Example 3-1

[0144] Unlike Embodiment 1 above, the outer surface of the powder metallurgy substrate layer is provided with only one surface protective layer, and the surface protective layer includes only the AlCrSiN layer and the WC-DLC nanolayer.

[0145] Other operations are the same as in Example 1.

[0146] Comparative Example 3-2

[0147] Unlike Embodiment 1 above, the outer surface of the powder metallurgy substrate layer is provided with only one layer of the aforementioned surface protective layer, and the surface protective layer includes only the CrN / DLC coating and the WC-DLC nanolayer.

[0148] Other operations are the same as in Example 1.

[0149] Comparative Example 3-3

[0150] Unlike Embodiment 1 above, the outer surface of the powder metallurgy substrate layer is provided with only one surface protective layer, and the surface protective layer includes only the CrN / DLC coating and the AlCrSiN layer.

[0151] Other operations are the same as in Example 1.

[0152] Comparative Example 4

[0153] Unlike Embodiment 1 above, the structural parameters of each layer of the powder metallurgy component are as follows:

[0154] Substrate: Powder substrate prepared by HIP, same as in Example 1;

[0155] Coating system:

[0156] In the surface protective layer, the elemental contents of the AlCrSiN layer are: 45 at% Al, 30 at% Cr, 8 at% Si, 22 at% N, and the balance is impurities.

[0157] Other operations are the same as in Example 1.

[0158] Comparative Example 5-1

[0159] Unlike Embodiment 1 above, the structural parameters of each layer of the powder metallurgy component are as follows:

[0160] Substrate: Powder substrate prepared by HIP, same as in Example 1;

[0161] Coating system:

[0162] The metallurgical bonding layer is composed of NiCrAlY and SiC, wherein the elemental contents of NiCrAlY are as follows:

[0163] 60 at% Ni, 35 at% Cr, 15 at% Al, 0.7 at% Y, balance being impurities.

[0164] Other operations are the same as in Example 1.

[0165] Comparative Example 5-2

[0166] Unlike Embodiment 1 above, the metallurgical bonding layer is composed only of NiCrAlY.

[0167] Other operations are the same as in Example 1.

[0168] Comparative Example 5-3

[0169] Unlike Embodiment 1 above, the metallurgical bonding layer is composed only of SiC.

[0170] Other operations are the same as in Example 1.

[0171] Comparative Example 6

[0172] Unlike Embodiment 1 above, the structural parameters of each layer of the powder metallurgy component are as follows:

[0173] Substrate: Powder substrate prepared by HIP, same as in Example 1;

[0174] Coating system:

[0175] The outer surface of the powder metallurgy matrix layer is provided with a transition layer, a bonding layer and a surface protective layer in sequence;

[0176] Other operations are the same as in Example 1.

[0177] Comparative Example 7

[0178] Unlike Embodiment 1 described above,

[0179] Replace the temperature in the HIP molding process parameters with 900℃, then hold it at that temperature and pressure, and finally cool it to room temperature in the furnace.

[0180] Other operations are the same as in Example 1.

[0181] Comparative Example 8

[0182] Unlike Example 1 above, in step S6, during the preparation of the transition layer, a single uniform flow rate of 200 sccm is selected instead of the original step-like flow rate control of "50 sccm-150 sccm-250 sccm-300 sccm" to prepare the Cr / CrN gradient layer.

[0183] Other operations are the same as in Example 1.

[0184] The metallurgical components prepared in Examples 1-3 and Comparative Examples 1-8 were tested according to different performance testing standards, and the performance test results are shown in Table 2.

[0185] Table 2 Performance Test Result Analysis Table

[0186] As can be seen from the comparison results in Table 2 above, the powder metallurgy element prepared by this invention uses HIP powder substrate as the matrix layer, and firstly uses a metallurgical bonding layer as an initial transition on its outer surface, which has the function of alleviating thermal mismatch and enhancing interfacial bonding force; then, a functional transition layer is used for secondary transition, and the gradient matching mode used not only further enhances the bonding force between interfaces, but also enhances the hardness of the element; the outermost surface protective layer adopts a sandwich structure combination mode of CrN / DLC layer, AlCrSiN layer, and WC-DLC nanolayer, which not only reduces the friction coefficient of the element, but also has excellent corrosion resistance.

[0187] In Example 1, the addition of Mn to the powder metallurgy matrix layer alters the alloy's lattice constant ratio c / a, significantly improving its plastic deformation capacity. The addition of Nb effectively improves the alloy's high-temperature strength and oxidation resistance. B in the alloy can refine the alloy grains during subsequent heat treatment. Scanning electron microscopy observation revealed that the powder metallurgy matrix layer in Example 1 exhibited good density in its initial microstructure, primarily composed of equiaxed α phases, with a content exceeding 50%. Notably, interlayer thermal expansion coefficient and interfacial shear strength tests were conducted on the product from Example 1. The results showed that the difference in interlayer thermal expansion coefficients was ≤2×10⁻⁶. -6 With an interface shear strength of ≥350MPa at ℃, all properties meet the usage standards, providing a new approach for the preparation of high-performance powder metallurgy components.

[0188] In Comparative Examples 1-3, a single-layer coating structure was used. Due to the absence of the other two layers, the performance was not as good as that of the three-layer composite. In Comparative Example 6, the adjustment of the coating structure affected the transition and adhesion between interfaces, and its performance was also not ideal. It should be noted that Comparative Examples 3-1 to 3-3 are missing the CrN / DLC coating, AlCrSiN layer, and WC-DLC nanolayer, respectively. In Comparative Example 3-1, the CrN / DLC coating is a homologous transition element with Cr in the transition layer, and its absence will affect the bonding force. DLC has excellent mechanical properties, and the absence of the CrN / DLC coating affects its friction coefficient and bonding force. Moreover, the DLC element and the outermost WC-DLC nanolayer are similar to a high-strength clamping structure as an outer protective layer for the AlCrSiN layer. In Comparative Example 3-2, the AlCrSiN core is missing, which affects the stable transition between the CrN / DLC coating and the WC-DLC nanolayer, thus affecting the bonding force. In Comparative Example 3-3, the WC-DLC nanolayer affects its friction coefficient and mechanical wear.

[0189] In Comparative Examples 5-2 and 5-3, the absence of either NiCrAlY or SiC negatively impacts the performance of the metallurgical components. The composition of NiCrAlY helps alleviate thermal mismatch and enhances interfacial bonding. SiC refines grains, inhibits dendrite growth, and improves the microstructure, thereby enhancing mechanical properties. The combined use of NiCrAlY and SiC provides a synergistic effect in improving the interface, enhancing overall microstructure stability and interfacial bonding. In Comparative Examples 5-1 and 4, the increase in Cr content represents changes in the elemental content between the metallurgical bonding layer and the surface protective layer, respectively. While Cr does influence interfacial adhesion and bonding strength, simply increasing its content negatively impacts overall performance.

[0190] Scanning electron microscopy (SEM) observations of the HIP substrate in Comparative Example 7 and the substrate in Example 1 revealed that in Comparative Example 7, improper process temperature affected the ratio and balance of the α2+β two-phase regions, resembling substrate collapse. This severely impacted the HIP densification effect, consequently affecting the stable adhesion of subsequent surface coatings. In Comparative Example 8, stable flow control was employed, and no gradient layer was observed, suggesting a single-layer Cr structure, which also provided some hardness enhancement to the HIP substrate.

[0191] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A powder metallurgy component with a gradient composite coating, comprising a powder metallurgy substrate layer (1), characterized in that: The outer surface of the powder metallurgy matrix layer (1) is provided with a bonding layer (2), a transition layer (3) and a surface protective layer (4) in sequence. The powder metallurgy matrix layer (1) is prepared by hot isostatic pressing of powder substrate; the bonding layer (2) is a metallurgical bonding layer; and the transition layer (3) is a functional transition layer. The surface protective layer (4) is a sandwich structure coating, which includes a CrN / DLC coating, an AlCrSiN layer and a WC-DLC nanolayer sequentially from the transition layer (3).

2. A powder metallurgy component with a gradient composite coating according to claim 1, characterized in that, The powder metallurgical matrix layer (1) is one or more of the following: HIP-formed WC-Co cemented carbide, 316L stainless steel, titanium-based alloy mixture, and titanium-aluminum-based composite material.

3. A powder metallurgy component with a gradient composite coating according to claim 1, characterized in that, The metallurgical bonding layer is composed of NiCrAlY and SiC, wherein SiC accounts for 15-25% vol% of the total volume of the metallurgical bonding layer material, and the thickness of the metallurgical bonding layer is 0.5-2 μm; wherein the elemental contents of NiCrAlY are as follows: 60 at% Ni, 10-30 at% Cr, 10-20 at% Al, 0.5-1.0 at% Y, with the balance being impurities.

4. A powder metallurgy component with a gradient composite coating according to claim 1, characterized in that, The thickness of the functional transition layer is 3-8 μm.

5. A powder metallurgy component with a gradient composite coating according to claim 1, characterized in that, The surface protective layer has a CrN / DLC coating thickness of 2.85-3.05 μm, an AlCrSiN layer thickness of 3.27-5.67 μm, and a WC-DLC nanolayer thickness of 6.48-6.68 μm.

6. A powder metallurgy component with a gradient composite coating according to claim 5, characterized in that, The AlCrSiN layer contains the following elemental contents: 41-49 at% Al, 23-27 at% Cr, 7-9 at% Si, 21-23 at% N, with the remainder being impurities.

7. A method for preparing a powder metallurgy component with a gradient composite coating as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Material pretreatment and preparation Select a 100-500 mesh sieve to sieve the alloy powder, use metal or gold powder with uniform particle size distribution, and perform pretreatment of the material by ball milling or pre-alloying. S2, Molding and Pre-densification The pre-treated material is loaded into a flexible mold and formed into a green material by cold isostatic pressing. Then the casing is removed to obtain the green material. S3, Packaging and HIP Molding The green blank is directly loaded into a homogeneous sheath of the alloy blank, and a vacuum is drawn to 10. -3 After degassing for 2-24 hours following the Pa process, the material is sealed. After sealing, the parameters are adjusted for HIP molding. The encapsulation is removed by acid pickling to obtain the HIP matrix, i.e., the powder metallurgy matrix layer. The oxygen content within the encapsulation is ≤480ppm. S4, Post-processing The HIP substrate from step S3 was subjected to solution treatment by water quenching at 1050℃ to optimize corrosion resistance. After cooling and drying, it was roughened by sandblasting to control the surface roughness Ra of the HIP substrate to 1.5-3.0μm, thus obtaining a roughened HIP substrate. S5, Preparation of the bonding layer The rough surface HIP substrate is placed on the rotary table of the processing chamber. NiCrAlY and SiC materials are prepared and mixed. The mixture is ball-milled under Ar gas protection, ball-to-material ratio of (9-11):1, and rotation speed of 300-500 rpm for 2-4 hours to obtain the bonding layer material. Then, the bonding layer material is sprayed onto the rough surface HIP substrate using a supersonic flame spraying process to form a dense coating, i.e., the bonding layer. S6, Transition Layer Preparation Based on step S5, turn on the TiAl target arc source with a current of 60A, select a Cr target and use magnetron sputtering process to prepare a Cr / CrN gradient layer, i.e., a transition layer, by controlling the N2 flow rate in a stepped flow rate of "50sccm-150sccm-250sccm-300sccm". S7. Preparation of Surface Protective Layer Based on step S6, a CrN / DLC layer is deposited on the surface of the transition layer using physical vapor deposition (PVD). Then, an AlCrSiN layer and a DLC-W coating are sequentially deposited on the surface of the CrN / DLC layer using plasma-enhanced chemical vapor deposition (PECVD). After standing for 2-8 hours, the metallurgical component is obtained for the next step. S8, Package Remove the metallurgical component from the rotating table in step S7, clean it with deionized water using ultrasonic cleaning, then dry it with N2 inert gas, and vacuum dry it at 50-80°C for 1-2 hours to completely remove moisture. Finally, encapsulate it with anti-scratch material to obtain the metallurgical component of the present invention.

8. The method for preparing a powder metallurgy component with a gradient composite coating according to claim 7, characterized in that, The cold isostatic pressing process parameters in step S2 are: The flexible mold material is polyurethane or rubber; Temperature: Room temperature, 20-25℃; Pressure range: 200-400MPa; Pressure holding time: 1-10 minutes; Pressure transmission medium: Glycerin; In step S3, the HIP molding process parameters are as follows: Heating rate: 5℃ / min; Temperature: 1200-1450℃; Pressure: 100-200 MPa; Keep the furnace under heat and pressure for 1-2 hours, and then cool it to room temperature with the furnace. The supersonic flame spraying process parameters in step S5 are as follows: Substrate preheating: 250±10℃; Particle velocity: ≥600m / s; Fuel: kerosene + oxygen, with a flow ratio of 1:(3.2-3.8).

9. The method for preparing a powder metallurgy component with a gradient composite coating according to claim 7, characterized in that, The alloy billet dimensions are Φ65×150mm.

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