An ultra-high thermal stability isomeric alloy piece and a preparation method thereof

Abstract

The application belongs to the field of surface engineering and metal materials, and discloses an ultrahigh thermal stability isomer alloy part and a preparation method thereof, which comprises a substrate and an ultrathin crystal composite coating prepared on the surface of the substrate, the ultrathin crystal composite coating is prepared from Ni-Cr-Nb-P-B-Si amorphous alloy powder, the average grain size is 400nm-1000nm, the ultrathin crystal composite coating is composed of Ni3P phase and Ni solid solution phase and is interwoven, a coherent interface is formed between the Ni3P phase and the Ni solid solution phase, a Nb-rich nano precipitate phase is in-situ precipitated at the grain boundary, and Nb elements and P elements are co-segregated, and the application further provides a preparation method thereof. The application solves the problem that the existing industrial part surface cannot be prepared with an ultrathin crystal coating which can maintain stable organization at an extremely high temperature.

Description

Technical Field

[0001] This application belongs to the field of surface engineering and metallic materials technology, and more specifically, relates to an ultra-high thermal stability heterogeneous alloy part and its preparation method. Background Technology

[0002] In the development of next-generation energy systems, aerospace, and high-performance chemical equipment, it is crucial to develop structural materials that can maintain excellent mechanical properties under extreme high-temperature environments. Particularly in the automotive industry, the implementation of Euro 7 emission standards has imposed strict limits on non-exhaust particulate emissions (such as brake dust). Traditional gray cast iron (such as HT250) brake discs are prone to softening and wear under high-temperature friction conditions, making it difficult to meet the requirements for wear resistance and low emissions.

[0003] Ultrafine-grained (UFG) metallic materials have attracted much attention due to their high strength, but their thermal stability is poor. Due to their extremely high grain boundary density, UFG materials experience immense driving forces at high temperatures (especially near their melting point Tm), making them highly susceptible to grain coarsening and leading to a sharp decline in mechanical properties (i.e., softening). Current stabilization strategies mainly include reducing grain boundary energy through solute segregation (thermodynamic stability) and hindering grain boundary migration through second-phase particle pinning (kinetic stability). However, maintaining the stability of the UFG structure remains a significant challenge in the high-temperature range above 0.6 Tm, especially near the melting point, due to the coarsening or dissolution of the precipitated phase.

[0004] Existing processes for preparing ultrafine-grained materials have significant limitations in industrial applications. Traditional methods rely heavily on severe plastic deformation (SPD), which are typically only suitable for small samples and difficult to apply to the surface strengthening of large, complex components, often resulting in defects such as porosity. In surface engineering, conventional laser cladding technology, due to its high laser energy density and large spot size, leads to enormous heat input to the molten pool and a relatively slow cooling rate, making it prone to grain coarsening during solidification and hindering the direct acquisition of uniform nanocrystalline or ultrafine-grained structures. While thermal spraying can prepare amorphous coatings, the coating and substrate are usually mechanically bonded, resulting in low bonding strength and difficulty in ensuring coating density.

[0005] Therefore, there is an urgent need for a new manufacturing method and product that can efficiently prepare a dense, metallurgically well-bonded, and structurally stable ultrafine-grained coating on the surface of large-size industrial components (such as brake discs and pipes). Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this application is to provide an ultra-high thermal stability heterogeneous alloy part and its preparation method, which aims to solve the problem that existing large-size industrial parts cannot be coated with ultra-fine grain coatings that can maintain microstructure stability at extreme high temperatures.

[0007] To achieve the above objectives, in a first aspect, this application provides an ultra-high thermal stability heterogeneous alloy part, comprising a substrate and an ultrafine-grained composite coating prepared on the surface of the substrate. The ultrafine-grained composite coating is prepared from Ni-Cr-Nb-PB-Si amorphous alloy powder. The ultrafine-grained composite coating has an average grain size of 400 nm to 1000 nm and is composed of a two-phase interwoven structure of Ni3P phase and Ni solid solution phase. A coherent interface is formed between the Ni3P phase and the Ni solid solution phase. The specific crystallographic relationship between the Ni3P phase and the Ni solid solution phase is that the crystal orientation (330) in the Ni3P phase is parallel to the crystal orientation (-11-1) in the Ni solid solution phase. The ultrafine-grained composite coating contains in-situ precipitates of Nb-rich nano-precipitates (e.g., Ni) at the grain boundaries. 66 Nb 14 P 10 It is a Cr3Si5B2 nanoprecipitate phase, and it exhibits co-segregation of Nb and P elements.

[0008] In the above invention, the ultrafine-grained composite coating prepared on the substrate surface is a Ni-Cr-Nb-PB-Si amorphous alloy. This amorphous alloy can form a biphase interwoven structure of Ni3P and Ni solid solution phases, with a unique low-energy coherent interface between them. The specific crystallographic relationship between the Ni3P and Ni solid solution phases is that the crystal orientation (330) in the Ni3P phase is parallel to the crystal orientation (-11-1) in the Ni solid solution phase. This low-energy coherent interface ensures thermodynamic stability. Furthermore, Ni is precipitated in situ at the grain boundaries. 66 Nb 14 P 10 The nanoprecipitated phase with Cr3Si5B2-type structural characteristics can act as grain boundary pinning. Furthermore, high concentrations of Nb and P elements co-segregate at the grain boundaries, which can act as solute drag. The synergistic effect of "low-energy coherent phase interface (thermodynamically stable)" and "nanoprecipitated phase Zener pinning + Nb and P element solute drag (kinetically stable)" maximally restricts grain growth at high temperatures, achieving a superstable microstructure near the melting point and obtaining an ultrafine-grained microstructure near the melting point.

[0009] Furthermore, the atomic percentage composition of the Ni-Cr-Nb-PB-Si amorphous alloy powder is as follows: Ni balance, Cr 8.0~9.5%, Nb 2.5~3.5%, P 15.0~17.0%, B 2.8~3.6%, and Si 0.3~0.8%. Preferably, the atomic percentage composition of the Ni-Cr-Nb-PB-Si amorphous alloy powder is as follows: Ni 68.6%, Cr 8.7%, Nb 3.0%, P 16.0%, B 3.2%, and Si 0.5%, which is an optimal formulation. This composition ratio is located near the deep eutectic point of the Ni-P binary system, exhibiting excellent amorphous forming ability. Combined with ultra-high-speed laser cladding technology, a dense amorphous / nanocrystalline precursor coating can be obtained. The added Nb and P elements cause strong segregation at the grain boundaries, forming Nb-P rich nanoprecipitates with extremely high melting points (approximately 1595 K). These thermally stable precipitates remain insoluble and do not coarsen at temperatures close to the alloy's melting point (~1109 K), providing strong kinetic pinning for grain boundary migration.

[0010] Furthermore, Nb-rich nanoprecipitates (such as Ni) 66 Nb 14 P 10 The particle size of the Cr3Si5B2 nanoprecipitate phase is less than 200 nm. Nb-rich nanoprecipitates with a particle size less than 200 nm exhibit significant grain boundary pinning. The effect of particle size on grain boundary pinning is as follows: based on the Zener pinning mechanism, the resistance (i.e., pinning pressure) exerted by second-phase particles on grain boundary migration is inversely proportional to the particle radius. Under the premise of a constant precipitate volume fraction, the Ni... 66 Nb 14 P 10 The smaller the particle size of the Cr3Si5B2 precipitate phase, the higher its number density per unit volume, which significantly increases the total area of ​​grain boundaries truncated by the particles, thus generating a stronger resistance to grain boundary movement. Furthermore, because this nanoprecipitate phase has a melting point much higher than the matrix (approximately 1595 K), it is less prone to Ostwald ripening at high temperatures, enabling it to maintain its fine nanoscale particle size for a long time. This continuously provides efficient grain boundary pinning, preventing abnormal growth of matrix grains at near-melting point temperatures.

[0011] Furthermore, it is at 0.97 T m After annealing at high temperature for 20 hours, the grain size of the ultrafine-grained composite coating on the surface remained less than 1000 nm, with no significant coarsening. After 1000 hours of heat exposure at 0.88 Tm, the microstructure of the ultrafine-grained composite coating on the surface remained uniform and dense, with the grain size still less than 1000 nm and no significant coarsening.T m This refers to the solidus temperature of the ultrafine-grained coating (i.e., the crystallized alloy), which is approximately 1109 K. The composition of the amorphous alloy powder is located at the eutectic point of the alloy system, causing the alloy to exhibit a single, sharp endothermic melting peak during heating, with an extremely narrow melting range. Therefore, in engineering, it can be considered to have a single melting point. The reason for such good high-temperature stability is that the Ni / Ni3P interwoven structure formed after crystallization generates a large number of low-energy heterogeneous interfaces, which significantly reduces the thermodynamic driving force of grain coarsening. Furthermore, the segregation of Nb and P solutes at the grain boundaries further reduces the grain boundary energy and free volume. Moreover, the Nb-P-rich nanoprecipitates precipitated in situ at the grain boundaries have a melting point much higher than that of the matrix (approximately 1595 K), do not remelt or coarsen at high temperatures, and provide a strong Zener pinning effect. Together with the grain boundary solute dragging effect, this effectively inhibits grain boundary migration.

[0012] Furthermore, after annealing in a wide temperature range of 673 K to 1073 K, the microhardness of the ultrafine-grained composite coating on the surface is 900. 50HV. HV hardness is Vickers hardness; the microhardness of the ultrafine grain composite coating is 900. At 50 HV, the coating exhibits good high-temperature hardness after wide-range annealing. This is due to two main factors: firstly, the retention of fine-grained strengthening. Thanks to the unique "dual inhibition" stabilization mechanism (heterogeneous interface energy reduces thermodynamic driving force + nano-precipitated phase provides kinetic pinning), the grain size of the coating does not significantly coarsen after heat treatment at 1073 K, remaining at the sub-micron level (<1 μm). This extremely high microstructural thermal stability ensures that the grain boundary strengthening mechanism does not degrade after high-temperature annealing, thus maintaining high hardness. Secondly, the coating benefits from nano-precipitation strengthening. The high-melting-point Nb-P-rich nano-precipitates precipitated in situ at the grain boundaries remain stable at high temperatures, not only inhibiting grain growth but also hindering dislocation movement through dislocation bypass or shearing mechanisms, providing additional precipitation strengthening contributions.

[0013] Furthermore, the substrate is a large-size industrial component, including aircraft / high-speed rail brake discs, offshore drilling platform drilling tools, petrochemical and energy valve connectors, high-temperature turbine components for aero-engines / gas turbines, and heat exchange pipes for industrial furnaces and waste heat recovery systems. These large-size industrial components are precisely the core application scenarios that this invention aims to address. They collectively face multiple harsh challenges such as high temperature, wear, corrosion, and thermal fatigue. The ultra-high thermal stability ultrafine-grained composite coating of this invention can bring revolutionary performance improvements to them. For example, during emergency braking, the instantaneous temperature of the friction surface can reach over 1000°C, accompanied by severe mechanical impact and thermal shock. Traditional materials are prone to thermal degradation (decreased coefficient of friction), cracks, and excessive wear. The ultrafine-grained composite coating has a thermal stability of 0.88Tm ~ 0.97Tm. Tm The grains do not coarsen at high temperatures, maintaining high hardness (approximately 900 HV), ensuring a stable friction coefficient during braking and preventing "braking failure." In deep / ultra-deep well operations, underground temperatures can reach 200°C to 300°C or higher, while the tool is subjected to high pressure, corrosive formation fluids (brine, H2S, CO2), and abrasive wear from rock cuttings. The ultrafine-grained coating maintains high hardness even at 673K ​​(approximately 400°C), significantly enhancing the tool's resistance to abrasive wear. The Cr and Ni-rich amorphous derivative coating is inherently corrosion-resistant, and the ultrafine-grained structure makes the passivation film denser. Nb / P co-segregation at grain boundaries strongly suppresses grain boundary corrosion susceptibility, which is crucial for preventing stress corrosion cracking (SCC) under high-pressure corrosive environments.

[0014] Secondly, a method for preparing the ultra-high thermal stability heterogeneous alloy parts as described above is provided, comprising the following steps: S1: Prepare Ni-Cr-Nb-PB-Si amorphous alloy powder, clean the substrate surface, and deposit the amorphous alloy powder onto the substrate surface using laser cladding to form a precursor coating for the ultrafine-grained composite coating. S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1000 K ~ 1073 K, and the holding time is at least 1 hour, so that the precursor coating is completely crystallized to form ultrafine crystals.

[0015] Furthermore, in step S2, during the crystallization and heat preservation treatment, an interwoven structure of Ni3P phase and Ni solid solution phase is formed, and Nb-rich nanoprecipitates are precipitated in situ at the grain boundaries, forming co-segregation of Nb and P elements.

[0016] In the above-mentioned inventive concept, crystallization heat treatment is a crucial step. This step completes the transformation from a metastable amorphous / nanocrystalline precursor to a thermodynamically stable Ni solid solution / Ni3P dual-phase ultrafine-grained structure. The temperature and holding time of the crystallization heat treatment need to be matched with the composition design to ensure complete crystallization transformation of the precursor coating, eliminating the amorphous phase and forming a Ni3P intermetallic compound phase and a Ni solid solution phase with a specific volume fraction ratio (specifically, the volume ratio of the Ni3P intermetallic compound phase to the Ni solid solution is approximately 58:42). Furthermore, it drives the sufficient diffusion of solute elements such as Nb and P to the grain boundaries, completing the rearrangement of the originally uniformly distributed solutes towards the grain boundaries, forming in situ a high-melting-point Nb-P-rich nanoprecipitate phase that plays a key pinning role.

[0017] Furthermore, in step S1, the laser cladding is ultra-high-speed laser cladding, with a laser power of 6kW~8kW, a scanning speed of 170m / min~190m / min, a powder feed rate of 25g / min~35g / min, an overlap rate of 70%~90%, and high-purity argon as the protective gas. Ultra-high-speed laser cladding is relative to traditional laser cladding, which typically operates at speeds below 2 meters per minute, while ultra-high-speed cladding can reach 200 meters per minute, significantly improving cladding efficiency. This is because the laser cladding equipment has been upgraded, and the amorphous alloy powder material used in this invention can withstand the stress brought about by high speeds without cracking.

[0018] The reason why the ultrafine-grained alloy coating of the present invention has such excellent performance lies in the construction of a comprehensive thermodynamic and kinetic synergistic stability system. According to calculations, the coarsening activation energies of the Ni solid solution phase and the Ni3P phase in the alloy of the present invention are as high as 357 kJ / mol and 355 kJ / mol, respectively, which are significantly higher than those of traditional nickel-based high-temperature alloys (usually 250 ~ 290 kJ / mol). This directly proves that the ultrafine-grained microstructure of the present invention has extremely high resistance to coarsening.

[0019] Furthermore, the Nb-rich nano-precipitates at the grain boundaries possess an extremely high melting point (Tm≈1595 K), far exceeding the melting point of the alloy matrix (the alloy matrix composition is Ni 68.6%, Cr 8.7%, Nb 3.0%, P 16.0%, B 3.2%, Si 0.5%, Tm≈1109 K; all figures are atomic percentages). This heterostructure of "high-melting-point phase pinning low-melting-point matrix" ensures that even when the matrix is ​​close to melting, the pinning points remain stable, effectively suppressing grain boundary migration and exhibiting a Zener pinning effect. In fact, the composition of the Nb-rich nano-precipitates is not necessarily specifically Ni. 66 Nb 14 P 10 Cr3Si5B2, when the atomic percentages in its composition are: Nb 10 ~ 18.5%, Cr 3.5 ~ 8.9%, P 10.0 ~ 14.5%, B 1.0 ~ 2.5%, Si 4.0 ~ 6.5%, and Ni balance, are all Nb-rich phases, all have high melting points, and all belong to Nb-rich nanoprecipitate phases.

[0020] Moreover, the strong segregation of multiple solutes such as Nb, P, and Si at the grain boundaries significantly reduces the grain boundary energy and grain boundary free volume, thereby reducing the driving force for grain growth from a thermodynamic perspective. A specific orientation relationship is formed between the Ni solid solution phase and the Ni3P phase (e.g., (330)Ni3P / / (-11-1)Ni(ss)). The interface energy of this coherent / semi-coherent interface is extremely low (calculated value is only tens of mJ / m², far lower than the approximately 1000 mJ / m² of ordinary large-angle grain boundary energy), which makes the system in a low-energy metastable state and does not tend to coarsen.

[0021] Finally, unlike traditional single-solute dragging, this invention forms high-concentration solute clusters and diffusely distributed solute atoms at the grain boundaries. This complex solute atmosphere generates extremely strong binding forces on the grain boundaries, and molecular dynamics simulations confirm that this structure can completely lock grain boundary movement even at 1200K~1300K.

[0022] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: The ultra-high thermal stability heterogeneous alloy parts prepared by this invention exhibit remarkable thermal stability at temperatures close to the coating melting point (approximately 0.97 Tm, or approximately 1073 K). Their surfaces maintain a hardness of approximately 900 HV and a submicron grain size (less than 1000 nm) without significant coarsening. When used in industrial components operating in extreme environments, such as aircraft / high-speed rail brake discs, drilling tools for offshore drilling platforms, valve connections in petrochemical and energy industries, high-temperature turbine components for aero-engines / gas turbines, and the surface layer of heat exchange pipes in industrial furnaces and waste heat recovery systems, they demonstrate excellent performance enhancement, especially in the field of brake discs.

[0023] The preparation method of the present invention is to perform crystallization heat treatment after laser cladding. The whole process is simple, and both laser cladding and heat treatment have mature equipment and processes, which makes the preparation method of the present invention highly operable. Attached Figure Description

[0024] Figure 1 This is a comparison of the XRD diffraction patterns of the amorphous alloy powder, the deposited coating, and the heat-treated ultrafine-grained composite coating (hereinafter referred to as HS alloy) provided in Example 1 of this application.

[0025] Figure 2 These are the DSC thermal analysis curves of the ultrafine crystalline composite coating and the original amorphous powder provided in Example 1 of this application.

[0026] Figure 3This is the microstructure of the ultrafine crystalline composite coating provided in Example 1 of this application after annealing at 1073 K (800 °C) for 1 hour.

[0027] Figure 4 The EBSD inverse pole figure (IPF) of the ultrafine crystalline composite coating provided in Example 1 of this application after annealing at 1073 K (800 °C) for 1 hour.

[0028] Figure 5 This is a TEM bright-field image and schematic diagram of the principle of the ultrafine crystal composite coating provided in Example 1 of this application after annealing at 1073 K (800℃) for 1 hour.

[0029] Figure 6 This is a high-resolution TEM image of the ultrafine crystalline composite coating provided in Example 1 of this application after annealing at 1073 K (800 °C) for 1 hour.

[0030] Figure 7 The images provided in Embodiment 1 of this application are HAADF-STEM images of the grain boundary region and corresponding EDS elemental surface scans (including elements Ni, Nb, P, and Si).

[0031] Figure 8 This is a comparison of the coefficient of friction (COF) versus time curves and wear track morphology of the ultrafine grain composite coating (HS alloy) provided in Example 1 of this application, Inconel 718 nickel-based high-temperature alloy, and HT250 gray cast iron under dry friction conditions.

[0032] Figure 9a and Figure 9b These are photographs of large-size industrial components prepared using the method described in this application. Figure 9a To prepare brake discs with ultrafine crystalline composite coatings, Figure 9b To prepare heat exchange pipes with ultrafine crystalline composite coatings. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0034] The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0035] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0036] This invention addresses the technical challenge of existing ultrafine-grained (UFG) metallic materials exhibiting rapid grain coarsening and a sharp decline in mechanical properties (i.e., "high-temperature softening") under high-temperature conditions, particularly near the melting point (Tm), due to the extremely high grain boundary driving force. It also addresses the problem of existing fabrication processes (such as traditional laser cladding) involving high heat input and slow cooling, making it difficult to obtain a uniform and dense ultrafine-grained structure on large-sized components. This invention provides an ultrafine-grained high-temperature thermally stable composite coating, its preparation method, and its applications. The aim of this invention is to achieve long-term microstructure stability and excellent mechanical properties in ultrafine-grained materials at temperatures above 0.9 Tm.

[0037] The embodiments of this application are described below with reference to the accompanying drawings. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0038] Examples 1-5 illustrate the preparation and characterization of ultrafine-grained composite coatings, while Comparative Examples 1-5 show the absence of key elements. Examples 6-8 demonstrate the application of these coatings in different industrial components.

[0039] Example 1 Matrix material: 304 stainless steel pipe (as a heat exchange pipe simulating high-temperature conditions). Amorphous powder composition, in atomic percentage (at%): Ni 68.6, Cr 8.7, Nb 3.0, P 16.0, B 3.2, Si 0.5.

[0040] The coating preparation method is ultra-high-speed laser cladding followed by crystallization heat treatment, as detailed below: S1: Clean the substrate surface, specifically by grinding and removing rust, and cleaning with alcohol to remove oil stains. Amorphous alloy powder is deposited onto the substrate surface using laser cladding to form a precursor coating for the ultrafine-grained composite coating. The laser cladding is ultra-high-speed laser cladding, and the equipment is a six-axis linkage ultra-high-speed laser cladding processing system integrating a high-power fiber laser (rated power 10000W) and a high-speed coaxial powder feeding nozzle. The laser power is 7kW, the scanning speed is 180 m / min, the powder feeding rate is 30g / min, the overlap rate is 80%, and the protective gas is high-purity argon.

[0041] S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1073K and the holding time is 1 hour. Then, it is air-cooled to make the precursor coating completely crystallize and form ultrafine crystals.

[0042] Coating characterization results: XRD analysis revealed that the annealed ultrafine-grained composite coating completely transformed from an amorphous to a crystalline state. EBSD and SEM results showed that the coating possessed a uniform equiaxed crystalline structure, composed of interwoven Ni3P and Ni(ss) phases, with an average grain size of approximately 450 nm. The Ni3P intermetallic compound phase and Ni(ss) phase were uniformly distributed, with Ni3P accounting for approximately 58% and Ni(ss) phase approximately 42%. Ni particles with a diameter of 50 nm to 140 nm were uniformly dispersed at grain boundaries and within the grains. 66 Nb 14 P 10 Cr3Si5B2 phase.

[0043] HR-TEM and FFT analyses confirmed that the (330) crystal orientation of the Ni3P phase is parallel to the (-11-1) crystal orientation of the Ni(ss) phase, forming a semi-coherent / coherent interface, which effectively reduces the interface energy.

[0044] HR-TEM (transmission electron microscopy) clearly shows that there is significant co-aggregation of Nb and P atoms at the grain boundaries, forming Nb / P-rich solute clusters.

[0045] Performance testing: After annealing at 0.97 Tm (approximately 1073 K) for 20 hours, the average grain size only increased to approximately 934 nm. After heat exposure at 0.88 Tm (approximately 700 K) for 1000 hours, the microstructure remained dense and uniform, with an average grain size of approximately 760 nm, showing no abnormal growth. After annealing over a wide temperature range of 673 K to 1073 K, the microhardness stabilized at 850-950 HV. 0.5 It exhibits excellent hardness retention over a wide temperature range.

[0046] Figure 1 The XRD diffraction patterns of the amorphous alloy powder, the deposited coating, and the heat-treated ultrafine-grained composite coating (hereinafter referred to as HS alloy) provided in Example 1 of this application are compared. The comparison shows the phase transformation process of the material from "amorphous powder" to "amorphous precursor" and then to "fully crystallized Ni / Ni3P dual-phase structure", proving that the final product is crystalline.

[0047] Figure 2The DSC thermal analysis curves of the ultrafine crystalline composite coating and the original amorphous powder provided in Example 1 of this application are shown. The comparison shows that the melting behavior of the material is demonstrated, the melting point of the material is marked, and it is proven that the alloy composition is located near the eutectic point and has a single sharp endothermic peak.

[0048] Figure 3 The microstructure of the ultrafine-grained composite coating provided in Example 1 of this application after annealing at 1073 K (800 °C) for 1 hour shows a two-phase interwoven morphology of Ni solid solution and Ni3P, with uniform equiaxed grains.

[0049] Figure 4 The image shows the EBSD inverse pole figure (IPF) of the ultrafine-grained composite coating provided in Example 1 of this application after annealing at 1073 K (800 °C) for 1 hour. It shows that the grain orientations of the coating are randomly distributed and no texture is produced.

[0050] Figure 5 This is a TEM bright-field image and schematic diagram of the ultrafine-grained composite coating provided in Example 1 of this application after annealing at 1073 K (800℃) for 1 hour. In the figure, the grains selected by the white dashed line area represent Ni3P, the yellow area represents Ni solid solution, the orange area represents nano-precipitated phase, and the upper right corner is a schematic diagram of the coating.

[0051] Figure 6 This is a high-resolution TEM image of the ultrafine-grained composite coating provided in Example 1 of this application after annealing at 1073 K (800 °C) for 1 hour. The green area represents Ni3P, and the purple area represents Ni solid solution. The interface between the two phases shows a coherent / semi-coherent interface relationship where the (330) crystal plane of the Ni3P phase is parallel to the (-11-1) crystal plane of the Ni solid solution phase.

[0052] Figure 7 The images provided in Example 1 of this application are HAADF-STEM images of the grain boundary region and corresponding EDS elemental surface scans (including elements Ni, Nb, P, and Si). They show the significant segregation of Nb and P elements at the grain boundaries and the compositional distribution of the Nb-P-rich nanoprecipitate phase.

[0053] Figure 8 This is a comparison of the coefficient of friction (COF) versus time curves and wear track morphology of the ultrafine-grained composite coating (HS alloy) provided in Example 1 of this application, Inconel 718 nickel-based superalloy, and HT250 gray cast iron under dry friction conditions. In the figure, the coefficient of friction of Inconel 718 nickel-based superalloy and HT250 gray cast iron is higher, and the friction surface is severely worn, while the coefficient of friction of the ultrafine-grained composite coating (HS alloy) is low and the friction surface is smooth.

[0054] Example 2 Matrix material: HT250 gray cast iron (used to simulate brake pad components). Amorphous powder composition, in atomic percentage (at%): Ni balance, Cr 9.5, Nb 3.5, P 17.0, B 3.6, Si 0.8.

[0055] The coating preparation method is ultra-high-speed laser cladding followed by crystallization heat treatment, as detailed below: S1: Clean the substrate surface, specifically by grinding and removing rust, and cleaning with alcohol to remove oil stains. Amorphous alloy powder is deposited onto the substrate surface using laser cladding to form a precursor coating for the ultrafine-grained composite coating. The ultra-high-speed laser cladding system is the same as in Example 1. The laser power is 6kW, the scanning speed is 150 m / min, the powder feed rate is 25g / min, the overlap rate is 70%, and the protective gas is high-purity argon.

[0056] S2: The precursor coating is subjected to crystallization heat treatment in a vacuum at a temperature of 1000 K and a holding time of 3 hours, so that the precursor coating is completely crystallized to form ultrafine crystals.

[0057] Coating characterization results: XRD analysis revealed that the annealed ultrafine-grained composite coating completely transformed from an amorphous to a crystalline state. EBSD and SEM results showed that the coating possessed a uniform equiaxed crystalline structure, composed of interwoven Ni3P and Ni(ss) phases, with an average grain size of approximately 530 nm. The Ni3P and Ni(ss) phases were uniformly distributed, with Ni3P accounting for approximately 60% and Ni(ss) approximately 40%. Ni particles with a diameter of 70 nm to 160 nm were uniformly dispersed at grain boundaries and within the grains. 60.48 Nb 15.4 P 13.54 Cr 3.88 Si 4.32 B 2.38 Mutually.

[0058] HR-TEM and FFT analyses confirmed that the (330) crystal orientation of the Ni3P phase is parallel to the (-11-1) crystal orientation of the Ni(ss) phase, forming a semi-coherent / coherent interface, which effectively reduces the interface energy.

[0059] HR-TEM (transmission electron microscopy) clearly shows that there is significant co-aggregation of Nb and P atoms at the grain boundaries, forming Nb / P-rich solute clusters.

[0060] Performance testing: After annealing at 0.97 Tm (approximately 1073 K) for 20 hours, the average grain size only increased to approximately 987 nm. After heat exposure at 0.88 Tm (approximately 700 K) for 1000 hours, the microstructure remained dense and uniform, with an average grain size of approximately 860 nm, showing no abnormal growth. The microhardness remained stable at 850-920 HV within the temperature range of 673 K to 1073 K. 0.5 It exhibits excellent hardness retention over a wide temperature range.

[0061] Example 3 Matrix material: 45 steel pipe (to simulate high-temperature wear-resistant parts). Amorphous powder composition, in atomic percentage (at%): Ni balance, Cr 8.0, Nb 2.5, P 15.0, B 2.8, Si 0.3.

[0062] The coating preparation method is ultra-high-speed laser cladding followed by crystallization heat treatment, as detailed below: S1: Clean the substrate surface, using the same method as in Example 1. The ultra-high-speed laser cladding system is the same as in Example 1. The laser power is 8kW, the scanning speed is 200 m / min, the powder feed rate is 35g / min, the overlap rate is 90%, and the protective gas is high-purity argon.

[0063] S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1073 K and the holding time is 1 hour, so that the precursor coating is completely crystallized to form ultrafine crystals.

[0064] Coating characterization results: XRD analysis revealed that the annealed ultrafine-grained composite coating completely transformed from an amorphous state to a crystalline state. EBSD and SEM results showed that the coating possessed a uniform equiaxed crystal structure, composed of interwoven Ni3P and Ni(ss) phases, with an average grain size of approximately 533 nm. The Ni3P and Ni(ss) phases were uniformly distributed, with Ni3P accounting for approximately 52% and Ni(ss) accounting for approximately 48%. Ni particles with a diameter of 60 nm to 150 nm were uniformly dispersed at grain boundaries and within the grains. 68.51 Nb 9.91 P 10.1 Cr 5.44 Si 5.02 B 1.02 Mutually.

[0065] HR-TEM and FFT analyses confirmed that the (330) crystal orientation of the Ni3P phase is parallel to the (-11-1) crystal orientation of the Ni(ss) phase, forming a semi-coherent / coherent interface, which effectively reduces the interface energy.

[0066] HR-TEM (transmission electron microscopy) clearly shows that there is significant co-aggregation of Nb and P atoms at the grain boundaries, forming Nb / P-rich solute clusters.

[0067] Performance testing: After annealing at 0.97 Tm (approximately 1073 K) for 20 hours, the average grain size only increased to approximately 995 nm. After heat exposure at 0.88 Tm (approximately 700 K) for 1000 hours, the microstructure remained dense and uniform, with an average grain size of approximately 853 nm, showing no abnormal growth. The microhardness remained stable at 850-910 HV within the temperature range of 673 K to 1073 K. 0.5 It exhibits excellent hardness retention over a wide temperature range.

[0068] Example 4 Matrix material: 42CrMo high-strength alloy structural steel (as a simulated oil drill rod subjected to high torque and impact loads). Amorphous powder composition, in atomic percentage (at%): Ni balance, Cr 9.1, Nb 2.7, P 15.8, B 3.3, Si 0.6.

[0069] The coating preparation method is ultra-high-speed laser cladding followed by crystallization heat treatment, as detailed below: S1: Clean the substrate surface, using the same method as in Example 1. The ultra-high-speed laser cladding system is the same as in Example 1. The laser power is 6.5kW, the scanning speed is 160 m / min, the powder feed rate is 32g / min, the overlap rate is 75%, and the protective gas is high-purity argon.

[0070] S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1073 K and the holding time is 1 hour, so that the precursor coating is completely crystallized to form ultrafine crystals.

[0071] Coating characterization results: XRD analysis revealed that the annealed ultrafine-grained composite coating completely transformed from an amorphous state to a crystalline state. EBSD and SEM results showed that the coating possessed a uniform equiaxed crystal structure, composed of interwoven Ni3P and Ni(ss) phases, with an average grain size of approximately 500 nm. The Ni3P and Ni(ss) phases were uniformly distributed, with Ni3P accounting for approximately 56% and Ni(ss) approximately 44%. Ni particles with a diameter of 55 nm to 150 nm were uniformly dispersed at grain boundaries and within the grains. 66 Nb 14 P 10 Cr3Si5B2 phase.

[0072] HR-TEM and FFT analyses confirmed that the (330) crystal orientation of the Ni3P phase is parallel to the (-11-1) crystal orientation of the Ni(ss) phase, forming a semi-coherent / coherent interface, which effectively reduces the interface energy.

[0073] HR-TEM (transmission electron microscopy) clearly shows that there is significant co-aggregation of Nb and P atoms at the grain boundaries, forming Nb / P-rich solute clusters.

[0074] Performance testing: After annealing at 0.97 Tm (approximately 1073 K) for 20 hours, the average grain size only increased to approximately 962 nm. After heat exposure at 0.88 Tm (approximately 700 K) for 1000 hours, the microstructure remained dense and uniform, with an average grain size of approximately 822 nm, showing no abnormal growth. The microhardness remained stable at 850-940 HV within the temperature range of 673 K to 1073 K. 0.5 It exhibits excellent hardness retention over a wide temperature range.

[0075] Example 5 Matrix material: Inconel 718 nickel-based superalloy (as a high-temperature component simulating a gas turbine blade). Amorphous powder composition, in atomic percentage (at%): Ni balance, Cr 8.9, Nb 3.1, P 16.2, B 3.1, Si 0.6.

[0076] The coating preparation method is ultra-high-speed laser cladding followed by crystallization heat treatment, as detailed below: S1: Clean the substrate surface, using the same method as in Example 1. The ultra-high-speed laser cladding system is the same as in Example 1. The laser power is 7kW, the scanning speed is 180 m / min, the powder feed rate is 30g / min, the overlap rate is 80%, and the protective gas is high-purity argon.

[0077] S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1050 K and the holding time is 1 hour, so that the precursor coating is completely crystallized to form ultrafine crystals.

[0078] Coating characterization results: XRD analysis revealed that the annealed ultrafine-grained composite coating completely transformed from an amorphous to a crystalline state. EBSD and SEM results showed that the coating possessed a uniform equiaxed crystal structure, composed of interwoven Ni3P and Ni(ss) phases, with an average grain size of approximately 510 nm. The Ni3P and Ni(ss) phases were uniformly distributed, with Ni3P accounting for approximately 55% and Ni(ss) approximately 45%. Ni particles with a diameter of 58 nm to 150 nm were uniformly dispersed at grain boundaries and within the grains.66 Nb 14 P 10 Cr3Si5B2 phase.

[0079] HR-TEM and FFT analyses confirmed that the (330) crystal orientation of the Ni3P phase is parallel to the (-11-1) crystal orientation of the Ni(ss) phase, forming a semi-coherent / coherent interface, which effectively reduces the interface energy.

[0080] HR-TEM (transmission electron microscopy) clearly shows that there is significant co-aggregation of Nb and P atoms at the grain boundaries, forming Nb / P-rich solute clusters.

[0081] Performance testing: After annealing at 0.97 Tm (approximately 1073 K) for 20 hours, the average grain size only increased to approximately 957 nm. After heat exposure at 0.88 Tm (approximately 700 K) for 1000 hours, the microstructure remained dense and uniform, with an average grain size of approximately 834 nm, showing no abnormal growth. The microhardness remained stable at 850-950 HV within the temperature range of 673 K to 1073 K. 0.5 It exhibits excellent hardness retention over a wide temperature range.

[0082] Comparative Example 1 Powder: Crystalline Ni-Cr-Nb-PB-Si alloy powder with the same composition as in Example 1, prepared by gas atomization.

[0083] Process: Same as in Example 1.

[0084] Result comparison: Initial state of the coating: After cladding, it exhibits a coarse dendritic structure with an average grain size >5 μm. Subsequent heat treatment cannot achieve an ultrafine grain structure.

[0085] Thermal stability: After exposure to 0.88 Tm for 500 hours, the grains rapidly coarsen to tens of micrometers.

[0086] It is known that amorphous powder precursors are key to obtaining a uniform, high-defect-density metastable structure after laser cladding, providing the necessary conditions for subsequent controllable crystallization to generate an ultrafine-grained interwoven structure.

[0087] Comparative Example 2 (lacking Nb element) Amorphous powder composition (at%): Nb removed from the composition of Example 1.

[0088] Process and heat treatment: Same as in Example 1.

[0089] Result comparison: The coating structure still consists of a two-phase structure of Ni3P and Ni solid solution (because the P content remains unchanged), but due to the lack of Nb, the key high-melting-point precipitate phase cannot be formed at the grain boundaries, resulting in non-uniform grain size with an average grain size of 710 nm.

[0090] HR-TEM analysis showed only P segregation at the grain boundaries, with a lack of Nb co-segregation. No significant Ni was observed. 66 Nb 14 P 10 Cr3Si5B2 nanophase precipitation.

[0091] Thermal stability decreased significantly: after annealing at 0.97 Tm for 20 hours, local grains grew abnormally to more than 3 μm. Hardness decreased significantly at high temperatures.

[0092] Reason: The absence of Nb renders the "cluster" drag effect ineffective. The co-segregation of Nb and P can form strong synergistic pinning points, effectively confining grain boundary migration. Without Nb, the pinning force is insufficient relying solely on P segregation and possible nanophases.

[0093] Comparative Example 3 (P content is too low, insufficient Ni3P phase cannot be formed) Amorphous powder composition (at%): Based on the composition of Example 1, P is removed.

[0094] Process and heat treatment: Same as in Example 1.

[0095] Result comparison: The coating is mainly composed of Ni(ss) phase, with no Ni3P particles and lacking a continuous two-phase interwoven structure. Nb segregation at grain boundaries is weakened, and nanophase precipitation is not obvious.

[0096] Extremely poor thermal stability: the grains coarsen rapidly during heat treatment and completely lose their fine-grained characteristics after exposure to high temperatures.

[0097] Therefore, it can be concluded that sufficient P is the basis for the formation of a continuous and stable coherent interwoven structure of Ni3P / Ni solid solution, which itself is a physical barrier to inhibit grain boundary migration.

[0098] Comparative Example 4 (Insufficient heat treatment temperature, insufficient crystallization, and inability to fully form a "cluster + dispersed" structure) Amorphous powder composition: same as in Example 1.

[0099] Preparation method: After laser cladding, annealing is performed only at 873 K (far below the complete crystallization temperature).

[0100] Results Comparison: The coating is in a partially crystalline state, containing residual amorphous phases. Nb / P co-segregates and Ni 66 Nb 14 P 10The Cr3Si5B2 nanophase was not fully formed. During subsequent simulated high-temperature service, the microstructure was extremely unstable, and residual non-phase transformation induced rapid crystallization and coarsening.

[0101] Therefore, it can be concluded that specific high-temperature crystallization heat treatment (1000 ~ 1073 K) is the driving force for the formation of Nb / P co-segregated clusters and Ni 66 Nb 14 P 10 The key process steps for in-situ precipitation of Cr3Si5B2 nanophases activate the dual stabilization mechanism of "cluster + dispersion".

[0102] Comparative Example 5 Amorphous powder composition: same as in Example 1.

[0103] Process and heat treatment: The precursor coating was prepared using the same ultra-high-speed laser cladding process as in Example 1. However, in the subsequent crystallization heat treatment step, the temperature was set to 1153 K (approximately 880 °C, higher than the alloy solidus temperature Tm 1109 K) and held for 1 hour.

[0104] Results Comparison: The coating underwent overheating and partial melting. Because the heat treatment temperature exceeded the alloy's solidus temperature (Tm≈1109 K), severe grain boundary liquefaction and partial remelting occurred during the heat treatment process. The "Ni / Ni3P dual-phase interwoven ultrafine-grained structure" that should have formed through solid-state phase transformation was completely destroyed. During subsequent cooling, the liquid phase re-solidified, no longer forming uniform equiaxed ultrafine grains, but instead forming coarse dendrites with an average grain size surging to approximately 10 μm, thus losing the grain-refining strengthening effect. The microhardness dropped significantly from approximately 900 HV to 450 HV, and the wear resistance decreased significantly, failing to meet the requirements for high-temperature service.

[0105] Therefore, the selection of crystallization heat treatment temperature has strict criticality. The treatment temperature must be strictly controlled below the solidus temperature of the alloy to ensure that the evolution of the microstructure is entirely within the kinetic control range of 'solid-state crystallization'. Only within this specific temperature range (1000 K ~ 1073 K) can a controlled amorphous devitrification process achieve a two-phase interwoven ultrafine-grained structure and a dispersed high-density nano-precipitate phase. Once the temperature exceeds the solidus, the alloy will undergo liquid-phase remelting, irreversibly destroying the non-equilibrium structural advantages of the precursor coating, leading to the final microstructure transforming into coarse cast dendrites. Example 6 Application demonstration of different industrial components: In this embodiment, the industrial component is an automotive brake disc, made of HT-250. An ultrafine crystalline composite coating with the composition of Example 1 is prepared on its surface.

[0106] The specific preparation method is as follows: S1: Prepare Ni-Cr-Nb-PB-Si amorphous alloy powder. Clean the brake disc surface by first mechanically grinding or sandblasting to remove surface oxide scale and fatigue layer, achieving a surface roughness Ra of 1.6~3.2 μm. Then, ultrasonically clean the disc for 15~30 minutes in anhydrous ethanol or acetone to thoroughly remove oil and impurities. Dry the disc with cold air for later use. Laser cladding is used to deposit the amorphous alloy powder onto the substrate surface, forming a precursor coating for the ultrafine-grained composite coating. The laser cladding is ultra-high-speed laser cladding with a laser power of 7kW, a scanning speed of 180 m / min, a powder feed rate of 30 g / min, an overlap rate of 80%, and high-purity argon as the protective gas.

[0107] S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1073 K and the holding time is 1 hour, so that the precursor coating is completely crystallized to form ultrafine crystals.

[0108] Application results: After coating, under the high temperature generated by repeated emergency braking (instantaneously close to 800°C), the coating was continuously tested on a bench for 500 hours. After observation, it was found that the coating had no cracks or softening. Compared with the uncoated HT-250 gray cast iron substrate, its wear rate was reduced by more than 90%, showing excellent resistance to thermal fading and wear life.

[0109] Example 7 This embodiment demonstrates the application of different industrial components. The industrial component in this example is a valve connector for an offshore drilling platform, which is made of duplex stainless steel, specifically 2205 duplex stainless steel (022Cr22Ni5Mo3N). An ultrafine-grained composite coating with the composition of Example 2 is prepared on its surface.

[0110] The specific preparation method is as follows: S1: Prepare Ni-Cr-Nb-PB-Si amorphous alloy powder. Clean the brake disc surface by first blasting with 120#~240# corundum sand to remove the surface oxide layer and pre-roughen (Ra 3.2~6.3 μm) to enhance adhesion. Then, ultrasonically clean in acetone or anhydrous ethanol for 20 minutes to remove oil and blasting residue. Finally, dry with compressed cold air. Then, deposit the amorphous alloy powder onto the substrate surface using laser cladding to form a precursor coating for the ultrafine-grained composite coating. The laser cladding is ultra-high-speed laser cladding with a laser power of 7kW, a scanning speed of 180 m / min, a powder feed rate of 30 g / min, an overlap rate of 80%, and high-purity argon as the protective gas.

[0111] S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1073 K and the holding time is 1 hour, so that the precursor coating is completely crystallized to form ultrafine crystals.

[0112] Application Results: After coating, in a high-temperature, high-pressure corrosive environment containing H2S / CO2, the coating exhibits excellent resistance to uniform corrosion and pitting corrosion, while also resisting intergranular corrosion susceptibility caused by temperature differences. Compared to before the preparation of the ultrafine-grained composite coating, the corrosion current density of this coating ( I corr The impedance modulus at low frequencies (|Z|) was reduced by 1-2 orders of magnitude. 0.01Hz The performance has been improved by more than 3 times, effectively preventing the formation of pitting corrosion and extending the expected service life of components in extreme corrosive environments by more than 2 times.

[0113] Example 8: Application Demonstration of Different Industrial Components. The industrial component in this example is a heat exchange pipe, which is made of 304 stainless steel with the following material composition: C ≤0.08%, Si ≤1.0%, Mn ≤2.0%, Cr 18.0%~20.0%, Ni 8.0%~11.0%, S≤0.03%, P ≤0.045%, and the balance being Fe. An ultrafine-grained composite coating with the composition of Example 3 is prepared on its surface.

[0114] The specific preparation method is as follows: S1: Prepare Ni-Cr-Nb-PB-Si amorphous alloy powder. Clean the brake disc surface using a rotary sandblasting process to remove oxide scale and oil from the pipe surface, resulting in a metallic luster and a roughness of Ra 3.2~6.3 μm. Then wipe with acetone or clean and dry to ensure the bonding quality of the cladding layer. Laser cladding is used to deposit the amorphous alloy powder onto the substrate surface, forming a precursor coating for the ultrafine-grained composite coating. The laser cladding is ultra-high-speed laser cladding with a laser power of 7kW, a scanning speed of 180 m / min, a powder feed rate of 30 g / min, an overlap rate of 80%, and high-purity argon as the protective gas.

[0115] S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1073 K and the holding time is 1 hour, so that the precursor coating is completely crystallized to form ultrafine crystals.

[0116] Application effect: After coating, after 200 hours of continuous service on the high-temperature corrosive flue gas side at 973 K (about 700℃), the coating inner wall grains were found to be uncoarsened and unpeeled, and the thermal conductivity was stable. Compared with the heat exchange pipe before coating, the service life was increased by 3 to 5 times.

[0117] Figure 9a and Figure 9b These are photographs of large-size industrial components prepared using the method described in this application. Figure 9a To prepare brake discs with an ultrafine crystalline composite coating, the surface should be smooth, intact, and free of defects. Figure 9b To prepare heat exchange pipes with ultrafine crystalline composite coatings, coatings of various pipe diameters can be prepared with smooth surfaces and no cracks.

[0118] In this invention application, amorphous components play a core role. As shown in Comparative Example 1, amorphous alloy powder is the "source" for the preparation of ultrafine crystalline coatings. Its homogeneous and metastable characteristics enable it to suppress traditional crystallization during laser rapid melting and solidification. Then, through subsequent controllable crystallization, it can be directly "inherited" and transformed into an ideal dual-phase ultrafine crystalline nanostructure. This is a process path that traditional crystalline powder alloy systems cannot achieve.

[0119] The ultra-high thermal stability of this invention stems from a unique grain boundary engineering technique, specifically a solute dragging effect formed by "clustering + dispersion". In the "clustering" effect, the synergistic co-aggregation of Nb and P at the grain boundaries forms a powerful solute gas, resulting in strong chemical pinning of the grain boundaries. In the "dispersion" effect, the in-situ precipitation of thermally stable Nb-rich nano-precipitates produces classic physical pinning of the grain boundaries. These two effects are not simply additive but synergistic. Co-aggregated clusters may preferentially form at the nanophase / matrix interface, further enhancing the pinning strength; simultaneously, the presence of the nanophase may also stabilize these aggregated clusters. As shown in Comparative Examples 2 and 4, the absence of either element significantly reduces thermal stability. This dual, synergistic dragging mechanism of "clustering (chemical pinning) + dispersion (physical pinning)" constitutes the decisive microstructural basis for effectively suppressing grain boundary migration and preventing grain coarsening even at extreme high temperatures near the melting point (0.97 Tm).

[0120] In the full text of this application: Ni(ss) phase refers to Ni-based solid solution phase.

[0121] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A heterogeneous alloy part with ultra-high thermal stability, characterized in that, It includes a substrate and an ultrafine-grained dual-phase composite coating prepared on the surface of the substrate. The ultrafine-grained composite coating is prepared from Ni-Cr-Nb-PB-Si amorphous alloy powder. The ultrafine-grained composite coating has an average grain size of 400 nm to 1000 nm and is composed of a two-phase interwoven structure of Ni3P phase and Ni solid solution phase. A coherent interface is formed between the Ni3P phase and the Ni solid solution phase. The crystal orientation (330) in the Ni3P phase is parallel to the crystal orientation (-11-1) in the Ni solid solution phase. The ultrafine-grained composite coating has Nb-rich nano-precipitates precipitated in situ at the grain boundaries, as well as co-segregation of Nb and P elements.

2. The ultra-high thermal stability heterogeneous alloy part as described in claim 1, characterized in that, The atomic percentage composition of the Ni-Cr-Nb-PB-Si amorphous alloy powder is as follows: Ni balance, Cr 8.0 ~ 9.5%, Nb 2.5 ~ 3.5%, P 15.0 ~ 17.0%, B 2.8 ~ 3.6%, and Si 0.3 ~ 0.8%.

3. The ultra-high thermal stability heterogeneous alloy part as described in claim 1, characterized in that, The particle size of the Nb-rich nanoprecipitate phase is less than 200 nm.

4. The ultra-high thermal stability heterogeneous alloy part as described in any one of claims 1-3, characterized in that, It is at 0.97 T m After annealing at high temperature for 20 hours, the grain size in the ultrafine-grained composite coating on the surface is less than 1000 nm. At 0.88 T m After being exposed to heat for 1000 hours, the microstructure of the ultrafine crystalline composite coating on the surface is uniform and dense, with a grain size of less than 1000 nm.

5. The ultra-high thermal stability heterogeneous alloy part as described in claim 4, characterized in that, After annealing in a wide temperature range of 673 K to 1073 K, the microhardness of the ultrafine-grained composite coating on the surface is 900. 50HV.

6. The ultra-high thermal stability heterogeneous alloy part as described in claim 1, characterized in that, The atomic percentage composition of the Ni-Cr-Nb-PB-Si amorphous alloy powder is as follows: Ni 68.6%, Cr 8.7%, Nb 3.0%, P 16.0%, B 3.2%, and Si 0.5%.

7. The ultra-high thermal stability heterogeneous alloy part as described in claim 1, characterized in that, The substrate consists of large-sized industrial components, including brake discs, drilling tools for offshore drilling platforms, valve connectors, high-temperature turbine components, and heat exchange pipes.

8. A method for preparing ultra-high thermal stability heterogeneous alloy parts as described in any one of claims 1-7, characterized in that, It includes the following steps: S1: Prepare Ni-Cr-Nb-PB-Si amorphous alloy powder, clean the substrate surface, and deposit the amorphous alloy powder onto the substrate surface using laser cladding to form a precursor coating for the ultrafine-grained composite coating. S2: The precursor coating is subjected to crystallization heat treatment under vacuum or protective atmosphere. The temperature of the crystallization heat treatment is 1000 K ~ 1073 K, and the holding time is at least 1 hour, so that the precursor coating is completely crystallized to form ultrafine crystals.

9. The method as described in claim 8, characterized in that, In step S2, during the crystallization heat treatment, an interwoven structure of Ni3P phase and Ni solid solution phase is formed, and Nb-rich nanoprecipitates are precipitated in situ at the grain boundaries, forming co-segregation of Nb and P elements.

10. The method as described in claim 9, characterized in that, In step S1, the laser cladding is ultra-high-speed laser cladding with a laser power of 6kW~8kW, a scanning speed of 150m / min~200m / min, a powder feeding rate of 25g / min~35g / min, an overlap rate of 70%~90%, and a protective gas of high-purity argon.

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