An end plate nickel-based alloy material and a preparation method thereof

Abstract

The application belongs to the technical field of metal materials, and relates to an end plate nickel-based alloy material and a preparation method. The end plate nickel-based alloy material contains nickel, chromium, molybdenum, tungsten, niobium, tantalum, rare earth elements yttrium and cerium. The microstructure of the end plate nickel-based alloy material is composed of an equiaxed gamma austenite matrix and a second phase dispersedly distributed, the second phase including a gamma prime phase Ni3(Nb, Ta) and a non-continuous chain M 23 The surface of the end plate nickel-based alloy material has a nickel-rich conductive layer, and the atomic ratio of metallic nickel to nickel oxide in the nickel-rich conductive layer is controlled to be 3:1 to 5:1. The end plate nickel-based alloy material is prepared through vacuum induction melting, protective atmosphere electroslag remelting, multi-directional precision forging, precision controlled rolling, graded solid solution-aging heat treatment and cathodic polarization surface electrochemical modification. The end plate nickel-based alloy material is suitable for alkaline water electrolysis hydrogen production electrolytic cells, and has corrosion resistance and low interface contact resistance in a high-temperature strong alkali environment.

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, specifically relating to a nickel-based alloy material for end plates and its preparation method, which is particularly suitable for end plates of alkaline water electrolysis hydrogen production electrolyzers. Background Technology

[0002] Among numerous hydrogen production technologies, alkaline water electrolysis has become dominant in the current hydrogen production industry due to its high technological maturity, relatively low equipment cost, and ease of large-scale industrial application. As a core component of the hydrogen electrolyzer structure, the end plate not only supports the overall mechanical structure and ensures a tight seal, but also plays a crucial role in current distribution and conduction during the electrochemical reaction. Considering the long-term dynamic conditions of high-concentration strong alkaline electrolyte and high temperature inside the hydrogen electrolyzer, the nickel-based alloy material for the end plate needs to possess chemical corrosion resistance, high conductivity, and structural stability during long-term thermal cycling. Nickel-based alloys, due to their chemical stability and mechanical strength, have become one of the preferred substrates for preparing high-performance end plates.

[0003] Patent CN111069574A discloses a method for preparing wide-width, fine-grained nickel-based alloy plates. This method utilizes electroslag remelting and water-cooled crystallization processes, employing resistance heating to melt electrodes and achieve controlled bottom-up crystallization of the molten metal. This approach significantly improves the uniformity of the material's macrostructure, breaks down coarse casting grains, and enhances the mechanical properties of the plate. It helps address the issues of compositional segregation and grain coarsening that often occur in traditional large-size plate production processes. The fine-grained structure obtained by this process demonstrates excellent performance in improving the overall strength and toughness of the material.

[0004] To address the lifespan requirements of end-plate electrolyzers operating at ultra-high current densities, the invention patent CN121137634A proposes a method to overcome the physical limitations of traditional electroplating thickness by applying a nickel-based alloy or titanium alloy as an alkali-resistant corrosion-resistant layer to the end-plate surface. This provides chemical shielding protection for the substrate. This multi-layered metal composite design decouples the mechanical support function of the substrate from the corrosion-resistant function of the surface layer, extending the equipment's operating cycle by increasing the thickness of the corrosion-resistant layer.

[0005] While electroslag remelting processes optimize grain size, they are primarily based on general metallurgical principles and have limited consideration for the electrochemical polarization characteristics in hydrogen production. At higher current densities, the electrochemical reaction kinetics on the end plate surface are influenced by the intrinsic microstructure of the material, and common alloy ratios struggle to maintain corrosion resistance while simultaneously achieving low contact resistance.

[0006] While composite layer technology solves the physical problem of "barrier thickness," it introduces stability issues under the coupling of multiple thermo-mechanical-chemical fields. The nickel-based composite layer differs from the substrate material in physical properties, particularly in its coefficient of thermal expansion. When the hydrogen electrolyzer undergoes frequent start-ups and shutdowns, temperature fluctuations generate cyclic thermal stress at the interface. With increasing service time, this stress accumulation may induce the initiation and propagation of interfacial microcracks, leading to localized delamination or failure of the composite layer. Furthermore, existing technologies still have room for improvement in optimizing the synergistic effect of "corrosion resistance, conductivity, and catalysis" in alloy composition design. Sometimes, adding passivating elements to improve pitting corrosion resistance may increase the electron transport resistance of the surface passivation film. Summary of the Invention

[0007] The purpose of this invention is to provide a nickel-based alloy material for end plates and a method for its preparation, which solves the technical problems of existing end plate materials having difficulty in achieving both corrosion resistance and conductivity under high temperature and strong alkaline conditions, and the composite layer structure being prone to peeling failure due to thermal stress.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention provides a nickel-based alloy material for end plates and its preparation method. This invention achieves this by controlling the microstructure composition of the nickel-based alloy and introducing a surface electrochemical modification process based on cathode polarization surface charge density control, further combining pulse-ultrasound synergy with rare-earth doping for microstructure regulation.

[0009] This invention provides a nickel-based alloy material for end plates, whose chemical composition, by mass percentage, includes: chromium 22.0% - 26.0%, molybdenum 8.0% - 12.0%, tungsten 3.5% - 5.5%, niobium 1.5% - 2.5%, tantalum 0.5% - 1.2%, iron ≤ 1.0%, manganese 0.2% - 0.8%, silicon ≤ 0.15%, carbon ≤ 0.015%, yttrium 0.02% - 0.08%, cerium 0.01% - 0.05%, with the balance being nickel and unavoidable impurities.

[0010] The microstructure of the nickel-based alloy material used for the end plates consists of an equiaxed γ-austenite matrix and a second phase dispersed within the matrix and at grain boundaries. The second phase includes a cubic γ' phase and chain-like M phases. 23 C6 type carbides. The chemical formula of the γ' phase is Ni3(Nb, Ta), the average particle size of the γ' phase is 40 nm to 70 nm, and the volume fraction of the γ' phase is 8% to 12%; the M... 23 C6 type carbides are distributed in discontinuous chain form at the grain boundaries, and the M 23 C6-type carbides cover 60% to 75% of the grain boundaries.

[0011] The pitting resistance equivalent value PREN of the nickel-based alloy material of the end plate satisfies the following formula:

[0012] in, The mass percentage of chromium in the nickel-based alloy material of the end plate; The mass percentage of molybdenum in the nickel-based alloy material of the end plate; The mass percentage of tungsten in the nickel-based alloy material of the end plate.

[0013] Furthermore, the surface of the nickel-based alloy material of the end plate has a nickel-rich conductive layer with a thickness of 20 nm to 50 nm; in the nickel-rich conductive layer, the atomic ratio of metallic nickel to nickel oxide is 3:1 to 5:1.

[0014] Furthermore, the nickel-rich conductive layer also contains uniformly distributed rare earth oxide nanoparticles, which are selected from at least one of yttrium oxide and cerium oxide, with an average particle size of 2 nm to 8 nm and a volume fraction of 0.5% to 2.0% in the nickel-rich conductive layer; the nickel-rich conductive layer is composed of nanocrystalline nickel and amorphous nickel oxide, wherein the average grain size of the nanocrystalline nickel is 5 nm to 15 nm, and the amorphous nickel oxide surrounds the nanocrystalline nickel in a continuous network; in the nickel-rich conductive layer, the atomic ratio of metallic nickel to nickel oxide is 3.5:1 to 4.5:1, and the thickness of the nickel-rich conductive layer is 25 nm to 45 nm; a layer with a thickness of 3 nm to 8 nm is formed between the nickel-rich conductive layer and the substrate. The elemental interdiffusion transition region is nm in which the concentrations of Ni, Cr, Mo, Y, and Ce are distributed in a gradient along the depth of the layer, and the mass fraction of Cr in the transition region is 40% to 60% of the Cr content in the matrix, and the total mass fraction of Y and Ce is 70% to 90% of the total Y and Ce content in the matrix.

[0015] The nickel-based alloy material of the terminal plate has a corrosion rate of less than 0.005 mm / a in a 30% KOH solution at 90°C, and an interfacial contact resistance of 3.5 mΩ·cm² to 5.0 mΩ·cm² at a current density of 2000 mA / cm².

[0016] This invention also provides a method for preparing the above-mentioned nickel-based alloy material for the end plate, the method comprising the following steps: Step 1: Vacuum Induction Melting. Prepare raw materials according to the stated chemical composition ratio, and melt them under a vacuum degree less than... The melting process takes place in an induction furnace. During melting, nickel, chromium, molybdenum, and tungsten are added first, and after complete melting and refining for 20-30 minutes, manganese, silicon, and carbon are added sequentially. Niobium, tantalum, yttrium, and cerium are added 3-5 minutes before casting, and the casting temperature is controlled at 1560℃ to 1610℃ to obtain a consumable electrode blank.

[0017] Step 2: Electroslag Remelting under Protective Atmosphere. The consumable electrode billet is placed in an electroslag furnace and remelted under argon protection. The slag composition used is as follows by mass percentage: CaF2 50%-55%, Al2O3 20%-25%, CaO 10%-15%, MgO 5%-8%, TiO2 2%-4%. The filling ratio during the remelting process is controlled at 0.45 to 0.55, the melting voltage is 28V to 34V, the melting current is 12kA to 16kA, and the temperature difference between the inlet and outlet cooling water is maintained at 10℃ to 15℃ to obtain an alloy ingot.

[0018] Step 3: Multi-directional precision forging. The alloy ingot is heated to 1180℃ to 1220℃ and held for 3 to 5 hours to carry out a multi-directional forging process. The total forging ratio is not less than 6.0, the initial forging temperature is not less than 1150℃, and the final forging temperature is not less than 950℃ to obtain a forged slab.

[0019] Step 4: Precision rolling control. The forged slab is heated to 1120°C to 1160°C and hot rolled in multiple passes, with the reduction rate per pass controlled between 15% and 25%, and the cumulative total reduction rate greater than 80%. Cold rolling is performed in the last two passes, with a reduction of 3% to 5%, to obtain the hot-rolled sheet.

[0020] Step 5: Graded solution treatment and aging heat treatment. The hot-rolled sheet undergoes a first-stage high-temperature solution treatment: heated to 1170℃ to 1190℃, held for 1.5 to 3 hours, and then subjected to high-pressure water quenching; followed by a second-stage strengthening aging treatment: heated to 760℃ to 780℃, held for 8 to 12 hours, cooled in the furnace to 550℃, and then air-cooled to obtain the heat-treated sheet.

[0021] Step Six: Surface Electrochemical Modification. The heat-treated plate is mechanically polished until the surface roughness Ra < 0.2 μm, and then subjected to cathodic polarization treatment in a solution containing 0.5 mol / L nickel sulfate and 0.2 mol / L boric acid to obtain the final nickel-based alloy material of the end plate.

[0022] Furthermore, in step one, the vacuum venting rate during the refining stage is less than 0.1 Pa / min, and argon gas is introduced into the furnace bottom permeable bricks for stirring during the refining stage, with the argon gas flow rate controlled between 10 L / min and 20 L / min.

[0023] Furthermore, in step two, the slag components used are pre-dried at 800°C to 900°C for more than 4 hours before use; during the remelting process, the slag pool depth is maintained at 60mm to 80mm.

[0024] Furthermore, in step three, the multi-directional forging process includes a three-drawing and three-punching process, and the reduction in each pass is not less than 20%. In step five, the cooling rate of the high-pressure water quenching is greater than 50°C / s.

[0025] Furthermore, in step six, the cathode polarization process is constrained by the cathode polarization surface charge density, which satisfies the following formula:

[0026] in, The cathode polarization surface charge density is expressed in coulombs per square decimeter (C / dm²). This refers to the polarization current density, measured in amperes per square decimeter (A / dm²). When DC polarization is used... This refers to the DC polarization current density; when pulse polarization is used, The average current density is equal to the product of the peak value of the pulse current density and the duty cycle. Polarization time, in seconds (s); In this invention, the input variables are restricted so that The value is controlled within the range of 150 to 450.

[0027] Further, in step six, the cathode polarization treatment uses pulsed current, with a peak pulse current density of 0.8 A / dm² to 1.5 A / dm², a pulse frequency of 50 Hz to 200 Hz, and a duty cycle of 30% to 60%. The solution containing 0.5 mol / L nickel sulfate and 0.2 mol / L boric acid also contains 0.01 mol / L to 0.05 mol / L yttrium nitrate and / or 0.005 mol / L to 0.02 mol / L cerium nitrate. The cathode polarization treatment time is 5 min to 15 min, the solution temperature is controlled at 25℃±2℃ during the treatment, and ultrasonic stirring is used, with an ultrasonic frequency of 40 kHz to 80 kHz and a power density of 0.5 W / cm² to 1.5 W / cm².

[0028] The synergistic addition of chromium, molybdenum, and tungsten in this invention constructs a passivation film on the alloy surface. The oxide layer formed by chromium provides basic chemical shielding, while the addition of molybdenum and tungsten helps improve the passivation film's resistance to pitting corrosion under chloride ion and strong alkaline environments. The introduction of niobium and tantalum promotes the formation of the γ' phase, thereby enhancing the material's mechanical strength. Simultaneously, the oxides of niobium and tantalum in the passivation film can affect the semiconductor properties of the film, potentially reducing the electron transfer resistance.

[0029] The microalloying of rare earth elements yttrium and cerium can segregate at grain boundaries and oxide / substrate interfaces, helping to enhance oxide film adhesion and reduce film peeling during thermal cycling. Simultaneously, rare earth elements can purify grain boundaries and inhibit the segregation of low-melting-point harmful impurities, thereby reducing the risk of stress corrosion cracking.

[0030] In terms of manufacturing processes, the combination of multi-directional precision forging and controlled rolling results in a high proportion of large-angle grain boundaries and a uniform equiaxed grain structure within the material. This helps to improve the intrinsic electrical conductivity of the material and ensures the consistent distribution of current in both the thickness and planar directions of the end plates. The staged heat treatment process can control the size and distribution of the γ' strengthening phase. The construction of discontinuous chain-like carbides at grain boundaries helps to block intergranular corrosion paths while maintaining intergranular conductivity.

[0031] In terms of surface electrochemical modification, this invention introduces cathode polarization surface charge density. As a control parameter. When Within the range of 150 to 450, the polarization process initiates a reduction reaction on the surface of the substrate passivation film. Some oxides in the original passivation film are reduced, and simultaneously, nickel ions from the solution deposit on the reduced lattice vacancies, forming a nickel-rich conductive layer. If... Below 150, the reduction reaction is incomplete; if Above 450, over-reduction and excessive deposition may occur.

[0032] Furthermore, the present invention controls Building upon this foundation, the introduction of pulsed current, rare earth salt doping, and ultrasonic assistance allows for the microstructural control of nickel-rich conductive layers. Rare earth oxide nanoparticles (Y₂O₃, CeO₂) can be distributed within the nickel-rich layer, synergistically interacting with the nanocrystalline nickel-amorphous nickel oxide composite structure. The interaction mechanism includes: (1) The composite structure formed by nanocrystalline nickel and amorphous nickel oxide network generates a local electric field enhancement effect at the interface. Electrons can tunnel through the defect energy level in the amorphous network. Rare earth oxide nanoparticles, as high dielectric constant centers, may further reduce the tunneling barrier. (2) Y2O3 and CeO2 nanoparticles can serve as oxygen vacancy trapping sites, inhibiting the expansion of film defects caused by oxygen vacancy migration. Meanwhile, the enrichment of rare earth elements in the transition region may affect the outward diffusion of Cr. (3) The periodic electric field generated by the pulse current affects Ni² + Nucleation on the substrate surface, combined with the ultrasonic cavitation effect, enables the deposited layer to form a micro-region diffusion coupling with the substrate. The gradient distribution of elements in the transition region helps to alleviate the thermal stress caused by the abrupt change in interface properties.

[0033] To achieve the aforementioned synergistic effect, there is a quantitative correlation between the process parameters in step six and the microstructure and interfacial contact resistance of the nickel-rich conductive layer. The volume fraction of rare earth oxides in the defined layer is... The empirical relationships between pulse parameters and rare earth salt concentration are as follows:

[0034] in, This represents the total concentration of rare earth ions in the electrolyte, expressed in mol / L. The diffusion coefficient of rare earth ions at a set electrolyte temperature is expressed in cm² / s and is determined by cyclic voltammetry. The test conditions are as follows: a platinum sheet is used as the counter electrode, a saturated calomel electrode (SCE) is used as the reference electrode, and the nickel-based alloy plate of this invention is used as the working electrode. The scan rate is 5 mV / s, and the test electrolyte is a mixed solution of 0.5 mol / L nickel sulfate and 0.2 mol / L boric acid (consistent with the cathodic polarization electrolyte).

[0035] Deposition time, in seconds; The average particle size of the precipitated rare earth oxide particles is in nm. This represents the peak value of the pulse current density, in A / dm². The reference current density is set to 1.0 A / dm². This refers to the ultrasonic frequency, measured in Hz. The reference frequency is set to 40000 Hz. The empirical fitting index for the pulse current is 0.65 in this system; The empirical fitting index for ultrasonic frequency is 0.38 in this system; It is a dimensionless proportionality constant, calibrated to 0.012.

[0036] Define interface contact resistance The empirical relationship with the structural parameters of the nickel-rich layer is as follows:

[0037] in, The actual measured thickness of the nickel-rich layer is in nm. The reference thickness is 30 nm. The ratio of metallic nickel to nickel oxide atoms in the layer; The baseline atomic ratio is set at 4.0. The volume fraction of rare earth oxides calculated above, % The base volume fraction is 1.0%. The critical load for interfacial bonding force is expressed in N (obtained using a nano-scratch tester). The reference critical load is set at 30 N. The reference resistance constant is fitted to 5.2 mΩ·cm² for this system; This is an empirical parameter for thickness, with a value of 0.72. This is an empirical parameter for the atomic ratio, with a value of 1.15. The parameter affecting the bonding force is set to 0.08.

[0038] The above formula is used for parameter screening during the process design stage to help achieve a synergistic state of the nickel-rich conductive layer in three dimensions: electron transport, chemical passivation, and mechanical bonding.

[0039] Compared with the prior art, the present invention has the following beneficial effects: This invention starts from the alloy design stage, breaking through the limitations of traditional nickel-based alloys that only focus on single corrosion resistance or mechanical properties. By precisely controlling the proportions of chromium, molybdenum, tungsten, niobium, tantalum, and rare earth elements yttrium and cerium, a homogeneous alloy system with high corrosion resistance, high electrical conductivity, and high structural stability is constructed. This is achieved by controlling the dispersion of the γ′ phase (Ni3(Nb, Ta)) at a size of 40nm to 70nm and a volume fraction of 8% to 12%, and by regulating the M-phase at grain boundaries. 23The C6-type carbides exhibit a discontinuous chain distribution with a coverage of 60% to 75%, achieving a synergistic effect between precipitation strengthening and grain boundary corrosion blocking mechanisms. This microstructure design enables the material to maintain high strength while effectively blocking intergranular corrosion paths, avoiding the risk of interfacial delamination caused by differences in thermal expansion coefficients in traditional composite layer structures.

[0040] This invention solves the technical problem of high intrinsic resistance of passivation films by precisely limiting the polarization surface charge density to the range of 150 to 450, forming a nickel-rich conductive layer with a thickness of 20 nm to 50 nm in situ on the substrate surface, and precisely controlling the atomic ratio of metallic nickel to nickel oxide to be between 3:1 and 5:1. In a preferred embodiment, pulsed current, rare earth salt doping, and ultrasonic stirring are further coupled to construct a gradient transition structure of nanocrystalline nickel and amorphous nickel oxide composite with uniformly dispersed rare earth oxide nanoparticles. This structure achieves electron tunneling conduction through a nanocrystalline-amorphous network, uses rare earth oxides to capture oxygen vacancies to suppress defect propagation, and forms an elemental interdiffusion transition region of 3 nm to 8 nm at the interface, achieving simultaneous improvement in conductivity, passivation, and interfacial adhesion, fundamentally avoiding the peeling failure of traditional electroplated layers or composite coatings during thermal cycling.

[0041] This invention employs a dual-process method combining vacuum induction melting and protective atmosphere electroslag remelting to ensure high purity and compositional uniformity of the alloy. The coupling of multi-directional precision forging and precision controlled rolling processes results in a uniform equiaxed grain structure and large-angle grain boundaries, guaranteeing a uniform distribution of overall conductivity in large end-plates. Staged solution treatment followed by aging heat treatment precisely controls the morphology and distribution of strengthening phases and carbides, providing the microstructure basis for final surface modification. This precise matching of processes and material composition ensures the stability and reliability of the constructed homogeneous alloy material throughout its entire lifespan. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0043] Figure 1 This is a microscopic electron microscope image of the tissue of the present invention.

[0044] Figure 2 This is an overall flowchart of the method described in this invention.

[0045] Figure 3 This is a simplified flowchart of the preparation process of the nickel-based alloy material for the end plate of the present invention. Detailed Implementation

[0046] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0047] The following is in conjunction with the appendix Figures 1-3 The technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0048] This invention provides a nickel-based alloy material for end plates, designed for use in hydrogen electrolyzers under high temperature, high pressure, strong alkali (such as 30% KOH solution by weight), and high current density (≥2000 mA / cm²). The chemical composition of this nickel-based alloy material, by mass percentage, includes: chromium 22.0% - 26.0%, molybdenum 8.0% - 12.0%, tungsten 3.5% - 5.5%, niobium 1.5% - 2.5%, tantalum 0.5% - 1.2%, iron ≤ 1.0%, manganese 0.2% - 0.8%, silicon ≤ 0.15%, carbon ≤ 0.015%, yttrium 0.02% - 0.08%, cerium 0.01% - 0.05%, with the balance being nickel and unavoidable impurities.

[0049] The amount of chromium added is controlled between 22.0% and 26.0% to construct a self-healing passivation film. The Cr2O3 oxide film formed by chromium on the alloy surface acts as a barrier against corrosion from potassium hydroxide electrolyte. When the chromium content is below 22.0%, the continuity and density of the passivation film may decrease under high-temperature and strong alkaline conditions; when the chromium content exceeds 26.0%, brittle σ phases may precipitate during hot working, affecting processing performance and impact toughness. The addition of molybdenum and tungsten enhances the yield strength of the matrix through solid solution strengthening. Simultaneously, the large atomic radii of molybdenum and tungsten allow them to fill oxygen vacancies in the passivation film, contributing to improved impedance performance. Their pitting resistance equivalent value, calculated using the formula, must meet the following requirements: ; The introduction of niobium and tantalum serves a dual purpose. At the microstructural level, niobium and tantalum are key elements in the formation of the strengthening phase γ'. By combining with nickel atoms, they precipitate a dispersed cubic second phase on the austenitic matrix, achieving precipitation strengthening. At the electrochemical level, the oxide doping of niobium and tantalum in the surface passivation film may alter the semiconductor energy level structure of the oxide film, affecting the carrier concentration and potentially reducing the resistance to electron transport at the interface between the terminal plate and the electrolyte. The addition of manganese and silicon is used for deoxidation and desulfurization during the smelting process, while also improving melt fluidity and reducing porosity and inclusions in the ingot. The carbon content is controlled below 0.015% to reduce the formation of continuous network carbides at grain boundaries, reducing the generation of chromium-depleted zones and thus reducing the risk of intergranular corrosion.

[0050] The microstructure of the nickel-based alloy material for the end plates consists of an equiaxed γ-austenite matrix and a second phase dispersed within the matrix and at grain boundaries. The second phase includes a cubic γ' phase and chain-like M phases. 23 C6 type carbides. The γ' phase has the chemical formula Ni3(Nb, Ta), with an average particle size of 40 nm to 70 nm and a volume fraction of 8% to 12%. M 23 C6-type carbides are distributed in discontinuous chain form at the grain boundaries, with a coverage of 60% to 75% at the grain boundaries.

[0051] The microalloying of rare earth elements yttrium and cerium, which segregate at the interface between the oxide film and the substrate on the alloy surface, can slow down the accumulation of internal stress in the oxide film and enhance its resistance to exfoliation. During thermal cycling, yttrium and cerium help reduce film cracking caused by differences in thermal expansion coefficients.

[0052] This invention provides a method for preparing the above-mentioned nickel-based alloy material for end plates, which includes the following six steps.

[0053] Step 1: Vacuum Induction Melting. Prepare raw materials with a purity higher than 99.9% according to the stated chemical composition. Melt the materials under a vacuum degree less than... The melting process takes place in an induction furnace at a pressure of Pa. During melting, nickel, chromium, molybdenum, and tungsten are added first. After complete melting, the mixture is refined for 20-30 minutes, during which the vacuum venting rate is controlled below 0.1 Pa / min. Subsequently, manganese, silicon, and carbon are added sequentially. 3-5 minutes before casting, niobium, tantalum, yttrium, and cerium are added through the alloy charging chamber. During the refining stage, argon gas is introduced through the permeable bricks at the furnace bottom for stirring, with a flow rate controlled between 10 L / min and 20 L / min. The casting temperature is controlled between 1560℃ and 1610℃ to obtain the consumable electrode billet.

[0054] Step Two: Protective Atmosphere Electroslag Remelting. The consumable electrode billet obtained in Step One is used as the electrode and remelted in an argon-protected electroslag furnace. The slag composition used is: CaF2 50%-55%, Al2O3 20%-25%, CaO 10%-15%, MgO 5%-8%, TiO2 2%-4%. The slag is pre-dried at 800℃ to 900℃ for at least 4 hours before use. During remelting, the filling ratio is controlled at 0.45 to 0.55, the melting voltage is 28V to 34V, and the melting current is 12kA to 16kA. The slag pool depth is maintained at 60mm to 80mm. The temperature difference between the inlet and outlet cooling water is controlled at 10℃ to 15℃ to obtain the alloy ingot.

[0055] Step 3: Multi-directional precision forging. Heat the alloy ingot to 1180℃ to 1220℃ and hold for 3 to 5 hours. Use a three-drawing, three-punching multi-directional forging process, with a total forging ratio of not less than 6.0. Control the initial forging temperature above 1150℃ and the final forging temperature not less than 950℃ to obtain a forged slab.

[0056] Step 4: Precision Controlled Rolling. The forged slab is heated to 1120℃ to 1160℃ for hot rolling. The reduction per pass is controlled between 15% and 25%, with a cumulative total reduction greater than 80%. In the last two rolling passes, cold rolling is performed, with a reduction of 3% to 5%.

[0057] Step 5: Staged Solution Treatment and Aging Heat Treatment. First Stage High-Temperature Solution Treatment: Heat to 1170℃ to 1190℃, hold for 1.5 to 3 hours, then use high-pressure water quenching at a cooling rate greater than 50℃ / s. Second Stage Strengthening Aging Treatment: Heat to 760℃ to 780℃, hold for 8 to 12 hours, then cool in the furnace to 550℃ before air cooling.

[0058] Step Six: Surface Electrochemical Modification. The heat-treated plate is mechanically polished until the surface roughness Ra < 0.2 μm. It is then subjected to cathodic polarization treatment in an electrolyte containing 0.5 mol / L nickel sulfate and 0.2 mol / L boric acid.

[0059] The specific performance of the material of the present invention is quantitatively demonstrated below through multiple embodiments and comparative examples. In these embodiments, the fine-tuning of each component and the fluctuation of process parameters are all within the scope of the claims of the present invention.

[0060] Example 1: A nickel-based alloy material for end plates, the composition (mass percentage) of which is: Cr 24.5%, Mo 10.2%, W 4.2%, Nb 2.1%, Ta 0.8%, Mn 0.5%, Si 0.08%, C 0.010%, Y 0.05%, Ce 0.03%, Fe 0.6%, Ni 56.93%.

[0061] The preparation process is as follows: vacuum induction melting vacuum degree Pa, casting temperature 1580℃. Electroslag remelting under protective atmosphere uses a slag system of CaF2-52%, Al2O3-22%, CaO-12%, MgO-7%, TiO2-3%, with a melting rate of 4.2 kg / min. Forging heating temperature 1200℃, total forging ratio 6.5. Hot rolling heating temperature 1150℃, total reduction 85%, final cold rolling reduction 4%. Staged heat treatment: solution treatment at 1180℃ for 2 hours, high-pressure water quenching (cooling rate 65℃ / s); aging at 770℃ for 10 hours, furnace cooling. Surface cathodic polarization: DC polarization is used, DC polarization current density... A / dm², time s, calculated C / dm², the electrolyte is 0.5mol / L nickel sulfate + 0.2mol / L boric acid, and it does not contain rare earth salts.

[0062] Example 2: A nickel-based alloy material for end plates, the composition (mass percentage) of which is: Cr 22.5%, Mo 11.5%, W 5.2%, Nb 1.8%, Ta 1.1%, Mn 0.3%, Si 0.12%, C 0.012%, Y 0.07%, Ce 0.01%, Fe 0.8%, Ni 56.588%.

[0063] The preparation process is as follows: vacuum induction melting vacuum degree Pa, casting temperature 1600℃. Electroslag remelting in a protective atmosphere with a melting rate of 3.8 kg / min. Forging heating temperature 1210℃, total forging ratio 7.0. Hot rolling heating temperature 1130℃, total reduction 82%, final cold rolling reduction 5%. Staged heat treatment: solution treatment at 1190℃ for 1.5 h, high-pressure water quenching; aging at 760℃ for 12 h, furnace cooling. Surface cathodic polarization: DC polarization, DC polarization current density... A / dm², time s, calculated C / dm², the electrolyte is 0.5mol / L nickel sulfate + 0.2mol / L boric acid, and it does not contain rare earth salts.

[0064] Example 3: A nickel-based alloy material for end plates, the composition (mass percentage) of which is: Cr 25.8%, Mo 9.5%, W 4.2%, Nb 2.4%, Ta 0.6%, Mn 0.7%, Si 0.05%, C 0.008%, Y 0.03%, Ce 0.04%, Fe 0.4%, Ni 55.772%.

[0065] The preparation process is as follows: vacuum induction melting vacuum degree Pa, casting temperature 1570℃. Electroslag remelting in a protective atmosphere with a melting rate of 4.8 kg / min. Forging heating temperature 1190℃, total forging ratio 6.2. Hot rolling heating temperature 1160℃, total reduction 88%, final cold rolling reduction 3%. Staged heat treatment: solution treatment at 1175℃ for 2.5 h, high-pressure water quenching; aging at 780℃ for 8 h, furnace cooling. Surface cathodic polarization: DC polarization, DC polarization current density... A / dm², time s, calculated C / dm², the electrolyte is 0.5mol / L nickel sulfate + 0.2mol / L boric acid, and it does not contain rare earth salts.

[0066] Example 4: Using the matrix composition and preparation process of Example 1 up to step five, a heat-treated plate was obtained.

[0067] The specific parameters for step six are as follows: Electrolyte composition added: 0.03 mol / L 0.01 mol / L .

[0068] Pulsed cathode polarization: peak pulse current density A / dm², pulse frequency 120 Hz, duty cycle 45%, processing time s.

[0069] Calculate the average current density: Since this embodiment uses pulsed polarization, the polarization current density in the formula is... The average current density, A / dm², calculated to C / dm².

[0070] Auxiliary conditions: constant temperature 25℃, ultrasonic stirring (frequency 60 kHz, power density 1.0 W / cm²).

[0071] After treatment, rinse with deionized water and dry with nitrogen.

[0072] The obtained nickel-rich conductive layer has a thickness of 35 nm ± 3 nm. XPS analysis showed that the atomic ratio of metallic nickel to nickel oxide was 4.0:1. TEM observation showed that Y2O3 and CeO2 nanoparticles with a particle size of 4-6 nm were uniformly distributed in the layer, with a volume fraction of about 1.2%. The average grain size of nanocrystalline nickel was 9 nm, and amorphous nickel oxide was coated with grains in a network. STEM-EDS line scanning showed that there was an interdiffusion region of about 5 nm between the layer and the substrate, the Cr content gradient decreased, and the Y and Ce contents remained at a high level in the transition region.

[0073] Example 5: The matrix composition and preparation process of Example 2 are used until step five is completed.

[0074] Step Six Parameters: Electrolyte composition added: 0.01 mol / L (Ce salt not included).

[0075] Pulsed cathode polarization: peak pulse current density A / dm², pulse frequency 80 Hz, duty cycle 35%, processing time s.

[0076] Calculate the average current density: Since this embodiment uses pulsed polarization, the polarization current density in the formula is... The average current density, A / dm², calculated to C / dm². Auxiliary conditions: constant temperature 25℃, ultrasonic stirring (frequency 40 kHz, power density 0.8 W / cm²).

[0077] The resulting nickel-rich conductive layer has a thickness of 28 nm; the atomic ratio of metallic nickel to nickel oxide is 3.6:1; the Y2O3 particles have a diameter of 3-5 nm and a volume fraction of 0.7%; the average grain size of nanocrystalline nickel is 12 nm; and the thickness of the transition region is approximately 4 nm.

[0078] Comparative Example 1: A conventional commercial-grade Hastelloy C276 alloy was used. The main components of this alloy are Cr 15.5%, Mo 16%, W 3.7%, Fe 5.5%, Co 2.5%, C 0.01%, and Ni balance.

[0079] Comparative Example 2: Conventional 316L stainless steel was used, with a 5μm thick pure nickel layer electroplated on the surface.

[0080] Comparative Example 3: The substrate and process of Example 1 were used, but the electrolyte in step six did not contain rare earth nitrates, and DC polarization was used (DC polarization current density). A / dm², no pulse, no ultrasound, time s), C / dm², the rest is the same as in Example 4.

[0081] Comparative Example 4: The substrate and process of Example 1 were used, but conventional DC polarization was performed in step six, with a DC polarization current density of... A / dm², time s, C / dm², electrolyte does not contain rare earth salts, no pulse, no ultrasound.

[0082] Comparative Example 5: The substrate and process of Example 1 were used, but in step six... Exceeding the specified range: DC polarization is used, DC polarization current density A / dm², time s, C / dm², the electrolyte does not contain rare earth salts.

[0083] The following experimental tests were conducted based on the above embodiments and comparative examples: Corrosion rate test: Each sample was placed in a 30% KOH solution at a temperature of 90℃ for 2000 hours of immersion. The annual corrosion rate (mm / a) was calculated by the weight loss method.

[0084] Interface contact resistance test: Using the four-probe method, the interface contact resistance (mΩ·cm²) was measured at an assembly pressure of 2.0 MPa after simulated polarization at a current density of 2000 mA / cm² and after 2000 h of service.

[0085] PREN calculation: Based on measured chemical composition, the formula is substituted into the formula for calculation.

[0086] Thermal cycling experiment: The material was switched from 90℃ to 25℃ and cycled 5000 times. The surface was observed for cracks or oxide film peeling, and the percentage of peeling area was statistically analyzed using image analysis.

[0087] Potentiodynamic polarization curves: Self-corrosion potentials were recorded at 90℃ and 30% KOH solution with a scan rate of 0.5 mV / s. With passivation current density .

[0088] Electrochemical impedance spectroscopy: at open circuit potential, frequency 10 - ²~10 5 Hz, amplitude 10 mV, fitted charge transfer resistance .

[0089] Surface layer adhesion: Critical load was recorded using the scratch method. .

[0090] Table 1: Comparative test results of the performance of nickel-based alloy materials for end plates (Examples 1-5);

[0091] Table 2: Comparative test results of the performance of nickel-based alloy materials for end plates (Comparative Examples 1-5);

[0092] The data in Tables 1 and 2 show that: Examples 1-3 employ DC polarization. The temperatures were 240, 380, and 180, all within the 150-450 range. The initial ICR was 3.8-4.3 mΩ·cm², and after 2000 h, the ICR was 4.2-4.9 mΩ·cm². No delamination was observed after thermal cycling. (Comparative Example 5) The value was 900, exceeding the specified range. Although the initial ICR was low (3.2 mΩ·cm²), it increased to 22.4 mΩ·cm² after 2000 hours, with a thermal cycling peeling rate of 24.2% and good adhesion. It is 15.8 N.

[0093] Examples 4 and 5 in While maintaining the optimal range (324, 283.5), a pulse-ultrasound-rare earth doping process was employed. Similar to Example 1 (same substrate, same...) Compared to the previous method (without the aforementioned process), the initial ICR of Example 4 decreased from 3.8 to 2.6 mΩ·cm², and after 2000 h, the ICR decreased from 4.2 to 2.9 mΩ·cm², indicating improved bonding strength. As the N increased from 28.5 N to 38.2 N, the passivation current density decreased from 0.55 μA / cm² to 0.32 μA / cm². The efficiency increased from 18.2 to 28.5 kΩ·cm². Comparative Examples 3 and 4... All were 300, but lacked rare earth doping or pulse-ultrasound process, and their ICR, bonding force and passivation performance were lower than those of Examples 4 and 5.

[0094] Microscopic tissue observations show, see Figure 1 In the embodiments of this invention, the γ' reinforcing phase exhibits a uniform, diffuse distribution with an average particle size of approximately 50 nm. M at the grain boundaries... 23 C6 type carbides exhibit a discontinuous chain-like characteristic.

[0095] In the engineering application of large-scale end plates, the preparation method described in this invention can produce circular plates with a diameter of 1500 mm and a thickness of 40 mm. Within this size, through a combination of protective atmosphere electroslag remelting and multi-directional precision forging, the composition deviation of major elements (Cr, Mo, W, Ni) from the edge to the core of the plate is within ±0.5% (test method: glow discharge mass spectrometry, sampling points are the center of the circular plate, half the radius, and the edge; each sampling point is taken at the midpoint of the thickness direction), and the hardness fluctuation is less than ±5% (test method: Brinell hardness tester, HBW scale, load 3000 kg, holding time 15 s, sampling points are consistent with the composition test, and the average value of 3 points is taken).

[0096] In actual hydrogen production electrolyzer installation tests, the terminal plate prepared with the material of Example 4 reduced the single-cell voltage of the hydrogen production electrolyzer by about 65mV compared with Comparative Example 1 and by about 20mV compared with Example 1 at a current density of 2000mA / cm².

[0097] Furthermore, in step two, by controlling the mass ratio of CaO+MgO to Al2O3+TiO2 at 0.8~1.2:1, and leveraging the high-temperature and high-conductivity characteristics of CaF2, the sulfur content in the alloy can be kept below 0.002%. In step three, during the multi-directional forging process, the reduction in each pass is no less than 20%. In step five, the high-pressure water quenching system employs omnidirectional spraying to control the heat treatment deformation to below 0.5 mm / m.

[0098] The composition range described in this invention provides adjustment flexibility for different operating conditions of hydrogen production electrolyzers. For example, in applications requiring lower interfacial resistance, the tantalum content can be adjusted to an upper limit of 1.2%; in hydrogen production systems using industrial by-product water containing higher impurities, the molybdenum content can be increased to an upper limit of 12.0%.

[0099] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nickel-based alloy material for end plates, characterized in that, Its chemical composition, by mass percentage, includes: Chromium 22.0%-26.0%, Molybdenum 8.0%-12.0%, Tungsten 3.5%-5.5%, Niobium 1.5%-2.5%, Tantalum 0.5%-1.2%, Iron ≤1.0%, Manganese 0.2%-0.8%, Silicon ≤0.15%, Carbon ≤0.015%, Yttrium 0.02%-0.08%, Cerium 0.01%-0.05%, with the balance being nickel and unavoidable impurities; The microstructure of the nickel-based alloy material of the end plate consists of an equiaxed γ-austenite matrix and a second phase dispersed in the matrix and at the grain boundaries. The second phase includes a γ′ phase with a cubic structure and a chain-like distribution of M phases. 23 C6 type carbides; wherein the chemical formula of the γ′ phase is Ni3(Nb,Ta), the average particle size of the γ′ phase is 40 nm to 70 nm, and the volume fraction of the γ′ phase is 8% to 12%; The M 23 C6 type carbides are distributed in discontinuous chain form at the grain boundaries, and the M 23 C6-type carbides cover 60% to 75% of the grain boundaries.

2. The nickel-based alloy material for end plates according to claim 1, characterized in that, The pitting resistance equivalent value PREN of the nickel-based alloy material of the end plate satisfies the following formula: PREN=%Cr+3.3×(%Mo+0.5×%W)≥62; Wherein, %Cr is the mass percentage of chromium in the nickel-based alloy material of the end plate; %Mo is the mass percentage of molybdenum in the nickel-based alloy material of the end plate; and %W is the mass percentage of tungsten in the nickel-based alloy material of the end plate.

3. The nickel-based alloy material for end plates according to claim 1, characterized in that, The surface of the nickel-based alloy material of the end plate has a nickel-rich conductive layer with a thickness of 20 nm to 50 nm; in the nickel-rich conductive layer, the atomic ratio of metallic nickel to nickel oxide is 3:1 to 5:

1.

4. The nickel-based alloy material for end plates according to claim 3, characterized in that, The nickel-rich conductive layer contains uniformly distributed rare earth oxide nanoparticles, which are selected from at least one of yttrium oxide and cerium oxide, with an average particle size of 2 nm to 8 nm, and a volume fraction of 0.5% to 2.0% in the nickel-rich conductive layer. The nickel-rich conductive layer is composed of nanocrystalline nickel and amorphous nickel oxide, wherein the average grain size of the nanocrystalline nickel is 5 nm to 15 nm, and the amorphous nickel oxide surrounds the nanocrystalline nickel in a continuous network. In the nickel-rich conductive layer, the atomic ratio of metallic nickel to nickel oxide is 3.5:1 to 4.5:1, and the thickness of the nickel-rich conductive layer is 25 nm to 45 nm. The nickel-rich conductive layer forms an element interdiffusion transition region with a thickness of 3 nm to 8 nm between itself and the substrate. Within the transition region, the concentrations of Ni, Cr, Mo, Y, and Ce elements are distributed in a gradient along the layer depth. The mass fraction of Cr element in the transition region is 40% to 60% of the Cr content in the substrate, and the total mass fraction of Y and Ce elements is 70% to 90% of the total Y and Ce content in the substrate.

5. A method for preparing a nickel-based alloy material for end plates according to any one of claims 1 to 4, characterized in that, The method includes the following steps: Step 1: Vacuum induction melting; Prepare raw materials according to the chemical composition ratio, under a vacuum degree of less than 5 × 10⁻⁶. -3 The melting process is carried out in an induction furnace of Pa. During the melting process, nickel, chromium, molybdenum and tungsten are added first. After they are completely melted and refined for 20-30 minutes, manganese, silicon and carbon are added in sequence. Niobium, tantalum, yttrium and cerium are added 3-5 minutes before casting. The casting temperature is controlled at 1560℃ to 1610℃ to obtain a consumable electrode blank. Step 2: Electroslag remelting under a protective atmosphere; The consumable electrode blank is placed in an electroslag furnace and remelted under argon protection. The slag system composition is as follows by mass percentage: CaF2 50%-55%, Al2O3 20%-25%, CaO 10%-15%, MgO 5%-8%, TiO2 2%-4%. The filling ratio during the remelting process is controlled at 0.45 to 0.55, the melting voltage is 28V to 34V, the melting current is 12kA to 16kA, and the temperature difference between the inlet and outlet cooling water is maintained at 10℃ to 15℃ to obtain an alloy ingot. Step 3: Multi-directional precision forging. The alloy ingot is heated to 1180°C to 1220°C and held for 3 to 5 hours to carry out multi-directional forging process. The total forging ratio is not less than 6.0, the initial forging temperature is not less than 1150°C, and the final forging temperature is not less than 950°C to obtain a forged slab. Step 4: Precision rolling control. The forged slab is heated to 1120°C to 1160°C and hot rolled in multiple passes. The reduction rate per pass is controlled at 15% to 25%, and the cumulative total reduction rate is greater than 80%. Cold rolling is used in the last two passes, with a reduction of 3% to 5%, to obtain hot-rolled sheet. Step 5: Graded solution treatment and aging heat treatment. The hot-rolled sheet is subjected to the first stage of high-temperature solution treatment: heated to 1170℃ to 1190℃, held for 1.5 to 3 hours and then subjected to high-pressure water quenching; then subjected to the second stage of strengthening aging treatment: heated to 760℃ to 780℃, held for 8 to 12 hours and then cooled in the furnace to 550℃ and then air-cooled to obtain the heat-treated sheet. Step Six: Surface Electrochemical Modification. The heat-treated plate is mechanically polished until the surface roughness Ra < 0.2 μm, and then subjected to cathodic polarization treatment in a solution containing 0.5 mol / L nickel sulfate and 0.2 mol / L boric acid to obtain the final nickel-based alloy material of the end plate.

6. The preparation method according to claim 5, characterized in that, In step one, the vacuum venting rate during the refining stage is less than 0.1 Pa / min, and argon gas is introduced into the furnace bottom permeable bricks for stirring during the refining stage, with the argon gas flow rate controlled between 10 L / min and 20 L / min.

7. The preparation method according to claim 5, characterized in that, In step two, the slag components used are pre-dried at 800°C to 900°C for more than 4 hours before use; during the remelting process, the slag pool depth is maintained at 60mm to 80mm.

8. The preparation method according to claim 5, characterized in that, In step three, the multi-directional forging process includes a three-drawing and three-punching process, and the reduction in each pass is not less than 20%.

9. The preparation method according to claim 5, characterized in that, In step five, the cooling rate of the high-pressure water quenching is greater than 50°C / s.

10. The preparation method according to claim 5, characterized in that, In step six, the cathode polarization process is controlled by the cathode polarization surface charge density, which satisfies the following formula: Qc = J × t; Where Qc is the cathode polarization surface charge density, in coulombs per square decimeter; J is the polarization current density, in amperes per square decimeter. When DC polarization is used, J is the DC polarization current density; when pulse polarization is used, J is the average current density, which is equal to the product of the peak value of the pulse current density and the duty cycle; t is the polarization time in seconds; and Qc is between 150 and 450.

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