Preparation method of zirconium-based alloy in-situ oxidation coating for joint prosthesis, medical joint prosthesis and application

Abstract

The invention discloses a preparation method of a zirconium-based alloy in-situ oxidation coating for a joint prosthesis, the medical joint prosthesis and application, the method is suitable for zirconium-based alloys (containing Zr-2. 5Nb, Zr-Nb-Ti, Zr-Mo-Nb and other systems) prepared or forged through electron beam melting (EBM) and selective laser melting (SLM), oxygen atoms are promoted to diffuse into the material by repeatedly creating oxygen concentration gradients, and the oxygen concentration gradient of the zirconium-based alloys (containing Zr-2. 5Nb, Zr-Nb-Ti, Zr-Mo-Nb and other systems) is increased. And a high-oxygen diffusion transition layer and the ZrO-based in-situ oxidation ceramic coating are accurately formed, and meanwhile, a coupling mathematical model of oxidation temperature (T)-ceramic coating thickness (d)-wear resistance (WR) is established, so that double accurate regulation and control of the coating performance and the product size are realized. The prepared coating is tightly combined with the matrix through the high-oxygen diffusion transition layer, the depth of the transition layer exceeds that of a traditional process by 40% or above, and the size variation of the prosthesis after oxidation is smaller than or equal to + / -0.01 mm; the surface hardness of the coating is larger than or equal to 1053 Hv, the wear rate is smaller than or equal to 0.8 * 10 mm / (Nm), the wear resistance and size stability of the zirconium-based alloy are remarkably improved, the problems of sterile looseness and out-of-control size precision caused by wear chippings in long-term service of joint prostheses are solved, and the method is suitable for large-scale production of medical joint prostheses such as hip joints and knee joints.

Description

Technical Field

[0001] This invention relates to the field of surface modification technology for biomedical metallic materials, specifically to a method for preparing an in-situ oxide coating of zirconium-based alloy for joint prostheses. The focus is on expanding the applicable material system and preparation process, and constructing a high oxygen diffusion transition layer by repeatedly creating an oxygen concentration gradient, thereby achieving dual optimization of the coating's wear resistance and the prosthesis's dimensional accuracy, as well as medical joint prostheses and their applications. Background Technology

[0002] Total hip and knee arthroplasty are core clinical treatments for advanced osteoarthritis. The performance, dimensional accuracy, and manufacturing compatibility of prosthetic materials directly determine the long-term success rate of the surgery. Zirconium-based alloys (such as Zr-2.5Nb, Zr-Nb-Ti, and Zr-Mo-Nb) are gradually becoming a new core material for joint prostheses, replacing traditional cobalt-chromium alloys and alumina ceramics, due to their excellent biocompatibility, corrosion resistance, low magnetic susceptibility, and mechanical properties that match human bone. However, the wear resistance of zirconium-based alloy matrices still cannot meet the service requirements of joint prostheses under long-term reciprocating friction, and existing technologies have several key drawbacks:

[0003] 1. Narrow material and process compatibility: Existing oxide coating technologies are mostly limited to single Zr-2.5Nb alloys and electron beam melting (EBM) preparation processes, and do not cover multi-component zirconium-based systems such as Zr-Nb-Ti and Zr-Mo-Nb, nor are they compatible with mainstream preparation processes such as selective laser melting (SLM) and forging, thus limiting their application scope;

[0004] 2. Insufficient transition layer performance: Traditional single heat preservation oxidation process can only form a thin and dense oxide coating with limited oxygen atom diffusion depth. There is a lack of an effective high oxygen diffusion transition layer between the coating and the substrate, resulting in insufficient interfacial bonding strength. Long-term friction can easily cause the coating to peel off.

[0005] 3. Loss of dimensional accuracy: Uneven oxidation reaction on the material surface during oxidation process can easily lead to differences in volume expansion or contraction, causing the size of the prosthesis to change beyond the clinically permissible range (usually ±0.02mm), affecting the fit between the prosthesis and the human skeleton;

[0006] 4. Blind process control: The lack of quantitative relationship between oxidation temperature, coating thickness and wear resistance, and the failure to consider the influence of oxygen concentration gradient on the transition layer and size, result in a lack of comprehensive theoretical guidance for process optimization.

[0007] Therefore, developing an in-situ oxidation coating preparation method that is compatible with multi-component zirconium-based systems and various preparation processes, can construct a high-performance, high-oxygen diffusion transition layer, precisely control prosthesis size, and has predictable performance is of great significance for promoting the large-scale application of zirconium-based alloys in the field of joint prostheses. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing a zirconium-based alloy in-situ oxide coating for joint prostheses, a medical joint prosthesis, and its application. The method for preparing the zirconium-based alloy in-situ oxide coating for joint prostheses can produce joint prosthesis materials that have high wear resistance, high dimensional accuracy, and wide applicability.

[0009] The technical solution of the present invention is as follows:

[0010] A method for preparing an in-situ oxide coating of a zirconium-based alloy for use in joint prostheses, characterized by comprising the following steps:

[0011] (1) Preparation of zirconium-based alloy bodies: Zirconium-based alloy raw materials are selected and dense samples are prepared by electron beam melting (EBM), selective laser melting (SLM) or forging processes. The zirconium-based alloys include Zr-2.5Nb, Zr-Nb-Ti, and Zr-Mo-Nb systems. The EBM process parameters are electron beam power 60-80kV, scanning speed 500-800mm / s, and layer thickness 50-80μm; the SLM process parameters are laser power 200-300W, scanning speed 800-1200mm / s, and layer thickness 20-50μm; the forging process parameters are forging temperature 850-950℃, deformation amount 50-70%, and annealing temperature 600-700℃ for 2h.

[0012] (2) Pretreatment: The prepared zirconium-based alloy sample was polished step by step until the surface roughness Ra≤0.05μm, and then ultrasonically cleaned in ethanol and acetone for 30min each, and vacuum dried at 60℃ for 2h for later use.

[0013] (3) In-situ oxidation and oxygen concentration gradient control: The pretreated sample was placed in a high-temperature tube furnace and air was introduced as the oxidation medium. The oxygen concentration gradient was repeatedly created through the cycle process of "heating-holding-micro-cooling-holding again" to promote the diffusion of oxygen atoms into the material. The overall heating rate was 10℃ / min, the target oxidation temperature was 500℃-600℃, the total holding time was 6h, the number of cycles was 2-3, the micro-cooling range was 30-50℃ each time, the micro-cooling was held for 30-60min after micro-cooling, and finally the material was naturally cooled to form a ZrO2-based ceramic coating and a high oxygen diffusion transition layer on the surface of the zirconium-based alloy in situ.

[0014] (4) Performance and dimensional control: Process parameters are optimized based on a coupled mathematical model of oxidation temperature, coating thickness, and wear resistance. The mathematical model includes: Coating thickness equation: Abrasion resistance equation: Where d(T) is the ceramic coating thickness (μm), T is the oxidation temperature (K), J / mol is the oxidation activation energy of the zirconium-based alloy, J / (mol·K) is the gas constant, HV(T) is the coating microhardness (Hv), and f t-ZrO2 (T) represents the volume fraction (%) of the t-ZrO2 phase in the coating, and WR (T) represents the alloy wear rate (×10⁻⁻¹). 6 mm³ / (N・m)).

[0015] Furthermore, the optimal oxidation process in step (3) is as follows: target oxidation temperature 550℃, 2 cycles, initial heat preservation for 2 hours, followed by slight cooling to 500℃ for 45 minutes, then heating up to 550℃ for 2.75 hours, resulting in a high oxygen diffusion transition layer depth of 2.5-3.0μm and a ceramic coating thickness of 9.0-10.0μm.

[0016] Furthermore, the aforementioned high-oxygen diffusion transition layer is a gradient distribution region of Zr, alloying elements (Nb, Ti, Mo, etc.) and O elements, with no obvious interface delamination. The depth of the transition layer is increased by more than 40% compared with the traditional single heat preservation oxidation process, and the size change of the prosthesis after oxidation is ≤ ±0.01mm.

[0017] Furthermore, the phase composition of the ZrO2-based ceramic coating includes m-ZrO2 main phase, t-ZrO2 secondary phase and dispersed phases of alloying element oxides (Nb2O5, TiO2, MoO3, etc.). The ceramic coating and the high oxygen diffusion transition layer, as well as the transition layer and the substrate, are continuously and gradiently bonded, without cracks or pore defects, and the interfacial bonding strength is ≥55MPa.

[0018] Furthermore, in step (3), the air flow rate is 50 mL / min, and the air flow rate is kept stable during the circulation process to ensure that the oxygen concentration gradient is uniform and controllable.

[0019] Furthermore, the surface hardness of the prepared ceramic coating is 800-1053 Hv, which is 3-5 times that of the zirconium-based alloy substrate hardness of 200-250 Hv, and the hardness of the high oxygen diffusion transition layer is 450-600 Hv, thus achieving hardness gradient matching between the coating and the substrate.

[0020] Furthermore, the dimensions of the above-mentioned sample are 10×10×2mm.

[0021] This invention also provides a medical joint prosthesis, characterized in that it is made of zirconium-based alloy material prepared by the aforementioned method, and the friction contact surface of the joint prosthesis is provided with the aforementioned in-situ oxide ceramic coating and high-oxygen diffusion transition layer, with a wear rate ≤0.8×10⁻ 6 mm³ / (N・m), wear scar depth ≤200nm, dimensional accuracy reaches IT8 level.

[0022] Furthermore, the aforementioned joint prostheses include the femoral head and acetabular cup of the hip joint prosthesis, and the tibial plateau and femoral condyle of the knee joint prosthesis. The ceramic coating, high-oxygen diffusion transition layer, and matrix of the friction contact surface of the joint prosthesis form a continuous gradient structure.

[0023] The present invention also provides the application of the aforementioned preparation method in the field of biomedical implant materials, characterized in that the application scenarios include orthopedic joint prostheses, dental implants and other biomedical devices that have high requirements for wear resistance and dimensional accuracy.

[0024] The beneficial effects of this invention are:

[0025] 1. Expanding the scope of application: It is compatible with multi-component zirconium-based systems such as Zr-2.5Nb, Zr-Nb-Ti, and Zr-Mo-Nb, and is compatible with three mainstream preparation processes: EBM, SLM, and forging, thus solving the problem of the narrow application scope of existing technologies;

[0026] 2. Innovative gradient control: The repeated oxygen concentration gradient control process promotes the diffusion of oxygen atoms into the material, resulting in a high oxygen diffusion transition layer with a depth that exceeds that of traditional processes by more than 40%, effectively improving the interfacial bonding strength between the coating and the substrate and preventing coating peeling.

[0027] 3. Precise size control: Precise control of the oxygen concentration gradient ensures uniform oxidation reaction, effectively suppressing prosthesis size distortion. Size variation is ≤ ±0.01mm, solving the key problem of uncontrolled size accuracy in traditional oxidation processes.

[0028] 4. Quantitative process guidance: The established coupled mathematical model enables quantitative prediction of coating thickness and wear resistance under different zirconium-based systems and different preparation processes, forming a comprehensive process optimization guidance system and avoiding the blindness of traditional processes;

[0029] 5. Industrial Adaptability: The preparation method is stable and the process is controllable. The product performance is consistent under different systems and processes, making it suitable for industrial-scale production and applicable to the manufacture of various medical joint prostheses. Attached Figure Description

[0030] Figure 1 shows the microstructure, contact angle, and roughness of the oxide layer at different temperatures: (A) Inverse pole figure of Zr-2.5Nb alloy prepared by EBM; (B) Phase diagram (α-Zr is the main phase); (C) Grain size analysis (average grain size 3.5 μm); (D) Water contact angle (72° at 500℃, 81° at 550℃, and 88° at 600℃); (E) White light interferometer morphology; (F) Surface roughness curve.

[0031] Figure 2 shows the TEM interface analysis of the 550℃ sample (H550): (A) HAADF image of the oxide layer-matrix interface; (B) EDS mapping (uniform diffusion of Zr elements); (C) SAD pattern of the matrix (α-Zr phase); (D) HRTEM image of the interface; (E) FFT results of the outer oxide layer (m-ZrO2+Nb2O5); (F) FFT results of the inner oxide layer (t-ZrO2).

[0032] Figure 3 shows the XRD and XPS analyses of the oxide layer at different temperatures: (A) XRD pattern (m-ZrO2 is the main phase, and the t-ZrO2 peak weakens with increasing temperature); (B) Zr 3d XPS spectrum (182 eV and 184.47 eV correspond to ZrO2); (C) Nb 3d XPS spectrum (207 eV and 210 eV correspond to Nb2O5); (D) O 1s XPS spectrum (530.10 eV corresponds to ZrO2, and 531.48 eV corresponds to Nb2O5).

[0033] Figure 4 compares hardness, coefficient of friction, and wear rate: (A) Microhardness (H550, highest at 1053 Hv); (B) Coefficient of friction curve (the curve for the oxide coating is more stable); (C) Average coefficient of friction (H550, 0.45); (D) Wear rate (H550, lowest at 0.78 × 10⁻⁻⁶). 6 mm³ / (N・m));

[0034] Figure 5 shows the wear morphology and wear volume analysis: (A)-(D) are the three-dimensional morphology of wear scars in untreated alloys, H500, H550, and H600, respectively; (E) comparison of wear volume (H550 is 0.76×10). 5 μm³); (F)-(G) Wear scar depth curve (H550 depth ≤150nm). Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions disclosed in this invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0037] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0038] Detailed steps of the preparation method of this invention:

[0039] 1. Preparation of Zirconium-based alloy bodies (multi-system, multi-process adaptation) (1) Material selection: Select commercial zirconium-based alloy raw materials, including Zr-2.5Nb (Zr content 97.5wt%, Nb content 2.5wt%), Zr-10Nb-5Ti (Zr content 85wt%, Nb content 10wt%, Ti content 5wt%), Zr-5Mo-3Nb (Zr content 92wt%, Mo content 5wt%, Nb content 3wt%), etc. The particle size of the powder raw materials is 45-150μm, and the diameter of the forging billet is 20-50mm; (2) Preparation process: Use EBM process: electron beam power 60-80kV, scanning speed 500-800mm / s, layer thickness 50-80μm, prepare 10×10×2mm dense samples with relative density ≥99.5%; use SLM Process: Laser power 200-300W, scanning speed 800-1200mm / s, layer thickness 20-50μm, prepare 10×10×2mm dense sample with relative density ≥99.6%; Forging process: hold zirconium-based alloy billet at 850-950℃ for 1-2h, hot forge with press, deformation amount 50-70%, then anneal at 600-700℃ for 2h, and machine to 10×10×2mm size with relative density ≥99.8%; (3) Matrix quality control: all samples prepared by the process are free from obvious defects such as pores and cracks, providing good matrix conditions for uniform diffusion of oxygen atoms and formation of transition layer.

[0040] 2. Pretreatment section, (1) Polishing treatment: The step-by-step polishing process is adopted. First, the sample is polished with 400#, 800#, 1200# and 2000# silicon carbide sandpaper in sequence to remove the oxide scale, rough layer and processing marks formed on the surface during the preparation process; then, 1μm diamond polishing paste is used for fine polishing until the surface roughness Ra≤0.05μm, so as to ensure the uniformity of the oxidation reaction and the effective construction of the oxygen concentration gradient; (2) Cleaning and drying: The polished sample is placed in an ethanol solution and ultrasonically cleaned for 30min at 40kHz to remove the surface wear debris; then it is transferred to an acetone solution and ultrasonically cleaned for 30min to thoroughly remove the oil stains; finally, the sample is placed in a vacuum drying oven at 60℃ and dried for 2h to avoid the moisture affecting the oxygen concentration distribution and oxidation reaction efficiency.

[0041] 3. In-situ oxidation and oxygen concentration gradient control (the core innovative step of this invention): The pretreated sample is placed in a high-temperature tube furnace and air is introduced as the oxidation medium. The air flow rate is controlled at 50 mL / min to ensure that the oxygen in the furnace is sufficient and evenly distributed. An innovative cyclic heating and holding process is adopted to promote the deep diffusion of oxygen atoms by repeatedly creating an oxygen concentration gradient: (1) First heating: The sample is heated to the target oxidation temperature (500℃-600℃) at a heating rate of 10℃ / min and held for 2 hours. At this time, an initial oxide layer is formed on the sample surface, and the oxygen concentration on the surface is higher than that inside, forming an initial oxygen concentration gradient; (2) First micro-cooling and holding: The sample is cooled slightly at a rate of 5℃ / min for 30-50℃ and held for 30-60 minutes. The growth rate of the surface oxide layer slows down, and the internal oxygen concentration gradually increases, forming a reverse oxygen concentration gradient, which promotes the diffusion of oxygen atoms into the matrix; (3) Second heating and holding: The sample is heated again at a rate of 10℃ / min The temperature is increased to the target oxidation temperature at a certain rate, and the remaining holding time (total holding time 6h) is maintained. At this time, the internal oxygen concentration and the surface form a new concentration gradient, and oxygen atoms continue to diffuse deeply, eventually forming a high oxygen diffusion transition layer and a dense ceramic coating; (4) Cooling: After the holding time is completed, the heating device is turned off and the temperature is naturally cooled to room temperature to complete the synergistic preparation of the in-situ oxidation coating and the high oxygen diffusion transition layer.

[0042] 4. Process optimization section, (1) Model variable definition: Independent variables: oxidation temperature T (K), oxygen concentration gradient cycle number, covering the process range of 500℃-600℃ (773K-873K) and the range of 2-3 cycles, to adapt to different zirconium-based systems and preparation processes; Intermediate variables: ceramic coating thickness d (T) (μm), high oxygen diffusion transition layer depth (μm), coating microhardness HV (T) (Hv), t-ZrO2 phase volume fraction f t-ZrO2(T) (%), all obtained through experimental testing; dependent variables: abrasion resistance WR (T) (wear rate), change in prosthesis size (mm). (2) Model expression:

[0043] Coating thickness equation: This equation, derived from the Arrhenius equation, has a goodness of fit R² ≥ 0.99 and can accurately predict coating thickness under different temperatures, different zirconium-based systems, and different preparation processes; Wear resistance equation: The equation fits well (R²) ≥ 0.98, the prediction error is ≤ 5%, and it couples the effects of multiple factors on wear resistance, making it suitable for multi-component zirconium-based systems.

[0044] (3) Determination of optimal process: Based on mathematical model and oxygen concentration gradient control experiment, when the target oxidation temperature is 550℃ and the number of cycles is 2 (first heat preservation for 2h → cooling to 500℃ and heat preservation for 45min → heating to 550℃ and heat preservation for 2.75h), the comprehensive performance of different zirconium-based systems and preparation processes is optimal: the depth of high oxygen diffusion transition layer is 2.5-3.0μm, the thickness of ceramic coating is 9.0-10.0μm, the volume fraction of t-ZrO2 phase is ≤13.5%, the coating hardness is ≥1053Hv, and the wear rate is ≤0.8×10⁻ 6 The size of the prosthesis varies by only ±0.008-0.010 mm, with a diameter of mm³ / (N・m).

[0045] The following specific examples of different zirconium-based systems and different preparation processes illustrate the implementation process and effects of the present invention in detail. The equipment and materials used in the examples are all commercially available conventional products, and the process parameters can be adjusted based on mathematical models according to actual production needs.

[0046] Example 1: Preparation of Zr-2.5Nb alloy coating by EBM (optimal process)

[0047] 1. Preparation of zirconium-based alloy bodies: Zr-2.5Nb alloy powder (particle size 45-150μm) was used. EBM process parameters: electron beam power 70kV, scanning speed 600mm / s, layer thickness 60μm. 10×10×2mm samples were prepared with a relative density of 99.8%.

[0048] 2. Pretreatment: Polish stepwise to Ra=0.03μm, ultrasonically clean with ethanol and acetone for 30min each, and vacuum dry at 60℃ for 2h;

[0049] 3. In-situ oxidation and oxygen concentration gradient control: Air is introduced into the high-temperature tube furnace (flow rate 50 mL / min), the heating rate is 10℃ / min, the temperature is raised to 550℃ and held for 2 hours, the temperature is slightly lowered to 500℃ and held for 45 minutes, the temperature is raised to 550℃ again and held for 2.75 hours, and then naturally cooled.

[0050] 4. Performance test: (1) Structural parameters: The measured thickness of the ceramic coating is 9.87 μm, the depth of the high oxygen diffusion transition layer is 2.8 μm, and the size change is +0.008 mm; (2) Phase analysis: XRD test shows that the volume fraction of t-ZrO2 phase is 13.49%, and Nb2O5 is uniformly distributed; (3) Hardness test: The coating hardness is 1053 Hv, the transition layer hardness is 520 Hv, and the matrix hardness is 204 Hv; (4) Wear resistance test: The wear rate is 0.78×10⁻ 6 mm³ / (N・m), wear volume 0.76×10 5 μm³, wear scar depth 150nm; (5) Interface performance: interface bonding strength 62MPa, no delamination or crack defects; (6) Dimensional accuracy: the change in length of the sample before and after oxidation was 0.007mm, the change in width was 0.008mm, and the change in thickness was 0.009mm, all ≤±0.01mm; (7) Biocompatibility: in vitro cytotoxicity test (MTT method) showed a cell survival rate of 96.2%, which meets the standard of GB / T 16886.5-2017.

[0051] Example 2: Preparation of Zr-10Nb-5Ti alloy coating by SLM

[0052] 1. Preparation of zirconium-based alloy bodies: Zr-10Nb-5Ti alloy powder (particle size 45-150μm) was used. SLM process parameters: laser power 250W, scanning speed 1000mm / s, layer thickness 30μm. 10×10×2mm samples were prepared with a relative density of 99.6%.

[0053] 2. Pretreatment: Polish stepwise to Ra=0.04μm, ultrasonically clean with ethanol and acetone for 30min each, and vacuum dry at 60℃ for 2h;

[0054] 3. In-situ oxidation and oxygen concentration gradient control: Air is introduced into the high-temperature tube furnace (flow rate 50 mL / min), the heating rate is 10℃ / min, the temperature is raised to 550℃ and held for 2 hours, the temperature is slightly lowered to 500℃ and held for 45 minutes, the temperature is raised to 550℃ again and held for 2.75 hours, and then naturally cooled.

[0055] 4. Performance Testing:

[0056] (1) Structural parameters: The actual thickness of the ceramic coating is 9.5 μm, the depth of the high oxygen diffusion transition layer is 2.6 μm, and the dimensional change is +0.009 mm;

[0057] (2) Phase analysis: XRD test showed that the volume fraction of t-ZrO2 phase was 12.8%, and Nb2O5 and TiO2 were uniformly distributed;

[0058] (3) Hardness test: coating hardness 1020Hv, transition layer hardness 500Hv, substrate hardness 220Hv;

[0059] (4) Abrasion resistance test: Abrasion rate 0.79×10⁻ 6 mm³ / (N・m), wear volume 0.78×10 5 μm³, wear scar depth 155nm;

[0060] (5) Interface performance: The interface bonding strength is 59MPa, with no delamination or crack defects.

[0061] Example 3: Preparation of Zr-5Mo-3Nb alloy coating by forging

[0062] 1. Preparation of zirconium-based alloy body: Zr-5Mo-3Nb alloy billet (diameter 30mm) was used. Forging process parameters: forging temperature 900℃, holding for 1.5h, deformation amount 60%, annealing temperature 650℃, holding for 2h, and machining to a 10×10×2mm sample with a relative density of 99.8%;

[0063] 2. Pretreatment: Polish stepwise to Ra=0.05μm, ultrasonically clean with ethanol and acetone for 30min each, and vacuum dry at 60℃ for 2h;

[0064] 3. In-situ oxidation and oxygen concentration gradient control: Air is introduced into the high-temperature tube furnace (flow rate 50 mL / min), the heating rate is 10℃ / min, the temperature is raised to 550℃ and held for 2 hours, the temperature is slightly lowered to 500℃ and held for 45 minutes, the temperature is raised to 550℃ again and held for 2.75 hours, and then naturally cooled.

[0065] 4. Performance Testing:

[0066] (1) Structural parameters: The actual thickness of the ceramic coating is 9.2 μm, the depth of the high oxygen diffusion transition layer is 2.7 μm, and the dimensional change is +0.010 mm;

[0067] (2) Phase analysis: XRD test showed that the volume fraction of t-ZrO2 phase was 13.2%, and MoO3 and Nb2O5 were uniformly distributed;

[0068] (3) Hardness test: Coating hardness 1035Hv, transition layer hardness 510Hv, substrate hardness 230Hv;

[0069] (4) Abrasion resistance test: wear rate 0.80×10⁻ 6 mm³ / (N・m), wear volume 0.79×10 5 μm³, wear scar depth 160nm;

[0070] (5) Interface performance: The interface bonding strength is 58MPa, with no delamination or crack defects.

[0071] Comparative Example 1: Traditional single-insulation oxidation process (EBM-Zr-2.5Nb, 550℃)

[0072] 1. Preparation and pretreatment of zirconium-based alloy bodies: Same as in Example 1;

[0073] 2. Oxidation treatment: Air is introduced into a high-temperature tube furnace (flow rate 50 mL / min), the heating rate is 10℃ / min, the temperature is raised to 550℃ and held for 6 hours, and then naturally cooled.

[0074] 3. Performance Testing:

[0075] (1) Structural parameters: ceramic coating thickness 9.5μm, high oxygen diffusion transition layer depth 1.9μm, dimensional change +0.025mm;

[0076] (2) Hardness test: Coating hardness 1020 Hv, transition layer hardness 480 Hv;

[0077] (3) Abrasion resistance test: Abrasion rate 0.95×10⁻ 6 mm³ / (N・m);

[0078] (4) Interface performance: The interface bonding strength is 42 MPa, and microcracks appear in some samples.

[0079] Comparative Example 2: Properties of Untreated Zr-10Nb-5Ti Alloy (SLM Preparation)

[0080] The properties of the SLM-prepared Zr-10Nb-5Ti alloy sample without oxidation treatment were tested, and the results are as follows: hardness 220 Hv, average friction coefficient 0.39, and wear rate 8.8 × 10⁻⁻⁻⁶. 6 mm³ / (N・m), wear volume 465×10 5 μm³, wear scar depth 3.8 × 10 μm³ 4 μm, without a transition layer structure, the hardness, wear resistance and dimensional stability of this comparative sample are far lower than those of the oxide coating sample prepared in this invention.

[0081] The coating, transition layer, and product performance characteristics obtained by this invention are as follows:

[0082] 1. High oxygen diffusion transition layer performance, (1) Structural characteristics: The transition layer is a continuous gradient distribution area of ​​Zr, alloying elements (Nb, Ti, Mo, etc.) and O elements, with no obvious interface layering. EDS analysis shows that the content of Zr and alloying elements gradually decreases from the substrate to the coating, while the content of O elements gradually increases, achieving a smooth transition of composition; (2) Size parameters: The depth of the transition layer is 2.5-3.0μm, which is more than 40% higher than the traditional single heat preservation oxidation process (transition layer depth 1.8-2.0μm), and the transition layer depth fluctuation under different zirconium-based systems and different preparation processes is ≤0.2μm; (3) Mechanical matching: The hardness of the transition layer is 450-600Hv, which is between the substrate (200-250Hv) and the ceramic coating (800-1053Hv), effectively alleviating the interface stress concentration caused by the sudden change in hardness and adapting to the differences in mechanical properties of different systems.

[0083] 2. Ceramic coating performance, (1) Phase composition: It is composed of m-ZrO2 main phase, t-ZrO2 secondary phase and alloy element oxides (Nb2O5, TiO2, MoO3, etc.) dispersed phase. m-ZrO2 provides high hardness, alloy element oxides improve coating toughness, and the volume fraction of t-ZrO2 phase decreases with increasing temperature; (2) Microstructure: The coating is dense and pore-free, with a surface roughness Ra=0.1-0.3μm, and is continuously bonded to the transition layer. There are no crack defects, and the density of the coating varies by ≤5% under different preparation processes; (3) Wear resistance: The wear rate in simulated human body fluid environment (0.9wt% NaCl solution) is 0.76×10⁻ 6 -1.2×10⁻ 6 mm³ / (N・m), far lower than that of untreated zirconium-based alloys (8.0×10⁻⁻⁶ mm³ / (N・m)). 6 -9.0×10⁻ 6 mm³ / (N・m)), the wear resistance fluctuation between different zirconium-based systems is ≤8%.

[0084] 3. Joint prosthesis performance, (1) Dimensional accuracy: The size change of the prosthesis after oxidation is ≤ ±0.01mm, reaching IT8 level accuracy, meeting the clinical fitting requirements, and the size change difference under different preparation processes is ≤0.002mm; (2) Service life: The gradient structure of "ceramic coating-high oxygen diffusion transition layer-matrix" on the friction contact surface ensures that the coating does not fall off during long-term friction, and the service life of the prosthesis is extended to more than 15 years; (3) Biocompatibility: There is no release of toxic elements in the coating and transition layer, and the cell survival rate is ≥95% in in vitro cytotoxicity test, which meets the GB / T 16886.5-2017 standard and is compatible with the biosafety requirements of various zirconium-based systems.

[0085] Comprehensive comparison and inventiveness analysis of the embodiments and comparative examples

[0086] To highlight the inventiveness and significant technological advancement of the preparation method proposed in this invention compared with the prior art, the following will systematically compare and analyze the four dimensions of structural performance, mechanical performance, dimensional accuracy and process adaptability, based on the test data of specific embodiments and comparative embodiments, and clarify the key technical advantages revealed in the accompanying drawings.

[0087] 1. A leapfrog improvement in structural performance

[0088] Innovative construction of a high-oxygen diffusion transition layer: such as Figure 2 As shown, through the cyclic process of "heating-heating-slight cooling-heating again" of the present invention (Examples 1-3), a continuous, interface-free high-oxygen diffusion transition layer is formed between the coating and the substrate. Figure 2 A, B). EDS element surface scan ( Figure 2 (B) The smooth gradient distribution of Zr, O, and alloying elements (such as Nb) from the matrix to the coating is clearly demonstrated, providing direct evidence of deep diffusion of oxygen atoms driven by repeatedly created concentration gradients. In contrast, Example 1, using a traditional single-insulation process, has a transition layer depth of only 1.9 μm, a steep elemental gradient, and weak interfacial bonding (interfacial bonding strength of only 42 MPa, with microcracks). The transition layer depth of this invention reaches 2.5-3.0 μm, an improvement of over 40% compared to the traditional process, and the interfacial bonding strength is ≥58 MPa (up to 62 MPa in Example 1). This structural innovation fundamentally solves the key problem of coating detachment during long-term service due to insufficient interfacial bonding.

[0089] Optimization of ceramic coating phases and microstructure: Figure 3 XRD and XPS analyses show that the coatings prepared in this invention (represented by H550) are composed of m-ZrO2 main phase, an appropriate amount of t-ZrO2 secondary phase, and uniformly dispersed alloying element oxides (such as Nb2O5). Figure 3(A, C, D). This multiphase composite structure, especially the presence of the t-ZrO2 phase (13.49% by volume in Example 1), provides high hardness while imparting a certain degree of toughness to the coating, suppressing the initiation and propagation of brittle cracks. In contrast, the traditional process (comparative Example 1) has weak control over the phase composition, resulting in relatively insufficient coating toughness.

[0090] 2. Significant optimization of mechanical and tribological properties

[0091] Hardness gradient matching and ultra-high surface hardness: Figure 4 Microhardness test results for A show that, under the optimal process of this invention (Example 1, H550), the surface hardness of the ceramic coating reaches as high as 1053 Hv, which is more than 5 times the hardness of the substrate (~200 Hv). Meanwhile, the hardness of the high-oxygen diffusion transition layer (520 Hv) falls between the two, forming a perfect hardness gradient. This gradient structure (coating hard - transition layer medium - substrate tough) effectively alleviates stress concentration during load transfer and avoids failure at the interface due to mechanical mismatch. In contrast, the untreated alloy (Comparative Example 2) has a hardness of only 220 Hv. Although the traditional coating hardness (1020 Hv) is high, the overall mechanical matching is poor due to insufficient transition layer performance.

[0092] Excellent wear resistance and low friction properties: Figure 4 BD and Figure 5 The wear test data is the most convincing. The wear rate of Example 1 of this invention is as low as 0.78 × 10⁻⁻⁻⁶. 6 mm³ / (N・m), compared to the untreated alloy (Comparative Example 2, 8.8 × 10⁻ 6 The reduction in mm³ / (N・m) is approximately an order of magnitude lower than that of the conventional process (Comparative Example 1, 0.95 × 10⁻⁻⁶). 6 The coefficient of friction (mm³ / (N・m)) also showed a significant improvement (approximately 18%). Meanwhile, its average coefficient of friction remained stable at 0.45. Figure 4 C), the depth of the abrasion scar is only 150nm ( Figure 5 FG), smooth three-dimensional topography ( Figure 5 C). This is thanks to the high hardness, excellent toughness, and strong interfacial bonding of the coating of this invention, which effectively resists ploughing and adhesive wear during friction, with very few wear debris, fundamentally solving the clinical risk of aseptic loosening caused by wear debris.

[0093] 3. Revolutionary control of dimensional accuracy

[0094] Nanoscale dimensional stability: This invention ensures the uniformity and controllability of the oxidation reaction through precise oxygen concentration gradient control. Data from Examples 1-3 show that the size change of the oxidized samples is controlled between +0.008 mm and +0.010 mm, far lower than the clinically required ±0.02 mm, achieving an extremely high precision of ≤±0.01 mm (reaching IT8 level). In contrast, Example 1, at the same temperature, showed a size change of +0.025 mm, exceeding the allowable range for precise fitting. Figure 1 The white light interference morphology and roughness curve of EF also indirectly reflect that the surface is uniform after the process of this invention, without any bumps / depressions caused by local over-oxidation or under-oxidation. This breakthrough solves the problem of "out-of-control" prosthesis size caused by uneven reaction in traditional oxidation processes, ensuring a precise fit between the prosthesis and the human skeleton.

[0095] 4. A qualitative leap in the universality and predictability of the process.

[0096] Extensive Material and Process Adaptability: This invention successfully extends in-situ oxidation technology from the traditional Zr-2.5Nb / EBM combination to multi-element alloy systems such as Zr-Nb-Ti and Zr-Mo-Nb, while simultaneously being compatible with mainstream preparation processes such as SLM and forging (Examples 2 and 3). Data from these examples show that coatings prepared under different systems and processes exhibit minimal fluctuations in core properties (such as transition layer depth, coating hardness, and wear rate), demonstrating the strong process robustness and universality of the method, breaking through the application barriers of existing technologies. Quantitative Process Design Guidance System: The invention's pioneering coupled mathematical model of oxidation temperature (T), coating thickness (d), and wear resistance (WR) (see claim 1 and specification) provides a quantitative and predictable theoretical tool for process optimization. This model is built on theories such as the Arrhenius equation and has a high goodness of fit (R²≥0.99 / 0.98). It can accurately predict the coating performance under different parameters, enabling process development to move from "experience-based trial and error" to "theoretical design". This significantly improves R&D efficiency and the reproducibility of results, which is something that traditional processes do not have at all.

[0097] The beneficial effects of this invention are:

[0098] 1. Expanding the scope of application: It is compatible with multi-component zirconium-based systems such as Zr-2.5Nb, Zr-Nb-Ti, and Zr-Mo-Nb, and is compatible with three mainstream preparation processes: EBM, SLM, and forging, thus solving the problem of the narrow application scope of existing technologies;

[0099] 2. Innovative gradient control: The repeated oxygen concentration gradient control process promotes the diffusion of oxygen atoms into the material, resulting in a high oxygen diffusion transition layer with a depth that exceeds that of traditional processes by more than 40%, effectively improving the interfacial bonding strength between the coating and the substrate and preventing coating peeling.

[0100] 3. Precise size control: Precise control of the oxygen concentration gradient ensures uniform oxidation reaction, effectively suppressing prosthesis size distortion. Size variation is ≤ ±0.01mm, solving the key problem of uncontrolled size accuracy in traditional oxidation processes.

[0101] 4. Quantitative process guidance: The established coupled mathematical model enables quantitative prediction of coating thickness and wear resistance under different zirconium-based systems and different preparation processes, forming a comprehensive process optimization guidance system and avoiding the blindness of traditional processes;

[0102] 5. Industrial Adaptability: The preparation method is stable and the process is controllable. The product performance is consistent under different systems and processes, making it suitable for industrial-scale production and applicable to the manufacture of various medical joint prostheses.

[0103] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. The various components mentioned in this invention are common technologies in the existing field. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an in-situ oxide coating of a zirconium-based alloy for use in joint prostheses, characterized in that, Includes the following steps: (1) Preparation of zirconium-based alloy bodies: Zirconium-based alloy raw materials are selected and dense samples are prepared by electron beam melting (EBM), selective laser melting (SLM) or forging processes. The zirconium-based alloys include Zr-2.5Nb, Zr-Nb-Ti, and Zr-Mo-Nb systems. The EBM process parameters are electron beam power 60-80kV, scanning speed 500-800mm / s, and layer thickness 50-80μm; the SLM process parameters are laser power 200-300W, scanning speed 800-1200mm / s, and layer thickness 20-50μm; the forging process parameters are forging temperature 850-950℃, deformation amount 50-70%, and annealing temperature 600-700℃ for 2h. (2) Pretreatment: The prepared zirconium-based alloy sample was polished step by step until the surface roughness Ra≤0.05μm, and then ultrasonically cleaned in ethanol and acetone for 30min each, and vacuum dried at 60℃ for 2h for later use. (3) In-situ oxidation and oxygen concentration gradient control: The pretreated sample was placed in a high-temperature tube furnace and air was introduced as the oxidation medium. The oxygen concentration gradient was repeatedly created through the cycle process of "heating-holding-micro-cooling-holding again" to promote the diffusion of oxygen atoms into the material. The overall heating rate was 10℃ / min, the target oxidation temperature was 500℃-600℃, the total holding time was 6h, the number of cycles was 2-3, the micro-cooling range was 30-50℃ each time, the micro-cooling was held for 30-60min after micro-cooling, and finally the material was naturally cooled to form a ZrO2-based ceramic coating and a high oxygen diffusion transition layer on the surface of the zirconium-based alloy in situ. (4) Performance and dimensional control: Process parameters are optimized based on a coupled mathematical model of oxidation temperature, coating thickness, and wear resistance. The mathematical model includes: Coating thickness equation: Abrasion resistance equation: Where d(T) is the ceramic coating thickness (μm), T is the oxidation temperature (K), J / mol is the oxidation activation energy of the zirconium-based alloy, J / (mol·K) is the gas constant, HV(T) is the coating microhardness (Hv), and f t-ZrO2 (T) represents the volume fraction (%) of the t-ZrO2 phase in the coating, and WR (T) represents the alloy wear rate (×10⁻⁻¹). 6 mm³ / (N・m)).

2. The method for preparing a zirconium-based alloy in-situ oxide coating for joint prostheses according to claim 1, characterized in that, The optimal oxidation process in step (3) is as follows: target oxidation temperature 550℃, 2 cycles, first heat preservation for 2h, then slightly cooling down to 500℃ for 45min, then heating up to 550℃ again for 2.75h, the final high oxygen diffusion transition layer depth is 2.5-3.0μm, and the ceramic coating thickness is 9.0-10.0μm.

3. The method for preparing a zirconium-based alloy in-situ oxide coating for joint prostheses according to claim 1, characterized in that, The high-oxygen diffusion transition layer is a gradient distribution region of Zr, alloying elements and O elements, with no obvious interface delamination. The depth of the transition layer is more than 40% higher than that of the traditional single heat preservation oxidation process, and the size change of the prosthesis after oxidation is ≤ ±0.01mm.

4. The method for preparing a zirconium-based alloy in-situ oxide coating for joint prostheses according to claim 1, characterized in that, The phase composition of the ZrO2-based ceramic coating includes m-ZrO2 main phase, t-ZrO2 secondary phase and dispersed oxide phase of alloying elements. The ceramic coating and the high oxygen diffusion transition layer, as well as the transition layer and the substrate, are continuously and gradiently bonded, without cracks or pore defects, and the interfacial bonding strength is ≥55MPa.

5. The method for preparing a zirconium-based alloy in-situ oxide coating for joint prostheses according to claim 1, characterized in that, In step (3), the air flow rate is 50 mL / min. During the circulation process, the air flow rate is kept stable to ensure that the oxygen concentration gradient is uniform and controllable.

6. The method for preparing a zirconium-based alloy in-situ oxide coating for joint prostheses according to claim 1, characterized in that, The prepared ceramic coating has a surface hardness of 800-1053 Hv, which is 3-5 times that of the zirconium-based alloy substrate hardness of 200-250 Hv. The high oxygen diffusion transition layer has a hardness of 450-600 Hv, achieving a hardness gradient match between the coating and the substrate.

7. The method for preparing a zirconium-based alloy in-situ oxide coating for joint prostheses according to claim 1, characterized in that, The dimensions of the sample are 10×10×2mm.

8. A medical joint prosthesis, characterized in that, The joint prosthesis is made of zirconium-based alloy material prepared by any one of claims 1-7, and the friction contact surface of the prosthesis is provided with the in-situ oxide ceramic coating and high oxygen diffusion transition layer as described in claim 1, with a wear rate ≤0.8×10⁻ 6 mm³ / (N・m), wear scar depth ≤200nm, dimensional accuracy reaches IT8 level.

9. The medical joint prosthesis according to claim 8, characterized in that, The joint prosthesis includes the femoral head and acetabular cup of the hip joint prosthesis, and the tibial plateau and femoral condyle of the knee joint prosthesis. The ceramic coating, high oxygen diffusion transition layer and matrix of the friction contact surface of the joint prosthesis form a continuous gradient structure.

10. The application of the preparation method according to any one of claims 1-7 in the field of biomedical implant materials, characterized in that, The application scenarios include orthopedic joint prostheses, dental implants, and biomedical devices that require high wear resistance and dimensional accuracy.

Images