CN111101089A

CN111101089A - Method for forming oxide layer on surface of zirconium or zirconium alloy and application

Info

Publication number: CN111101089A
Application number: CN202010099471.8A
Authority: CN
Inventors: 申宇; 俞天白; 姚美意; 孙国成
Original assignee: Suzhou Microport Orthorecon Co Ltd
Current assignee: Suzhou Microport Orthorecon Co Ltd
Priority date: 2020-02-18
Filing date: 2020-02-18
Publication date: 2020-05-05

Abstract

The invention belongs to the technical field of medical implant materials, and particularly relates to a method for forming an oxide layer on the surface of zirconium or zirconium alloy and application of the method. Which comprises the following steps: reacting zirconium or zirconium alloy with water or water vapor at the temperature of 500 ℃ and 9-20MPa to form a ceramic oxide layer with the thickness of 2-10 mu m on the surface of the metal substrate. The medical implant comprises a metal substrate and a surface oxidation layer, wherein the surface ceramic oxidation layer is prepared by adopting a method for forming an oxidation layer on the surface of the zirconium or zirconium alloy. The technical scheme provided by the invention adopts water or steam to oxidize zirconium and zirconium alloy at lower temperature, so that the metal substrate has higher strength during oxidation and stronger constraint capacity on the ceramic oxide layer, thereby obtaining the ceramic oxide layer with fewer internal defects and a straight O/M interface, further improving the quality of the ceramic oxide layer and improving the wear resistance of the medical implant of zirconium and zirconium alloy.

Description

Method for forming oxide layer on surface of zirconium or zirconium alloy and application

Technical Field

The invention belongs to the technical field of medical implant materials, and particularly relates to a method for forming an oxide layer on the surface of zirconium or zirconium alloy and application of the method.

Background

The advantage of using metallic materials for medical implants is their good strength, plasticity, especially when applied to components that need to carry large loads, such as hip joints, knee joints, etc. Although ceramic materials also provide sufficient strength to the medical implant, there is a risk of chipping when impacted. Of course, metallic materials also have corresponding weaknesses compared to ceramic materials: firstly, the surface hardness is lower, and the particles are easier to be scratched into by third parties; secondly, the surface roughness of the metal material is difficult to be polished to the extent that the surface of the ceramic can reach, resulting in a higher coefficient of friction of the sliding surface, and therefore the metal material has poorer frictional wear resistance than the ceramic material.

Preparing a more wear-resistant ceramic layer on the surface of a metal material is a way to obtain a high wear-resistant surface and avoid the risk of cracking.

The traditional processing technology is that a layer of hard wear-resistant material is added on the surface of metal, for example, a layer of titanium nitride ceramic layer is prepared on the surface of cobalt-chromium-molybdenum alloy by physical vapor deposition technology, so that the surface hardness of the alloy is improved, and the alloy can be used as a barrier for metal ion diffusion to prevent adverse reaction of human body caused by the escape of metal ions. However, the ceramic layer produced by this method has a problem of poor bonding with a metal substrate, and when the ceramic layer is used as a sliding surface of a joint such as a hip joint or a knee joint, there is a risk that the ceramic layer is peeled off after a long-term friction, and the ceramic particles peeled off have a very high hardness, and once the ceramic particles are peeled off, the abrasion is further accelerated.

The interface bonding problem can be effectively solved by directly converting the surface of the metal material into the ceramic layer on the metal substrate by an oxidation or nitridation method, and the ceramic layer formed by the method is bonded with the metal substrate by a chemical bond instead of a mechanical bond, so that the ceramic layer has extremely high bonding strength. However, very high temperatures are usually required for nitride formation, which results in changes in the texture and mechanical properties of the metal substrate and also in dimensional changes of the product, and therefore in practice, oxidation is usually used.

The oxidation effect of zirconium and zirconium alloys is very excellent in all metallic materials for medical implants, and can be evaluated by the P-B ratio (balling-Bedworth ratio), i.e. the ratio of the volume of oxide produced to the volume of metal consumed: the closer the P-B value is to 1, the smaller the stress generated in the oxide ceramic layer is, and the more difficult the crack is generated; when the P-B ratio is less than 1, the internal part of the generated ceramic oxide layer is tensile stress, the volume of the formed ceramic oxide layer is smaller than that before the formation, the ceramic oxide layer can not completely cover the metal substrate, the protection effect can not be achieved, and the oxidation effect is very poor; when the P-B ratio is larger than 1, the ceramic oxide layer can completely cover the metal substrate, the internal part of the generated ceramic oxide layer is compressive stress, the larger the P-B ratio is, the larger the internal compressive stress of the generated ceramic oxide layer is, and the tendency of microcrack initiation is more obvious. For example, iron has a P-B ratio of about 2.14, and therefore stainless steel is not suitable for forming a ceramic oxide layer having a large number of microcracks inside and a loose structure; the P-B ratio of titanium is about 1.73, so that a compact ceramic oxide layer can be formed on the surface of titanium and titanium alloy by means of color anodic oxidation and the like, but the thickness of the prepared compact ceramic oxide layer is thinner, only about 2 mu m, the improvement on the wear resistance is limited, if the thickness is further improved, a large number of defects such as microcracks and the like begin to appear in the ceramic oxide layer, and the protection effect of the compact ceramic oxide layer is lost; zirconium has a lower P-B value of only 1.56, so that the compressive stress in the formed ceramic oxide layer is small, a ceramic oxide layer with a thickness of 10 μm or more can be formed, and the interior of the ceramic oxide layer is dense and has few defects, so that zirconium and zirconium alloys are one of the most suitable materials for preparing the ceramic oxide layer in common medical implant metals.

However, the zirconia and zirconia alloy ceramic oxide layers obtained by the conventional oxidation method still have the following problems: 1. some microcracking still exists in the oxide ceramic layer; 2. large waviness is generated at the interface (O/M interface) of the oxide ceramic layer and the metal substrate.

The occurrence of microcracks can weaken the bonding property of the ceramic oxide layer, possibly leading to the situation that oxide particles are stripped in the process of long-time friction and abrasion, and the oxide particles on the friction surface can aggravate abrasion; the surface roughness of the oxide ceramic layer is increased by the wavy fluctuation formed at the O/M interface, the roughness requirement of a finished product can be met only by removing the oxide ceramic layer with larger thickness in use, and the thickness of the residual oxide ceramic layer after polishing is not uniform at each part, so that the thickness of the oxide ceramic layer at the position of the O/M interface protruding to the outer surface is too thin. Therefore, there is room for improvement in conventional oxidation treatment.

Disclosure of Invention

The invention provides a method for forming an oxide layer on the surface of zirconium or zirconium alloy, which is used for solving the problem that a ceramic oxide layer is easy to generate micro cracks or large wavy fluctuation is generated on an O/M interface at present.

In order to solve the technical problems, the technical scheme of the invention is as follows: the method for forming the oxide layer on the surface of the zirconium or the zirconium alloy comprises the following steps: reacting zirconium or zirconium alloy with water or water vapor at the temperature of 500 ℃ and 9-20MPa to form a ceramic oxide layer with the thickness of 2-10 mu m on the surface of the metal substrate.

Alternatively, the zirconium or zirconium alloy is reacted in water at 300-.

Alternatively, the zirconium or zirconium alloy is reacted in water vapor at 450-500 ℃ and 9-11 MPa.

Optionally, the thickness of the ceramic oxide layer is 3-7 μm.

In addition to the high temperature reaction, the ceramic oxide layer may be less constrained by the metal substrate, and the thickness of the ceramic oxide layer may also be less constrained by the metal substrate, i.e. defects such as holes or micro cracks may also be formed inside the ceramic oxide layer, or wavy undulations may be formed at the O/M interface.

Optionally, the method specifically includes the following steps:

1) reducing the surface roughness of zirconium or zirconium alloy needing oxidation treatment to below 0.05 μm;

2) putting the zirconium or zirconium alloy subjected to surface pretreatment in the step 1) into a reaction kettle, adding water or introducing water vapor, controlling the reaction temperature and pressure, and keeping the temperature and pressure until a ceramic oxide layer with the required thickness is formed;

3) and taking out the product after the reaction kettle is cooled or taking out the product to be cooled in the air.

Optionally, the pressure of the water vapor introduced in the step 2) is 9-11 MPa.

Optionally, the surface roughness is reduced to below 0.02 μm in step 1).

Optionally, the method for reducing the surface roughness in step 1) is selected from one or more of grinding, polishing, finishing and vibratory polishing.

Optionally, after said step 3), at least part of the surface of the zirconium or zirconium alloy is further polished to reduce the surface roughness to below 0.02 μm, preferably below 0.01 μm.

The invention also provides a medical implant which comprises a metal substrate and a surface oxidation layer, wherein the metal substrate is zirconium or zirconium alloy, and the surface ceramic oxidation layer is prepared by adopting the method for forming the oxidation layer on the surface of the zirconium or zirconium alloy.

The oxide layer formed here can be used to oxidize the metal substrate of the formed medical implant in a reaction kettle to form a ceramic layer, or the material surface of the metal substrate is oxidized to form a ceramic layer and then the ceramic layer is processed into the medical implant.

Optionally, the zirconium alloy is a zirconium alloy doped with a metallic element selected from niobium, titanium, molybdenum, iron, tin, copper or chromium, or a non-metallic element selected from oxygen, nitrogen, carbon or sulfur.

Optionally, the zirconium alloy is doped with niobium.

Optionally, the niobium content in the zirconium alloy is between 1 wt% and 20 wt%, preferably between 2.4 and 2.8 wt%.

Optionally, the medical implant is an implant in a shoulder, hip or knee joint having a region of relative sliding with other bearing surfaces.

The mechanism by which the ceramic oxide layer is likely to form microcracks or the O/M interface forms large wavy undulations in the oxidation treatment of zirconium and zirconium alloys has not been known, but the inventors of the present invention have found through diligent studies that this may be related to an excessively high oxidation temperature. The conventional oxidation methods for zirconium and zirconium alloys are carried out in an oxygen-containing atmosphere, including air, oxygen, ozone, etc., and the oxidation reaction is carried out at a high temperature, usually 550 ℃ or higher, in order to provide a sufficient driving force for the oxidation reaction. The inventors believe that this may lead to a reduction in the ability of the metal substrate to constrain the ceramic oxide layer as the reaction temperature increases, and thus the formation of the ceramic oxide layer is prone to the formation of defects such as microcracks. The inventor tries to adopt water or steam to oxidize zirconium and zirconium alloy at lower temperature, so that the metal substrate has higher strength during oxidation and stronger constraint capacity on the ceramic oxide layer, thereby obtaining the ceramic oxide layer with fewer internal defects and a straight O/M interface, further improving the quality of the ceramic oxide layer and improving the wear resistance of the medical implant of zirconium and zirconium alloy.

Drawings

FIG. 1 is a cross-sectional structural view of a medical implant according to an embodiment;

FIG. 2 is a metallographic cross-sectional photograph of the ceramic oxide layer of sample 1 described in example 1;

FIG. 3 is a metallographic cross-sectional photograph of the ceramic oxide layer of sample 2 described in example 1;

FIG. 4 is a scanning electron micrograph of a cross section of the ceramic oxide layer of sample 1 described in example 1;

FIG. 5 is a scanning electron micrograph of a cross section of the ceramic oxide layer of sample 2 described in example 1;

FIG. 6 is a ceramic oxide layer nanoindentation hardness curve for sample 1 described in example 1;

FIG. 7 is a ceramic oxide layer nanoindentation hardness curve for sample 2 described in example 1;

FIG. 8 is a metallographic cross-section of the ceramic oxide layer of sample 3 described in example 2;

FIG. 9 is a metallographic cross-section of the ceramic oxide layer of sample 4 as described in example 2;

FIG. 10 is a scanning electron micrograph of a cross section of the ceramic oxide layer of sample 3 described in example 2;

FIG. 11 is a scanning electron micrograph of a cross section of the ceramic oxide layer of sample 4 described in example 2;

FIG. 12 is a ceramic oxide layer nanoindentation hardness curve for sample 3 described in example 2;

FIG. 13 is a ceramic oxide layer nanoindentation hardness curve for sample 4 described in example 2;

FIG. 14 is a metallographic cross-section of the ceramic oxide layer of sample 5 described in example 3;

FIG. 15 is a metallographic cross-section of the ceramic oxide layer of sample 6 as described in example 3;

FIG. 16 is a scanning electron micrograph of a cross section of the ceramic oxide layer of sample 5 described in example 3;

FIG. 17 is a scanning electron micrograph of a cross section of the ceramic oxide layer of sample 6 described in example 3;

FIG. 18 is a ceramic oxide layer nanoindentation hardness curve for sample 5 described in example 3;

FIG. 19 is a ceramic oxide layer nanoindentation hardness curve for sample 6 described in example 3;

FIG. 20 is a metallographic photograph of the cross-section of the ceramic oxide layer of sample 7 described in example 4;

FIG. 21 is a scanning electron micrograph of a cross section of the ceramic oxide layer of sample 7 described in example 4.

Shown in the figure:

10-metal matrix, 20-ceramic oxide layer, 30-O/M interface.

Detailed Description

The method for forming the oxide layer on the surface of the medical implant comprises the following specific implementation steps:

(1) reducing the surface roughness of zirconium and zirconium alloy medical implants requiring an oxidation treatment to less than 0.05 μm, preferably less than 0.02 μm, by a method comprising grinding, polishing, finishing, vibratory polishing, and any combination thereof;

(2) cleaning and drying the medical zirconium and zirconium alloy implant with reduced surface roughness, placing the medical zirconium and zirconium alloy implant in a high-temperature high-pressure kettle, sealing the high-temperature high-pressure kettle, adding deionized water for oxidation, heating the temperature in the kettle to 400 ℃ of 300-; or introducing overpressure (9-11MPa) steam for oxidation, heating the temperature in the kettle to 450-500 ℃, and preserving the temperature in the steam environment of 9-11MPa for 1-7 days, preferably 3-5 days, so as to form a surface ceramic oxide layer with the thickness of 1-20 μm, preferably the thickness of 2-10 μm, more preferably the thickness of 3-7 μm on the zirconium and zirconium alloy;

(3) stopping heating, taking out the medical zirconium and zirconium alloy implant when the temperature in the high-temperature and high-pressure kettle is reduced to room temperature, or discharging high-temperature and high-pressure water or overpressure water vapor, directly taking out the medical zirconium and zirconium alloy implant and then cooling in the air;

(4) for areas needing relative sliding with other bearing surfaces, such as the outer femoral head surface of a hip joint, the inner surface of an acetabular cup, the surface of a femoral condyle of a knee joint and a tibial tray in relative motion, further polishing is needed until the surface roughness is lower than 0.02 μm, preferably lower than 0.01 μm; for areas that do not need to slide relative to other bearing surfaces, it can be used directly.

The metal substrate used for forming the surface ceramic oxide layer may be pure zirconium or a zirconium alloy, and the zirconium alloy may be a zirconium alloy doped with a metal element such as niobium, titanium, molybdenum, iron, tin, copper, chromium, etc., and a non-metal element such as oxygen, nitrogen, carbon, sulfur, etc., preferably a zirconium alloy with niobium as an alloying element, and more preferably a zirconium alloy with a niobium content of 1 wt% to 20 wt%.

As shown in fig. 1, the medical implant comprises a metal matrix 10 and a ceramic oxide layer 20, the interface of the ceramic oxide layer with the metal substrate being an O/M interface 30, preferably a load bearing implant with load bearing requirements in a hip or knee joint.

In the metallographic microscope photograph, the ceramic oxide layer 20 is darker and the metal base 10 is lighter.

For the convenience of understanding, the method for forming the oxide layer on the surface of the medical implant is described in the following examples, which are to be construed as merely illustrative and not limitative of the scope of the present invention.

The materials and reagents used in the examples are commercially available, unless otherwise specified, and the procedures and parameters of the methods may be carried out by conventional techniques, unless otherwise specified.

Example 1

Two sets of Zr — 2.5Nb alloys (zirconium alloys containing 2.5 wt% niobium) were ground and polished to have surface roughnesses Ra 0.0156 μm and Ra 0.0149 μm, respectively, as measured by a roughness meter, and the samples were designated as sample 1 and sample 2, respectively. And (3) putting the sample 1 and the sample 2 into alcohol, cleaning for 10 minutes by using an ultrasonic cleaning machine, then putting into deionized water, cleaning for 10 minutes by using the ultrasonic cleaning machine, taking out, and then putting into a drying oven for drying.

And (3) putting the sample 1 into a high-temperature high-pressure autoclave, introducing overpressure water vapor, treating under the conditions of 500 ℃ and 10.3MPa, stopping heating after 3 days, and taking out the sample after the temperature is reduced to room temperature.

And putting the sample 2 into a muffle furnace, heating to 600 ℃ in an air environment, preserving the heat for 80 minutes, slowly cooling to below 100 ℃ at a cooling speed of 5 ℃/min, and taking out.

The surface roughness of the sample was measured by a roughness meter, and the surface roughness Ra of sample 1 was 0.0265 μm and the surface roughness Ra of sample 2 was 0.0472 μm. The cross-sectional photograph of the ceramic oxide layer of sample 1 is shown in fig. 2 and the cross-sectional photograph of the ceramic oxide layer of sample 2 is shown in fig. 3, as observed by a metallographic microscope. By counting 5 metallographic photographs of random positions, as shown in fig. 2, the average thickness of the ceramic oxide layer 20 of the sample 1 is about 3.6 +/-0.2 μ M, the O/M interface of the sample 1 is relatively flat, and the thickness of the ceramic oxide layer at each position is uniform; as shown in fig. 3, the thickness of the ceramic oxide layer 20 of sample 2 is about 3.4 ± 0.3 μ M, and a part of the O/M interface thereof has large fluctuation, the thickness of the ceramic oxide layer 20 on the surface of sample 2 is more uneven, and the surface roughness of sample 2 is also larger than that of sample 1, so that sample 2 needs to consume more ceramic oxide layer than sample 1 to polish to the required roughness, and the thickness of the remaining ceramic oxide layer is uneven.

In order to observe the microcrack condition inside the ceramic oxide layers of the samples 1 and 2, the cross section of the ceramic oxide layer of the sample is observed under 10000 times of magnification in a backscattering electron mode by using a scanning electron microscope, and a photograph is taken at 10 positions randomly, as shown in fig. 4, the ceramic oxide layer of the sample 1 is compact; as shown in fig. 5, the oxide ceramic layer of sample 2 has many micro-cracks inside it as shown by arrows. The number of microcracks in 10 photos is counted, and the result shows that: the total number of microcracks of sample 1 is 20, and the total number of microcracks of sample 2 is 117, and it is obvious that the quality of the oxide ceramic layer of sample 1 is better, and oxide particles are not easy to be stripped due to microcrack expansion under long-term wear.

The hardness of the ceramic oxide layers of the sample 1 and the sample 2 is compared by a nano-indenter in a continuous rigidity measurement mode, the indentation depth is set to be 500 nanometers, the average hardness value corresponding to a 200-400 nanometer depth area is taken to represent the hardness value of the indentation point, the sample 1 and the sample 2 are respectively measured at 3 points, the average values are taken to compare, and the nano-indentation hardness curves of the sample 1 and the sample 2 are respectively shown in fig. 6 and fig. 7. The ceramic oxide layer of sample 1 had an average nanoindentation hardness of 13.8GPa, the ceramic oxide layer of sample 2 had an average nanoindentation hardness of 12.4GPa, and the ceramic oxide layer of sample 1 had a higher hardness value, which may be caused by fewer internal microcracks and the like in the ceramic oxide layer of sample 1 and a denser ceramic oxide layer.

By comparing the appearance, the number of microcracks and hardness values of the ceramic oxide layer of the sample obtained by the Zr-2.5Nb alloy under the conditions of 500 ℃ overpressure steam oxidation and 600 ℃ air oxidation, the novel high-temperature high-pressure autoclave oxidation process can obtain a better surface ceramic oxide layer under the condition of generating basically the same thickness of the ceramic oxide layer, so that the medical zirconium and zirconium alloy implant with more excellent performance can be prepared.

Example 2

Two Zr — 2.5Nb (Zr alloy containing 2.5 wt% Nb) alloys were ground and polished to obtain surface roughnesses Ra 0.0136 μm and Ra 0.0114 μm, respectively, and the measured surfaces were designated as sample 3 and sample 4, respectively. Putting the two samples into alcohol, cleaning for 10 minutes by using an ultrasonic cleaning machine, then putting the samples into deionized water, cleaning for 10 minutes by using the ultrasonic cleaning machine, taking the samples out, and drying the samples in a drying oven.

Putting the sample 3 into a high-temperature high-pressure kettle, adding deionized water with a certain water level, placing for 180 days in a high-temperature high-pressure environment of 360 ℃ and 18.6MPa, taking out after the temperature is reduced to room temperature, and measuring the surface roughness Ra of the sample to be 0.0284 mu m after the sample is taken out;

sample 4 was placed in air at 550 ℃ for 8 hours, cooled to room temperature at a cooling rate of 5 ℃/min, and then taken out, and the surface roughness Ra was measured to be 0.0492 μm.

The metallographic photographs of the cross sections of the ceramic oxide layers of the samples 3 and 4 are respectively shown in fig. 8 and 9, 5 metallographic photographs of random positions are counted, the thickness of the ceramic oxide layer 20 of the sample 3 is 6.8 +/-0.4 mu M, the thickness of the ceramic oxide layer 20 is uniform, and the O/M interface is very straight; the thickness of the ceramic oxide layer 20 of the sample 4 is 7.0 +/-0.6 μ M, the thickness of the ceramic oxide layer is not uniform at each position, the O/M interface has very obvious fluctuation, and a small part of the ceramic oxide layer is stripped on the surface of the sample.

And observing the cross section of the ceramic oxide layer of the sample in a backscattering electron mode under the magnification of 10000 times by using a scanning electron microscope, and randomly selecting 10 positions for shooting each sample. Fig. 10 is a typical photograph of the cross section of the ceramic oxide layer of the sample 3, fig. 11 is a typical photograph of the cross section of the ceramic oxide layer of the sample 4, the number of microcracks in 10 photographs is counted, the total number of microcracks in the sample 3 is 17, the total number of microcracks in the sample 4 is 122, the number of microcracks in the two photographs is greatly different, the number of microcracks in the ceramic oxide layer of the sample 3 is extremely small, the quality is obviously better, and microcracks with larger sizes exist in the ceramic oxide layer of the sample 4.

The hardness of the ceramic oxide layers of the samples 3 and 4 is compared by using a nano-indenter in a continuous rigidity measurement mode, the indentation depth is set to be 500 nanometers, the average hardness value corresponding to the 200-400 nanometer depth area is taken to represent the hardness value of the indentation point, the samples 3 and 4 are respectively measured for 3 points, the average values are taken to compare, and the nano-indentation hardness curves are respectively shown in fig. 12 and 13. The ceramic oxide layer of sample 3 had an average nanoindentation hardness of 13.2GPa, the ceramic oxide layer of sample 4 had an average nanoindentation hardness of 12.7GPa, and the ceramic oxide layer hardness value of sample 3 was relatively high.

By comparing the shapes, the micro-crack conditions and the nano-indentation hardness of the ceramic oxide layer of the sample of the Zr-2.5Nb alloy under the conditions of 360-DEG C high-temperature high-pressure water oxidation and 550-DEG C air oxidation, although the nano-indentation hardness values of the Zr-2.5Nb alloy are not different greatly, the ceramic oxide layer of the Zr-2.5Nb alloy oxidized by the 360-DEG C high-temperature high-pressure water has obviously fewer micro-cracks, and the ceramic oxide layer has a compact structure and uniform thickness, and is more suitable for medical implant products.

Example 3

Two E110 (Zr alloy containing 1 wt% Nb) alloys were ground and polished, and then surface roughness Ra 0.0141 μm and Ra 0.0129 μm were measured and designated as sample 5 and sample 6, respectively. And (3) putting the two samples into alcohol, cleaning for 10 minutes by using an ultrasonic cleaning machine, then putting the samples into deionized water, cleaning for 10 minutes by using the ultrasonic cleaning machine, taking the samples out, and drying the samples in a drying oven.

Putting the sample 5 into a high-temperature high-pressure kettle, adding deionized water with a certain water level, treating at 360 ℃ under the high-temperature high-pressure environment of 18.6Mpa, stopping heating after 180 days, and taking out after the temperature is reduced to room temperature;

and putting the sample 6 into a muffle furnace, heating to 550 ℃ in an air environment, preserving heat for 8 hours, slowly cooling to below 100 ℃ at a cooling speed of 5 ℃/min, and taking out.

The surface roughness Ra of sample 5 was measured to be 0.0373 μm, and the surface roughness Ra of sample 6 was measured to be 0.0602 μm. The cross-sectional photographs of the ceramic oxide layer of sample 5 and 6 are shown in fig. 14 and 15, respectively, by metallographic observation. By counting 5 metallographic photographs of random positions, the average thickness of the ceramic oxide layer 20 of the sample 5 is about 5.8 +/-0.3 mu M, the thickness of the ceramic oxide layer 20 of the sample 6 is about 5.6 +/-0.6 mu M, the O/M interface of the sample 5 is very flat, and the thickness of the ceramic oxide layer at each position is very uniform; the O/M interface of sample 6 shows obvious fluctuation, the thickness difference of the oxide ceramic layer at each position is large, and the phenomenon of oxide ceramic layer stripping exists in a small part of the surface of the sample.

And observing the cross section of the ceramic oxide layer of the sample in a backscattering electron mode under the magnification of 10000 times by using a scanning electron microscope, and randomly selecting 10 positions for shooting each sample. Fig. 16 is a typical photograph of the cross section of the oxide ceramic layer of the sample 5, fig. 17 is a typical photograph of the cross section of the oxide ceramic layer of the sample 6, the number of microcracks in 10 photographs is counted, the total number of microcracks in the sample 5 is 47, the total number of microcracks in the sample 6 is 225, and the difference between the numbers of microcracks in the two is significant. It should be noted that the scanning electron micrograph of sample 6 also shows that the ceramic oxide layer is slightly peeled off, so that the ceramic oxide layer of sample 5 has a significantly better quality.

The hardness of the ceramic oxide layers of the sample 5 and the sample 6 is compared by using a nano-indenter in a continuous rigidity measurement mode, the indentation depth is set to be 500 nanometers, the average hardness value corresponding to the 200-400 nanometer depth region is taken to represent the hardness value of the indentation point, the sample 5 and the sample 6 are respectively measured for 3 points, the average values are taken to compare, and the nano-indentation hardness curves are respectively shown in fig. 18 and fig. 19. The ceramic oxide layer of sample 5 had an average nanoindentation hardness of 15.1GPa, the ceramic oxide layer of sample 6 had an average nanoindentation hardness of 13.7GPa, and the ceramic oxide layer of sample 5 had a significantly higher hardness.

By comparing the appearance, microcrack condition and nanoindentation hardness of the ceramic oxide layer of the sample of the E110 alloy under the conditions of 360-DEG C high-temperature and high-pressure water oxidation and 550-DEG C air oxidation, the method shows that the ceramic oxide layer with higher quality than that obtained by the traditional oxidation method can be obtained on the surface of zirconium and zirconium alloy under the treatment of a novel high-temperature and high-pressure autoclave oxidation process, and the surface performance of the medical implant of zirconium and zirconium alloy is further improved.

Example 4

After the E110 (Zr alloy containing 1 wt% Nb) alloy was ground and polished, the surface roughness was measured to Ra 0.0101 μm, which was designated as sample 7, and sample 7 was put into alcohol and washed with an ultrasonic washer for 10 minutes, then put into deionized water and washed with an ultrasonic washer for 10 minutes, and after taking out, it was put into a drying oven to be dried.

And (3) putting the dried sample 7 into a high-temperature high-pressure kettle, introducing overpressure water vapor, oxidizing for 11 days at 500 ℃ in a 11MPa water vapor environment, stopping heating, naturally cooling, taking out, and measuring that the surface roughness is increased to 0.01124 micrometers.

A metallographic photograph of the cross section of the ceramic oxide layer of the sample 7 is taken, and it is found that a large amount of ceramic oxide layers are peeled off in the sample preparation process of the ceramic oxide layer of the sample 7, and the metallographic photograph of the cross section of the relatively complete one ceramic oxide layer is shown in FIG. 20, wherein the thickness of the ceramic oxide layer is about 12.7 +/-0.6 μ M, and the O/M interface is in a black thick line shape, which indicates that the ceramic oxide layer and the metal substrate are not continuous and integral any more, and the ceramic oxide layer is prone to being peeled off.

When the cross section of the ceramic oxide layer of sample 7 is observed in a scanning electron microscope at 10000 times magnification in a back-scattered electron mode and a scanning electron microscope photograph (fig. 21) is taken, it is surprisingly found that there are very many large-sized micro cracks inside the ceramic oxide layer of sample 7, the ceramic oxide layer on the surface layer is completely peeled off, and the thickness of the ceramic oxide layer 20 is measured to be about 12.7 ± 0.6 μm.

The inventors of the present invention speculate that the peeling of the ceramic oxide layer in sample 7 is caused by the fact that the internal stress increases with the increase of the thickness of the ceramic oxide layer, and exceeds the constraint capacity of the metal substrate, so that a large number of microcracks with larger sizes appear in the ceramic oxide layer. In the process of preparing the cross section sample, the microcracks are expanded under the action of stress, and when the microcracks are expanded to a certain degree, the ceramic oxide layer is stripped.

Finally, it should be noted that: the above examples are only for illustrating the technical solutions of the present invention, and are not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: it is to be understood that modifications may be made to the technical solutions described in the foregoing embodiments, or some or all of the technical features may be equivalently replaced, and such modifications or replacements may not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for forming an oxide layer on the surface of zirconium or zirconium alloy is characterized in that under the conditions of 300-500 ℃ and 9-20MPa, zirconium or zirconium alloy reacts with water or water vapor to form a ceramic oxide layer with the thickness of 2-10 mu m on the surface of a metal substrate.

2. The method as claimed in claim 1, wherein the zirconium or zirconium alloy is reacted in water at 400 ℃ and 15-20MPa at 300 ℃.

3. The method as claimed in claim 1, wherein the zirconium or zirconium alloy is reacted in water vapor at 450-500 ℃ and 9-11 MPa.

4. The method for forming an oxide layer on the surface of zirconium or zirconium alloy according to claim 1, wherein the thickness of the ceramic oxide layer is 3 to 7 μm.

5. The method for forming the oxide layer on the surface of the zirconium or zirconium alloy according to claim 1, which comprises the following steps:

6. The method for forming an oxide layer on the surface of zirconium or zirconium alloy according to claim 5, wherein the surface roughness in step 1) is reduced to 0.02 μm or less.

7. The method for forming an oxide layer on the surface of zirconium or zirconium alloy according to claim 5, wherein the method for reducing the surface roughness in step 1) is one or more selected from grinding, polishing, finishing and vibration polishing.

8. The method for forming an oxide layer on the surface of zirconium or zirconium alloy as claimed in claim 5, wherein after the step 3), at least part of the surface of zirconium or zirconium alloy is further polished to reduce the surface roughness to below 0.02 μm.

9. A medical implant comprising a metal substrate and a surface oxide layer, wherein the metal substrate is zirconium or zirconium alloy, and the surface ceramic oxide layer is prepared by the method for forming the oxide layer on the surface of the zirconium or zirconium alloy according to any one of claims 1 to 8.

10. The medical implant according to claim 9, wherein the zirconium alloy is a zirconium alloy doped with a metallic element selected from niobium, titanium, molybdenum, iron, tin, copper or chromium or a non-metallic element selected from oxygen, nitrogen, carbon or sulfur.

11. The medical implant of claim 10, wherein the zirconium alloy is doped with niobium.

12. The medical implant of claim 9, wherein the medical implant is an implant in a shoulder, hip or knee joint having regions of relative sliding with other bearing surfaces.