CN111826603B

CN111826603B - Method for preparing ceramic oxide layer on surface of metal substrate and application

Info

Publication number: CN111826603B
Application number: CN202010705896.9A
Authority: CN
Inventors: 俞天白; 姚夏睿
Original assignee: Suzhou Microport Orthorecon Co Ltd
Current assignee: Suzhou Microport Orthorecon Co Ltd
Priority date: 2020-07-21
Filing date: 2020-07-21
Publication date: 2022-09-30
Anticipated expiration: 2040-07-21
Also published as: CN111826603A; WO2022017240A1

Abstract

The invention relates to a method for preparing a metal substrate surface ceramic oxide layer and application thereof, wherein the method comprises the following steps: heating the metal substrate to a predetermined temperature under an inert atmosphere and then stopping heating; introducing mixed gas to oxidize the metal substrate while cooling the metal substrate to form a ceramic oxide layer on the surface of the metal substrate; the mixed gas comprises oxygen and inert gas, and the content of the oxygen in the mixed gas is increased along with the reduction of the temperature. The method is used for forming the ceramic oxide layer on the surface of the metal substrate, so that internal stress generated by the metal substrate can be reduced, the bearing capacity of the metal substrate to the internal stress is improved, the release of the internal stress is reduced, defects generated by the ceramic oxide layer can be reduced, and the quality of the ceramic oxide layer is improved.

Description

Method for preparing ceramic oxide layer on surface of metal substrate and application

Technical Field

The invention relates to the technical field of medical implant materials, in particular to a method for preparing a ceramic oxide layer on the surface of a metal substrate and application thereof.

Background

Compared with ceramic materials, when the metal material is used as a base material of a medical implant, the metal material has good strength and plasticity and is not easy to break, and when the metal material is applied to parts needing to bear larger load, such as hip joints, knee joints and the like, the metal base material has more remarkable advantages. However, the metal material also has a certain weakness, and specifically, the metal material has a low surface hardness and is easily scratched by third party particles, and the metal material has a high surface roughness, which results in a large sliding surface friction coefficient and poor wear resistance. Therefore, preparing a ceramic layer on the surface of the metal material is an effective way to obtain a high wear-resistant surface and to avoid the risk of chipping.

One conventional method for forming a ceramic layer on the surface of a metal material is to add a layer of hard wear-resistant material on the surface of the metal material, for example, a titanium nitride ceramic layer is prepared on the surface of a cobalt-chromium-molybdenum alloy by a physical vapor deposition technology. However, this ceramic layer has a problem of poor bonding with a metal material, and when used as a key sliding surface such as a hip joint or a knee joint, there is a risk that the ceramic layer is peeled off due to long-term friction, and the hardness of the peeled ceramic particles is very high, and if the peeling occurs, the abrasion is further accelerated. Another conventional method for forming a ceramic layer on the surface of a metal material is to directly convert the surface of the metal material into a ceramic layer by oxidation or nitridation. In the method, the ceramic layer and the metal material are combined through chemical bonds, so that the ceramic layer has extremely high bonding strength and can be effectively prevented from being peeled. However, very high reaction temperatures are generally required for forming nitrides, which causes changes in the texture and mechanical properties of the metal material and dimensional changes of the product, and thus, in practical applications, oxidation treatment is generally used to form the ceramic layer.

When zirconium or zirconium alloy is used as a metal substrate to generate a ceramic oxide layer, the formed ceramic oxide layer has the advantages of small volume expansion rate, small internal compressive stress, thickness of more than 10 mu m, compact internal structure, few defects and the like, so that the zirconium or zirconium alloy becomes a medical implant metal material with high use frequency. In the prior art, a typical method for forming a ceramic oxide layer on the surface of zirconium or zirconium alloy is to heat a metal substrate to a certain temperature in an oxygen-containing atmosphere, and cool the metal substrate to normal temperature after holding the temperature for several hours. However, in practice, it has been found that the zirconia or zirconia alloy surface ceramic oxide layer produced in this way can be subject to oxide particle separation during prolonged rubbing, and in particular oxide particle separation on the sliding surface further increases wear. Therefore, it is desirable to develop a new method for preparing a zirconia or zirconium alloy surface ceramic oxide layer to overcome the above-mentioned drawbacks.

Disclosure of Invention

The invention aims to provide a method for preparing a ceramic oxide layer on the surface of a metal substrate and application thereof, so as to overcome the defects.

In order to achieve the above object, the present invention provides a method for preparing a ceramic oxide layer on a surface of a metal substrate, wherein the metal substrate is zirconium or a zirconium alloy, comprising the steps of:

heating the metal substrate to a predetermined temperature under an inert atmosphere and then stopping heating;

introducing mixed gas for oxidation treatment while cooling the metal substrate to form a ceramic oxide layer on the surface of the metal substrate; the mixed gas comprises oxygen and inert gas, and the content of the oxygen in the mixed gas is increased along with the reduction of the temperature.

Alternatively, the content of oxygen in the mixed gas is increased in a gradient manner as the temperature of the oxidation treatment is lowered.

Optionally, the content of oxygen in the mixed gas increases in volume percentage with a gradient of rate of change from 5%/100 ℃ to 20%/100 ℃.

Optionally, the rate of introducing the mixed gas is 50/min to 1000 ml/min.

Optionally, the initial content of oxygen in the mixed gas is 0-20% and the final content of oxygen in the mixed gas is 20-100% by volume percentage.

Optionally, the predetermined temperature is 500-700 ℃, the cooling rate is 5-15 ℃/min, and the end point temperature of cooling is not higher than 150 ℃.

Optionally, before heating the metal substrate, the method further comprises: and carrying out roughness reduction treatment on an oxidation treatment target area on the surface of the metal substrate so as to reduce the surface roughness of the oxidation treatment target area to be less than 0.05 um.

Optionally, after the oxidizing treatment, further comprising: and carrying out treatment for reducing the surface roughness on the prepared ceramic oxide layer.

Optionally, after the oxidation treatment, the surface roughness of the prepared ceramic oxide layer is reduced to 0.02um or less.

In order to achieve the above object, the present invention also provides a material for a medical implant, comprising a metal substrate and a ceramic oxide layer formed by a method of preparing a ceramic oxide layer on the surface of the metal substrate as described in any one of the above.

In order to achieve the above object, the present invention further provides a medical implant, which is made of the material for medical implant as described above.

Compared with the prior art, the method for preparing the ceramic oxide layer on the surface of the metal substrate and the application thereof have the following advantages:

the method for preparing the ceramic oxide layer on the surface of the metal substrate comprises the following steps: heating the metal substrate to a predetermined temperature under an inert atmosphere and then stopping heating; cooling the metal substrate, and introducing mixed gas to oxidize the metal substrate so as to form a ceramic oxide layer on the surface of the metal substrate; the mixed gas comprises oxygen and mixed gas, and the content of the oxygen in the mixed gas increases along with the decrease of the temperature. The metal substrate is zirconium or a zirconium alloy. Therefore, the oxidation process and the cooling process are simultaneously carried out in the same direction, so that the accumulation of thermal stress and oxidative expansion stress in the heating process is avoided, the volume shrinkage in the cooling process is utilized to offset partial volume expansion caused by oxidation reaction, and the total internal stress of the ceramic oxide layer is reduced. The temperature of the metal substrate close to the surface can be reduced by instant cooling, so that the strength is improved, the constraint capacity on a surface oxide layer is enhanced, the bearing capacity of the metal substrate and the oxide ceramic layer on internal stress is improved, the defect caused by the release of the internal stress is reduced, and the generation of a compact oxide ceramic layer with small surface roughness is facilitated. The content of oxygen in the mixed gas rises along with the reduction of the oxidation treatment temperature, and the oxidation reaction can be continuously and uniformly generated through the reasonable matching of the reaction temperature and the oxygen content, thereby being beneficial to generating a ceramic oxide layer with less defects, high quality and enough thickness.

Drawings

The drawings are included to provide a better understanding of the invention and are not to be construed as unduly limiting the invention. Wherein:

FIG. 1 is a flow chart of a method for producing a ceramic oxide layer on a surface of a metal substrate according to one embodiment of the present invention;

FIG. 2 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 1 according to a first embodiment of the present invention, wherein the magnification is 3000 times;

FIG. 3 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 1 according to a first embodiment of the present invention, wherein the magnification is 10000 times;

FIG. 4 is a graphical representation of nano-indentation hardness curves of the ceramic oxide layer of sample 1 provided in accordance with one embodiment of the present invention;

FIG. 5 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 2 provided in example two of the present invention, wherein the magnification is 3000 times;

FIG. 6 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 2 provided in example two of the present invention, wherein the magnification is 10000 times;

FIG. 7 is a graphical representation of the nano-indentation hardness curve of the ceramic oxide layer of sample 2 provided in accordance with example two of the present invention;

FIG. 8 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 3 provided in a third example of the present invention, showing a magnification of 3000;

FIG. 9 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 4 provided in example four of the present invention, showing a magnification of 3000;

FIG. 10 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 5 provided in comparative example of the present invention, showing a magnification of 3000 times;

FIG. 11 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 5 provided in comparative example of the present invention, showing a magnification of 10000 times;

FIG. 12 is a graphical representation of the nano-indentation hardness curve of the ceramic oxide layer of sample 5 provided by comparative example of the present invention;

FIG. 13 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 6 provided in example five of the present invention, wherein the magnification is 4000 times;

FIG. 14 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 6 provided in example five of the present invention, wherein the magnification is 10000 times;

FIG. 15 is a graphical representation of the nano-indentation hardness curve of the ceramic oxide layer of sample 6 provided in example five of the present invention;

FIG. 16 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 7 provided by comparative example of the present invention, showing a magnification of 4000 times;

FIG. 17 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 7 provided by comparative example of the present invention, showing a magnification of 10000 times;

FIG. 18 is a graphical representation of the nano-indentation hardness curve of the ceramic oxide layer of sample 7 provided by comparative example of the present invention;

FIG. 19 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 8 according to comparative example of the present invention, shown at a magnification of 10000 times;

FIG. 20 is a scanning electron micrograph of a cross section of a ceramic oxide layer of sample 9 provided by comparative example four of the present invention, showing the magnification of 4000 times.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.

Furthermore, each of the embodiments described below has one or more technical features, and thus, the use of the technical features of any one embodiment does not necessarily mean that all of the technical features of any one embodiment are implemented at the same time or that only some or all of the technical features of different embodiments are implemented separately. In other words, those skilled in the art can selectively implement some or all of the features of any embodiment or combinations of some or all of the features of multiple embodiments according to the disclosure of the present invention and according to design specifications or implementation requirements, thereby increasing the flexibility in implementing the invention.

The inventors have intensively studied and found that the phenomenon that oxide particles are peeled off during long-term friction of a zirconia or zirconium alloy surface ceramic oxide layer is caused by pores or microcracks generated inside the ceramic oxide layer, thereby weakening the bondability of the ceramic oxide layer itself. The inventor finds out through further research that the generation of the holes or the microcracks is caused by the fact that the heating oxidation process is carried out from outside to inside, the zirconium atoms on the surface expand in volume after being oxidized to generate internal stress, and the internal stress is further increased in the temperature reduction process after the oxidation is finished. The large internal stress not only generates pores or microcracks inside the ceramic oxide layer when released, but also forms wave-like undulations at the interface (O/M interface) between the ceramic oxide layer and the metal substrate.

Specifically, on one hand, during heating, a zirconia layer is formed on the surface of zirconium or zirconium alloy, so that the overall thermal expansion of zirconium or zirconium alloy is limited, and the internal thermal stress is increased. And in the temperature rising process, the strength of the zirconium or zirconium alloy is reduced along with the temperature rising, namely the constraint capacity of the metal substrate to the zirconium or zirconium alloy ceramic oxide layer is weakened along with the temperature rising, and when the internal stress accumulated in the zirconium or zirconium alloy exceeds the constraint capacity of the zirconium or zirconium alloy to the ceramic oxide layer, the internal stress is released to form holes and microcracks in the ceramic oxide layer or form wavy fluctuation on the interface (O/M interface) between the ceramic oxide layer and the metal substrate. On the other hand, in the cooling process after the oxidation is finished, the internal temperature of the zirconium or zirconium alloy is high, the oxidation diffusion is still carried out, the surface of the ceramic oxide layer shrinks due to cooling, the thermal stress generated by cooling is amplified, and when the thermal stress is released, pores and microcracks are further formed in the ceramic oxide layer, or the wavy fluctuation at the O/M interface is intensified. The occurrence of pores or microcracks weakens the bonding property of the oxide ceramic layer itself, reduces the wear resistance of the oxide ceramic layer, and causes the oxide particles to peel off during long-term friction. The wavy fluctuation formed at the O/M interface can increase the roughness of the surface of the ceramic oxide layer, the ceramic oxide layer with larger thickness needs to be removed in the using process to meet the using requirement of the medical implant, and the thickness of the residual ceramic oxide layer after polishing is not uniform at each part, so that the thickness of the ceramic oxide layer protruding to the outer surface is too thin. For medical implants to be implanted into the human body, there is a great risk of both oxide particles peeling off and the oxide ceramic layer having too thin a thickness.

In view of the above, the core idea of the present invention is to provide a method for preparing a ceramic oxide layer on the surface of a metal substrate, wherein the metal substrate is zirconium or zirconium alloy. The method can reduce the internal stress generated on the surface of the metal substrate in the forming process of forming the oxide ceramic layer, and can also reduce the release of the internal stress, thereby achieving the purpose of improving the quality of the oxide ceramic layer. The method for preparing the ceramic oxide layer on the surface of the metal substrate comprises the following steps: the heating is stopped after the metal substrate is heated to a predetermined temperature under an inert atmosphere. And cooling the metal substrate, and introducing mixed gas to oxidize the metal substrate so as to form a ceramic oxide layer on the surface of the metal substrate. The mixed gas is formed by mixing oxygen and inert gas, and the content of the oxygen in the mixed gas is increased along with the reduction of the temperature.

According to the method for preparing the ceramic oxide layer on the surface of the metal substrate, oxidation treatment is carried out in the cooling process to form the ceramic oxide layer, so that on one hand, accumulation of thermal stress and internal stress generated by oxidation expansion in the heating process is avoided, and on the other hand, volume contraction of the metal substrate in the cooling process can partially offset volume expansion generated by oxidation, and the total stress of the ceramic oxide layer is reduced. Further, the temperature of the metal substrate close to the surface can be reduced by instant cooling, the strength of the metal substrate is improved, the constraint force on the oxide ceramic layer is enhanced, the bearing capacity on internal stress is enhanced, the release of the internal stress is reduced, and further the defects of forming holes and microcracks in the oxide ceramic layer or forming wavy fluctuation on an O/M interface and the like are reduced. Furthermore, in the temperature reduction process, the content of oxygen in the mixed gas rises along with the reduction of the temperature, and the insufficient oxygen diffusion power caused by the temperature reduction is compensated through the increase of the content of the oxygen, so that the oxidation reaction can be continuously and uniformly carried out, and the ceramic oxide layer with enough and uniform thickness is obtained.

The invention also provides a material for a medical implant, the material comprising a metal substrate and a ceramic oxide layer, the ceramic oxide layer being formed by the method of preparing a metal-based ceramic oxide layer as described above.

The invention also provides a medical implant which is made of the material of the medical implant.

To further clarify the objects, advantages and features of the present invention, a more particular description of the invention will be rendered by reference to the appended drawings.

Fig. 1 shows a flow chart of a method for preparing a ceramic oxide layer on a surface of a metal substrate according to a preferred embodiment of the present invention. As shown in fig. 1, the method for preparing the ceramic oxide layer on the surface of the metal substrate comprises the following steps:

step S11: the heating is stopped after the metal substrate is heated to a predetermined temperature under an inert atmosphere.

Step S12: and cooling the metal substrate, and introducing mixed gas to oxidize the metal substrate to form a ceramic oxide layer on the surface of the metal substrate, namely, performing oxidation treatment while cooling the metal substrate. The mixed gas comprises oxygen and inert gas, and the content of the oxygen in the mixed gas is increased along with the reduction of the temperature.

Wherein the metal substrate comprises zirconium or a zirconium alloy. The zirconium alloy may be a zirconium alloy doped with at least one metal element of niobium, titanium, molybdenum, iron, tin, copper, or chromium, and at least one non-metal element of oxygen, nitrogen, carbon, or sulfur. Preferably, the zirconium alloy is a zirconium niobium alloy, more preferably a zirconium niobium alloy with a niobium content of 1 to 20 wt.%. The inert gas (inert atmosphere) refers to a gas environment that does not chemically react with the metal substrate, and specifically may be helium, neon, argon, or the like. The predetermined temperature in step S11 is 500 ℃ to 700 ℃. In the step S12, the cooling rate of the metal substrate is 5 ℃/min to 15 ℃/min, the end point temperature of the cooling is from room temperature to 150 ℃, and the room temperature is determined according to the environment temperature when the ceramic oxide layer on the surface of the metal substrate is actually prepared, and is generally 20 ℃ to 30 ℃.

In step S12, the content of oxygen in the mixed gas preferably increases in a gradient manner as the temperature decreases. Preferably, the content of oxygen in the mixed gas increases in a gradient of 5%/100 ℃ to 20%/100 ℃ in percentage by volume (i.e., the content of oxygen in the mixed gas increases by 5% to 20% for every 100 ℃ decrease in temperature). Optionally, the initial content of oxygen in the mixed gas is 0-20%, preferably 5-15%, more preferably 8-12%. The end-point content of oxygen (i.e. the content of oxygen in the mixed gas at the end-point temperature of the drop in temperature) reaches 20% to 100%, preferably 50 to 90%, more preferably 60 to 80%, corresponding to the rate of change of oxygen. In addition, the rate of introducing the mixed gas is 50ml/min to 1000 ml/min. When the initial content of oxygen and the final content of oxygen are within the above preferred ranges, the thickness of the resulting ceramic oxide layer is within the preferred range (3-7um), and has less defects and higher denseness.

Further, with continued reference to fig. 1, before performing step S11, the method further includes step S10: the surface roughness of the oxidation treatment target region of the metal base surface is reduced to 0.05um or less, preferably 0.02um or less by performing a treatment for reducing the roughness. The oxidation treatment target area refers to a part directly contacted with other bearing surfaces. In this embodiment, the method of reducing the surface roughness of the oxidation treatment target region includes at least one of grinding, polishing, finishing, and vibratory polishing.

Referring further to fig. 1, the method further includes step S13: the prepared ceramic oxide layer is subjected to a roughness-reducing treatment to reduce the surface roughness of the ceramic oxide layer to 0.02um or less, preferably to 0.01um or less. The aim of this is that after the ceramic oxide layer is formed on the surface of the metal substrate by the method, the remanufactured medical implant can slide relative to other bearing surfaces, for example, the outer femoral head surface of a hip joint, the inner acetabular cup surface, the surface of a knee joint where the femoral condyle moves relative to the tibial tray, and the like. Of course, if the medical implant does not need to slide relative to other bearing surfaces, the step S13 can be omitted.

The method for preparing the surface ceramic oxide layer of the metal substrate and the advantages thereof will be described with reference to the following specific examples and comparative examples.

Example one

The metal substrate is a zirconium niobium alloy with a niobium content of 2.5 wt%.

The zirconium niobium alloy was ground and polished to obtain sample 1, and the surface roughness Ra of sample 1 was 0.0101 um. And (3) placing the sample 1 in alcohol for ultrasonic cleaning for 10min, then performing ultrasonic cleaning in deionized water for 10min, taking out and drying.

And (3) placing the dried sample 1 in an atmosphere furnace, introducing argon, heating to 700 ℃, and stopping heating.

A mixed gas of argon and oxygen was introduced into the atmosphere furnace, and the temperature in the atmosphere furnace was controlled to be decreased at a rate of 10 ℃/min until the temperature in the atmosphere furnace was decreased to room temperature (about 25 ℃), and sample 1 was taken out and measured for surface roughness Ra of 0.0232 um. In this example, the flow rate of the mixed gas introduced into the atmosphere furnace was 500 ml/min. The initial content of oxygen in the mixed gas is 10% by volume, the change rate of the oxygen content is 10%/100 ℃, and when the temperature in the atmosphere furnace is reduced to the room temperature, the oxygen content in the mixed gas reaches 70%.

A scanning electron microscope is used for shooting the topography of the cross section of the ceramic oxide layer of the sample 1, fig. 2 is a topography of the cross section of the ceramic oxide layer enlarged by 3000 times in a back scattering electron mode, and fig. 3 is a topography of the cross section of the ceramic oxide layer enlarged by 10000 times in the back scattering electron mode.

As shown in fig. 2, the gray layer in the graph is the ceramic oxide layer, and in the scanning electron micrograph of the statistical sample 1 in the backscattered electron mode at five random positions, the average thickness of the ceramic oxide layer is about 5.7 ± 0.3 um. As shown in fig. 3, the number of microcracks in the sem image of ten randomly located backscattered electron patterns of sample 1 was counted to be 21.

The hardness of the ceramic oxide layer of the sample 1 is tested by adopting a nano-indenter under continuous rigidity, the indentation depth is 500nm, and the hardness value of an indentation point is represented by taking the average hardness value corresponding to the depth region of 200nm-400 nm. Three indentation points were measured in this example, and the hardness curves of the three indentation points are shown in fig. 4. The average hardness of the three indentation points was taken as the hardness of the ceramic oxide layer of sample 1, and the value was 15.1 GPa.

The method for preparing the ceramic oxide layer on the surface of the metal substrate is utilized to form the ceramic oxide layer on the surface of the zirconium-niobium alloy, and the ceramic oxide layer has few microcracks, compact structure, uniform thickness and high hardness, so that the method for preparing the ceramic oxide layer on the surface of the metal substrate can be applied to the surface oxidation requirements of zirconium and zirconium alloy.

Example two

The metal substrate was a zirconium niobium alloy with a niobium content of 2.5 wt.%.

The zirconium niobium alloy was ground and polished to obtain sample 2, and the surface roughness Ra of sample 2 was 0.0136 um. And (3) placing the sample 2 in alcohol for ultrasonic cleaning for 10min, then performing ultrasonic cleaning in deionized water for 10min, taking out and drying.

And (3) placing the dried sample 2 in an atmosphere furnace, introducing argon, heating to 700 ℃, and stopping heating.

And introducing mixed gas of argon and oxygen into the atmosphere furnace, controlling the temperature in the atmosphere furnace to reduce the temperature at the speed of 5 ℃/min until the temperature in the atmosphere furnace is reduced to 150 ℃, and taking out the sample 2. After the sample was cooled to room temperature, the surface roughness Ra was measured to be 0.0310 um. In this example, the flow rate of the mixed gas introduced into the atmosphere furnace was 1000 ml/min. The initial content of oxygen in the mixed gas is 20% by volume, the change rate of the oxygen content is 20%/100 ℃, and when the temperature in the atmosphere furnace is reduced to 150 ℃, the oxygen content in the mixed gas reaches 100%.

A scanning electron microscope is used for shooting the topography of the cross section of the ceramic oxide layer of the sample 2, fig. 5 is a topography of the cross section of the ceramic oxide layer enlarged by 3000 times in a back scattering electron mode, and fig. 6 is a topography of the cross section of the ceramic oxide layer enlarged by 10000 times in the back scattering electron mode.

As shown in fig. 5, the gray layer in the graph is the ceramic oxide layer, and in the scanning electron micrograph of the statistical sample 2 in the backscattered electron mode at five random positions, the average thickness of the ceramic oxide layer is about 8.9 ± 0.3 um. In FIG. 5, the interface between white and light gray is the O/M interface, which is relatively flat and uniform in thickness. As shown in fig. 6, the number of microcracks in the sem image in the backscattered electron mode of ten random positions of sample 2 was counted to be 17.

The hardness of the ceramic oxide layer of sample 2 was measured with a nanoindenter at continuous stiffness with an indentation depth of 500nm, and the hardness value of the indentation point was expressed as the average hardness value corresponding to the 200nm-400nm depth zone. Three indentation points were measured in this example, and the hardness curves of the three indentation points are shown in fig. 7. The average hardness of the three indentation points was taken as the hardness of the ceramic oxide layer of sample 1, and the value was 13.2 GPa.

EXAMPLE III

The zirconium niobium alloy was ground and polished to obtain sample 3, and the surface roughness Ra of sample 3 was 0.0157 um. And (3) placing the sample 3 in alcohol for ultrasonic cleaning for 10min, then performing ultrasonic cleaning in deionized water for 10min, taking out and drying.

And (3) placing the dried sample 3 in an atmosphere furnace, introducing argon, heating to 600 ℃, and stopping heating.

Introducing a mixed gas of argon and oxygen into the atmosphere furnace, controlling the temperature in the atmosphere furnace to reduce the temperature at a speed of 10 ℃/min until the temperature in the atmosphere furnace is reduced to room temperature (about 25 ℃), taking out a sample 3, and measuring the surface roughness Ra of the sample 3 to be 0.0304 um. In this example, the flow rate of the mixed gas introduced into the atmosphere furnace was 500 ml/min. The initial content of oxygen in the mixed gas is 5% by volume, the change rate of the oxygen content is 10%/100 ℃, and when the temperature in the atmosphere furnace is reduced to the room temperature, the oxygen content in the mixed gas reaches 50%.

The shape of the cross section of the ceramic oxide layer of the sample 3 is photographed by a scanning electron microscope, fig. 8 is a shape of the cross section of the ceramic oxide layer enlarged 3000 times in a back-scattered electron mode, a gray layer in the figure is the ceramic oxide layer, and the average thickness of the ceramic oxide layer is about 3.1 +/-0.1 um in a scanning electron microscope picture in the back-scattered electron mode of five random positions of the sample 3. The number of microcracks in the SEM image in the backscattered electron mode for ten random positions of sample 3 was counted to be 13.

Example four

The zirconium niobium alloy was ground and polished to obtain sample 4, and the surface roughness Ra of sample 4 was 0.0113 um. And (3) placing the sample 4 in alcohol for ultrasonic cleaning for 10min, then performing ultrasonic cleaning in deionized water for 10min, taking out and drying.

And (3) placing the dried sample 4 in an atmosphere furnace, introducing argon, heating to 700 ℃, and stopping heating.

The mixed gas of argon and oxygen was introduced into the atmosphere furnace, and the temperature in the atmosphere furnace was controlled to be lowered at a rate of 10 ℃/min until the temperature in the atmosphere furnace was lowered to room temperature (about 25 ℃), and sample 4 was taken out and measured for surface roughness Ra of 0.0226 um. In this example, the flow rate of the mixed gas introduced into the atmosphere furnace was 500 ml/min. The initial content of oxygen in the mixed gas is 15% by volume, the rate of change of the oxygen content is 10%/100 ℃, and when the temperature in the atmosphere furnace is reduced to room temperature, the oxygen content in the mixed gas reaches 90%.

The shape of the cross section of the ceramic oxide layer of the sample 4 is photographed by a scanning electron microscope, fig. 9 is a shape of the cross section of the ceramic oxide layer enlarged 3000 times in a back-scattered electron mode, a gray layer in the figure is the ceramic oxide layer, and the average thickness of the ceramic oxide layer is about 7.2 +/-0.2 um in a scanning electron microscope picture in the back-scattered electron mode of five random positions of the sample 4. The number of microcracks in the sem image in the backscattered electron mode for ten random positions of sample 4 was counted to be 23.

Comparative example 1

The metal substrate was ground and polished to obtain sample 5, and the surface roughness Ra of sample 5 was 0.0114 um. And (3) placing the sample 5 in alcohol for ultrasonic cleaning for 10min, then ultrasonic cleaning in deionized water for 10min, taking out and drying.

Forming a ceramic oxide layer on the surface of a metal substrate by adopting the prior art: and (3) placing the dried sample 5 in a muffle furnace, heating to 700 ℃ in an air atmosphere, and preserving heat for 2 h. Then, the temperature was decreased to 150 ℃ at a rate of 5 ℃/min, the sample 5 was taken out, cooled to room temperature in the air, and the surface roughness Ra of the sample 5 was measured to be 0.0492 um.

Scanning electron microscopy is adopted to shoot the topography of the cross section of the ceramic oxide layer of the sample 5, fig. 10 is a topography of the cross section of the ceramic oxide layer enlarged 3000 times in a back scattering electron mode, and fig. 11 is a topography of the cross section of the ceramic oxide layer enlarged 10000 times in the back scattering electron mode.

As shown in fig. 10, in the scanning electron micrographs of five random positions of the statistical sample 5, the average thickness of the ceramic oxide layer is about 9.9 ± 0.5 um. In sample 5, the O/M interface had large undulations in a partial region, the thickness of the ceramic oxide layer was not uniform, and the ceramic oxide layer was partially peeled off from the surface of sample 5. As shown in fig. 11, the number of microcracks in the scanning electron micrograph of ten random positions of the statistical sample 5 is 122.

Sample 5 had a lower surface roughness before the oxidation treatment and a higher roughness after the formation of the oxide ceramic layer compared to sample 2, resulting in sample 5 requiring more of the oxide ceramic layer to be worn to polish to the desired roughness, resulting in a more non-uniform thickness of the remaining oxide ceramic layer. The number of microcracks in the ceramic oxide layer of sample 5 is much greater than the number of microcracks in the ceramic oxide layer of sample 2.

And (3) measuring the hardness of the ceramic oxide layer of the sample 5 by adopting a nano-indenter, wherein the indentation depth is 500nm, and the average hardness value corresponding to the depth region of 200nm-400nm is taken as the hardness value of the indentation point. Three indentation points were selected on sample 5, and the hardness curves for the three indentation points are shown in fig. 12. The average nano indentation hardness of three indentation points is 12.7 GPa. The hardness value is lower than that of the surface ceramic oxide layer of sample 2.

Comparing sample 5 with sample 2, it is found that the method for preparing the metal substrate surface ceramic oxide layer provided by the invention has lower surface roughness, better compactness and higher hardness of the obtained ceramic oxide layer compared with the prior art.

EXAMPLE five

The zirconium niobium alloy was ground and polished to obtain sample 6, and the surface roughness Ra of sample 6 was 0.0156 um. And (3) placing the sample 6 in alcohol for ultrasonic cleaning for 10min, then performing ultrasonic cleaning in deionized water for 10min, taking out and drying.

And (3) placing the dried sample 6 in an atmosphere furnace, introducing argon, heating to 500 ℃, and stopping heating.

And introducing mixed gas of argon and oxygen into the atmosphere furnace, and controlling the temperature in the atmosphere furnace to reduce at a speed of 15 ℃/min until the temperature in the atmosphere furnace is reduced to room temperature. Sample 6 was taken out and its surface roughness Ra was measured to be 0.0265 um. In this example, the flow rate of the mixed gas introduced into the atmosphere furnace was 50 ml/min. The initial content of oxygen in the mixed gas is 0 percent by volume, the change rate of the oxygen content is 5 percent/100 ℃, and when the temperature in the atmosphere furnace is reduced to the room temperature, the oxygen content in the mixed gas reaches 25 percent.

A scanning electron microscope is used to photograph the topography of the cross section of the ceramic oxide layer of sample 6, fig. 13 is a topography of the cross section of the ceramic oxide layer enlarged 4000 times in the back-scattered electron mode, and fig. 14 is a topography of the cross section of the ceramic oxide layer enlarged 10000 times in the back-scattered electron mode.

As shown in fig. 13, the gray layer in the graph is a ceramic oxide layer, and in the scanning electron micrograph of five random positions of the statistical sample 6, the average thickness of the ceramic oxide layer is about 2.1 ± 0.2 um. In FIG. 14, the interface between white and light gray is the O/M interface, which is relatively flat and uniform in thickness. As shown in fig. 14, the ceramic oxide layer of sample 6 is dense, and the number of microcracks in the sem image of ten random positions of sample 6 in the backscattered electron mode is counted to be 20.

The hardness of the ceramic oxide layer of the sample 6 is tested by adopting a nano-indenter under continuous rigidity, the indentation depth is 500nm, and the hardness value of an indentation point is represented by taking the average hardness value corresponding to the depth area of 100nm-200 nm. Three indentation points were measured in this example, and the hardness curves of the three indentation points are shown in fig. 15. The average hardness of the three indentation points was taken to be the hardness of the ceramic oxide layer of sample 6, which was 15.8 GPa.

Comparative example No. two

The zirconium niobium alloy was ground and polished to obtain sample 7, and the surface roughness Ra of sample 7 was 0.0149 um. And (3) placing the sample 7 in alcohol for ultrasonic cleaning for 10min, then performing ultrasonic cleaning in deionized water for 10min, taking out and drying.

And (3) placing the dried sample 7 in a muffle furnace, heating to 500 ℃ in an air atmosphere, keeping the temperature for 30min, taking out, and cooling to room temperature, wherein the cooling rate in the cooling process is 15 ℃/min. The surface roughness Ra of sample 7 was measured to be 0.0472 um.

A scanning electron microscope is used to photograph the topography of the cross section of the ceramic oxide layer of sample 7, fig. 16 is a topography of the cross section of the ceramic oxide layer enlarged 4000 times in the back-scattered electron mode, and fig. 17 is a topography of the cross section of the ceramic oxide layer enlarged 10000 times in the back-scattered electron mode.

As shown in fig. 16, the gray layer in the graph is the ceramic oxide layer, and the average thickness of the ceramic oxide layer in the scanning electron micrograph of the statistical sample 7 in the backscattered electron mode at five random positions is about 2.9 ± 0.4 um. The white and light gray interface is the O/M interface, the O/M interface has fluctuation in the partial area, and the thickness of the ceramic oxide layer on the surface of the sample 7 is not uniform. As shown in fig. 17, the ceramic oxide layer has many micro cracks indicated by arrows, and the number of micro cracks in 10 photographs was counted, which indicates that the number of micro cracks in the ceramic oxide layer of sample 7 was about 117.

The hardness of the ceramic oxide layer of the sample 7 is tested by adopting a nano-indenter under continuous rigidity, the indentation depth is 500nm, and the hardness value of an indentation point is represented by taking the average hardness value corresponding to the depth area of 100nm-200 nm. Three indentation points were measured in this example, and the hardness curves of the three indentation points are shown in fig. 18. The average hardness of the three indentation points was taken to be the hardness of the ceramic oxide layer of sample 7, which was 12.4 GPa.

Comparing the ceramic oxide layer of sample 7 with the ceramic oxide layer of sample 6, the ceramic oxide layer of sample 6 is clearly more dense than the ceramic oxide layer of sample 7. The hardness of the ceramic oxide layer of sample 6 is higher than that of the ceramic oxide layer of sample 7, and may be caused by less defects such as microcracks in the ceramic oxide layer of sample 6 and better compactness. Comparing the fifth example with the second comparative example, it can be seen that the surface ceramic oxide layer prepared by the method for preparing the surface ceramic oxide layer of the metal substrate provided by the invention can obtain a ceramic oxide layer with better compactness and higher hardness compared with the prior art.

Comparative example No. three

The metal substrate was polished to obtain sample 8, and the surface roughness Ra of sample 8 was 0.0141 um. And (3) placing the sample 8 in alcohol for ultrasonic cleaning for 10min, then placing in deionized water for ultrasonic cleaning for 10min, taking out and drying.

And (3) placing the dried sample 8 in an atmosphere furnace, heating to 600 ℃ in an argon atmosphere, introducing mixed gas of argon and oxygen, simultaneously controlling the temperature in the atmosphere furnace to be reduced to 100 ℃ at a speed of 10 ℃/min, taking out the sample 8, cooling the sample 8 to room temperature in the air, and measuring the surface roughness Ra of the sample 8 which is 0.0746 um. In the comparative example, the flow rate of the mixed gas introduced into the atmosphere furnace was 500ml/min, and the oxygen content in the mixed gas was kept constant at 70% throughout the cooling process.

The cross-sectional topography of the ceramic oxide layer of sample 8 was taken using a scanning electron microscope and is shown in fig. 19. Scanning electron micrographs of random positions of five samples 8 are counted, and the average thickness of the ceramic oxide layer of the sample 8 is about 15.4 +/-0.5 um. The appearance of the ceramic oxide layer of the sample 8 at ten random positions is selected, and the ceramic oxide layer of the sample 8 is found to be broken in a large area, a large number of micro cracks exist inside the ceramic oxide layer, and the quality of the ceramic oxide layer is poor. The reason for this may be that a constant oxygen concentration is adopted in the oxidation process, and the oxygen concentration is too high, which results in too severe oxidation reaction, rapid expansion of the volume of the metal substrate, and the stress cannot be released slowly, but only released through the form of micro-cracks, etc., thereby causing the ceramic oxide layer to crack.

Comparative example No. four

The metal substrate was ground and polished to obtain sample 9, and the surface roughness Ra of sample 9 was 0.0129 um. And (3) placing the sample 9 in alcohol for ultrasonic cleaning for 10min, then placing the sample in deionized water for ultrasonic cleaning for 10min, taking out and drying.

And (3) placing the dried sample 9 into an atmosphere furnace, heating to 600 ℃ in an argon atmosphere, introducing mixed gas of argon and oxygen, simultaneously controlling the temperature in the atmosphere furnace to be reduced to 100 ℃ at a speed of 10 ℃/min, taking out the sample 9, cooling the sample 9 to room temperature in the air, and measuring the surface roughness Ra of the sample to be 0.0170 um. In the comparative example, the flow rate of the mixed gas introduced into the atmosphere furnace was 500ml/min, and the oxygen content in the mixed gas was kept constant at 10% throughout the cooling process.

The cross-sectional topography of the ceramic oxide layer of sample 9 was photographed using a scanning electron microscope and is shown in fig. 20. Scanning electron micrographs of random positions of five samples 9 are counted, and the average thickness of the ceramic oxide layer of the sample 9 is about 0.6um +/-0.5 um. The reason why the thickness of the ceramic oxide layer obtained in this comparative example was too thin is probably because the oxygen concentration was kept constant and low during the oxidation treatment, and the diffusion kinetics of oxygen during the oxidation reaction was insufficient as the temperature in the atmospheric furnace was lowered, so that a ceramic oxide layer having a sufficient thickness could not be formed.

In the method for preparing the oxide ceramic layer on the surface of the metal substrate provided by the present invention, the oxidation treatment is performed during the temperature reduction process, and the oxygen concentration is increased along with the temperature reduction, so that the insufficient power of oxygen beam expansion caused by the temperature reduction is compensated in time by gradually increasing the oxygen concentration, thereby generating the oxide ceramic layer having few defects, high hardness and sufficient thickness.

Further, the embodiment of the invention also provides a material for a medical implant, which comprises a metal substrate and a ceramic oxide layer, wherein the ceramic oxide layer is formed by the method for preparing the ceramic oxide layer on the surface of the metal substrate.

Still further, the embodiment of the invention also provides a medical implant which is made of the material for the medical implant. Such as hip joints, acetabular cups, femoral condyles of knee joints, etc.

The embodiment of the invention provides a method for preparing a ceramic oxide layer on the surface of a metal substrate, which comprises the following steps: heating the metal substrate to a target temperature under an inert atmosphere and then stopping heating; introducing mixed gas, and carrying out oxidation treatment on the metal substrate while reducing the temperature so as to form a ceramic oxide layer on the surface of the metal substrate. In the method, temperature reduction and oxidation treatment are carried out simultaneously, volume expansion caused by oxidation is compensated by volume contraction during temperature reduction, and the internal stress of the metal substrate is reduced. In the oxidation process, the temperature of the metal substrate close to the surface is reduced, the strength of the metal substrate is improved, the bearing capacity of the metal substrate to internal stress is enhanced, the stress release is reduced, and further the defects generated in the oxide ceramic layer are reduced. The content of oxygen in the mixed gas rises along with the reduction of the temperature, so that the oxidation reaction can be continuously and uniformly carried out, and a ceramic oxide layer with enough thickness, uniform thickness and good compactness can be obtained.

Although the present invention is disclosed above, it is not limited thereto. Various modifications and alterations of this invention may be made by those skilled in the art without departing from the spirit and scope of this invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A method for preparing a ceramic oxide layer on the surface of a metal substrate, wherein the metal substrate is zirconium or zirconium alloy, and the method is characterized by comprising the following steps:

2. The method for preparing a ceramic oxide layer on the surface of a metal substrate according to claim 1, wherein the content of oxygen in the mixed gas is increased in a gradient manner as the temperature of the oxidation treatment is lowered.

3. The method of claim 2, wherein the oxygen content in the mixed gas increases in a gradient of a rate of change of 5%/100 ℃ to 20%/100 ℃ in percentage by volume.

4. The method for preparing the ceramic oxide layer on the surface of the metal substrate according to claim 1, wherein the mixed gas is introduced at a rate of 50ml/min to 1000 ml/min.

5. The method for preparing the ceramic oxide layer on the surface of the metal substrate according to any one of claims 1 to 4, wherein the initial content of oxygen in the mixed gas is 0 to 20% and the final content of oxygen in the mixed gas is 20 to 100% in percentage by volume.

6. The method for preparing the ceramic oxide layer on the surface of the metal substrate according to any one of claims 1 to 4, wherein the predetermined temperature is 500 ℃ to 700 ℃, the temperature reduction rate is 5 ℃/min to 15 ℃/min, and the temperature reduction end point is not higher than 150 ℃.

7. The method for preparing the ceramic oxide layer on the surface of the metal substrate according to claim 1, further comprising, before heating the metal substrate: and carrying out roughness reduction treatment on an oxidation treatment target area on the surface of the metal substrate so as to reduce the surface roughness of the oxidation treatment target area to be less than 0.05 um.

8. The method for preparing the ceramic oxide layer on the surface of the metal substrate according to claim 7, further comprising, after the oxidizing treatment: and carrying out treatment for reducing the surface roughness on the prepared ceramic oxide layer.

9. The method for preparing a ceramic oxide layer on the surface of a metal substrate according to claim 8, wherein the surface roughness of the prepared ceramic oxide layer is reduced to 0.02um or less after the oxidation treatment.

10. The method of claim 1, wherein the zirconium alloy is a zirconium niobium alloy.

11. A material for a medical implant, comprising a metal substrate and a ceramic oxide layer formed by the method of preparing a metal substrate surface ceramic oxide layer according to any one of claims 1 to 10.

12. A medical implant made of the material for a medical implant according to claim 11.