JPH04200557A - Implant material for living body - Google Patents

Abstract

PURPOSE:To obtain the novel implant material for living bodies by having a surface layer consisting of a nitrogen diffused and hardened layer which exists in the lower layer section, in contact with a surface reforming layer essentially consisting of titanium nitrite, and is formed by diffusing and solutionizing nitrogen atoms into a titanium base material on the surface of a base material consisting of titanium or titanium alloy. CONSTITUTION:The surface layer 4 consisting of the surface reforming layer 2 essentially consisting of the titanium nitrite and the nitrogen diffused and hardened layer 3 which exists in the lower layer part in contact with the surface reforming layer 2 and is diffused and solutionized with the nitrogen atoms so as to have the gradient compsn., i.e., to have the high nitrogen concn. right under the surface reforming layer 2 on the front surface side, to have the low nitrogen concn. (nearly the same as the concn. in the base material), in the part in contact with the base material at the end point of the nitrogen diffused layer on the base material side, and to have the nitrogen concn. changing continuously between these parts is formed on the surface of the titanium material 1. The thickness of this surface layer 4 is 0.3 to 100mum, more preferably 0.3 to 30mum.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to biomedical implant materials.

More specifically, the present invention relates to a biomedical implant material that has excellent biocompatibility and can exhibit stable performance over a long period of time.

(Prior art) Titanium or titanium alloy (hereinafter referred to as titanium material)
It has strength comparable to steel materials, exhibits better corrosion resistance than stainless steel, and has a specific gravity that is approximately 1/2 that of steel.
Because of its small size, it is a lightweight and strong material with excellent specific strength. Furthermore, titanium's biocompatibility is unique and not found in other metals. That is, body tissues and fluids have a strong effect on titanium, while titanium also has only a small effect on tissues and, unlike other metals, may cause inflammation, hypersensitivity, It does not cause allergies or tissue rejection reactions (and it also rarely causes coagulation reactions when it comes into contact with blood. This kind of biocompatibility is not limited to pure titanium; for example, T 1
A similar phenomenon is observed in titanium alloys such as -6AΩ-4Va, and is also applied clinically.

For this reason, in recent years, such titanium has been used as a hard tissue substitute such as artificial bones, artificial joints, and artificial tooth roots, and as an implant material for living organisms such as artificial organs such as cardiac pacemaker housings and artificial heart valves. It is proposed that.

The biocompatibility described above is found not only in pure titanium, but also in titanium alloys such as T1-6AΩ-4Va, and is also applied clinically.

However, while titanium materials have the above-mentioned characteristics such as excellent biocompatibility, strength, corrosion resistance, and lightness,
Because the surface hardness is not sufficient, the surface is easily damaged and has poor abrasion resistance. Therefore, the service life of biomedical implant materials made of titanium material is shortened, and the wear particles cause damage to the surface. This caused problems.

In order to deal with the problem of surface hardness of biological implant materials made of titanium materials, various surface modification methods have been attempted. Surface modification technology for titanium materials applies already developed CVD and PVD methods to modify titanium nitride (T i N), titanium carbide (TiC), titanium boride (T i B), or these materials. By applying a thin film of a composite material such as a titanium compound to the surface (for example, JP-A-62-122669), or by applying a catalytic reaction using a reactive gas, etc., it is possible to harden nitrogen, carbon, oxygen, boron, etc. Titanium nitride, titanium carbide, titanium boride, -titanium oxide (T
i O) or a composite compound of these, such as titanium carbonitride (TiCN), to form a thin stable titanium compound layer, and at the same time inject hardening elements such as nitrogen, carbon, oxygen, and boron into the titanium matrix from the surface toward the inside. There is a known technology for diffusing and solid-dissolving.

However, in surface modification in which a titanium compound is directly deposited on the surface of a titanium material, adhesion during use may be insufficient due to extremely large discontinuities in the physical properties of the material at the boundary between the base material and the coating. .

For this reason, under harsh conditions of use as an implant material, there is a risk that the coating may peel off as a result of uneven microscopic strain distribution occurring over many years of use.

Furthermore, in surface modification in which a stable compound layer is formed by applying a catalytic reaction, it is necessary to carry out the reaction and diffusion at a relatively high temperature. In other words, the surface of titanium is covered with a protective oxide film, and the reaction temperature for proceeding with the contact reaction is as high as possible, since reactivity is poor at low temperatures, and the processing time becomes long, reducing productivity. It is hoped that For example, in a direct reaction with nitrogen gas, the preferred heating temperature for the reaction has conventionally been 850°C or higher. Note that the upper limit of the heating temperature has been set at 1050° C. from the viewpoint of maintenance and management of the heating furnace, operating energy cost, etc. Therefore, in this surface modification treatment, the titanium base material is also heated to high temperatures, and at this time, the titanium base material is exposed to the risk of contamination and deterioration due to high temperature heating, and the internal metal structure is damaged due to heating. This results in changes such as changes and coarsening of crystal grains. Such thermal history, including changes in the microscopic metal structure and α=β transformation of titanium, affects the material quality of the titanium base material, causing problems such as deterioration of mechanical properties such as strength and toughness. was there.

By the way, the hardness of a stable compound of titanium and the above hardening elements is micro-Vickers hardness (Hv) or 2000
~3000, which is extremely hard compared to the hardness of titanium materials, which has a hardness of 100 to 400, and the crystal shapes and other physical properties are also completely different.

However, as a living body implant material, it is not necessary to have a hardness of Hv 2000 to 3000, which is extremely hard, but Hv 70, which is the level of tempered special steel.
There are many cases in which a value of about 0 to 1000 is sufficient, and in such cases, it is desirable to have a stable surface modification layer and less deterioration of the properties of the titanium material that is the base material. was.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a novel implant material for living bodies. The present invention also provides excellent surface properties such as surface hardness, abrasion resistance, biocompatibility, and ion elution properties, and does not reduce the mechanical properties of the titanium-based base material, especially the toughness. The purpose is to provide the following.

(Means for solving the problems) The above-mentioned features include a surface-modified layer mainly made of titanium nitride and a lower layer located in contact with the surface-modified layer on the surface of a base material made of titanium or a titanium alloy. This is achieved by a biomedical implant material that suppresses ion elution and has a surface layer consisting of a nitrogen diffusion hardened layer in which nitrogen atoms are diffused and dissolved in a titanium base material with an average thickness of 0.3 to 100 μm. Ru.

(Function) As described above, the biomedical implant material of the present invention has a surface-modified layer mainly composed of titanium nitride on the surface and a lower layer in contact with the surface-modified layer, in which nitrogen atoms are tilted to the titanium base material. It is composed of a titanium material having a surface layer consisting of a nitrogen diffusion hardened layer which is diffused and solid-dissolved according to the composition.

Titanium nitride, which exists at a nitrogen concentration of 12.75% and below 1100°C, is extremely stable in the chemical environment of various aqueous solutions, just like titanium nitride, and is generally more stable than untreated titanium materials. Shows good corrosion resistance. Its hardness is micro Vickers hardness (Hv) 1400.
~1500 and extremely hard. In fact, the hardness of the surface film mainly composed of titanium nitride in the biological implant material according to the present invention varies depending on finer differences in processing conditions such as processing temperature and holding time, so there is a wide range of measured values. , HV is about 800 to 1500. This hardness is HvlOO which is the hardness of titanium material without any treatment.
It is much larger than ~400 and has a hardness comparable to or even higher than that of special steel that has been subjected to heat treatment such as quenching, and is considered to be sufficient as a surface hardness for biological implant materials. It will be done.

In addition, in the biological implant material of the present invention, the composition of the interface between the titanium base material and the surface modified layer changes continuously as a nitrogen diffusion hardened layer, so the adhesion of the surface layer to the base material is In good condition.

Furthermore, the surface layer consisting of a surface modification layer mainly composed of titanium nitride and a nitrogen diffusion layer can be created by heating and holding the titanium material at approximately 740 to 820°C in a high purity nitrogen gas atmosphere. can be formed. As is well known, titanium (pure titanium) undergoes a phase transformation of α=β at 880°C, and in the β phase region of the metal structure, rapid crystal grain growth occurs and the crystal grains become coarse. It is known that coarse grains retained in the β-phase region form coarse acicular crystals during the cooling process, which deteriorates material properties related to toughness in mechanical properties. Further, the α=β phase transformation temperature of a titanium alloy changes depending on the alloy composition, that is, the types of compounded elements and their compounded amounts.゛Here, α-stable elements such as oxygen and nitrogen shift the α-β phase transformation temperature to the high temperature side, but most metal elements are β-stable elements, and the combination of metal elements such as iron, cobalt, and nickel Therefore, the α=β phase transformation temperature shifts to the lower temperature side. In practical titanium alloys, in order to adjust the α=β phase transformation temperature, α-stable elements and β-stable elements are simultaneously blended to adjust the transformation temperature. In order to suppress the deterioration of material properties related to toughness while adding thermal history to titanium materials, it is important not only to heat above the transformation temperature, but also to choose a temperature as low as possible even just below the transformation temperature. be. Since the surface layer of the biological implant material of the present invention is formed in a relatively low temperature region as described above, the inherent toughness of the titanium material is ensured in the biological implant material of the present invention. becomes.

The titanium material used as the base material in the biological implant material of the present invention is not particularly limited as long as it is physiologically safe. Various β-type titanium alloys may be used, specifically, for example, T 1-6Aρ-4V or T 1-6AΩ- with 0.13% or less of oxygen and 0.25% or less of iron.
Preferably, alloys such as 4V ELI are used.

Therefore, in the biological implant material of the present invention, as schematically shown in FIG.
A surface modified layer 2 containing titanium nitride as a main component and a surface modified layer 2 located at a lower layer in contact with the surface modified layer 2 with a gradient composition of nitrogen atoms in the titanium base material, that is, a surface modified layer 2 on the surface side. The nitrogen concentration is high immediately below the base metal, and the nitrogen concentration at the end point of the nitrogen diffusion layer 3 on the base metal side, which is in contact with the base metal, is low (almost the same as the base metal), and during this time, the nitrogen concentration changes continuously. A surface layer 4 is formed of a nitrogen diffusion hardened layer 3 which has been diffused and dissolved into solid solution.

The thickness of this surface layer 4 is preferably 0.3 to 100 μm1. It is 3 to 30 μm. That is, if the thickness of the surface layer 4 is less than 0.3 μm, sufficient surface modification of the titanium material may not be achieved, and the desired surface hardness 1, abrasion resistance, ion elution properties, etc. may not be obtained. On the other hand, even if the thickness of the surface layer 4 is greater than 100 μm, the surface modification effect is substantially the same as in the case of a thickness of 100 μm or less, and it takes a very long time to manufacture. This is not only economically disadvantageous, but also because there is a risk that the physical properties of the titanium base material may deteriorate if the titanium base material is exposed to heating conditions for a long period of time. The thickness of the surface modified layer 2 of this surface layer 4 depends on the thickness of the surface layer 4, but is about 0.3 to 0.8 μm, and the remaining part is the nitrogen diffusion hardened layer. It is 3.

The surface modified layer 2 contains titanium nitride (T 1
2N), the presence of titanium nitride (T i N) is observed, or the amount of titanium nitride present is extremely small.

In addition, in the biomedical implant material of the present invention, since the surface roughness of the surface modified layer 2 is affected by the crystalline pulverized coal of the base material, it is possible to adjust the crystal grain size of the base material to 10 to 80 μm. It is thought that the surface roughness obtained by this treatment is preferable from the viewpoint of biocompatibility, and the biocompatibility of the biological implant material is improved.

In addition, in the nitrogen diffusion hardened layer 3, the concentration of nitrogen atoms dissolved and diffused into the titanium base material decreases as the distance from the surface modified layer 2 increases, that is, it is inversely proportional to the depth. Since the composition changes continuously from the surface modified layer 2 to the nitrogen diffusion hardened layer 3 to reach the titanium base material, there is extremely little risk that the surface layer 4 will separate from the base material even under severe conditions.

In order to obtain the biological implant material of the present invention, first, a molded product made of titanium or titanium alloy as described above is produced by any forming method such as powder sintering, casting, or forging, and precision molding is performed as necessary. It is processed into the desired shape, and then cleaned if necessary. Subsequently, the titanium material molded into the desired shape is heated at 740°C to 820°C, more preferably 750 to 800°C, and even more preferably 77°C in a nitrogen gas atmosphere.
A surface layer as described above is formed on the surface of the molded product by heating and maintaining the molded product at a temperature in the range of 0°C to 790°C. Note that if the treatment temperature in this nitrogen gas atmosphere is less than 740°C, the reaction between titanium and nitrogen will not proceed sufficiently, and the surface hardness of the titanium material will not improve even if it is maintained for a long time. 82
When the temperature exceeds 0°C, titanium nitride (T) forms on the surface of the titanium material.
A modified layer containing a large amount of (N) is now formed,
Sufficient surface hardness can be obtained even with short-time treatment, but on the other hand, heating in this temperature range coarsens the microscopic metal structure of the titanium material, impairing properties such as mechanical strength and toughness. Therefore, the implant material intended by the present invention cannot be obtained.

Further, in this surface modification treatment of titanium H, the nitrogen gas atmosphere during the reaction needs to be of high purity so as not to contaminate the titanium material. Furthermore, the pressure of the nitrogen gas atmosphere is 5 to 760 Torr.

More preferably, it is about 76 to 760 Torr.

Furthermore, in such a method for surface modification of titanium materials, the heating holding time depends on the treatment temperature, but
30 hours, more preferably 4 to 16 hours considering productivity
It is said to be about an hour. If the heat treatment temperature is the same,
The thickness and content of the surface-modified layer mainly composed of titanium nitride depends on the holding time, and the longer the holding time, the thicker it becomes (
Become.

Next, some reference data will be shown to specifically explain the characteristics of the biological implant material of the present invention.

Reference example 1 and reference example 2 Made of titanium (industrial pure titanium) with a thickness of 1 mm.

A plate-shaped sample with a length of 15 mm and a width of 10 nm (Reference Example 1) and a plate-shaped sample of the same shape made of titanium alloy (Ti-6Aρ-4V) (Reference Example 2) were placed in a vacuum furnace, and then heated under high vacuum ( 10-5 Torr or less), the sample of Reference Example 1 was heated to 750°C, and the sample of Reference Example 2 was heated to 800°C, and the temperature was 0°C.
The temperature was increased at a rate of 1/min. When the temperature inside the furnace reaches the desired temperature, while keeping it constant at this temperature, the atmosphere inside the furnace is replaced with high-purity nitrogen gas to make the nitrogen gas pressure 760 Torr, and the sample of Reference Example 1 is heated for 25 hours. Sample No. 2 was heated and held for 9 hours, and then cooled to 500°C at a cooling rate of about 20°C/min.
After that, it was furnace cooled (naturally cooled).

The surface composition of the plate-shaped sample subjected to surface modification treatment in this manner was investigated by X-ray diffraction. The results obtained are shown in FIG. X-ray diffraction was performed using a monochromator.
This was done using K line.

α In FIG. 2, the horizontal axis shows the diffraction angle when the characteristic line of copper is used as the X-ray diffraction condition, and the vertical axis shows the relative concentration of the diffraction line from each crystal plane. Figure 2(a)
is the diffraction pattern obtained from the pure titanium sample of Reference Example 1,
FIG. 2(b) is a diffraction pattern obtained from the titanium alloy sample of Reference Example 2, and FIG. 2(C) to (e) are the diffraction patterns of T i 2 of standard composition for providing evaluation guidelines, respectively.
X-ray diffraction patterns of N%TiN and titanium (α-Ti).

As is clear from Figure 2, in both the diffraction patterns of Reference Example U and Reference Example 2, the main substance present is T.
In the L 2 N phase, overlapping diffraction lines from TiN and α-Ti are observed, but both are weak.

In addition, in surface modification treatment that utilizes the reaction between titanium material and nitrogen gas, increasing the heating temperature makes it easier to generate a TiN phase, and the ionic crystal structure unique to the TiN phase becomes clear in the X-ray diffraction pattern. In the treatment at 1050°C, the main component becomes a TiN phase. On the other hand, if the heating and holding temperature is lowered, almost no reaction between the titanium material and nitrogen gas will occur, so when processing at 700°C, the total amount of titanium nitride generated on the surface of the titanium material is small, so X-ray In the diffraction pattern, the diffraction lines from the TiN phase and the T 12 N phase are weak, nitriding is insufficient, and the surface hardness is insufficient.

Reference Examples 3 to 5 and Comparative Examples 1 to 2 Made of titanium (industrial pure titanium), thickness 1 mm, length 1
A plate-shaped sample with a size of 5 mm and a width of 10 mm and a titanium alloy (T
Platy samples of the same shape (Reference Example 2) consisting of 1-6Aρ-4V) were placed in a vacuum furnace, and then placed in a high vacuum (10-4V).
While evacuation was maintained to maintain a temperature of 750° C. for pure titanium samples (Reference Example 3), and 700° C. for titanium alloy samples (Comparative Example 1),
750°C (Reference Example 4), 800°C (Reference Example 5), 85
The temperature was increased to 0°C (Comparative Example 2) at a rate of about 0°C/min.

When the temperature inside the furnace reaches the desired temperature, while keeping it constant at this temperature, the atmosphere inside the furnace is replaced with high-purity nitrogen gas to bring the nitrogen gas pressure to 760 Torr, heated and maintained for 1 to 16 hours, and then heated to 500°C. It was cooled at a temperature decreasing rate of about 0° C./min until then, and then it was cooled in a furnace.

The surface hardness of the plate sample subjected to the surface modification treatment in this manner was measured using a micro Vickers hardness meter. The results obtained are shown in FIG.

In Figure 3, the vertical axis is micro Vickers hardness (Hv)
, and the horizontal axis indicates the heating holding time.

As is clear from the results shown in Figure 3, the surface hardness increases as the heating holding temperature increases and as the heating holding time increases. Sufficient hardness could not be obtained due to insufficient reaction between the steel and nitrogen gas. On the other hand, when the treatment temperature was 750°C or higher (Reference Examples 3 to 5 and Comparative Example 2), the hardness was approximately Hv800 to 1500, which was comparable to or higher than the hardness of tempered special steel. .

Reference Examples 6 to 7 and Comparative Example 3 A smaller plate-like tensile test piece (total length is 45 mm, and the width and length of the parallel part are 4 mm x 12 mm) is cut out from a 1 mm thick plate of titanium (industrial pure titanium). , this specimen was placed in a vacuum furnace and placed under high vacuum (10-5 Torr).
The temperature was increased at a rate of approximately 0°C/min to 750°C (Reference Example 6), 800°C (Reference Example 7), and 850°C (Comparative Example 3) while evacuation was maintained to maintain . When the temperature inside the furnace reaches the desired temperature, while keeping it constant at this temperature, replace the atmosphere inside the furnace with high-purity nitrogen gas to bring the nitrogen gas pressure to 760 Torr, keep it heated for 1 to 16 hours, and then Approximately 0℃ up to 500℃/
The temperature was lowered at a temperature drop rate of 100 min, and then the furnace was cooled.

The tensile strength, elongation, and fracture mode of the test pieces subjected to surface modification treatment in this manner were observed.

FIG. 4 is a diagram showing tensile test data of a pure titanium test piece subjected to the above-mentioned surface modification treatment. In FIG. 4, the vertical axis represents elongation and tensile strength, and the horizontal axis represents heating holding time.

As is clear from the results shown in FIG. 4, the tensile strength is about 32 to 34 kgf/mm2 in all cases, and tends to increase as the heating temperature increases and the holding time increases. On the other hand, elongation has a tendency opposite to that of tensile strength, at 750°C (Reference Example 6) and 800°C (Reference Example 7).
The material treated at 850°C showed almost the same properties as the untreated material, and the toughness of the base material was maintained, but the material treated at 850°C (Comparative Example 3) showed a remarkable elongation value as the heating holding time became longer. descend.

Furthermore, according to observation of the fracture surface after fracture, in the specimen treated at 850°C (Comparative Example 3), necking was not observed at the fracture part, indicating a brittle fracture mode, and the parallel part of the tensile test piece had a tensile axis. Many cracks in the direction perpendicular to the surface were observed.

In addition, in the case of titanium alloy (Ti-6AN-4V), almost the same tendency as in the case of pure titanium is observed, and 75
Those treated at 0℃ and 800℃ showed almost the same tensile strength and elongation as the untreated ones, and the toughness of the base material was maintained, but the fracture mode of the one treated at 850℃ was brittle. The elongation value also decreases.

Reference examples 8 and 9 5 mm thick made of titanium (industrial pure titanium).

A disk-shaped sample with a diameter of 30 mm (Reference Example 8) and a disk-shaped sample of the same shape (Reference Example 9) made of titanium alloy (T i -6A, Q 4V) were placed in a vacuum furnace, and then heated under high vacuum ( The temperature was increased to 750° C. at a rate of about 0° C./min while evacuation was maintained at a temperature of 10 −5 Torr or less. When the temperature inside the furnace reached 750℃, while keeping it constant at this temperature, the atmosphere inside the furnace was replaced with high-purity nitrogen gas to bring the nitrogen gas pressure to 760 Torr, and the temperature was kept heated for 9 hours. Approximately 0℃/
The sample was cooled at a temperature decreasing rate of 10 minutes, and then furnace-cooled.

The change in hardness from the surface to the inside of the cut surface of the sample subjected to surface modification treatment was investigated using a micro Vickers hardness meter. The results obtained are shown in FIG.

In FIG. 5, the vertical axis represents the micro-Vickers hardness, and the horizontal axis represents the distance (μm) from the surface.

As shown in Figure 5, in the surface-modified pure titanium material (Reference Example 8), hardening was observed up to about 30 μm from the surface, which was thought to be due to solid solution diffusion of nitrogen atoms, and the hardness of the base material The hardness gradually decreases from the surface toward Hv of about 170. On the other hand, in the surface-modified titanium alloy material (Reference Example 9), hardening is observed up to about 10 μm from the surface, which appears to be due to solid solution diffusion of nitrogen atoms. In either material, the hardness transition is continuous, and the adhesion between the hardened surface layer and the base material is good.

Reference Examples 10-11 and Comparative Examples 4-5 Titanium (industrial pure titanium) powder and titanium alloy (Ti
-6Aρ-4V) powders were placed in a vacuum furnace and heated to 750° C. at a rate of approximately 0° C./min while evacuating to maintain a high vacuum (10 −5 Torr or less). When the temperature inside the furnace reached 750°C, while keeping it constant at this temperature, the atmosphere inside the furnace was replaced with high-purity nitrogen gas to bring the nitrogen gas pressure to 760 Torr, and the temperature was kept heated for 18 hours, and then the temperature was increased to 500°C. Approximately 0
It was cooled at a temperature decreasing rate of °C/min, and then furnace-cooled.

Pure titanium subjected to surface modification treatment in this way (Reference Example 10)
) and titanium alloy (Reference Example 11), untreated pure titanium (Comparative Example 4) and titanium alloy (Comparative Example 5),
The samples were immersed in 5% hydrochloric acid, 5% phosphoric acid, 5% acetic acid, and pure water heated to 40° C. in the amounts shown in Table 1, and held for 6 hours while being shaken. After that, the treated liquid was filtered and 200ml
The concentrations of Ti, Aρ, and ■ in each treatment solution were examined.

The results obtained are shown in Table 2. The concentration in the treatment solution was analyzed using a luminescence analyzer (CP), and the concentration was measured by a calibration curve method. In addition, in the combination of untreated pure titanium or titanium alloy with hydrochloric acid, the luminescence intensity was saturated for Ti, so a 1000-fold diluted solution was used for measurement, and a 10-fold diluted solution was used for Aρ and ■ in the Kaiso combination. Using.

Table 1 Note that for those that were subjected to surface treatment, the weight increase due to this surface treatment was corrected.

As is clear from the results shown in Table 2, the surface-treated products according to the present invention (Reference Examples 10 and 11) are stable in various environments, and their ion elution properties are lower than that of the untreated products (comparison). Compared with Examples 4 and 5), it was equivalent to or even better.

(Effects of the invention) As described above, the biological implant material of the present invention has
On the surface of the base material made of titanium or titanium alloy, there is a surface-modified layer mainly made of titanium nitride, and a nitrogen layer that is located in the lower layer in contact with the surface-modified layer and diffuses and solidly dissolves nitrogen atoms into the titanium base material. The surface layer consisting of a diffusion hardened layer has a thickness of 0.3 to 10
It is characterized by having an average thickness of 0 μm, and has the characteristics required as a biological implant material, such as surface hardness, abrasion resistance, biocompatibility, toughness, corrosion resistance, and light weight. Because of its excellent properties, it can be suitably used as hard tissue substitutes such as artificial bones, artificial joints, and artificial tooth roots, or as artificial organs such as cardiac pacemaker housings and artificial heart valves.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing the structure near the surface of the biological implant material of the present invention, and FIG. 2 is an X-ray diffraction pattern of the surface of a reference example of the biological implant material of the present invention and its evaluation. Ti2N with standard composition as a guideline for
X-ray diffraction patterns of TiN and α-Ti; FIG. 3 is a graph showing the relationship between surface hardness and heating retention time of reference and comparative examples of uninvented biological implant materials; FIG. FIG. 5 is a graph showing the relationship between the tensile strength and elongation and the heating holding time of Reference Examples and Comparative Examples related to the biological implant materials of the present invention, and FIG. It is a graph showing the transition of hardness from to the inside. DESCRIPTION OF SYMBOLS 1...Titanium material, 2...Surface modification layer, 3...Nitrogen diffusion hardening layer, 4...Surface layer. Patent applicant Waki Bussan Co., Ltd. Agent Patent attorney 8 1) Mikio (and 1 other person) p.
Men's
; 134 cm Hime Sekii Honmi - Sun Ro Ripan 5 I Takumachi R So 1 Cho A (hr
) Figure 4

Claims (1)

[Claims] (1) On the surface of the base material made of titanium or titanium alloy,
A surface layer consisting of a surface modified layer mainly composed of titanium nitride and a nitrogen diffusion hardened layer located in the lower layer in contact with the surface modified layer and in which nitrogen atoms are diffused and dissolved in the titanium base material with a gradient composition. An implant material for biological use that suppresses ion elution, characterized by having an average thickness of 3 to 100 μm.