JPH0610113A - Method for strengtheing, hardening and joining titanium or titanium alloy - Google Patents

Abstract

PURPOSE:To subject the surface part or whole body of titanium or an titanium alloy to alloying, strengthening and hardening or diffusion joining by utilizing the diffusion reaction of alloy components in the solid state as they are. CONSTITUTION:The surface of titanium or a titanium alloy is brought into contact with alloy forming substances capable of alloying in the solid or gaseous state, and heat treatment is executed at less than the temp. at which a liq. phase is formed, by which diffusion reaction occurs to form a new titanium alloy. Or, two titanium materials are closely brought into contact with via a master alloy capable of alloying, and heat treatment is similarly executed to allow diffusion joining. In this way, the surface of the titanium or titanium alloy is strengthened and hardened to improve its wear resistance and fatigue resistance, or, the thin sheet of the titanium or titanium alloy is formed into a new titanium alloy thin sheet furthermore increased in strength, by which a high strength titanium alloy thin sheet which can not be obtd. by a rolling method is manufactured. Moreover, by joining plural titanium parts, complicated net shaped parts or composite material can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for strengthening or hardening the surface or the whole of titanium or a titanium alloy to impart wear resistance or hardness and strength, and a method for joining titanium or a titanium alloy.

[0002]

2. Description of the Related Art Conventional surface hardening methods include physical vapor deposition of a thin layer of titanium nitride, chromium nitride or the like on the surface, or thermal oxidation in air to form a thin oxygen-containing layer on the surface. In both cases, since the hardened layer is very thin and the difference in hardness between the surface and the inside is large, when the pressing force acts locally or on an impact, the hardened layer on the surface cracks and is useless. Titanium alloys are usually alloyed by adding alloying elements during the melting stage. The titanium alloy has high strength and is extremely difficult to work even in hot working because the working temperature range is narrow. Therefore, high-cost methods such as isothermal forging and superplastic working, or simple shapes are used, weak pure titanium that is easy to work is used instead.

[0003]

The conventional surface hardening method has a problem that the hardened layer is too thin and hard to peel off. In the present invention, by performing heat treatment in a specific atmosphere close to vacuum, the hardened layer on the surface can be made to have a moderate hardness and gradually come close to the internal hardness, and peeling can be prevented and good wear resistance can be obtained. Can be given. Also, titanium alloy thin plates are difficult to roll and difficult to manufacture,
By heat-treating a thin plate of pure titanium in a specific atmosphere, alloy components can be diffused from the surface, and an extremely thin plate of high-strength titanium alloy can be easily manufactured. In addition, titanium alloys are difficult to machine, and it takes enormous cost to manufacture parts with complicated shapes. In the present invention, titanium or titanium alloy raw material,
Alternatively, a plate, a bar, a wire, and a mold material may be adhered to each other with an alloy-forming substance (hereinafter referred to as a mother alloy) interposed therebetween, and heat-treated in a specific atmosphere to bond them to form a complex-shaped component or a composite material. .

[0004]

A method of strengthening, hardening and joining titanium or a titanium alloy according to the present invention comprises treating a material to be treated made of titanium or a titanium alloy with oxygen, nitrogen,
By heat treatment in a specific atmosphere of a gas with an extremely low partial pressure such as carbon dioxide or carbon monoxide, excessive reaction on the surface of the material to be treated is suppressed, and the constituent elements of the gas are diffused deep from the surface to the inside. The feature is that it keeps the strength up to the part. By changing the atmosphere, temperature, and time of heat treatment, the surface layer portion can be strengthened, and the entire interior can be alloyed and strengthened to increase the strength of the whole. Since strength is proportional to hardness, hardness is improved where strength is improved.

Al, C, O, N, Mo, Nb, Ta,
V, Ag, Cu, Fe, Mn, Ni, Co, Cr, P
b, Si, W, Zr, Sn, Zn, Sb, Au, Ag,
Ti, a gas containing these elements, a gas containing these elements, or a single metal thereof, or a fine powder of a master alloy that is a prealloy that can be mixed or melted with a plurality of these elements in advance to form titanium alloy Alternatively, when the surface of the material to be treated made of titanium alloy is evenly adhered and heat-treated in a specific atmosphere, the gas or mother alloy diffuses and permeates from the surface of the material to be treated, and a new titanium alloy is generated in the surface layer portion. Strength and hardness are improved. At this time, not only the surface layer portion is alloyed and strengthened and hardened by changing the atmosphere, temperature, and time of the heat treatment, but also the inside can be alloyed with a new composition to increase the strength and hardness of the whole. In the case of the master alloy fine powder, the size is preferably 0.1 mm or less, and if it is more than that, it takes a long time for diffusion. Moreover, the average optimum particle size is 1/10 or less of the thickness of the material to be treated. In addition, the fine powder of the mother alloy is evenly dispersed or applied to the material to be treated made of titanium or titanium alloy, or the metal foil of the above element or the foil of the mother alloy is placed and another material to be treated is placed in close contact and specified. When heat-treated in the above atmosphere, the mother alloy diffuses and alloys with both the materials to be processed, and the two materials to be processed are bonded on the surface. The basic technique of the present invention is that in a titanium base material, an alloy-forming substance having a high diffusion rate and capable of alloying with titanium is brought into contact with titanium to form a diffusion alloy during heat treatment to partially or entirely increase the strength. It is a high hardness titanium alloy.

The specific atmosphere referred to here is oxygen, nitrogen, carbon dioxide gas, carbon monoxide, in a vacuum or an inert gas,
Indicates an atmosphere or vacuum atmosphere in which an active gas such as hydrocarbon, alcohol, ammonia, metal halide gas, or air is used alone or a mixed gas thereof is made so that the partial pressure of these active gases is not more than 100%. . Fine powder of mother alloy,
The method of adhering foil etc. to the material to be treated is roll, press,
A process of press-fitting by hammering, hammering, extruding, drawing, or the like, or a process of attaching by dipping in a molten mother alloy, plating, or the like may be used. In the case of press-bonding, it is preferable to apply the powder thinly, and when it is desired to apply the powder thickly, the operations of applying and press-bonding may be repeated. When applying, it is convenient to mix the mother alloy with water, solvent, adhesive, lubricant, etc. to form a slurry or paste, but the density of the mother alloy when pressed properly is 70% The above is recommended. The heat treatment conditions are such that when only the surface layer of the material to be treated is cured, the gas partial pressure is high, the temperature is low, and the time is short.
When alloying and strengthening the inside of the material to be treated to improve wear resistance, it is basically necessary to use a low gas partial pressure and high temperature for a long time. It is important that the temperature at this time is lower than the temperature at which a liquid phase is formed between the titanium to be treated and the mother alloy, and the temperature is between 700 ° C and 1500 ° C and the time is 0.
Conditions between 1 hour and 1000 hours are good.

[0007]

When a material to be treated made of titanium or a titanium alloy is placed in a vacuum heating container and heated in oxygen with a partial pressure of 10 ^-1 torr, oxygen reacts on the surface of the material to be treated and melts to form an alloy. However, the oxygen immediately diffuses inside the material to be treated and alloys the inside. The surface portion reacts with oxygen again and diffuses inside, and this is repeated, but the oxygen content in the surface portion does not become so high because the oxygen partial pressure in the atmosphere is low. Therefore, the oxygen content in the material to be treated gradually increased from the inside toward the surface, and the hardness and strength gradually increased toward the surface, and the wear resistance was significantly improved. When the above reaction is continued for a long time, oxygen can be diffused throughout the material to be processed, and the whole can be alloyed to increase the strength of the material to be processed. That is, a thin plate of pure titanium and a case can be alloyed to enhance the strength. When carbon monoxide, carbon dioxide, alcohol, hydrocarbons, nitrogen, ammonia, or another gas is used instead of oxygen, carbon, nitrogen, etc. are also dissolved in titanium to form an alloy, and similarly high-strength titanium can be obtained.

In addition, 60Al-40 is placed on a pure titanium plate.
A fine powder paste of V mother alloy is uniformly applied, another pure titanium plate is placed on it, and it is sandwiched, and at the same time, the two plates are brought into close contact with each other by pressing. When this molded product is degreased and placed in a vacuum heating container for heat treatment, the mother alloy diffuses into both plates and becomes a titanium 6Al-4V alloy, and at the same time the two titanium plates are joined to form a strong housing. The same effect can be obtained when press-forming and heat-treating only one pure titanium plate coated with the fine powder paste of the mother alloy. Further, the half alloy processed material can be made into a full alloy strong molded product by the same treatment. α or α +
It is difficult to cold work a β titanium alloy plate into such a complicated shape, and the effect of the present invention is well shown. The material to be processed such as pure titanium and half alloy is soft and easy to process.When the mother alloy powder is hard and pressure-bonded with a press, etc., the mother alloy bites into the material to be processed and sticks to it due to the anchoring effect so that diffusion does not easily occur. It is characterized by being exposed.

[0009]

EXAMPLE A material to be treated of pure titanium or a titanium alloy was placed in a closed heating vessel, the inside was evacuated and filled with pure oxygen.
When kept at 0 ° C. for 1000 hours, oxygen diffuses and permeates from the surface of the material to be treated to the inside. However, at this time, since the temperature is low, the diffusion rate is slow, and the oxygen content in the material to be treated is limited to only the surface portion due to the ridge as shown by the distribution of the thin solid line in Distribution chart 1.
And since the oxygen partial pressure on the surface is too high, only the surface is extremely oxidized. In this case, since the strength and hardness of the surface are high and the inside is low, the surface is easily peeled off and wear resistance is poor. Therefore, if oxygen at a partial pressure of 1/100 atm is put in vacuum or pure argon gas and heat-treated at 900 ° C for 10 hours, the oxygen partial pressure of the atmosphere is low, so that surface oxidation is suppressed and the diffusion rate becomes faster. Oxygen diffuses into the interior as indicated by the broken line 1 and the strength and hardness distribution in the depth direction becomes gentle. The same effect can be obtained by keeping the same atmosphere at 700 ° C. for 1000 hours. Such hardness distribution shows good wear resistance. Next, in an atmosphere with an oxygen partial pressure of 1 / 100,000 atm, 150
Heat treatment at 0 ° C for 0.1 hour suppresses surface oxidation,
The diffusion rate becomes faster, and as shown by the thick solid line in Fig. 1, urine oxygen permeates and diffuses deeper, the strength and hardness distribution in the depth direction becomes gentler, and the distribution is almost the same as that of carburizing in steel. . The wear resistance at this time was as good as that of carburized steel. When the same experiment was attempted by replacing oxygen with nitrogen in the above-mentioned example, the results shown in FIG. 2 were obtained, showing good wear resistance.

When the material to be treated of pure titanium or titanium alloy is placed in an atmosphere in which the partial pressure of CO gas or CO ₂ gas is less than 1 / 10,000 atmospheric pressure, and heat-treated at 1000 ° C. for 1 hour,
Oxygen and carbon simultaneously infiltrate and diffuse from the surface of the material to be treated, and exhibit the content distribution as shown in FIGS. 3 and 4. Therefore, the strength and hardness distributions are as shown in the figure. This is similar to that the surface CO and CO ₂ partial pressure influences the effect of the surface hardness in the carburization phenomenon of steel. When the hardness is gradually increased from the inside toward the surface in this way, the wear resistance is remarkably improved. In this case, both oxygen and carbon can be strengthened and the curing ability is exerted, so that the effect is further enhanced.

A slurry of fine powder of TiO ₂ is thinly and evenly applied on the surface of the material to be treated of pure titanium or titanium alloy,
When this is pressed with a press or the like, placed in a vacuum heating container and heat-treated in a vacuum or in an inert gas atmosphere, T
Oxygen in iO ₂ permeates and diffuses from the surface of the material to be treated, and the oxygen content, strength, and hardness have distributions as shown in FIG. This is very similar to FIG. 1 and shows that oxygen or a gas in a solid state can be brought into contact with the material to be treated to bring about the same effect. Abrasion resistance was also improved. Where Ti
When TiN fine powder was used instead of O ₂ fine powder, FIG.
And the same effect was obtained. Further, the same effect was obtained in the case of TiC fine powder. Instead of pressing fine powder of TiO _2, TiN, or TiC, the surface may be oxidized, nitrided, or carbonized in advance to form a coating film of TiO _2, TiN, or TiC on the surface and then heat-treated to diffuse. Similar effects were obtained. TiO ₂ layer or TiN on the surface after heat treatment
If the coating of the layer and the TiC layer remains, it can be removed by shot blasting. When shot blasting is applied, the fatigue strength is improved due to the residual stress on the surface.

When a 0.5 mm-thick material to be treated made of pure titanium or a titanium alloy or a thin plate is heat-treated in an atmosphere having an oxygen partial pressure of not more than 1/100 atm, oxygen permeates and diffuses from both sides of the plate.
Since the oxygen content has a distribution as shown in FIG. 7, both strength and hardness of the whole plate are increased, and a plate having characteristics like a thin plate of high strength titanium alloy can be obtained. Next, a heat treatment is performed in a nitrogen partial pressure atmosphere of not more than one-tenth atmospheric pressure of nitrogen to obtain a distribution as shown in FIG. 8, and similarly, the strength and hardness of the plate can be increased. The same effect can be obtained even when fine powders of TiO ₂ and TiN are pressure-bonded to the surface of the plate, or the surface is oxidized and nitrided and then heat-treated in vacuum.

On the surface of the pure titanium material to be treated, 60% Al
Fine powder (100 μm or less) of 40% V mother alloy is sprinkled or applied and pressed by a press or a roll. Then, place it in a vacuum or in an inert gas atmosphere such as argon gas 9
When heat-treated at 00 ° C for 1 hour, Al and V permeated and diffused from the surface into the material to be treated, and as shown in Fig. 9, the surface layer portion with a depth of 200 µm became approximately 6Al4V titanium alloy and the strength and hardness of the surface layer portion were improved. did. Although some unreacted layer remained on the surface, a clean surface was obtained when removed by shot blasting. When a fine powder of mother alloy of 52% Mo, 27% Zr and 21% Sn was sprinkled on the surface of the 6Al4V titanium alloy material to be treated and heat-treated in the same manner, 11
A β-titanium alloy containing 6% Mo, 6% Zr and 4% Sn was formed, transformed into BCC and expanded, so that compressive residual stress was exerted on the surface and fatigue strength was improved. Next, 0.5 mm of pure titanium
Powder or slurry in which fine powder of 60% Al 40% V mother alloy (20μ or less) and lubricant is mixed is sprayed or applied to each surface of the thin plate to a thickness of 0.05 mm, and cold pressed. It was molded into a case and the material to be treated and the mother alloy were brought into close contact with each other. When this was heated in vacuum or degreased with a solvent and then subjected to the same heat treatment in an argon atmosphere, Al and V were diffused throughout the thin plate as shown in FIG.
A 4V titanium alloy thin plate housing was completed. When this was used as a camera housing, it became a very light and strong camera body with less surface flaws.

Although a master alloy of 60% Al 40% V was used here, if a master alloy having a composition compatible with various titanium alloys is used, a thin plate of titanium alloy corresponding thereto can be manufactured. For example, Al-Sn, Al-Mo, Al-V-Sn,
Al-V-Cr, Al-V-Fe, Al-V-Fe-M
A mother alloy such as o may be used, but if a small amount of transition metal is pre-alloyed with this, the high diffusion rate of the transition metal during heat treatment will accelerate the diffusion of other metals, and an alloy with a uniform composition. Is built. If a thin plate of 3Al2V titanium alloy of a half alloy is used as a material to be treated, a half amount of the mother alloy is sufficient, and therefore a light heat treatment is sufficient. The weight of the mother alloy in the case of increasing the strength of the whole material to be treated is preferably in the range of 1% to 25% of the weight of the material to be treated.

60% on a thick plate of 6Al4V titanium alloy
A fine powder of a master alloy of Al 40% V is evenly dispersed, a thin plate of pure titanium is placed thereon, and the two plates are rolled by a roll to bring the master alloy and the two plates into close contact with each other. Then, when a heat treatment was applied at 900 ° C. for 2 hours in a vacuum or in an inert gas atmosphere, the two plates were joined by the diffusion of the mother alloy and a composite material was produced. The composition distribution inside the plate at this time is shown in FIG.
The surface of the pure titanium plate side remains pure titanium and the corrosion resistance is maintained as it is. Used in tanks of chemical plants where strength and corrosion resistance are required.

Fine powder of a mother alloy of 60% Al 40% V is evenly applied to the surfaces on which two 6Al4V titanium alloy parts are to be joined, and the surfaces are strongly pressed together by a pressing press, and then in a vacuum or an inert gas. 1300 ℃ in the atmosphere,
When heat treatment was applied for 1 hour, the two parts were firmly joined due to the diffusion of the mother alloy, and a part having a complicated shape was formed.
As for the composition distribution inside the component, as shown in FIG. 12, Al and V are slightly higher only in the welded joint portion, but they are completely alloyed and the strength is sufficient.

[0017]

The present invention is constructed as described above and exhibits the effects as described below. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6, excessive hardening of only the surface can be suppressed, and moderate strength and hardness can be gradually given to the inside. Hardened layer is difficult to peel off. FIG.
As shown in Fig. 5, the material which was gradually strengthened and hardened from the surface layer to the inside of the material to be treated had the effect of significantly improving the wear resistance.

The thin plate subjected to the treatment shown in FIGS. 7, 8 and 10 was subjected to a tensile test and the results shown in FIG. 14 were obtained. Oxygen, nitrogen,
The strength of the pure titanium sheet with carbon diffused improved, but the elongation decreased slightly. Further, the 6Al4V alloy thin plate obtained by diffusing and alloying the 60% Al40% V mother alloy was able to greatly improve the strength without reducing the elongation, and was close to the strength characteristics of the ordinary titanium 6Al4V alloy thin plate.

When the material to be treated in FIG. 12 in which two titanium 6Al4V alloy parts were diffusion-bonded through a mother alloy was pulled in the direction perpendicular to the joint surface, it was not cut at the joint surface and was cut at other portions. Since the joint surface was completely alloyed and the alloy composition was high, the joint strength was high and the joint strength in this part was higher than that of the welded material.

[Brief description of drawings]

FIG. 1 is a diagram showing an oxygen dissolution amount distribution and strength / hardness distribution in titanium when heat-treated in an oxygen atmosphere.

FIG. 2 is a diagram showing a nitrogen dissolution amount distribution and strength / hardness distribution in titanium.

FIG. 3 is a diagram showing an oxygen-carbon dissolved amount distribution and strength / hardness distribution in titanium.

FIG. 4 is a diagram showing an oxygen-carbon dissolved amount distribution and strength / hardness distribution in titanium.

FIG. 5 is a diagram showing an oxygen dissolution amount distribution and a strength / hardness distribution in titanium when TiO ₂ fine powder is pressure-bonded or an oxide layer is formed on the surface and heat treatment is performed.

FIG. 6 is a diagram showing a nitrogen dissolution amount distribution and strength / hardness distribution in titanium.

FIG. 7 is a diagram showing an oxygen dissolution amount distribution and a strength / hardness distribution in a titanium thin plate.

FIG. 8 is a diagram showing a nitrogen dissolution amount distribution and a strength / hardness distribution in a titanium thin plate.

FIG. 9 is a diagram showing a dissolution amount distribution of Al and V diffused in titanium.

FIG. 10 is a diagram showing a distribution of the amounts of Al and V dissolved in a titanium thin plate.

FIG. 11 is a view showing Al and V dissolution amount distributions of a pure titanium and titanium alloy joint surface.

FIG. 12 is a view showing a joint surface of two titanium alloy parts and distributions of Al and V dissolution amounts.

FIG. 13 is a diagram showing the wear resistance of the product of the present invention.

FIG. 14 is a diagram showing strength and elongation characteristics of the thin plate of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C23C 10/52 7516-4K

Claims (6)

[Claims] 1. A method for strengthening, hardening, and joining titanium or a titanium alloy, which comprises subjecting a material to be treated made of titanium or a titanium alloy to a heat treatment in a specific atmosphere to diffuse the material. 2. The material to be treated has a shape of a thin plate or foil, a case formed by molding a thin plate or foil, a plurality of plates or cases in which the cases are superposed and adhered to each other, or a thick plate, a bar, a wire, a mold material, or an element. Shaped materials or those in which they are adhered to each other, and an alloy-forming substance is placed on the surface of the material to be treated or between the adhered materials to be treated, or the alloy-forming material is preliminarily formed by reaction on the surface of the material to be treated Reinforcement of titanium or titanium alloy according to claim 1,
Curing method and joining method. 3. The alloy forming material has a composition of Al, C,
O, N, Mo, Nb, Ta, V, Ag, Cu, Fe, M
n, Ni, Co, Cr, Pb, Si, W, Zr, Sn,
Composed of elements such as Zn, Sb, Au, Ag, Ti,
A gas containing these elements, or a single metal of these, or a mother alloy in which a plurality of these elements are alloyed, and the mother alloy is a fine powder of 0.1 mm or less, or a thin plate of 0.1 mm or less. A method of strengthening, hardening, and joining titanium or a titanium alloy according to claim 2. 4. A fine powder of a mother alloy as it is, or with water,
Slurry or paste that is uniformly mixed with solvent, adhesive, etc. is evenly spread and applied on the surface of the material to be treated,
3. The method for strengthening, hardening and joining titanium or titanium alloy according to claim 2, wherein the titanium or titanium alloy is further made to adhere by alloying by pressing such as rolling, pressing, forging, extrusion, drawing or the like, or by plating. 5. The specific atmosphere is a vacuum, or an active gas such as oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrocarbon, alcohol, ammonia, metal halide gas, air, or a mixture thereof. The method for strengthening, hardening, and joining titanium or a titanium alloy according to claim 1, wherein the partial pressure is 100% or less. 6. The titanium according to claim 1, wherein the temperature of the heat treatment is 700 ° C. or higher and lower than the temperature at which a liquid layer is formed between the material to be treated and the alloy-forming substance, and the time is 0.1 hour or more and 1000 hours or less. Alternatively, a method of strengthening, hardening and joining a titanium alloy.