KR100822303B1 - Manufacturing method of tasi2-si3n4 nanocomposite coating - Google Patents

Abstract

A new TaSi2-Si3N4 nanocomposite coating layer formed on a surface of tantalum or tantalum alloys is provided to improve isothermal oxidation resistance and repeated oxidation resistance of the coating layer at high temperatures and improve mechanical properties of the coating layer at high temperatures, and a manufacturing method of the nanocomposite coating layer is provided. A manufacturing method of a TaSi2-Si3N4 nanocomposite coating layer comprises the steps of: (a) simultaneously vapor-depositing tantalum and nitrogen onto a surface of tantalum or tantalum alloys as a matrix to form a TaN coating layer on the surface of the matrix, and forming a Ta2N coating layer on the TaN coating layer; and (b) vapor-depositing silicon onto the surface of the tantalum nitride coating layer to form a TaSi2-(28.4-11.7) vol.% Si3N4 nanocomposite coating layer, wherein the nanocomposite coating layer is gradient structured such that the Si3N4 volume fraction of the nanocomposite coating layer is reduced as it goes from the matrix side to the surface side.

Description

Manufacturing Method of TASi₂-Si₃N₄ Nanocomposite Coating Layer {MANUFACTURING METHOD OF TASi2―Si3N4 NANOCOMPOSITE COATING}

1 is an optical microscope photograph of a cross section of a TaSi ₂ coating layer having a columnar structure prepared on a tantalum surface by a conventional reaction diffusion method.

Figure 2 is a scanning electron micrograph of the cross section of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer formed on the tantalum surface in Example 1 of the present invention.

3 is a transmission electron micrograph of the cross section of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer formed on the tantalum surface in Example 1 of the present invention.

4 is TaSi ₂ -Si ₃ N ₄ according to Example 1 of the present invention; It is a graph showing the isothermal oxidation resistance of the nanocomposite coating layer measured at 1300 ℃ and 1400 ℃ in 80% Ar-20% O ₂ atmosphere.

FIG. 5 is a graph showing isothermal oxidation resistance measured at 1300 ° C. and 1400 ° C. under an 80% Ar-20% O ₂ atmosphere using a TaSi ₂ coating layer prepared by a conventional reaction diffusion method.

The present invention relates to a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer having excellent oxidation resistance and corrosion resistance formed on the surface of tantalum (Ta) or tantalum alloys used as a high temperature structural material, and a method of manufacturing the same.

Tantalum or tantalum alloys have excellent corrosion resistance in acidic solutions such as hydrochloric acid, nitric acid, sulfuric acid, etc., and are used as materials for heaters for chemical industries, reactors for heat exchangers, and impellers for pumps. space - reacts with oxygen in the core material or the high temperature utilized in aviation, high-temperature structural materials for nuclear power easily tantalum oxide (Ta ₂ O ₅₎ in the formation and diffusion of oxygen through the oxide much faster Ta ₂ O ₅ oxide Since it cannot be used as a surface protective oxide film for protecting a tantalum base material, the use condition has a big disadvantage of being limited to vacuum, reducing or inert atmosphere.

The addition of alloying elements to improve the high temperature oxidation resistance of tantalum or tantalum alloys degrades the high temperature mechanical properties. Therefore, tantalum alloys having excellent high temperature oxidation resistance and high temperature mechanical properties have not been developed until now. Therefore, a method of coating a tantalum base material surface with a tantalum silicide compound or an aluminide compound having excellent high temperature oxidation resistance is widely used.

Generally, in order to give high temperature oxidation resistance to a tantalum alloy, the performance of the coating layer is determined by the ability of the alloy to react with oxygen to form a dense oxide film when exposed to a high temperature oxidizing atmosphere. Stable oxide films include Al ₂ O ₃ and SiO ₂ . Therefore, a coating layer of tantalum aluminide or tantalum silicide composition has been developed as a surface protective film of tantalum alloys. However, as the use temperature of tantalum alloy is gradually increased, much research is being conducted on improving the oxidation resistance of the tantalum silicide coating layer. Research is focused on solving two problems.

First, TaSi ₂ reacts with oxygen at high temperature to form a composite oxide layer consisting of Ta ₂ O ₅ and SiO ₂ , respectively, but Ta ₂ O ₅ Since the diffusion of oxygen through the oxide is very fast, the composite oxide layer grows quickly and easily peels off from the coating layer, so that isothermal oxidation resistance that can be maintained at high temperature for a long time is bad.

Second, the thermal expansion coefficient of the base material (6.3 x 10 ^-6 / ℃) and the thermal expansion coefficient of the coating layer (8.9 x 10 ^-6 /) after fabricating the TaSi ₂ coating layer at high temperature or cooling the coated TaSi ₂ at room temperature after use. Due to the cracks introduced into the coating layer due to the difference of ℃), it is necessary to develop a new coating layer that can solve the problem of poor high temperature repeat oxidation resistance.

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a novel nanocomposite coating layer which can improve isothermal oxidation resistance and repetitive oxidation resistance at high temperature on the surface of tantalum or tantalum alloys, and improve the high temperature mechanical properties of the coating layer. It is to provide a manufacturing method.

TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer according to an aspect of the present invention for achieving this object is, TaSi ₂ of equiaxed crystals coated on the surface of the base material tantalum or tantalum alloys Si ₃ N ₄ particles are distributed in the grain boundary.

In this case, the average particle size of the TaSi ₂ grains is 200 nm or less and the microstructure of the Si ₃ N ₄ particles has an average size of 60 nm or less, and the volume of Si ₃ N ₄ particles in the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer. By controlling the fraction, it provides a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer similar to the thermal expansion coefficient of the base material.

In addition, the present invention is (a) by vapor deposition of nitrogen in the base metal surface of tantalum or tantalum alloy, tantalum nitride tantalum nitride (TaN and Ta ₂ N) coating layer to the (TaN and Ta ₂ N) phase, or the sputtering method for forming the coating layer And (b) vapor-depositing silicon on the surface of the tantalum nitride coating layer to form a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer, wherein the TaSi _2- (11.7-28.4) vol.% Si ₃ N ₄ Provided is a method for preparing a nanocomposite coating layer (method 1). In addition, in the case of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared by Method 1, the volume fraction of Si ₃ N ₄ increases from the base material side toward the surface.

In addition, the present invention comprises (a) Ta or Ta by simultaneously vapor depositing the tantalum and nitrogen in the base metal surface of the alloy to a step or a sputtering method to form an N coating layer Ta ₂ forming a Ta ₂ N coating layer and (B) Ta Method of manufacturing a TaSi _2- (11.7-16.5) vol.% Si ₃ N ₄ nanocomposite coating layer comprising the step of forming a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer by vapor-depositing silicon on the surface of the ₂ N coating layer (method) Provide 2).

In addition, the present invention (A) forming a TaN coating layer by the vapor phase deposition of tantalum and nitrogen on the surface of the base material of Ta or Ta alloy or forming a TaN coating layer by sputtering method, and (b) on the surface of the TaN coating layer The present invention provides a method for preparing a TaSi ₂ -28.4 vol.% Si ₃ N ₄ nanocomposite coating layer, comprising the step of vapor-depositing silicon to form a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer.

In addition, the present invention comprises (a) depositing vapor of tantalum and nitrogen in the base metal surface of the Ta or Ta alloy at the same time by forming a TaN coating layer to form a TaN coating layer to a step or a sputtering method to form a Ta ₂ N coated layer thereon, and over that A TaSi _2- (28.4-11.7) vol. Comprising the step of forming a Ta ₂ N coating layer and (b) vapor-depositing silicon on the surface of the tantalum nitride coating layer to form a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer. It provides a method (method 4) of manufacturing a% Si ₃ N ₄ nanocomposite coating layer. In addition, the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared by the method 4 is characterized in that the volume fraction of the Si ₃ N ₄ particles in the coating layer decreases from the base material toward the surface.

Hereinafter, a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer and a method of manufacturing the same according to an embodiment of the present invention will be described in detail.

The TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer according to the present invention is coated on the surface of tantalum and tantalum alloys, and TaSi _{2 of} equiaxed crystal It has a microstructure in which Si ₃ N ₄ nanoparticles are distributed at grain boundaries.

In the nanocomposite coating layer, TaSi ₂ has an equiaxed crystal structure, and the thermal expansion coefficients of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layers are adjusted by controlling the volume fraction of Si ₃ N ₄ particles formed in the nanocomposite coating layer. Similar to the base materials, due to the thermal stress due to the difference in the coefficient of thermal expansion between the base material and the coating layer during the production of the coating layer at a high temperature and then cooling to room temperature or repeatedly using the coated base material at high temperature and room temperature. The production of microcracks can be suppressed or eliminated fundamentally.

The Si ₃ N ₄ particles formed in the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer are TaSi ₂ TaSi ₂ due to limitations of employment on site It is formed preferentially at grain boundaries.

In addition, the coefficient of thermal expansion of the Si ₃ N ₄ particles is about 2.9 × 10 ⁻⁶ / ° C., and thus in pure TaSi ₂ having a coefficient of thermal expansion of about 8.9 × 10 ⁻⁶ / ° C. As a result of the complexation, it is matched to have a coefficient of thermal expansion similar to that of the base material, thereby suppressing the generation of fine cracks, thereby improving the repeated high temperature oxidation resistance of the coating layer.

In addition, when the Si ₃ N ₄ particles are exposed to oxygen in a high temperature oxidizing atmosphere, the Si ₃ N ₄ particles preferentially react with oxygen to form a dense SiO ₂ protective film, and diffusion of oxygen through the SiO ₂ protective film is prevented. Since it is very slow, it is excellent in high temperature isothermal oxidation resistance and maintains its performance as a surface protective coating layer for a long time at high temperature.

In addition, the Si ₃ N ₄ particles play a role of inhibiting TaSi ₂ grain growth, thereby preventing the mechanical properties of the coating layer from deteriorating due to grain coarsening.

TaSi ₂ - Si ₃ N ₄  Nano composite Cladding  Produce

TaSi ₂ -Si ₃ N ₄ nano-manufacturing method of the composite coating layer according to the invention will contain the four methods according to the change of the volume fraction and distribution of the amount of Si ₃ N _4, the volume fraction of Si ₃ N ₄ and in the cover layer The change in distribution depends on the concentration of nitrogen in tantalum nitride.

First, when a TaSi _2- (11.7-28.4) vol.% Si ₃ N ₄ nanocomposite coating layer is prepared on the surface of a Ta or Ta alloy base material (method 1), (a) nitrogen is added to the surface of the base material of Ta or Ta alloys. Vapor deposition to form a tantalum nitride (TaN and Ta ₂ N) coating layer or sputtering to form a tantalum nitride (TaN and Ta ₂ N) coating layer; and (b) vapor deposition of silicon on the surface of the tantalum nitride coating layer. Forming a TaSi _2- (11.7-28.4) vol.% Si ₃ N ₄ nanocomposite coating layer, wherein in the case of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared by the above method, The volume fraction of Si ₃ N ₄ increases in the coating layer toward the surface.

In step (a), nitrogen is vapor-deposited on the surface of the base material maintained in a high temperature, high purity argon atmosphere by chemical vapor deposition. Here, when nitrogen is deposited by chemical vapor deposition, nitrogen or ammonia gas may be generally used.

In this case, nitrogen deposited on the surface of the base material chemically reacts with the base material to form tantalum nitride (TaN and Ta ₂ N) coating layers, and as the deposition time elapses, nitrogen deposited on the surface of the base material is deposited through the tantalum nitride coating layer. After moving to the tantalum nitride / tantalum interface, it reacts with the new tantalum to continue to produce a tantalum nitride coating layer.

Alternatively, in the step (a), TaN and Ta ₂ N coating layers may also be manufactured in a N ₂ / Ar atmosphere by sputtering using a Ta sputtering target.

Step (b) is to prepare a tantalum nitride coating layer having a predetermined thickness on the surface of tantalum or tantalum alloys, and then vaporize the silicon for a predetermined time by chemical vapor deposition using SiCl ₄ , SiH ₂ Cl ₂ , SiH ₃ Cl or SiH ₄ . Deposit.

In this case, a method for vapor-depositing silicon includes a powder for pack siliconizing treatment having a composition of (1-70) wt% Si / (1-10) wt% NaF / (20-98) wt% Al ₂ O ₃ . The pack siliconization method used can also be used.

When the deposited silicon is diffused into the tantalum nitride coating layer, the TaSi ₂ phase and the Si ₃ N ₄ phase are formed by the solid phase substitution reaction as shown in the following reaction formulas (a) to (b).

4Ta ₂ N + 19Si → 8TaSi ₂ + Si ₃ N ₄ (a)

4TaN + 11Si → 4TaSi ₂ + Si ₃ N ₄ (b)

Since in the TaSi ₂ the nitrogen solubility is very low, Si ₃ N ₄ particles formed by the reaction formula (a) ~ (b) are TaSi ₂ It is mainly formed at grain boundaries.

Silicon deposited on the surface of the tantalum nitride layer continues to move through the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer and reacts with the tantalum nitride coating layer to form new TaSi ₂ and Si ₃ N ₄ particles, which results in tens to hundreds of micrometers. It is possible to produce a TaSi _2- (11.7-28.4) vol.% Si ₃ N ₄ nanocomposite coating layer of thickness.

When the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer was prepared according to the above reaction formula (a), the volume fraction of theoretically formable Si ₃ N ₄ particles was determined using TaSi ₂ (26.13 cm ³ / mol) and Si ₃ N ₄ (44.3). Calculated using the volume per mole of cm ³ / mol) is as follows.

Si ₃ N ₄ vol% = [44.3 / (44.3 + 8 x 26.13] x 100 = 17.5%, but considering the nonstoichiometric composition of nitrogen (14 at.% N) in the Ta ₂ N phase, The volume fraction of the Si ₃ N ₄ particles was about 12.4 to 18.4%, but the volume fraction of the experimentally formed Si ₃ N ₄ particles was about 11.7 to 16.5%.

However, when preparing the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer by the reaction scheme (b), the volume fraction of theoretically formable Si ₃ N ₄ particles is calculated as follows.

Si ₃ N ₄ vol% = [44.3 / (4 x 26.13+ 44.3)] × 100 = 29.8%, but theoretically formable Si considering the non-stoichiometric composition range of nitrogen (1 at.% N) in the TaN phase ₃ N ₄ particles or the volume fraction of approximately 28.9 ~ 29.8%, Si ₃ N ₄ particles, the volume fraction of Experimental formed in is about 28.4 percent.

Therefore, when manufacturing a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer using a tantalum nitride coating layer, it is possible to control the volume fraction of the Si ₃ N ₄ phase present in the nano coating layer according to the nitrogen content present in the tantalum nitride. As a result, the thermal expansion coefficients of the respective base materials and the nanocomposite coating layer can be matched to each other, so that the nanocomposites are cooled at high to low temperatures by thermal stress generated by the difference in coefficient of thermal expansion between the base materials and the nanocomposite coating layer. It is possible to control the amount of cracks formed in the coating layer, and in some cases it is possible to manufacture a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer without crack at all, in the present invention TaSi ₂ formed on the surface of the Ta and Ta alloy base material Including three other coating methods that vary the volume fraction and distribution of Si ₃ N ₄ present in the -Si ₃ N ₄ coating layer. All.

Second, when a TaSi _2- (11.7-16.5) vol.% Si ₃ N ₄ nanocomposite coating layer is prepared on the surface of a Ta or Ta alloy base material (method 2), (a) tantalum is formed on the surface of the base material of Ta or Ta alloys. Vapor deposition of nitrogen and nitrogen at the same time to form a Ta ₂ N coating layer or by sputtering to form a Ta ₂ N coating layer, (b) TaSi ₂ -Si ₃ N by vapor deposition of silicon on the surface of the Ta ₂ N coating layer include _{(11.7-16.5) vol% Si 3 N} 4 to form a nanocomposite coating - ₄ TaSi ₂ consisting of forming a nanocomposite coating.

In the step (a), nitrogen or ammonia (NH ₃ ) may be deposited on the surface of the base material of Ta and Ta alloys maintained at a high temperature by using nitrogen or ammonia (NH ₃ ), and tantalum by chemical vapor deposition. Tantalum pentachloride (TaCl ₅ ), tantalum hexa fluoride (TaF ₆ ), thallium penta bromide (TaBr ₅ ), and the like may be used when depositing.

In this case, a Ta ₂ N coating layer is formed by nitrogen and tantalum deposited on the base materials, and the Ta ₂ N coating layer continues to grow in proportion to the deposition time.

Alternatively, in the step (a), the Ta ₂ N coating layer may be manufactured by the sputtering method using the Ta sputtering target.

The step (b) is to prepare a Ta ₂ N coating layer of a constant thickness on the surface of the base material and vapor-deposited silicon for a predetermined time by chemical vapor deposition using SiCl ₄ , SiH ₂ Cl ₂ , SiH ₃ Cl or SiH ₄ . .

In this case, for the vapor deposition of silicon, a powder for pack siliconizing treatment having a composition of (1-70) wt% Si / (1-10) wt% NaF / (20-98) wt% Al ₂ O ₃ is used. It is also possible to use a pack siliconizing method.

Third, when a TaSi ₂ -28.4 vol.% Si ₃ N ₄ nanocomposite coating layer is prepared on the surface of a Ta or Ta alloy base material (Method 3), (a) tantalum and nitrogen are simultaneously added to the surface of the base material of Ta or Ta alloy. Forming a TaN coating layer by vapor deposition or forming a TaN coating layer by sputtering; and (b) forming a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer by vapor-depositing silicon on the surface of the TaN coating layer. Forming a TaSi ₂ -28.4 vol.% Si ₃ N ₄ nanocomposite coating layer.

When the TaN coating layer is formed by the step (a), the TaN coating layer can be manufactured by increasing the flow rate of the nitrogen source supplied to the reaction tube than in the manufacturing process of the Ta ₂ N coating layer according to the method 2.

In comparison with the amount of ammonia gas supplied in the production of the Ta ₂ N coating layer, the amount of ammonia gas of about 2.5 to 3 times or more should be supplied in the production of the TaN coating layer.

Alternatively, in the step (a), the TaN coating layer may be manufactured by the sputtering method using the Ta sputtering target.

Fourth, in the production of TaSi _2- (28.4-11.7) vol.% Si ₃ N ₄ nanocomposite coating layer on the surface of the Ta or Ta alloy base material, the volume fraction of Si ₃ N ₄ decreases from the base material to the surface. In the case of manufacturing a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer (Method 4), (A) TaN coating layer is formed by simultaneously vapor-depositing tantalum and nitrogen on the surface of a base material of Ta or Ta alloy, and forming a Ta ₂ N coating layer thereon. Forming a TaN coating layer by sputtering or forming a Ta ₂ N coating layer thereon, and (b) vapor-depositing silicon on the surface of the tantalum nitride coating layer to form a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer. Forming a TaSi _2- (28.4-11.7) vol.% Si ₃ N ₄ nanocomposite coating layer composed of the forming step.

The main contents and features of the present invention will be described more clearly through the following examples, and the present invention is not limited to the following examples and various modifications and applications can be made within the scope of the claims.

Example  One

The purity of the tantalum specimen used as the base material was 99.95%, and was prepared in a plate shape having a size of 10 mm × 10 mm × 1 mm.

After polishing the tantalum specimen to silicon carbide (SiC) abrasive paper # 1200, clean it for 30 minutes in an ultrasonic cleaner in the order of acetone, alcohol, and distilled water to remove organic substances that may exist on the surface and to dry them. It was.

It is charged into a high purity alumina reaction tube capable of vapor-chemically depositing nitrogen on the surface of the pretreated tantalum, blown with high purity argon gas (99.9999%) to remove oxygen from the reaction tube, and a high purity argon gas of 100 to 2,000 cm / min While flowing at a flow rate and heated to 800 ~ 1500 ℃ at a heating rate of 5 ~ 20 ℃ / min, and maintained for about 10 to 20 minutes to stabilize the deposition temperature, ammonia gas at a flow rate of 3 ~ 2,000 cm / min Nitrogen was deposited on the tantalum surface for 10 minutes to 200 hours while supplying.

Nitrogen deposited on the surface of the base material chemically reacts with tantalum to form two coating layers of TaN and Ta ₂ N compositions. As the deposition time elapses, the nitrogen deposited on the tantalum metal surface moves through the tantalum nitride coating layer to the tantalum nitride / tantalum interface and reacts with the new tantalum so that the tantalum nitride coating layer grows in proportion to the square root of the deposition time.

Therefore, the deposition temperature and time for producing a tantalum nitride coating layer of a certain thickness can be calculated kinetically. For example, vapor deposition of nitrogen for about 30 hours at a deposition temperature of 1500 ° C. results in growth of a Ta ₂ N coating layer having a thickness of about 21 μm and a TaN coating layer having a thickness of about 10 μm on a tantalum metal surface.

After preparing a tantalum nitride coating layer of a certain thickness, supply of ammonia gas was stopped, and high purity argon was supplied to the reaction tube at a flow rate of 30 to 3,000 cm / min, and cooled to 1100 ^o C at a cooling rate of 5 ^o C / min. Thereafter, the flow rate ratio of silicon tetrachloride gas and hydrogen was about 0.005 to 0.5, and the total flow rate of the two gases was fixed to be about 30 to 4,000 cm / min, and then fed into the reaction tube on the surface of the tantalum nitride coating layer for about 30 minutes to 30 hours. Silicon is vapor deposited.

The deposited silicon forms TaSi ₂ phase and Si ₃ N ₄ phases by solid phase substitution with tantalum nitride phase. As the deposition time elapses, the deposited silicon continues to move through the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer and reacts with the tantalum nitride coating layer to form new TaSi ₂ and Si ₃ N ₄ particles to form TaSi ₂ -Si _{A 3} N ₄ nanocomposite coating layer is prepared.

Since the thickness of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer grows in proportion to the square root of the vapor deposition time of silicon, the deposition temperature and time for preparing the composite coating layer having a specific thickness can be calculated kinetically. As an example, 72 µm of silicon having a high oxidation resistance and corrosion resistance on the surface of tantalum by vapor-depositing silicon on the surface of the tantalum nitride coating layer for 11 hours by vapor phase chemical vapor deposition on the surface of the tantalum nitride coating layer at a deposition temperature of 1100 ° C. A thick TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer can be prepared.

After preparation of the nanocomposite coating layer, high-purity argon gas is cooled to room temperature while flowing at a flow rate of 100 to 2,000 cm / min.

Hydrogen and silicon tetrachloride gases used in Example 1 of the present invention used a high purity gas used in the semiconductor field. Particularly, since silicon tetrachloride gas has a vaporization temperature of about 54 ° C., hydrogen is injected into a silicon tetrachloride solution into a bubbler maintained at a temperature of 0 to 30 ° C. using a bubbling device. It was bubbled with gas and fed into the reaction tube. In the present invention, vapor phase chemical vapor deposition was carried out in a tubular furnace equipped with a reaction tube made of a high purity quartz tube having an inner diameter of about 20 mm.

Alternatively, Si may be deposited by pack siliconization. To this end, a tantalum matrix coated with a tantalum nitride of constant thickness was embedded in a mixed powder of (1 to 70) wt% Si / (1 to 10) wt% NaF / (20 to 98) wt% Al ₂ O ₃ composition. It is then charged to a reaction tube for pack siliconization.

Blowing high-purity argon gas to remove oxygen in the reaction tube, heating high-purity argon gas at a flow rate of 100 ~ 2,000 cm / min, heating each to 800 ~ 1500 ℃ at a heating rate of 5 ~ 20 ℃ / min, and 30 minutes It is maintained for ˜30 hours to vapor-deposit silicon on the metal surface to diffuse the reaction into the tantalum nitride coating layer.

After preparing a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer on the metal surface and the high-purity argon gas flowing at a flow rate of 100 ~ 2,000 cm / min and cooled to room temperature.

Since the thickness of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared by the pack siliconization increases in proportion to the square root of the silicon deposition time as in the case of chemical vapor deposition, the deposition temperature and Time can be predicted kinetically.

Pack siliconizing powder is rotated after weighing 50g of powder corresponding to (1 ~ 70) wt% Si / (1 ~ 10) wt% NaF / (20 ~ 98) wt% Al ₂ O ₃ composition The powder was mixed for 24 hours using a mixer that performs the up and down movement simultaneously. The silicon powder used had a purity of 99.5%, an average particle size of 44 μm, the active agent used NaF of reagent grade, and the filler used a high purity alumina having an average size of 44 μm.

Pack siliconization performed at a temperature of 1100 ° C. or lower was carried out in a tubular furnace equipped with a reaction tube made of Inconel 600 having an internal diameter of 60 mm, and a high purity alumina tube was used at 1200 ° C. or higher. The mixed pack siliconizing powder was filled into 40 cc of alumina crucible, with tantalum metal coated with tantalum nitride in the center, and then closed with an alumina cover.

FIG. 1 is a result of observing a cross-sectional structure of a TaSi ₂ coating layer having columnar textures prepared by chemical vapor deposition, fax siliconization, melt immersion, etc., which are conventional surface treatment methods, respectively, using an optical microscope. 3 is a result of observing the cross-sectional structure of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared according to Example 1 used in the present invention with a scanning electron microscope and a transmission electron microscope.

The TaSi ₂ coating layer prepared by depositing silicon by a chemical vapor deposition method, which is a conventional surface treatment method, on a tantalum base material and the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared in Example 1 according to the present invention are as follows.

As shown in FIG. 3, the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared by the solid phase substitution reaction of tantalum nitride and silicon according to the present invention is ultrafine at an equiaxed TaSi ₂ grain boundary. ₃ N ₄ particles are precipitated, and the average grain size of equiaxed TaSi ₂ is about 250 to 320 nm, and the average size and volume ratio of the Si ₃ N ₄ precipitate particles are measured using an image analyzer. About 38 to 56 nm and 11.7 to 28.4%.

Furthermore, the Si ₃ N ₄ particles are mainly TaSi ₂ crystal formation at the grain boundaries is suppressed, whereby growth of the crystals TaSi ₂ Preparation of TaSi ₂ coating layer having an average grain size of a nanometer can be realized.

On the other hand, TaSi ₂ coating layer prepared by depositing silicon by chemical vapor deposition, which is a conventional surface treatment method, exhibits columnar structure as shown in FIG. 1, and the average diameter of columnar crystal grains is about 1.2 μm. It was.

In particular, the results of calculating the frequency of occurrence of cracks (number of cracks per unit length in the cross-section of the coating layer) obtained by observing the cross section of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared in Example 1 according to the present invention with an optical microscope. In the case of the conventional TaSi ₂ coating layer, no cracks were formed at all compared with about 71 pieces / cm. Therefore, it can be seen that the thermal expansion coefficient of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared in Example 1 is very similar to that of the base material.

Example  2

In Example 2, TaSi _2- (11.7-16.5) vol.% Si ₃ N ₄ , TaSi ₂ -28.4 vol.% Si ₃ N ₄ or TaSi _2- (28.4-11.7) vol. In order to manufacture the% Si ₃ N ₄ nanocomposite coating layer, TaSi ₂ -Si ₃ N ₄ nanoparticles by the vapor phase chemical vapor deposition method of the manufacturing method according to the present invention A composite coating layer was prepared.

The base material was charged into a reaction tube made of a quartz tube capable of simultaneously vapor-phase chemical vapor deposition of nitrogen and tantalum on the surface of the pretreated base materials as in the method of Example 1, and then blown with high purity argon gas (99.9999%). After evacuating to 5 x 10 ^-2 torr with a pump to remove oxygen that may be present in the reaction tube, a heating rate of 5 to 20 ° C / min while flowing high purity argon (99.9999%) at a flow rate of 100 to 2,000 cm / min Heated to 400-1200 ° C., and maintained for about 10-20 minutes to stabilize the deposition temperature, followed by ammonia gas, tantalum pentachloride (TaCl ₅ ), and hydrogen 3 to 2,000, 5 to 2,000, 5 to 2,000 cm / Vapor chemical vapor deposition of nitrogen and tantalum at the same time on the surface of these metals is performed for 10 minutes to 50 hours while supplying a flow rate of min.

In comparison with the amount of ammonia gas supplied in the production of the Ta ₂ N coating layer, at least about 2.5 to 3 times more ammonia gas should be supplied in the production of the TaN coating layer.

Nitrogen and tantalum deposited on the surface of the base material react chemically to form a coating layer of Ta ₂ N or TaN composition, and the Ta ₂ N or TaN coating layer continues to grow in proportion to the deposition time.

Therefore, the deposition temperature and time for producing a Ta ₂ N or TaN coating layer of a certain thickness can be calculated kinetically. For example, vapor deposition of nitrogen and tantalum simultaneously for about 5 hours at a deposition temperature of 900 ° C. results in the growth of about 13 μm thick TaN and about 7 μm Ta ₂ N coating layers on the base metal surfaces.

After preparing a Ta ₂ N or TaN coating layer having a predetermined thickness, supply of ammonia gas and tantalum pentachloride gas was stopped, and argon was supplied to the reaction tube for about 1 to 10 minutes at a flow rate of 30 to 3,000 cm / min. After removing the ammonia gas and tantalum pentachloride gas that may exist, the flow rate ratio between silicon tetrachloride gas and hydrogen is about 0.005 to 0.5 and the total flow rate of the two gases is fixed to be about 30 to 4,000 cm / min. After vapor deposition of silicon on the surface of the TaN or Ta ₂ N coating layer for about 30 to 30 hours, high-purity argon is flowed at a flow rate of 100 to 2,000 cm / min and cooled to room temperature.

The deposited silicon forms TaSi ₂ and Si ₃ N ₄ phases by solid phase substitution with TaN or Ta ₂ N phases. As the deposition time elapses, the deposited silicon continues to move through the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer and react with the TaN or Ta ₂ N coating layer to form new TaSi ₂ and Si ₃ N ₄ phases. _{. 2 -28.4 vol% Si 3 N} 4 or _{TaSi 2 -. (11.7-16.5) vol} % Si 3 N 4 , and the production of the nanocomposite coating layer enables forming a coating layer on TaN Ta base metal surface and that on the Ta ₂ N After forming the coating layer, the solid-substituted reaction with silicon decreases the volume fraction of Si ₃ N ₄ particles from the base material to the surface of the coating layer. The inclined structured TaSi _2- (28.4-11.7) vol.% Si ₃ N ₄ nanocomposite coating layer Can be manufactured.

On the other hand, the tantalum pentachloride gas used in Example 2 of the present invention used a purity of about 99.5%. Especially tantalum pentachloride has a weak boiling point In this study, tantalum pentachloride solid was injected into a bubbler maintained at a temperature of 30 to 200 ° C. using a bubbling device, and then bubbled with argon gas to be fed into the reaction tube. In the present invention, the vapor chemical vapor deposition was carried out in a tubular furnace equipped with a reaction tube made of a quartz tube having an inner diameter of about 20 mm. When vaporizing molybdenum pentachloride solid using a bubbling device and injecting it into the reaction tube, when the vaporization temperature becomes higher than room temperature, all the connecting parts from the bubbling device to the reaction tube are heated or above by using a heating tape. Always maintained.

In addition, as described in Example 1, the base materials on which the TaN or Ta ₂ N coating layer having a predetermined thickness are formed are (1 to 70) wt% Si / (1 to 10) wt% NaF / (20 to 98) wt% Al ₂ Buried in a mixed powder of O ₃ composition, followed by pack siliconization at 1100 ^o C for 5 hours to remove TaSi ₂ -28.4 vol.% Si ₃ N ₄ , TaSi _2- (11.7-16.5) vol.% Si ₃ N ₄ or TaSi _2- (28.4-11.7) vol.% Si ₃ N ₄ nano A composite coating layer was prepared.

TaSi ₂ -28.4 vol.% Si ₃ N ₄ , TaSi _2- (11.7-16.5) vol.% Si ₃ N ₄ or TaSi _2- (28.4-11.7) vol.% Si prepared in Example 2 according to the present invention ₃ N ₄ microstructure of nanocomposite coating layers was similar to that of example 1.

Example  3

In Example 3, TaSi ₂ -28.4 vol.% Si ₃ N ₄ , TaSi _2- (11.7-16.5) vol.% Si ₃ N ₄ or TaSi _2- (28.4-11.7) vol. In order to prepare a% Si ₃ N ₄ nanocomposite coating layer, TaSi ₂ -Si ₃ N ₄ nano A composite coating layer was prepared.

After charging the base materials and the Ta target pretreated as in the method of Example 1 to the RF magnetron sputtering equipment and evacuated to 5 x 10 ^-7 torr and then supplying N ₂ / Ar gas while supplying 5 x 10 ^-2 torr While maintaining the TaN and Ta ₂ N coating layer was deposited. At this time, the RF power was 250 W, the substrate bias was 0 V, and the N ₂ / Ar gas ratio was maintained at about 0.1, and the distance between the target and the base material was about 7.5 cm.

The deposition rate of the TaN coating layer was about 4.5 nm / min, and the deposition rate of the Ta ₂ N coating layer was about 3 nm / min.

TaSi ₂ -28.4 vol.% Si ₃ N ₄ , TaSi _2- (11.7-) on the surface of the base metals of Ta and Ta alloys by vapor-depositing Si on the tantalum nitride surface prepared in Example 3 in the same manner as in Example 1 16.5) vol.% Si ₃ N ₄ or TaSi _2- (28.4-11.7) vol.% Si ₃ N ₄ nanocomposite coating layer was prepared.

A TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared on the tantalum matrix surface using the method of Example 1 and a simple TaSi ₂ prepared by conventional reaction diffusion method The high temperature isothermal oxidation resistance of the coating layer is evaluated as follows at 1300 ^o C and 1400 ^o C.

Comparative example

1300 ^o C and 1400 ^o C, using a tantalum specimen coated with a TaSi ₂ layer having a thickness of about 80 μm and a tantalum specimen having a 72 μm thick TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer prepared according to Example 1, The following isothermal oxidation test was conducted in an atmosphere of 80% Ar-20% O ₂ .

The high temperature isothermal oxidation test was performed using a Thermogravimetric analyzer (ThermoCahn 700) as follows. After loading the specimen on a high purity alumina boat, heating it to 1300 ^o C and 1400 ^o C at a heating rate of 15 ^o C / min under high purity argon atmosphere, and then subjecting the specimen to oxidation treatment time under an atmosphere of 80% Ar-20% O ₂ . The change in weight per unit area was observed and the results are shown in FIGS. 4 and 5. As shown in FIG. 4, the isothermal oxidation resistance of the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer was much better than that of the pure TaSi ₂ coating layer. Therefore, it can be seen that the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layers developed in the present invention have a significantly improved lifespan at a high temperature compared with the pure TaSi ₂ coating layers.

Through the present invention, the manufacturing process of the coating layer is simple, economical and fine equiaxed crystal shape on the surface of tantalum and tantalum alloys by using the vapor chemical vapor deposition method and the pack siliconization method, which has the advantage of excellent interfacial bonding force between the base material and the coating layer. a TaSi ₂ -Si ₃ N ₄ nanocomposite coating was finely form the Si ₃ N ₄ particles on the grain boundaries TaSi ₂ showing the organization may provide a technique capable of producing.

Formation of fine cracks in the nanocomposite coating layer by reducing the difference in coefficient of thermal expansion between the nanocomposite coating layer and the base material by adjusting the volume fraction and distribution of Si ₃ N ₄ particles formed in the TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer The high temperature oxidation resistance is improved by suppressing or completely removing the metal oxide, and the high temperature oxidation resistance is improved by increasing the fraction of SiO ₂ phase in the oxide layer formed by reacting with oxygen at high temperature, and the mechanical properties of the coating layer are improved by refining grains (heat Suppresses propagation of microcracks due to stress).

Although the present invention has been described with reference to the illustrated embodiments, it is merely exemplary, and the present invention may encompass various modifications and equivalent other embodiments that can be made by those skilled in the art. Will understand.

Claims (24)

delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete (A) vapor-depositing tantalum and nitrogen on the surface of tantalum or tantalum alloy as a base material simultaneously to form a TaN coating layer on the surface of the base material and to form a Ta ₂ N coating layer thereon; And (B) vapor-depositing silicon on the surface of the tantalum nitride coating layer to form a TaSi _2- (28.4-11.7) vol.% Si ₃ N ₄ nanocomposite coating layer, Si ₃ N ₄ volume fraction of the nanocomposite coating layer characterized in that the inclined structure so as to decrease from the base material toward the surface Method for preparing TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer. (A) forming a TaN coating layer on the surface of the tantalum or tantalum alloy as a base material by sputtering and forming a Ta ₂ N coating layer thereon; And (B) vapor-depositing silicon on the surface of the tantalum nitride coating layer to form a TaSi _2- (28.4-11.7) vol.% Si ₃ N ₄ nanocomposite coating layer, Si ₃ N ₄ volume fraction of the nanocomposite coating layer characterized in that the inclined structure so as to decrease from the base material toward the surface Method for preparing TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer. delete 20. The method of claim 19, wherein in step (a), nitrogen or ammonia (NH ₃ ) is used to chemically deposit nitrogen, and at the same time TaCl ₅ . Method for producing a TaSi ₂ -Si ₃ N ₄ nanocomposite coating layer characterized in that the chemical vapor deposition of tantalum using TaI ₅ , TaBr ₅ or TaF ₆ . 21. The method of claim 19 or 20, wherein in step (b) TaSi _2- (28.4-11.7) characterized in that the chemical vapor deposition of silicon using SiCl ₄ , SiH ₂ Cl ₂ , SiH ₃ Cl or SiH ₄ . Method for producing vol.% Si ₃ N ₄ nanocomposite coating layer. The process of claim 19 or 20, wherein in step (b) a pack silico having a composition of (1-70) wt% Si / (1-10) wt% NaF / (20-98) wt% Al ₂ O ₃ A method for producing a TaSi _2- (28.4-11.7) vol.% Si ₃ N ₄ nanocomposite coating layer, characterized by chemically depositing silicon by a pack siliconization method using a powder for aging treatment.

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