JPH08225901A - Amorphous nickel alloy high in corrosion resistance - Google Patents

Abstract

PURPOSE: To provide an alloy hardly passivated in non-oxidative environment such as high temp. phosphoric acid and capable of withstanding the environment provided with a very severe corrosiveness. CONSTITUTION: This amorphous nickel alloy high in corrosion resistance consists of 1-30atom% Ta, 15-30atom% total amount of Mo and W together with Ta, 10-24atom% P and the balance essentially Ni. Also the amorphous nickel alloy high in corrosion resistance consists of 3-30atom% Mo and 15-30atom% total amount of W together with Mo, 10-24atom% P and the balance essentially Ni. This alloy high in corrosion resistance is not corroded since a stable protective film is formed even in a severe corrosive environment such as high temp. phosphoric acid low in oxidizing force. In a production of the alloy, a special device is not required and either amorphous alloy producing technology already used widely is applied.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a highly corrosion resistant amorphous nickel alloy suitable as a corrosion resistant material in a severe corrosive environment such as high temperature concentrated phosphoric acid.

[0002]

2. Description of the Related Art At present, 309, 310, 446Mo stainless steel, chrome molybdenum titanium steel, Hastelloy C, etc. are used as structural materials for high temperature concentrated phosphoric acid plants. It does not have sufficient corrosion resistance in severe corrosive environments.

Usually, alloys are crystallized in the solid state, but a method that does not form long periodic regularity in the atomic arrangement in the process of solid formation, such as limiting the alloy composition and solidifying from the molten state by rapid quenching, is applied. Then, an amorphous structure similar to a liquid is obtained without a crystal structure, and such an alloy is called an amorphous alloy. Amorphous alloys are mostly single-phase alloys with a supersaturated solid and have extremely high strength as compared with conventional practical alloys, and exhibit various characteristics such as abnormally high corrosion resistance depending on the composition.

The inventors of the present invention have conducted research to utilize the characteristics of such amorphous alloys, and as a result, have found that pitting corrosion, crevice corrosion and crevice corrosion can be achieved even in a highly corrosive aqueous solution such as an aqueous solution containing a strong acid or a high concentration of chlorine ions. A high-corrosion-resistant amorphous nickel-based alloy that does not undergo general corrosion has been found, and first, Japanese Patent Application No. 51-132290 (Japanese Patent Publication No. 59-50745).
No.), and found a highly corrosion resistant amorphous alloy that can be used in a severe corrosive environment containing boiling concentrated nitric acid or an oxidizer, and Japanese Patent Application No. 60-5103.
Patent application No. 6 (Japanese Patent Publication No. 6-15706), and further found a highly corrosion resistant amorphous alloy that can be used in a severe corrosive environment such as boiling concentrated hydrochloric acid.
No. 2860 (Japanese Patent Publication No. 5-35212) and Japanese Patent Application No. 6
A patent application was filed as 0-172861 (Japanese Patent Publication No. 4-65895). All of these are amorphous nickel alloys. As described above, since concentrated phosphoric acid has a high boiling point, it is particularly corroded at high temperatures, and corrosion resistance cannot be obtained unless the alloy itself has the ability to form a stable protective film.

As a result of further research while studying various characteristics of amorphous alloys, the present inventors have found that Japanese Patent Application Nos. 51-132290, 60-51036 and 60-172860. And Japanese Patent Application No. 60-1728
Among the alloys described in No. 61, by adding an element which further enhances the protective film forming ability to an alloy having a particularly high protective film forming ability, or a similar alloy, it has a poor oxidizing power such as high temperature concentrated phosphoric acid and severe corrosion. It has been found that an amorphous nickel alloy having a high corrosion resistance can be obtained by forming a stable protective film even in a strong acid.
No. 435 (Japanese Patent Publication No. 6-76631) and Japanese Patent Application No. 61
A patent application was filed as No. 224536 (Japanese Patent Laid-Open No. 63-79931).

[0006]

Since concentrated phosphoric acid has a high boiling point, it is particularly corrosive at high temperatures, and no ordinary commercially available metallic material can be safely used. Even in such an environment, Japanese Patent Application No. 61-225435 and Japanese Patent Application No. 61-225435.
Although the alloy described in No. 224536 exhibits high corrosion resistance, there is a demand for the development of various new metallic materials that can withstand use in such a corrosive environment in which ordinary metallic materials are extremely difficult to use. It is an object of the present invention to provide an alloy which is non-oxidizing such as high temperature concentrated phosphoric acid, which does not easily passivate a metal, and has an environment with extremely severe corrosiveness.

[0007]

As a result of continuing research on the corrosion resistance of amorphous alloys, the inventors of the present invention have found that the above-mentioned Japanese Patent Application Nos. 61-225435 and 61-2245.
In addition to the alloy described in No. 36, it was found that an amorphous nickel alloy exhibiting high corrosion resistance in high temperature concentrated phosphoric acid can be obtained by combining various elements, and the present invention has been accomplished. The present invention comprises the inventions set forth in claims 1 and 2, and the following Table 1 shows the constituent elements and the content of the present invention.

[0008]

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Amorphous alloys obtained by various methods for producing amorphous alloys, such as ultra-quick solidification or sputter deposition of a molten alloy having the above composition, are single-phase solid solutions of the above-mentioned elements. It is an alloy. Therefore, the amorphous nickel alloy of the present invention,
A protective film is formed which ensures a very uniform and high corrosion resistance. Metallic materials in high temperature concentrated phosphoric acid solution with weak oxidizing power
Since it dissolves easily, in order to use a metallic material in such an environment, it is necessary to give the metallic material the ability to form a stable protective film. This is achieved by making an alloy containing the required amount of active elements. However, in the case of a crystalline metal, when a large amount of various metal elements are added, a multiphase structure having different chemical properties is often obtained, and it may not be possible to achieve a predetermined corrosion resistance. Also, the occurrence of chemical heterogeneity is rather detrimental to corrosion resistance.

On the other hand, since the amorphous alloy of the present invention is a uniform solid solution and uniformly contains a required amount of effective elements capable of forming a stable protective film, such an amorphous nickel alloy has a uniform protective property. A film is formed and exhibits sufficiently high corrosion resistance. That is, the condition that a metal material having a weak oxidizing power and that can withstand concentrated phosphoric acid at high temperature is to have a high protective film-forming ability that a stable protective film is uniformly formed on the material in a non-oxidizing environment. This is realized by the alloy composition of the present invention, and the fact that the alloy has an amorphous structure allows an alloy having a complicated composition to be prepared as a single-phase solid solution, and ensures uniform formation of a protective film.

Next, the reasons for limiting the composition of each component in the present invention will be described. Ni is an element that forms the basis of the alloy of the present invention, is an element that forms an amorphous structure when a total amount of Mo and Ta coexist in a predetermined amount, and an element that forms an amorphous structure even when coexisting with P. Is. Furthermore,
Ni is an element that assists the actions of Mo, Ta and W, which are responsible for corrosion resistance. Mo, Ta and W are all elements that form a protective film and bear corrosion resistance.

On the other hand, the Ni-P alloy produces an amorphous structure as a metal-metalloid alloy if it contains a sufficient amount of P.
However, excessive addition of P hinders the formation of an amorphous structure. Therefore, in order to generate an amorphous structure, P is 10-24 atomic% in the present invention.

In such an amorphous metal-semimetal alloy containing a sufficient amount of P, the alloy of the present invention has a high ability to form a protective film.
And the sum of W and 15 atomic% or more, or
If the total amount of Mo and W of 3 atomic% or more is 15 atomic% or more, sufficient corrosion resistance can be obtained even in high-temperature concentrated phosphoric acid that is highly corrosive.

In the case of a metal-metalloid alloy, M is excessive.
Since addition of o, Ta and W makes it difficult to obtain an amorphous structure, the total content of Ta, Mo and W in the alloy of the present invention is 30 atomic% or less (that is, T
The upper limit of a is less than 30 atom%). For the same reason, the sum of Mo and W is set to 30 atomic% or less (that is, the upper limit of Mo is less than 30 atomic%). Also,
Even if the amorphous nickel alloy of the present invention contains 10 atomic% or less of Nb and 5 atomic% or less of Ti and Zr, the object of the present invention is not hindered.

Various methods which are already widely used for producing the amorphous nickel alloy of the present invention, that is,
Any method for producing an amorphous alloy may be used, such as a method of rapidly quenching and solidifying a liquid alloy, various methods of forming an amorphous alloy through a gas phase, or a method of destroying a long-periodic structure of a solid by an ion implantation method.

As an example, an apparatus for producing the amorphous alloy of the present invention is shown in FIG. The part surrounded by the dotted line is filled with an inert gas after being evacuated. In the figure, 2 is a quartz tube having a vertical nozzle 3 at its lower end, and a raw material 4 and an inert gas for preventing the raw material from being oxidized can be fed from an inlet 1 provided at the upper end of the quartz tube 2. it can. A heating furnace 5 is installed around the quartz tube 2 to heat the sample 4. A high-speed rotating roll 7 is vertically below the nozzle 3.
Is placed and is rotated by the motor 6.

In order to produce an amorphous alloy, a predetermined raw material 4 is put in a quartz tube 2 and the apparatus is first set to 10 ^-3 Torr.
After applying a degree of vacuum, fill with an inert gas. Then, the raw material 4 is heated and melted by the heating furnace 5, and the molten metal is heated by the motor 6 to 1000-10000 r.p.m. p. m. It is performed by injecting a pressurized inert gas onto the outer peripheral surface of the roll 7 which is rotating at high speed. By this method, for example, thickness 0.1 mm, width 10 mm, length several meters
The amorphous alloy of the present invention can be obtained as a long thin plate.

[0018]

[Examples] Raw material metals were mixed so as to have a composition shown in the column of alloy composition in Table 2, and a raw material alloy was produced by an argon arc melting furnace. These alloys are remelted in an argon atmosphere and are rapidly quenched and solidified using the single roll method shown in FIG. 1 to give a thickness of 0.01-0.05 mm and a width of 1-
An amorphous alloy thin plate having a length of 3 mm and a length of 3 to 20 m was obtained. The formation of the amorphous structure was confirmed by X-ray diffraction. The surface of these alloys is coated with silicon carbide paper 10
Polished in cyclohexane up to number 00.

Then, an alloy sample of a predetermined length was cut out, and 63% P ₂ O _{5 at} 150 ° C. and 72% at 200 ° C.
The corrosion rate (g / hm ² ) of the alloy of the present invention in the phosphoric acid solution was determined by immersing the alloy in a P ₂ O ₅ solution for 7-10 days and measuring the weight before and after the immersion using a microbalance. The obtained results are shown in the column of corrosion rate in Table 2.

[0020]

The corrosion rate of the amorphous alloy of the present invention is extremely low. In addition, as a result of analyzing the alloy of the present invention using X-ray photoelectron spectroscopy, the alloy has a hydrated oxide or hydrated oxyhydroxide protective film in which Mo and Ta are concentrated, which is It was found to be the cause of high corrosion resistance.

[0022]

As described in detail above, the amorphous nickel alloy of the present invention forms a stable protective film even in a severe corrosive environment such as high temperature phosphoric acid, which has a poor oxidizing power, and is a highly corrosion resistant alloy that does not corrode. is there. In addition, since the alloy of the present invention can be applied to any of the widely used techniques for producing an amorphous alloy, a special device is not required again, and the alloy of the present invention is excellent in practicality. .

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for producing an amorphous alloy of the present invention.

[Explanation of symbols]

 1: Raw material inlet 2: Quartz tube 3: Nozzle part 4: Raw material 5: Heating furnace 6: Motor 7: High rotation roll

Claims (2)

[Claims] 1. Ta of 1 atomic% or more and less than 30 atomic% and M
O and W are contained in a total amount of 15 to 30 atomic% with Ta, further 10 to 24 atomic% of P is contained, and the balance is substantially N.
A highly corrosion-resistant amorphous nickel alloy composed of i. 2. Mo of 3 atomic% or more and less than 30 atomic% and W
Is a high corrosion-resistant amorphous nickel alloy containing 15 to 30 atomic% of Mo and 10 to 24 atomic% of P in total, and Ni being the balance.