JPS5825744B2 - Solutions and methods for alloy removal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the chemical removal of nickel alloys containing gold, phosphorus, or chromium from stainless steel or nickel-based alloy substrates.

More particularly, the present invention provides a method for producing gold/nickel/nickel/phosphorus from a substrate formed of 300 or 400 series stainless steel or a nickel-rich chromium alloy such as Hastelloy, Inconel, or equivalent alloys. , or solutions and methods for selectively removing nickel/chromium alloys.

Gold/nickel alloys, typically 70-80% gold and 18-30% nickel, are used to bond substrates such as iron and nickel alloys in applications requiring structural strength and excellent heat resistance. It has traditionally been used as a hardening wax.

Gold/nickel hard oral cavity alloy 000oF (537,8
C) and is applied in various thicknesses by melting a paste or preformed segments with flux.

Depending on the application, nickel (97-85%) and phosphorus (3
~15%) are used as hard solder alloys or coatings.

The nickel/chromium alloy is applied by flame or plasma spray or as a coating.

Removal of these alloys as necessary to disassemble or inspect parts on which they are installed or coated
Preferably, this is done by chemical methods rather than reheating.

Although the present invention is not limited to specific applications in which gold/nickel, nickel/phosphorus, or nickel/chromium are used as hard solder alloys or coating alloys, these hard solder alloys are used in the internal structure of jet engines. Preferably and advantageously, it is used to selectively remove alloys from segments of the elements as they are used to join them.

For example, gold/nickel braze alloys are used to secure airfoil vanes to stators used in the turbine section of jet engines.

These airfoil vanes are stationary members located downstream of the combustion chamber and are exposed to very high temperatures and stresses.

However, it is necessary to maintain and inspect these parts.
Such procedures require periodic removal of these components for inspection or replacement.

Therefore, it is necessary to selectively remove the gold/nickel alloy from these components without adversely affecting or degrading the matrix alloy that makes up the stator or other components. Removal must take place.

Iron alloys, usually containing chromium and sometimes nickel, or chromium alloys containing large amounts of nickel (some of which also contain iron), e.g. EVA stainless steel, Hastelloy, Inconel, or equivalent alloys. , used in the manufacture of such components.

Furthermore, the time required to completely remove hard solder metals from jet engine components is particularly important since the aircraft cannot be used during this time.

For example, conventional methods for chemically removing gold/nickel solder alloys include a series of steps and various chemical solutions.

In order to sufficiently remove the hard solder alloy, a long period of time, such as 9 to 18 days, was required (although this time could be shortened to 3 to 5 days if ultrasonic stirring was employed).

Additionally, prior art methods use large amounts of electrical power or use aqueous solutions of cyanide and/or nitro-substituted aromatics and chelating agents, and therefore pose toxicity and environmental pollution problems. It is disadvantageous.

Furthermore, prior art methods typically
, 8-85°C).

Examples of prior art methods for removing gold-containing solder alloys are U.S. Pat.
No. 958,984.

However, the processes described in these US patents suffer from the disadvantages mentioned above, especially regarding the use of cyanide, and are also very slow compared to the process according to the invention.

Another gold/nickel hard alloy removal solution known in the art contains concentrated nitric acid along with copper, iron, and sodium chlorides.

Not only does this solution act much more slowly than the solution according to the invention, but it also poses the problem of pitting and deteriorating the matrix alloy, especially when treated for a long time.

Additionally, the long processing times required to remove hard solder alloys with conventional solutions make substrates such as stainless steel more susceptible to corrosion, resulting in deterioration due to pitting, fouling, or intergranular corrosion.

In accordance with the present invention, it is used to remove gold/nickel, nickel/phosphorus, or nickel/chromium alloys from substrates made of 300 and 400 series stainless steel, Hastelloy, Inconel, and equivalent alloys. An improved solution (used by itself in preferred embodiments) is obtained.

The novel solution of the present invention and its method of removing hard solder alloys or coated alloys as described above removes such alloys in substantially less time than prior art methods or solutions. and do not adversely affect or degrade the underlying matrix of these alloys.

The novel solutions and methods of the present invention are also particularly useful for the selective removal of gold/nickel hard solder alloys used in jet engines where short processing times and no deterioration of the underlying matrix are of paramount importance. suitable for

The improved solutions of the present invention have a wide range of utility, particularly with respect to processing bath or spray temperatures, preferably functioning at room temperature, but capable of functioning at elevated temperatures.

This is particularly advantageous in that ultrasonic agitation can be used, which tends to increase temperature as a result of converting electrical energy into mechanical energy.

According to the invention, gold, An improved solution for selectively removing nickel alloys containing phosphorus or chromium is obtained.

This improved solution is compatible with concentrated nitric acid and chloride ions provided by one or more chloride salts, organic corrosion inhibitors that are effective in preventing substrate degradation and reduce its surface tension. and organic surfactants that are effective to protect against corrosion and provide additional corrosion protection.

The organic corrosion inhibitor is acetylene alcohol (preferably 2-butyne 1,4 diol, ethoxyl butyne 1
. , or N,N',N'-polyoxyethylene (15)-N-tallow 1,3 diaminopropane.

According to the present invention, a substrate formed of and coated with an iron alloy containing chromium and optionally also nickel, or a chromium alloy containing high amounts of nickel, such as Hastelloy, Inconel, or equivalent alloys thereof, is coated with chromium. A method is provided for removing nickel alloys containing gold, phosphorus, or chromium, including applying an improved solution according to the invention.

In this case, application of the solution is preferably carried out by dipping or spraying, and the solution is preferably applied at a temperature of 70-130'F (21,1-2
Removal of the hard solder alloy or coating alloy at a temperature of 4.4 DEG C.) is completed in about 2 to 24 hours.

The method according to the invention further includes subjecting the substrate and/or solution to mechanical or ultrasonic agitation to further increase the rate of alloy removal.

In accordance with the present invention, gold/nickel, nickel/phosphorus, or nickel/chromium alloys can be used to improve jet engine structural configurations more efficiently than using prior art materials or methods, and without degrading the matrix alloy. It is selectively removed from the substrate that makes up the element.

Accordingly, one object of the present invention is to avoid adversely affecting or degrading the substrate in a substantially shorter time than is currently possible using prior art solutions or methods. over a wide range of operating parameters, especially temperature and chloride concentration, without
0-400 series stainless steel or Hastelloy,
An object of the present invention is to provide an improved alloy removal solution for selectively removing gold/nickel, nickel/phosphorous, or nickel/chromium alloys from substrates made of Inconel or equivalent alloys thereof.

Another object of the present invention is that alloys such as those described above can be selectively removed from internal components such as jet engines, and in substantially less time than was possible with prior art methods. It is an object of the present invention to provide an improved method that allows alloy removal to be carried out within a short period of time without degrading the substrate alloy.

Yet another object of the present invention is to remove alloys, with or without mechanical or ultrasonic agitation, in a substantially shorter time than was possible with conventional methods. An object of the present invention is to provide an improved alloy removal solution and method that can perform the following steps.

Yet another object of the present invention is to provide an alloy removal solution and method that allows gold, phosphorous, chromium, and/or nickel components to be easily recovered using conventional recovery methods.

Yet another object of the present invention is to have a wide range of commercially advantageous implementation possibilities, especially with respect to time and temperature, and to avoid the toxicity, dumping, and environmental pollution problems that arise when using cyanide. It is an object of the present invention to provide an improved alloy removal solution and method that does not require the use of multiple solutions or processes as in the prior art.

The present invention will be described in detail below with reference to Examples.

According to a preferred embodiment of the invention, from a substrate composed of a nickel alloy containing chromium and optionally also nickel, or a nickel-rich chromium alloy (which may also contain iron), A novel solution is obtained that is useful for removing alloys containing nickel together with gold, phosphorus, or chromium, preferably gold/nickel or nickel/phosphorous alloys.

This new alloy removal solution has been found to cause little substrate deterioration, particularly with respect to intergranular corrosion of 410 stainless steel.

Therefore, this solution is particularly useful for removing gold/nickel or nickel/phosphorous solders or coatings from critical structural components that are exposed to high levels of temperature and/or stress.

However, it should be noted that the substrate from which the alloy is removed as described above is not a limiting factor in the present invention.

Similarly, the present invention is not limited to the structure, shape, or size of the component from which the above-mentioned alloy can be removed by the present invention.

However, the structure, shape, and size of the substrate can affect the time and specific manner in which the improved alloy removal solution of the present invention is applied, as will be apparent to those skilled in the art.

The improved solutions and methods of the present invention are suitable for removing gold/nickel alloys from substrates formed of stainless steel, preferably 300 or 400 series stainless steel, or Hastelloy, Inconel, or equivalent alloys thereof. It has been found to be particularly useful.

However, other related high temperature nickel alloys, such as nickel/phosphorus alloys or nickel/chromium alloys (which may be used either as coatings or hard solders in high temperature applications), may also be removed more efficiently than the substrates described above. can be done.

Therefore, it should be noted that in this specification, reference to gold/nickel alloys includes other nickel alloys, particularly nickel/phosphorus alloys and nickel/chromium alloys.

In one preferred embodiment, the improved solution of the present invention combines concentrated nitric acid and chloride ions provided by at least one salt to prevent the gold/nickel alloy from degrading the substrate from which it is being removed. an organic surfactant that is compatible with the solution and effective to reduce its surface tension and preferably provides additional corrosion protection.

As nitric acid, it is preferred to use nitric acid having a concentration in the aqueous solution in the range from 40 to 72% by weight.

Nitric acid having a concentration of less than about 40% will work, but generally results in an unacceptably slow rate of solder alloy removal.

Furthermore, the use of a nitric acid aqueous solution with a concentration of about 40% or less may weaken the passivity of the substrate, especially formed of stainless steel, due to the increase in water as a component, and may also have an adverse effect on the substrate. This is undesirable because it increases the potential for degrading the properties and matrix alloy.

Also, more than about 72% nitric acid by weight may be used, although such concentrated nitric acid is not available in large quantities or commercially at such concentrations.

According to the present invention, the alloy removal solution is preferably formed by mixing the other ingredients with concentrated nitric acid on a grams per liter nitric acid basis.

The chloride ion is present in the improved solution of the invention as at least one chloride salt, preferably an inorganic chloride salt such as an alkali metal chloride, especially potassium chloride, ferric chloride, calcium chloride, nickel chloride, magnesium chloride. , aluminum chloride, or a combination thereof.

The total chloride ion concentration is at least 3 per liter of concentrated nitric acid.
．． Should be 75g, preferably about 3.75-90
ji/l, more preferably 15 to 17.59/l.

In one preferred embodiment of the invention, chloride ions are provided by a combination of potassium chloride and ferric chloride.

The concentrations of potassium chloride and ferric chloride are each 1:1 of concentrated nitric acid.
It should be at least 3.75 g/l, preferably about 375-60 g/l, more preferably about 7.5-15 g/l.

Potassium ions and/or ferric ions are potassium salts and/or ferric salts other than chloride salts, such as potassium nitrate, potassium iodide, potassium sulfate, potassium metaphosphate, potassium periodate, potassium selenate, and citric acid. It may be supplied from potassium, potassium tartrate, ferric nitrate, ferric sulfate, or ferric phosphate.

Most preferably potassium chloride is used according to the invention.

This is because potassium chloride has excellent solubility and therefore can provide higher levels of chloride ions in solution than other chloride salts, such as sodium chloride.

Furthermore, the presence of potassium ions in the solutions of the present invention improves the solubility of gold during removal of hard wax from the matrix.

It is also preferred to use ferric chloride as a source of chloride ions, preferably in combination with potassium chloride.

It is believed that ferric ions function preferably as a second oxidizing agent in addition to nitric acid, which is the first oxidizing agent.

Furthermore, the presence of ferric ions in the alloy removal solution of the present invention further enhances the removal of the hard solder alloy by acting as an electrical coupling agent and generating an electromotive force that contributes to the removal of the hard solder alloy. This is thought to improve the situation.

In particular, it has been found that the use of hydrochloric acid as the sole source of chloride ions is undesirable, as the use of hydrochloric acid results in a solution that is incapable of functioning in accordance with the present invention.

The use of hydrochloric acid as a chloride ion source can also remove gold/nickel hard solder alloys, but this exposes the matrix alloy to severe corrosion and deterioration.

Therefore, substantial amounts of hydrochloric acid must be avoided in the improved alloy removal solution of this invention.

Hydrochloric acid may be added in small amounts, however, such that its presence does not adversely affect or degrade the matrix alloy.

Copper chloride is known to cause problems, particularly with respect to pitting of the matrix alloy, which is believed to be caused by local cell effects occurring in the presence of copper ions and ferrous metals.

The presence of copper ions, especially in the form of copper chloride, in the improved solutions of the invention must therefore be avoided.

However, the presence of steel ions is acceptable if they do not adversely affect or degrade the base alloy.

The organic corrosion inhibitor used in the alloy removal solution of the present invention is acetylene alcohol, preferably 2-butyne 1,
4 diol, ethoxyl butyne 1.4 diol, or propargyl alcohol.

This organic corrosion inhibitor must be effective in preventing the substrate from being degraded by the solution according to the invention since the alloy removal solution according to the invention contains a strong oxidizing agent.

This organic corrosion inhibitor is approximately 1 to 30% based on the amount of nitric acid.
Preferably, it is provided at a concentration ranging from about 1 to 39 g/l, preferably about 1 to 39 g/l.

This organic corrosion inhibitor not only helps the alloy removal solution perform its function in a fairly short processing time without adversely affecting or degrading the substrate, but also works over a wide range of temperatures and chloride ion concentrations. can do.

In accordance with the present invention, an organic surfactant that is compatible with the alloy removal solution and effective in reducing its surface tension, and preferably provides additional corrosion protection, is about 1% based on the amount of nitric acid. It is preferably added to the alloy removal solution in a concentration range of ~309 g/l, preferably in a concentration range of about 1.0 to 3.0 g/13.

Examples of the organic surfactant include polyethoxyl amine or diamine, such as polyoxyethylene cocamine, polyoxyethylene gloss amine, polyoxyethylene oleylamine, polyoxyethylene octadecylamine, or N, N', N' -Polyoxyethylene(15)-N-tallow 1,3 diaminoprobanca may be used.

These organic surfactants not only maintain the solubility of the organic corrosion inhibitor, but also have a synergistic effect in working with the organic corrosion inhibitor to provide excellent protection against intergranular corrosion and deterioration of the substrate alloy. There is.

According to the method of the present invention, an alloy removal solution according to any of the preferred embodiments described above is provided to facilitate the physical removal of gold/nickel alloy from areas of the surface of a hard-brazed or coated substrate. It is applied to the substrate in such a way that it

In this case, the substrate is about 50-130'F (10-54.48
C), preferably about 70 to 115'F (21,1 to 46
．． Preferably, the alloy is immersed in or sprayed with the alloy removal solution of the present invention at a temperature in the range of 1 DEG C.).

Alloy removal time (processing time) will vary depending on the structure of the substrate, the thickness of the solder alloy or coated alloy, the concentration of solution components, the temperature, and the type of agitation employed.

In general, when ultrasonic stirring is used to remove alloys,
Complete within 24 hours.

If ultrasonic stirring is not used, the alloy removal time is approximately 10
~120 hours.

It should be noted that although the solution and method of the present invention works well without employing ultrasonic agitation, the time required to remove the hard solder alloy is reduced to about 175 minutes when ultrasonic agitation is employed. .

Additionally, when ultrasonic agitation is employed, the ultrasonic transducer converts electrical energy into mechanical energy, thereby heating the alloy removal solution, which should be handled in accordance with the present invention. It does not have a negative effect on the matrix alloy or cause it to deteriorate.

In accordance with the present invention, gold/nickel solder alloys or coating alloys are selectively removed by using conventional wax or other low-profile masks to cover surface areas of the substrate from which the alloy does not need to be removed. be able to.

For example, a substrate with hard-brazed parts of a gold/nickel alloy is dipped into wax, and after the wax has solidified, the wax is selectively removed from the areas with the hard-brazed alloy, and the substrate is then The hard solder alloy may be removed by treatment with the solution of the present invention.

Although such masking materials are not necessary in all cases, the use of such masking materials is preferred in many cases.

This is because the portion of the substrate that is not brazed with the hard solder alloy is more effectively protected by the strong oxidizing agent contained in the alloy removal solution of the present invention.

Several examples of the invention are described to further illustrate the improved alloy removal solutions and methods of the invention, but these examples are not intended to limit the scope of the invention.

Examples 1 through 3 were conducted to illustrate the functionality of the preferred organic corrosion inhibitor of the present invention under experimental conditions, and the low temperatures used in the tests and the operating parameters. No organic surfactant was included due to limitations.

Example 1 An alloy removal solution was prepared by mixing the following ingredients.

Concentrated nitric acid (70%, 42°Be) 1 l Potassium chloride 19 g Ferric chloride
19.92-Butyne 1,4 Diol 1.6El This solution contained 21 g/l of chloride ions.

1 inch x 1 inch x 0O625 inch (25
, 4m1 x 25.4mm x 1.59mm) 410
Two strips of stainless steel, joined in a T-shape with a gold/nickel alloy containing 80% gold and 20% nickel, were immersed in the solution for 30 minutes. It was done.

In this case ultrasonic agitation was performed using an ultrasonic transducer.

The temperature of the solution is 70-78°F (21,1-25.6°C)
and the average temperature was 74'F (23.3°C).

Observation of the specimen after 30 minutes revealed that 100% of the gold/nickel solder had been removed and that the matrix of the specimen had not been corroded or degraded in any way.

Example 2 An alloy removal solution was prepared by mixing the following ingredients.

Concentrated nitric acid (70%, 42°Be) 1 l Potassium chloride 1 (1 ferric chloride
19g Ethoxyl Butyne 1,4 Diol 3.16.9 Ethoxyl Butyne consisting of Butyne 1,4 Diol ethoxy-substituted with ethylene oxide such that the ratio of ethylene oxide to Butyne Diol was 1.8 to 1.0. 1,4 diol was used.

This solution contained 219/l chloride ions.

1 inch x 1 inch x 0.0625 inch (2
Two strips of 410 stainless steel measuring 5.4mm x 25.4ii x 1.59mm) joined in a T-shape with a gold/nickel alloy hard solder containing 80% gold and 20% nickel. Specimens were immersed in the solution for 30 minutes.

In this case ultrasonic agitation was performed using an ultrasonic transducer.

The temperature of the solution is 66-76°F (18.9-24.48C)
) and the average temperature was 71°F (21.7°C).

Observation of the specimen after 30 minutes revealed that 100% of the gold/nickel solder had been removed and that the matrix of the specimen had not been corroded or deteriorated in any way.

Example 3 An alloy removal solution was prepared by mixing the following ingredients.

Concentrated nitric acid (70%, 42°Be) 1 l Potassium chloride 1 (1 ferric chloride
19g Propargyl Alcohol 1.079 This alloy removal solution also contained 21 g/l chloride ions.

Thirty specimens similar to those used in Examples 1 and 2 were
immersed in this solution for minutes.

Ultrasonic stirring was also performed in this example, and the temperature was 70°C.
~74°F (21.1-23.38C), with an average temperature of 74°F (23.3°C).

Examination of the specimen after 30 minutes revealed that 98% of the gold/nickel solder had been removed and the specimen matrix was not corroded or degraded in any way.

Example 4 An alloy removal solution was prepared by mixing the following ingredients.

Concentrated nitric acid (70%, 42°Be) 11 Potassium chloride 19 g Anhydrous ferric chloride 18 g 2-Butyne 1.4 diol 1.69 N, N', N'-polyoxyethylene (15) N-tallow 1,3 diaminopropane
2.1g specimens similar to those used in Examples 1 to 3 were tested at 98-118°F (36.7-47.8°C).
The sample was immersed in the aforementioned alloy removal solution at a temperature of .

However, no ultrasonic stirring was performed in this example.

After 70 minutes, inspection of the specimen revealed that only half of the gold/nickel solder alloy had been removed, but that the specimen matrix had not undergone any appreciable corrosion.

Examination of the specimen after 7 hours and 50 minutes revealed that 95% of the solder alloy had been removed and the matrix was not visibly corroded or degraded.

However, when ultrasonic stirring was performed using the same alloy removal solution, a specimen similar to the one described above was found to have an 80 to 1
45 in the range 00'F (26,7-37.8°C)
Within minutes, the hard solder alloy was completely removed.

EXAMPLE 5 For the purpose of comparison with the above sides, tests were carried out by mixing nitric acid and hydrochloric acid to form the following solution, which corroded and degraded the substrate alloy; It was found that the performance was not satisfactory.

56 g of hydrochloric acid (37%, AR grade) was mixed with concentrated nitric acid (70%, 42°B) to a chloride ion concentration of 209/l.
e) mixed with 1 l.

Specimens similar to those used in each of the previous examples were
It was immersed in this solution at a temperature of 66-81°F (18.9-27.2°C) and ultrasonically agitated.

Upon inspection of the specimen after 15 minutes, it was observed that the specimen matrix had undergone significant corrosion.

When the specimen was inspected after 45 minutes, it was found that all of the gold/nickel solder alloy had been removed, but the specimen matrix was severely corroded and degraded.

The foregoing sections are presented for purposes of illustrating the present invention; solutions and methods for selectively removing alloys containing nickel along with gold, phosphorus, or chromium are described in accordance with the present invention. It is to be understood that variations and modifications may be made within scope.

Claims (1)

[Claims] 1 Hard solder containing gold, phosphorus, or chromium and nickel from a substrate formed of an iron alloy containing only chromium or chromium and nickel, or a chromium alloy containing a large amount of nickel. In an improved method for selectively removing alloys or coating alloys, from 70 to 130 degrees Fahrenheit until the solder alloy or coating alloy is removed from the substrate.
(21.1-24.4°C) for 2-24 hours,
applying to said substrate by dipping or spraying a solution comprising concentrated nitric acid, chloride ions provided by at least one chloride salt, and an organic corrosion inhibitor effective to prevent said substrate from being degraded; A method characterized by comprising. An improved method for selectively removing gold/nickel, nickel/phosphorus, or nickel/chromium alloys from substrates formed of 2300 or 400 series stainless steel, Hastelloy, Inconel, or equivalent alloys. Concentrated nitric acid, one or more chloride salts selected from the group consisting of alkali metal chloride, ferric chloride, aluminum chloride, calcium chloride, nickel chloride, magnesium chloride, and acetylene alcohol, forming an alloy removal solution with polyethoxyl amine or diamine;
．． 4° C.) for 2 to 24 hours. 3. For selectively removing gold, phosphorus, or an alloy containing nickel together with chromium from a substrate formed of an iron alloy containing only chromium or chromium and nickel, or a chromium alloy containing a large amount of nickel. An improved solution comprising concentrated nitric acid, chloride ions provided by at least one chloride salt, and an organic corrosion inhibitor effective to prevent degradation of the substrate by the solution. A solution characterized by: In an improved solution for the selective removal of gold/nickel solder alloys from substrates made of 4300 or 400 series stainless steel, Hastelloy, Inconel, or equivalent alloys, approximately Nitric acid at a concentration of 40-72%, potassium ions at a concentration of about 3.75-60 g per 111 nitric acid, chlorine ions at a concentration of about 3.75-90 g per 11 nitric acid, and about 3.75-60 g per 11 nitric acid. Ferric ion at a concentration of 60 g and polyethoxyl at a concentration of about 1.0 to 31 per 11 nitric acid.
A solution comprising: an amine or diamine; and acetylene alcohol at a concentration of about 1.0 to 30 g per 14 nitric acid. An improved solution for the selective removal of gold/nickel, nickel/phosphorous, or nickel/chromium alloys from substrates made of 5300 or 400 series stainless steel Hastelloy, Inconel, or equivalent alloys. In this case, nitric acid with a concentration of about 40 to 72% by weight and nitric acid 1
potassium ions at a concentration of 7.5 to 15 g per 17 g of nitric acid, and chlorine ions at a concentration of about 3.75 to 15 g per 11 g of nitric acid. ferric ion at a concentration of 09; acetylene alcohol at a concentration of about 1.0 to 3.0 g per 11 nitric acid; and about 1.0 to 3 g per 11 nitric acid;
A solution characterized in that it contains a polyethoxyl amine or diamine in a concentration of Og.