JP4218818B2 - Method for removing metal sulfide and forming corrosion-resistant covering member - Google Patents

Description

この表１から明らかなように、Ｈ_２ガス中（比較例１）では、１０００℃以上の高温雰囲気において、水素ガスによる還元反応によって若干の金属硫化物の分解が行われているが、完全に除去されていない。これに対し、空気中（実施例１−１）及び水蒸気中（実施例１−２）では、６００℃以上の温度でほぼ完全に金属硫化物は除去され、除去された金属面は、非常に薄い酸化膜は生成するものの、試験片全体としては全く異常は認められなかった。
【００３４】
以上の結果から、Ｎｉ基合金上に生成した金属硫化物の除去には、水素ガスによる還元反応より、空気（Ｏ_２）及び水蒸気（Ｈ_２Ｏ）による酸化反応を利用する方が有効であることが判る。
【００３５】
（実施例２）
約６００℃の硫化水素を含む石油分解ガスの中で、３万時間運転したＮｉ基タービン翼（化学組成：２０％Ｃｒ-１４％Ｃｏ-４％Ｍｏ-３％Ｔｉ-１.５％Ａｌ-残りＮｉ（質量％））の翼根部分に生成している金属硫化物の除去について調査した。このような実機翼では、金属硫化物の生成部を目視判定することが難しいため、翼根部を研磨紙によって丁寧に磨いた後、印画紙に１０％Ｈ_２ＳＯ_４を含浸させた紙を貼り、さらにその上に錫板を置いて陰極とし、印画紙が乾燥しないように、３０分間、Ｈ_２ＳＯ_４を滴下し続けながら、翼根部を陽極として直流による電解を行った。その後、印画紙を剥離すると、金属硫化物が存在していたところは、金属硫化物の生成に起因してセピア色となる現象を利用して判定した。
【００３６】
この実施例では、運転後のタービン翼の翼根部には、全数、金属硫化物の存在が認められた。このタービン翼をＨ_２ガス中で１０００℃×１６ｈ加熱したところ、金属硫化物は全く除去できなかった。これに対し、空気中１０００℃×５ｈ、水蒸気中１０００℃×５ｈの加熱処理を施したところ、金属硫化物の存在は全く認められず、完全に除去されていた。念のためタービン翼を切断して光学顕微鏡によって観察しても、金属硫化物は発見できなかった。なお、金属硫化物除去後、露出した金属面及び金属硫化物が生成していない健全部には、金属酸化膜の生成が認められたが、全体に薄く、１０％塩酸によって除去可能であった。
【００３７】
（実施例３）
実施例１で作製した硫化物除去試験片を用い、そのままの状態（比較例３−１）と金属硫化物を完全に除去した後に硬質Ｃｒめっきにより表面処理してめっき皮膜を形成した時（実施例３−１ａ，３−１ｂ）、同じく、そのままの状態（比較例３−２）とＣｒ拡散処理により表面処理被覆を形成した時（実施例３−２ａ，３−２ｂ）の密着性を調査した。供試表面処理被覆とその条件は以下の通りである。
（ａ）硬質Ｃｒめっき：めっき液組成（ＣｒＯ_３：２５０g/dm^３，Ｈ_２ＳＯ_４：２.５g/dm^３）温液５３℃、電流密度１５Ａ/dm^２ で８μｍ厚のＣｒめっきを析出させた。
（ｂ）Ｃｒ拡散処理：Ｃｒ粉末３０質量％，Ａｌ_２Ｏ_３６９質量％，ＮＨ_４Ｃｌ１質量％の組成を有する浸透剤中に試験片を埋め込み、９５０℃×１６ｈ、Ｈ_２ガスを通しつつ処理を行った。
【００３８】
表面処理後の試験片を切断し、その断面について光学顕微鏡により観察した。その結果を表２に示す。
【表２】

この結果から明らかなように、試験片の表面に金属硫化物層が形成されていると、Ｃｒめっき、Ｃｒ拡散処理とも良好な被覆は形成されない。これに対し、金属硫化物を完全に除去した試験片面には、良好な密着性を示すＣｒめっき膜及びＣｒ拡散被覆が形成されることが確認された。
【００３９】
（実施例４）
各種の金属材料について、実施例１の場合と同様な硫化物除去用試験片を作製した後、金属硫化物の除去を行った。供試材料、及び金属硫化物除去法とその条件は以下の通りである。
（１）供試材料
（ａ）Ｃｏ基合金：２６％Ｃｒ-１１％Ｎｉ-７.５％Ｗ-２％Ｆｅ-残りＣｏ（質量％）
（ｂ）Ｆｅ基耐熱合金：１５％Ｃｒ-２６％Ｎｉ-１.３％Ｍｏ-２％Ｔｉ-残りＦｅ（質量％）
（２）金属硫化物除去法とその条件
空気中で１０００℃×１０ｈ加熱
以上の条件で加熱した後、試験片を切断し、その断面を光学顕微鏡で観察したところ、全試験片とも金属硫化物が除去されていた。
【００４０】
【発明の効果】
以上説明したように、本発明によれば、金属製部品に形成された金属硫化物を完全に除去できるうえ、金属製部品の強度低下や寸法、形状に変化を与えないので、金属製部品を再度使用することができる。また再使用時には、耐高温硫化腐食性を向上させるための表面処理被覆も容易に形成することができる。
【００４１】
従って、タービン動静翼やディスクなどに適用すれば、高価な部材の再使用が可能となり、消耗部材費の大幅な削減、耐食性の向上による長時間連続運転が可能となるほか、保守点検費の節減、運転効率の向上などが期待できる。
【図面の簡単な説明】
【図１】硫黄化合物を含む高温の石油分解ガス中で使用されていたＮｉ基超合金製タービン動翼の翼根部に生成している金属硫化物の模式図で、（ａ）は、金属硫化物が金属面に対して平行に生成している模式図、（ｂ）は、金属硫化物が結晶粒界に沿って深く内部へ浸食している模式図である。
【符号の説明】
１ 金属硫化物
２ 結晶粒界
３ 結晶粒子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing metal sulfide, which removes metal sulfide formed as a corrosion product on the surface of a gas turbine or jet engine member exposed to a high-temperature combustion gas containing a sulfur compound, for example, and metal sulfide The present invention relates to a method for forming a corrosion-resistant covering member that reuses a part from which an object has been removed. The present invention is used in boilers, diesel engines, heat treatment furnaces, reaction furnaces, etc. that use combustion gas of fossil fuels containing sulfur compounds as heat sources, or in petrochemical equipment that handles petroleum distillation, cracked gas, reaction gas, etc. also it applies to the removal of metal sulphide generated heat alloy surfaces that are.
[0002]
[Prior art]
For example, in a driving engine such as a diesel engine, a boiler, a gas turbine, and a jet engine, energetic development research is being carried out for the purpose of improving thermal efficiency. Here, the improvement in thermal efficiency is also the result of forcing a severe heat load on the components. Therefore, the metal material used in the high temperature part of these prime movers is required to have high mechanical strength in the environment of use and excellent resistance to high temperature oxidation and high temperature corrosion. In particular, when a fuel containing impurities such as V, Na, and S is used, an inorganic compound containing these impurities causes the metal material to be severely corroded and worn at high temperatures, so that it is stable for a long time even in such an environment. It is necessary to maintain the state.
[0003]
In order to meet such demands, many heat-resistant alloys called superalloys, which are mainly composed of non-ferrous metal elements such as Cr, Ni, Mo, Co, W, Ta, Al and Ti, have been developed. It was. In these superalloys, high temperature strength is given the highest priority, so the addition of metal elements that are not useful for improving strength inevitably tends to be kept at a low rate. Typical examples of such metal elements that are not useful for improving the strength are Cr, Al, Si, and the like. On the other hand, these elements are excellent in oxidation resistance and high temperature corrosion resistance. Superalloys that prioritize high-temperature strength are generally poor in oxidation resistance and high-temperature corrosion resistance.
[0004]
In view of such a situation, the surface of a heat-resistant alloy member used in a high-temperature environment is previously coated with a metal element or a plurality of metal elements (alloys) having corrosion resistance. For example, a metal such as Cr, Al, or Si is coated by a diffusion treatment method, a heat-resistant / high-temperature oxidation-resistant alloy is coated by a spraying method, or a heat-resistant alloy is further spray-coated, and then Al is coated thereon. Various materials that have been made to diffuse and penetrate have been developed.
[0005]
In order to prevent chemical and physical damage (erosion damage due to fine powder) of turbine blades handling petroleum cracked gas, the inventors have proposed a technique in which a chromium carbide cermet is spray-coated to provide not only corrosion resistance. Efforts have been made to develop a coating with excellent wear resistance.
[0006]
[Problems to be solved by the invention]
For example, Ni-base superalloys and Co-base superalloys with excellent high-temperature strength are generally used for high-temperature exposed members (turbine rotor blades, disks, combustor liners, etc.) of gas turbines and jet engines. These alloys always contain Ni and Cr as refractory metal elements. These Ni and Cr react with sulfur compounds contained in the high-temperature combustion gas to generate metal sulfides having poor heat resistance such as NiSx and CrSx. Since these metal sulfides grow while selectively eroding the crystal grain boundaries of the alloy, the life of turbine rotor blades and the like is significantly shortened, and sometimes the members are damaged.
[0007]
The above metal sulfide generation also occurs in places where extremely high finishing accuracy is required, such as the fitting part of turbine blades and discs. Since the anticorrosion coating cannot be applied, it is extremely dangerous. In other words, a large centrifugal stress is applied to these parts during turbine operation, so the generation of a small amount of metal sulfides, especially the generation of metal sulfides at grain boundaries, is a major damage accident. Cause inducing.
[0008]
However, all of the above prior arts are designed to prevent the corrosion reaction performed between the metal member and the gas component constituting the environment, and are generated as a result of the corrosion reaction on the surface of the metal member. None of the technology for removing metal sulfides or the technology for imparting corrosion resistance after removal has been known.
[0009]
For this reason, for example, in a turbine rotor blade, even if the blade surface is protected by a corrosion-resistant coating, the fitting portion with the disk cannot be protected by the corrosion-resistant coating, and this is discarded after a certain period of operation. There was a problem that it was a big economic burden because it was necessary to reject it.
[0010]
The present invention has been made in view of the above, and reused a metal sulfide removal method for removing metal sulfide as a corrosion product generated on the surface of a metal member, and a component from which metal sulfide has been removed. It aims at providing the formation method of a corrosion-resistant coating | coated member.
[0011]
[Means for Solving the Problems]
The invention according to claim 1 is made of a heat-resistant alloy, and a metal member having a metal sulfide formed on the surface by a reaction between a heat-resistant metal element and a sulfur compound in the heat-resistant alloy is oxidized at 600 ° C. to 1200 ° C. It is a method for removing a metal sulfide, characterized by heating in an atmosphere for 3 to 30 hours. Metal sulfides, both NiS _X and CrS _X , generate gaseous SO ₂ when heated to 600 ° C. or higher in an oxidizing atmosphere, and NiO, Cr ₂ O that can be easily removed by brushing with a very rough residue. ₃ is generated. For this reason, the metal sulfide generated in the metal member can be completely removed, and the metal member can be reused because it does not change in shape and dimensions.
[0012]
The invention according to claim 2 is the method for removing metal sulfide according to claim 1, wherein any one of air, oxygen and water vapor, or a mixture thereof is used as the oxidizing atmosphere. is there.
[0013]
The invention according to claim 3 is made of a heat-resistant alloy, and a metal member having a metal sulfide formed on the surface by a reaction between a heat-resistant metal element and a sulfur compound in the heat-resistant alloy is oxidized at 600 ° C. to 1200 ° C. A method for forming a corrosion-resistant covering member, characterized in that, after heating in an atmosphere for 3 to 30 hours to remove metal sulfides and cleaning the surface, a high-temperature sulfide-resistant coating is formed on the surface . This makes it possible to form a high-temperature sulfide-resistant coating having good adhesion and to reuse expensive members.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The types of sulfur compounds contained in fossil combustion gas and petroleum cracked gas can be classified into gaseous and solid or molten salt. Examples of gaseous substances include SO ₂ , SO ₃ , H ₂ S, and COS. Examples of solid or molten salt substances include M _X SO ₄ , M _X S ₂ O ₇ , M _X Fe (SO ₄ ). ₂ , M _X Al (SO ₄ ) _{3 and the} like. Here, M represents Na or K.
[0015]
The gaseous sulfur compound reacts with the metal component in a high temperature environment to produce a solid sulfur compound, and also causes a direct corrosion reaction with the metal member to form a sulfide with the metal member component on the surface. (NiS _X , CrS _X ) is generated. The solid or molten salt-like sulfur compound adheres exclusively to the surface of the metal member, dissolves the protective oxide film formed on the surface of the metal member and loses its function. Product.
[0016]
For this reason, for example, in a turbine moving blade and disk, a disk material, and the like, if a small amount of sulfur compound is contained in the atmospheric gas, a metal sulfide is generated on the surface thereof. Since these metal sulfides generally have a low melting point (for example, the eutectic of Ni ₃ S ₂ and Ni exhibits a molten state at 645 ° C.), the sulfidation reaction rate becomes abnormally fast, and this is the crystal grain boundary of the member. If it is formed, the grain boundary peels off early and the mechanical strength is lost, which makes it extremely dangerous.
[0017]
FIG. 1 schematically shows a result of observing a cross section of a metal sulfide generated on the surface of a blade root portion of a turbine rotor blade made of an Ni-based alloy with an electron microscope. In FIG. 1, 1 is a metal sulfide, 2 is a grain boundary, and 3 is a crystal grain. As shown in FIG. 1A, some metal sulfides 1 are generated in parallel with the surface of the turbine rotor blade in a relatively dense state. As shown in FIG. Some grow deeply into the interior almost vertically, and others grow while selectively eroding metal grain boundaries. These metal sulfides may be generated over the entire surface of the turbine blade, or may be generated locally, and there is a feature that the appearance cannot be visually determined.
[0018]
Next, a method for removing the metal sulfide thus generated on the surface of the metal member such as the turbine blade will be described. This method utilizes a so-called high-temperature oxidation method that oxidizes and removes metal sulfides formed on the surface of a metal member in an oxidizing high-temperature atmosphere containing air, O ₂ , H ₂ O, and the like. is there.
[0019]
That is, metal sulfides such as NiS _X and CrS _X are oxidized by the following reaction formula when heated to 600 ° C. or higher in an oxidizing atmosphere.
NiS _X + 1 · 1/2 O ₂ → XSO ₂ + NiO
CrS _X + 1 · 1/2 O ₂ → XSO ₂ + CrO
[0020]
Gaseous SO ₂ generated by this oxidation is scattered and NiO and Cr ₂ O ₃ remain on the surface of the metal member as residues, but these are very rough and can be easily removed by brushing. As a result, in the turbine blade, the metal sulfide produced on the blade surface is completely removed from both the blade surface and the blade root, and the shape and dimensions of the turbine blade are not changed. Can be used and reused.
[0021]
Here, air can be used as it is as an oxidizing atmosphere, but water vapor (H ₂ O) or O ₂ can also be used, and further, a hydrocarbon combustion gas, for example, a city gas (CH ₄ ) combustion gas can be used. it can. In this case, since the main components CO ₂ and H ₂ O of the combustion gas both have oxidizing power, the combustion energy can be used effectively.
[0022]
The high temperature oxidation treatment temperature is suitably in the range of 600 ° C. to 1200 ° C., and the treatment time is suitably in the range of 3 to 30 hours. When the temperature is lower than 600 ° C., it takes a long time to remove the metal sulfide, and when the temperature is higher than 1200 ° C., the metallurgical structure change of the metal member such as the turbine blade material becomes large, and the mechanical strength is deteriorated. There is a drawback that makes it difficult.
[0023]
As a method for removing metal sulfides,
(1) A mechanical method using polishing with a grindstone and blasting by spraying fine particles of ceramics or metal,
(2) A chemical method using a dissolution reaction with a chemical such as acid or alkali,
(3) An electrochemical method in which an object to be treated is electrolytically removed as an anode in an electrolytic solution containing acid or alkali,
(4) Method of reducing metal sulfide in high-temperature H ₂ gas (in this case, for example, the metal sulfide is volatilized as hydrogen sulfide by the reduction reaction of NiS _X + H ₂ → H ₂ S _X + Ni) ,
Etc. are considered.
[0024]
Here, the mechanical method {circle around (1)} not only requires a great deal of time for polishing metal parts such as turbine blades having a complicated shape, but also has already been used after being finished to precise dimensions. Since the blades and the like are further polished, a great design problem arises. In addition, this method has a drawback in that it is not possible to confirm the removal as well as the formation of metal sulfide, and the reliability of the treatment is poor.
[0025]
In the chemical method (2), metal sulfides are less likely to dissolve in acids and alkalis, and there is a risk of erosion of sound parts such as turbine blades. It is not preferable. The electrochemical method (3) has a problem of using a chemical as an electrolyte, and it is almost impossible to pass a uniform current through the surface of a turbine blade having a complicated shape. There is a high risk of dissolving the healthy part. The reduction method (4) has the disadvantage of using H ₂ gas, which is dangerous in handling, and its reduction power is limited, and it is generated on the surface of gas turbine blades etc. by thermodynamic examination and experiment. It was found that the metal sulfide cannot be removed.
[0026]
On the other hand, according to the high temperature oxidation method of the present invention, these disadvantages are not present, and in the turbine blade, the metal sulfide generated on the blade surface without any change in the shape and dimensions of the turbine blade. Can be completely removed.
[0027]
Next, in order to reuse metal parts such as turbine blades from which metal sulfide has been removed, first, the whole is lightly brushed and cleaned, and then coated with excellent resistance to high-temperature sulfidation corrosion and high-temperature oxidation. Is processed. As this processing method, there is a Cr or Al diffusion penetration method.
[0028]
This is because a metal member (turbine blade material from which metal sulfide has been removed) is buried in a penetrant containing metal Cr particles, alumina, NH ₄ Cl, etc., and then H ₂ gas or Ar gas is allowed to flow, while 800 Heating is performed for 5 to 20 hours in an atmosphere of ˜1000 ° C. By this operation, Cr diffuses over the entire surface of the metal member and the high-temperature sulfidation resistance is improved. Since this process is a kind of chemical vapor deposition involving generation of HCl by thermal decomposition of NH ₄ Cl and generation of CrCl ₂ gas by reaction with Cr powder, the turbine from which metal sulfide has been removed There is a feature that fine Cr particles adhere even in small recesses on metal parts such as wings. The above chemical reaction is specifically shown as follows.
[0029]
NH ₄ Cl → NH ₃ + HCl (decomposition reaction)
2HCl + Cr (particles) → CrCl ₂ + H ₂ (chromium halide formation reaction)
CrCl ₂ + H ₂ → Cr + 2HCl (Cr vapor phase precipitation reaction)
If metal Al, Al—Cr alloy, Al—Ni alloy or the like is used instead of metal Cr particles, an Al diffusion / permeation layer is obtained on the surface of the metal part.
[0030]
In addition to this Cr or Al diffusion penetration method, an alloy film containing Ni, Cr, Al, Co, etc. is formed by plasma spraying method or high-speed flame spraying method, or metal parts are formed by electroplating method. After coating with a plating film such as Cr or Ni having good adhesion or removing air, the corrosion-resistant alloy is evaporated by an electron beam heat source in a reduced pressure state of 50 to 500 hPa by introducing Ar, By attaching this metal vapor to the surface of the object to be treated (Physical Vapor Deposition method), a coating having corrosion resistance can be easily formed.
[0031]
Needless to say, after the thermal spray coating is formed, the Cr or Al diffusion treatment may be performed on the composite treatment or electroplating film in which the Cr or Al diffusion treatment is performed thereon.
[0032]
【Example】
Example 1
Specimen from Ni-base superalloy (20% Cr-14% Co-4% Mo-3% Ti-1.5% Al-remaining Ni (mass%)) used as turbine blade material (dimension: width 10mm) X 30 mm long x 3 mm thick), and then heated to 850 ° C. for 10 h in an atmosphere of 1000 ppm hydrogen sulfide and the remaining N ₂ gas to form a metal sulfide layer over the entire surface of the test piece What was made to produce was made as a test piece for sulfide removal.
[0033]
Then, _{H 2} gas using a test piece (Comparative Example 1) and heated air (Example 1-1) and water vapor (Example 1-2) at 500 ° C. to 1250 in an atmosphere of ° C. was circulated for 5 hours Then, the presence or absence of the metal sulfide produced | generated on the test piece surface was observed with the optical microscope. The results are shown in Table 1.
[Table 1]

As is apparent from Table 1, in the H ₂ gas (Comparative Example 1), some metal sulfide is decomposed by a reduction reaction with hydrogen gas in a high-temperature atmosphere of 1000 ° C. or higher. It has not been removed. On the other hand, in air (Example 1-1) and water vapor (Example 1-2), the metal sulfide is almost completely removed at a temperature of 600 ° C. or higher, and the removed metal surface is very Although a thin oxide film was formed, no abnormality was found in the entire test piece.
[0034]
From the above results, it is more effective to use the oxidation reaction with air (O ₂ ) and water vapor (H ₂ O) than the reduction reaction with hydrogen gas to remove the metal sulfide formed on the Ni-based alloy. I understand that.
[0035]
(Example 2)
Ni-based turbine blades (chemical composition: 20% Cr-14% Co-4% Mo-3% Ti-1.5% Al-) operated for 30,000 hours in petroleum cracked gas containing hydrogen sulfide at about 600 ° C The removal of the metal sulfide generated in the blade root portion of the remaining Ni (mass%) was investigated. In such an actual blade, it is difficult to visually determine the generation portion of the metal sulfide. Therefore, after carefully polishing the blade root portion with abrasive paper, a paper impregnated with 10% H ₂ SO ₄ is attached to the photographic paper. Further, a tin plate was placed thereon as a cathode, and direct electrolysis was performed using the blade root as an anode for 30 minutes while keeping H ₂ SO ₄ dropwise, so that the photographic paper was not dried. Thereafter, when the photographic paper was peeled off, the presence of the metal sulfide was determined using the phenomenon of sepia due to the formation of the metal sulfide.
[0036]
In this example, the presence of metal sulfide was found in all the blade roots of the turbine blade after operation. When this turbine blade was heated in H ₂ gas at 1000 ° C. for 16 hours, no metal sulfide could be removed. In contrast, when heat treatment was performed at 1000 ° C. for 5 hours in air and 1000 ° C. for 5 hours in water vapor, the presence of metal sulfide was not recognized at all and was completely removed. As a precaution, metal sulfide was not found even when the turbine blade was cut and observed with an optical microscope. In addition, after removal of metal sulfide, formation of a metal oxide film was observed on the exposed metal surface and on a healthy part where metal sulfide was not formed, but it was thin as a whole and could be removed with 10% hydrochloric acid. .
[0037]
(Example 3)
Using the sulfide removal test piece prepared in Example 1 as it is (Comparative Example 3-1) and after completely removing the metal sulfide, surface treatment by hard Cr plating to form a plating film (Implementation) Example 3-1a, 3-1b), similarly, as it is (Comparative Example 3-2) and when the surface treatment coating is formed by Cr diffusion treatment (Examples 3-2a, 3-2b) did. The test surface treatment coating and its conditions are as follows.
(A) Hard Cr plating: plating solution composition (CrO ₃ : 250 g / dm ³ , H ₂ SO ₄ : 2.5 g / dm ³ ) Precipitate 8 μm thick Cr plating at 53 ° C. warm solution and 15 A / dm ² current density. I let you.
(B) Cr diffusion treatment: a test piece was embedded in a penetrant having a composition of 30% by mass of Cr powder, 69% by mass of Al ₂ O _{3, and 1} % by mass of NH ₄ Cl, while passing H ₂ gas at 950 ° C. × 16 h. Processed.
[0038]
The test piece after the surface treatment was cut, and the cross section was observed with an optical microscope. The results are shown in Table 2.
[Table 2]

As is clear from this result, when a metal sulfide layer is formed on the surface of the test piece, a good coating is not formed for both Cr plating and Cr diffusion treatment. On the other hand, it was confirmed that a Cr plating film and a Cr diffusion coating exhibiting good adhesion were formed on the test piece surface from which the metal sulfide was completely removed.
[0039]
Example 4
For various metal materials, the same sulfide removal test piece as in Example 1 was prepared, and then the metal sulfide was removed. The test materials and metal sulfide removal method and the conditions are as follows.
(1) Test material (a) Co-based alloy: 26% Cr-11% Ni-7.5% W-2% Fe-remaining Co (mass%)
(B) Fe-based heat-resistant alloy: 15% Cr-26% Ni-1.3% Mo-2% Ti-remaining Fe (mass%)
(2) Metal sulfide removal method and its conditions Heating in air at 1000 ° C. for 10 hours After heating under the above conditions, the test piece was cut and the cross section was observed with an optical microscope. Had been removed.
[0040]
【The invention's effect】
As described above, according to the present invention, the metal sulfide formed on the metal part can be completely removed, and the strength and size and shape of the metal part are not reduced. Can be used again. In addition, a surface treatment coating for improving high-temperature sulfidation corrosion resistance can be easily formed during reuse.
[0041]
Therefore, if applied to turbine blades and vanes, disks, etc., it is possible to reuse expensive components, which can greatly reduce the cost of consumables, enable continuous operation for a long time by improving corrosion resistance, and reduce maintenance and inspection costs. Improvement of driving efficiency can be expected.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram of a metal sulfide generated at the root of a Ni-based superalloy turbine blade used in a high-temperature petroleum cracking gas containing a sulfur compound. FIG. 5B is a schematic diagram in which a product is generated in parallel to the metal surface, and FIG. 5B is a schematic diagram in which the metal sulfide is eroded deeply into the interior along the crystal grain boundary.
[Explanation of symbols]
1 Metal sulfide 2 Grain boundary 3 Crystal grain

Claims (3)

A metal member made of a heat-resistant alloy and having a metal sulfide formed on the surface by a reaction between a heat-resistant metal element in the heat-resistant alloy and a sulfur compound is heated in an oxidizing atmosphere at 600 ° C. to 1200 ° C. for 3 to 30 hours. A method for removing metal sulfides.   2. The method for removing metal sulfide according to claim 1, wherein any one of air, oxygen and water vapor, or a mixture thereof is used as the oxidizing atmosphere. A metal member made of a heat-resistant alloy and having a metal sulfide formed on the surface by a reaction between a heat-resistant metal element in the heat-resistant alloy and a sulfur compound is heated in an oxidizing atmosphere at 600 ° C. to 1200 ° C. for 3 to 30 hours. A method for forming a corrosion-resistant coating member, comprising removing a metal sulfide and cleaning the surface, and then forming a high-temperature sulfide coating on the surface .

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