JPH07188890A - Ni-base alloy powder for thermal spraying and composite member obtained by thermally spraying the powder - Google Patents

Abstract

PURPOSE:To provide Ni-base alloy powder for thermal spraying to form the thermal spraying coating excellent in the sulfuric acid dew point corrosion resistance and the adhesion CONSTITUTION:The objective Ni-base alloy for thermal spraying has the composition (1) consisting of 19-31% Cr, 3-10% Fe, 3-15% Si, 1-9% Mo, 0.005-0.2% N, 0.001-0.02% P, 0.001-0.9% B, and the balance Ni with inevitable impurities, the composition (2) consisting of one or two or more kinds of 0.3-5% Ta+Nb, 0.5-4% W, and 1-4% Cu in addition to the above composition (1), or the composition (3) having the composition (1) or (2), and further having the composition where the content of Si and Mo satisfies the inequalities 9%<=Si+Mo<=20%. The composite member is obtained by thermal spraying the Ni base alloy having the composition as indicated in (1), (2) or (3).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-based alloy powder for thermal spraying and its Ni for forming a sulfuric acid dew-point corrosion sprayed coating on the surface of a member that is exposed to a sulfuric acid dew-point corrosion environment for a long time.
The present invention relates to a composite member such as a composite plate formed by spraying a base alloy powder on the above member to form a sprayed film.

[0002]

2. Description of the Related Art In a thermal power plant, fossil fuels such as heavy fuel oil B, heavy fuel oil C, and coal are burned in a combustion chamber of a boiler, and waste gas generated as a result of the combustion is SO ₂ , SO ₃ , C.
It contains many kinds of gases such as O ₂ , H ₂ O, O ₂ and N ₂ , and also contains soot and dust.

The waste gas emitted from this boiler passes through an electric dust collector, an air preheater, and a desulfurizer, and is finally discharged from the chimney. In such an exhaust gas environment, when the exhaust gas temperature or the surface temperature of the metal member in contact with the exhaust gas becomes 150 ° C. or lower, water (H ₂ O) in the exhaust gas and S
It is also known that H ₂ SO ₄ reacts with O ₃ to form H ₂ SO ₄ .

Therefore, in the process in which the waste gas generated in the boiler is finally discharged from the chimney through the electrostatic precipitator, the air preheater and the desulfurizer, the temperature of the metal member is 15
Sulfuric acid is condensed on the surface of the member in the equipment on the downstream side from the air preheater at 0 ° C or lower.

At this time, the concentration of H ₂ SO ₄ exposed on the surface of the member varies depending on the temperature, but at 130 ° C., for example, 80% or more concentrated sulfuric acid is produced.

Further, fine carbon, which is the main body of soot in waste gas, and Fe ²⁺ and Fe ^{3+ which} are oxidizing ions contained in dust
Etc. are attached, the sulfuric acid condensation part is carbon, Fe ²⁺ , F
Concentrated sulfuric acid containing e ^3+, etc. is generated, and not only sulfuric acid but also many corrosive factors complicately influence each other to create a more severe corrosive environment. The corrosion phenomenon that occurs in this environment is H ₂
It is called sulfuric acid dew point corrosion because it is characterized by the fact that SO ₄ (sulfuric acid) is condensed.

In such a sulfuric acid dew point corrosion environment, low alloy steel and SUS304, which is a typical corrosion resistant material,
Stainless steel such as SUS316L does not show sufficient corrosion resistance for long-term use. Therefore, Ni-9% called Hastelloy D (trade name), which has better corrosion resistance, is used.
Ni-based alloy having a compositional composition of Si-3% Cu, Cr: 20 to described in U.S. Pat. No. 2,103,855.
30%, Fe: 2 to 12%, Si: 3.5 to 5%, M
Ni-based alloy containing o: 2 to 6%, W: 1 to 3%, Cu: 3.5 to 7%, and the balance of Ni and inevitable impurities, described in US Pat. No. 2,938,786. C
r: 19 to 26%, Fe: 10% or less, Si: 1.5 to
7.5%, Mo: 5-9%, Cu: 4-7%, Mn:
Ni-based alloys containing 1.5% or less and the balance consisting of Ni and unavoidable impurities, Cr: 11 to 29%, Co: 20% or less, Fe: described in US Pat. No. 5,063,023. 19% or less, Nb: 3% or less, Cu: 1 to
3.5%, Mn: 2% or less, Mo: 1 to 6.5%, N:
0.2% or less, Si: 3.5 to 6.5%, W: 2.5%
Hereinafter, a Ni-based alloy containing Ti: 0.2% or less (however, the following also includes O) and the rest being Ni is described.

All of the above Ni-based alloys are considered to be excellent in sulfuric acid dew point corrosion resistance because they are excellent in corrosion resistance to sulfuric acid, but they are expensive materials.
There was a problem in terms of cost when used for large-scale facilities such as thermal power plants.

Therefore, in recent years, it has been attempted to spray a Ni-base alloy powder onto the surface of a low-alloy steel or stainless steel member to use a composite member having a Ni-base alloy coating formed thereon (for example, Japanese Unexamined Patent Application Publication No. Hei 2). -44103).

[0010]

However, a conventional Ni-based alloy powder having the above-mentioned composition is sprayed on the surface of a low alloy steel or stainless steel member to prepare a composite member having a Ni-based alloy sprayed film, In thermal power plant facilities constructed using composite materials, the sprayed film of the composite material may be peeled off during operation due to insufficient adhesion of the sprayed film. There were problems such as the progress of corrosion.

[0011]

Therefore, the present inventors have
As a result of research to develop a Ni-based alloy powder for thermal spraying capable of forming a thermal sprayed film having excellent adhesion to a low alloy steel or stainless steel as a base material, (a) Cr: 19 to 31 %, Fe3 to 10%, S
i: 3 to 15%, Mo: 1 to 9%, N: 0.005
.About.0.2% with the balance being Ni, with a Ni-based alloy having a composition of P: 0.001 to 0.02% and B: 0.001.
The Ni-based alloy obtained by adding ˜0.9% at the same time has almost the same sulfuric acid dew point corrosion resistance as the conventional Ni-based alloy, and the thermal spraying obtained by spraying this Ni-based alloy powder. The film has better adhesion to members than before, and the thermal power plant equipment manufactured using the composite plate with this sprayed film does not peel off during operation and has long-term corrosion resistance in a sulfuric acid dew point corrosion environment. Can hold,
(B) The above Si and Mo are 9% ≦ Si + Mo ≦ 2
It is more preferably 0%.

(C) Ta + Nb: 0.3-5%, W:
It was found that one or more of 0.5 to 4% and Cu: 1 to 4% may be further added.

The present invention has been made on the basis of such findings, and in terms of weight%, (1) Cr: 19 to 31.
%, Fe: 3 to 10%, Si: 3 to 15%, Mo: 1 to
9%, N: 0.005-0.2%, P: 0.001-
Ni-based alloy powder for thermal spraying, which contains 0.02%, B: 0.001 to 0.9%, and the balance Ni and unavoidable impurities. (2) In addition to the component composition of (1) above,
Ta + Nb: 0.3-5%, W: 0.5-4%, Cu:
Ni-based alloy powder for thermal spraying having a composition containing 1 or 2 or more of 1 to 4%, (3) The content of Si and Mo has a composition satisfying 9% ≦ Si + Mo ≦ 20% ( 1) or Ni-based alloy powder for thermal spraying according to (2),
(4) A composite member having a sprayed film obtained by spraying a Ni-based alloy powder for thermal spraying having the composition as described in (1), (2) or (3) above.

Next, the reason why the composition of the Ni-based alloy powder for thermal spraying of the present invention is limited as described above will be explained.

(A) Cr The Cr component has the function of improving the sulfuric acid dew point corrosion resistance, but if the content thereof is less than 19%, the desired sulfuric acid dew point corrosion resistance cannot be obtained, while if it exceeds 31%. If it is contained, it is not preferable because the sulfuric acid dew point corrosion resistance deteriorates. Therefore,
The Cr content was set to 19 to 31%.

(B) Fe Fe contains S which is a protective film on the surface of the alloy and has excellent corrosion resistance.
Although it has the effect of increasing the ability to form an iO ₂ film, if the content is less than 3%, the desired ability to form a SiO ₂ film cannot be obtained, while if it exceeds 10%, the amount of Fe in the alloy is large. Since it becomes too much, the corrosion resistance is lowered, which is not preferable. Therefore, the Fe content is set to 3 to 10%.

(C) Si and Mo Both Si and Mo are components that improve the sulfuric acid dew point corrosion resistance, but when Si is less than 3% and Mo is less than 1%, the desired sulfuric acid dew point corrosion resistance is obtained. Is not obtained, while S
If i exceeds 15%, the toughness of the thermal sprayed layer is lowered and cracking tends to occur, and even if Mo exceeds 9%, the sulfuric acid dew point corrosion resistance is saturated. Therefore, Si: 3 to 15% and Mo: 1 to 15% are set. S
Although i and Mo are contained together to enhance the effect of improving the sulfuric acid dew point corrosion resistance, Si: 3 to 15%, M
o: 1 to 15% and 9% ≦ Si + Mo ≦ 20%
It is most preferable to contain so as to satisfy the condition of.

(D) N 2 N is also a component effective in improving the sulfuric acid dew point corrosion resistance, but if the content is less than 0.005%, the desired effect cannot be obtained.
On the other hand, if the content exceeds 0.2%, the sulfuric acid dew point corrosion resistance is rather deteriorated, which is not preferable. Therefore, the content of N is set to 0.005 to 0.2%.

(E) P P is a component effective in improving the adhesiveness of the sprayed layer due to the synergistic action with B, but if the content is less than 0.001%, the desired adhesiveness improving effect is obtained. Not, on the other hand, 0.0
If the content exceeds 2%, the toughness of the sprayed layer is lowered and the sulfuric acid dew point corrosion resistance is deteriorated, which is not preferable. Therefore, the content of P is set to 0.001 to 0.02%.

(F) BB B has the effect of improving the adhesion of the thermal sprayed layer to the substrate by containing it together with P, but its content is 0.001.
%, The desired effect of improving adhesion cannot be obtained, while
If the content exceeds 0.9%, the effect of improving adhesion is saturated,
In addition, boloids are generated in the sprayed layer to reduce toughness and cracks are generated, which is not preferable. Therefore, the content of B is set to 0.001 to 0.9%.

(G) Nb + Ta, W, Cu All of these components are components that can be optionally added in order to enhance the effect of improving the sulfuric acid dew point corrosion resistance, but the total amount of Nb and Ta is less than 0.3%. W: less than 0.5%, C
Addition of less than u: 1% does not produce the desired effect, while Nb + Ta: more than 5%, W: more than 4%, Cu: 4
The effect of improving the sulfuric acid dew point corrosion resistance is saturated even if it is contained so as to exceed 5%. Therefore, Nb + Ta, W, and Cu are Nb + Ta: 0.3 to 5%, W: 0.5 to 4%, and C, respectively.
u: set to 1 to 4%.

[0022]

EXAMPLE A molten Ni-based alloy having the composition shown in Tables 1 to 5 was pulverized by a usual gas atomizing method, and the average particle diameter was:
Ni-based alloy powder for thermal spraying of the present invention (hereinafter referred to as thermal spraying powder of the present invention) 1 to 33, Ni-based alloy powder for comparative thermal spraying (hereinafter referred to as comparative thermal spraying powder) 1-1 within a range of 40 to 100 μm
4 and conventional Ni-based alloy powders for thermal spraying (hereinafter referred to as conventional thermal spraying powders) 1 to 3 were produced. These sprayed powders of the present invention 1
~ 33, comparative spray powders 1-14 and conventional spray powders 1 ~
The following evaluation test was performed using the sample No.

(1) Corrosion test A stainless steel plate made of SUS304 was prepared, and the surface of this stainless steel plate was pretreated by blasting with an alumina grid # 20.
A substrate was prepared by cutting so as to have a plane size of 25 mm × 50 mm.

The thermal spray powder 1 of the present invention is formed on the surface of the substrate.
~ 33, comparative spray powders 1-14 and conventional spray powders 1 ~
No. 3, using a normal plasma spraying method, film thickness: 0.4 mm
The entire surface was coated with the sprayed film of No. 1 to produce a composite plate.

Furthermore, the concentration: 30% in 80% concentrated sulfuric acid solution
A test solution was prepared by simulating a sulfuric acid dew point corrosive environment at a temperature of 120 ° C. in which 0 g / l of activated carbon was mixed.

The above composite plate was immersed in the above test solution for 24 hours, and the amount of change in weight before and after immersion was measured.
The results are shown in Table 8.

(2) Membrane Adhesion Test Two stainless round bars were prepared, and the tips of the stainless round bars were pretreated by blasting with an alumina grid # 20. The tip of one of the pretreated stainless round bars was tested. The above-mentioned thermal spray powders 1 to 33 of the present invention and comparative thermal spray powders 1 to 1 on the surface.
4 and the conventional sprayed powders 1 to 3 were used to form a sprayed film having a thickness of 0.5 mm by a usual plasma spraying method.

After the sprayed film of one stainless steel round bar on which this sprayed film is formed and the tip of the other stainless steel round bar are connected by bonding, one stainless steel round bar is separated from the other stainless steel round bar. The tensile strength and the peeling fracture stress of the sprayed coating were measured, and the results are shown in Tables 6 to 8.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

[Table 6]

[0035]

[Table 7]

[0036]

[Table 8]

[0037]

From the results shown in Tables 1 to 8, the sprayed films formed by the sprayed powders 1 to 33 of the present invention are all resistant to sulfuric acid dew point as compared with the sprayed films formed by the conventional sprayed powders 1 to 3. It can be seen that although the corrosiveness is almost the same, the adhesiveness to the substrate is remarkably excellent in the sprayed film formed of the sprayed powders 1 to 33 of the present invention.

However, the thermal spray coatings prepared from the comparative thermal spray powders 1 to 14 having the composition outside the conditions of the present invention,
At least one of the sulfuric acid dew point corrosion resistance and the adhesion to the substrate is deteriorated, and even if the sulfuric acid dew point corrosion resistance and the adhesion are excellent, the unfavorable characteristics shown in the remarks column of Tables 6 to 8 are You can see that it appears.

As described above, the use of the Ni-based alloy powder for thermal spraying of the present invention makes it possible to use the composite powder for a long period of time in a humid corrosive environment mainly caused by sulfuric acid dew point corrosion such as occurs in thermal power plant facilities. It is possible to provide a plate, which has an excellent industrial effect.

In the examples, the thermal spraying Ni of the present invention is used.
A composite plate was prepared by spraying a base alloy powder by a plasma spraying method to form a sprayed film, but the Ni-based alloy powder for thermal spraying of the present invention is not limited to the plasma spraying method.
It is also possible to form a film by another method such as an ordinary build-up method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeaki Sahira 1-297 Kitabukuro-cho, Omiya City, Saitama Prefecture Central Research Laboratory, Mitsubishi Materials

Claims (6)

[Claims] 1. By weight%, Cr: 19-31%, Fe: 3-10%, Si: 3-15%, Mo: 1-9%, P: 0.001-0.02%, N: 0.005-
Ni-based alloy powder for thermal spraying, characterized in that it contains 0.2%, B: 0.001 to 0.9%, and the balance is Ni and inevitable impurities. 2. By weight%, Cr: 19-31%, Fe: 3-10%, Si: 3-15%, Mo: 1-9%, P: 0.001-0.02%, N: 0.005-
0.2%, B: 0.001 to 0.9%, and Ta + Nb: 0.3 to 5%, W: 0.5 to 4%, and 1 or 2 kinds. A Ni-based alloy powder for thermal spraying, characterized in that the balance consists of Ni and unavoidable impurities. 3. By weight%, Cr: 19-31%, Fe: 3-10%, Si: 3-15%, Mo: 1-9%, P: 0.001-0.02%, N: 0.005-
0.2%, B: 0.001 to 0.9%, and further, Cu: 1 to 4%, with the balance being Ni and unavoidable impurities. Base alloy powder. 4. By weight%, Cr: 19-31%, Fe: 3-10%, Si: 3-15%, Mo: 1-9%, P: 0.001-0.02%, N: 0.005-
0.2%, B: 0.001 to 0.9%, and Ta +
Nb: 0.3 to 5%, W: 0.5 to 4%, one or two kinds are contained, and further, Cu: 1 to 4% is contained, and the rest is Ni and inevitable impurities. A Ni-based alloy powder for thermal spraying, which comprises: 5. Si according to claim 1, 2, 3 or 4.
And Mo are contained so that Si: 3 to 15%, Mo: 1 to 9%, and 9% ≦ Si + Mo ≦ 20% are satisfied, a Ni-based alloy powder for thermal spraying. 6. N according to claim 1, 2, 3, 4 or 5.
A composite member having a sprayed film formed by spraying an i-based alloy powder.