JPS62280355A - Reduction and oxidation resistant composite material for use at high temperature - Google Patents

Abstract

PURPOSE:To produce a composite material having reduction and oxidation resistances at high temp. successively forming a specified metallic layer and an oxide ceramic layer on Mo-oxide cermet by spraying. CONSTITUTION:An Ni-Cr-Al-X (X is at least one kind of rare earth element such as Y, Hf or Sc) or Ni-Cr-Al alloy layer of about 100-200mu thickness and an oxide ceramic layer of about 100-500mu thickness are successively formed on Mo-oxide cermet having about 10:0.5-1:5 ratio by thermal spraying. The Mo-oxide cermet consists of Mo and at least one among ZrO2, Al2O3, Cr2O3 and TiO2. The oxide ceramic is Al2O3 or a mixture of Al2O3 with ZrO2, Cr2O3, MgO, CaO or TiO2. The alloy has a composition consisting of about 10-35% Cr, about 3-20% Al, <=5% X and the balance Ni. The alloy layer and the ceramic layer are formed by thermal spraying so that an alloy-ceramic mixed layer is present between the layers.

Description

[Detailed Description of the Invention] Product number 1 summer U 艷広! ! ? The present invention relates to a composite material that is resistant to reduction and oxidation at high temperatures. More specifically, the present invention relates to a composite material used as a member for a reduction furnace for processing fossil fuels and metal oxides.

Moxibustion of coal, coke, heavy oil, etc.: Reduction furnaces that generate hydrogen and carbon monoxide using 5 fuels as raw materials, and reduction furnaces that produce metals by reducing -Ir group oxides with carbon, etc. The parts used, such as the protective tube and nozzle of the thermoelectric N thermometer, are exposed to the harsh environment inside the furnace, so it is a national problem to use them for a long period of time.

In general, the operation of a reduction furnace involves the introduction of raw materials and heating them to a predetermined temperature in advance. This heating is obtained by burning the fuel in a 7A atmosphere enriched with oxygen.

Thereafter, the amount of oxygen added is reduced to create a reducing atmosphere in the furnace. Therefore, the members used in the reduction furnace are exposed to both the oxidizing atmosphere and the reducing atmosphere.

Depending on the fuel, the sulfur content is -1! - Some have a high genus or natural content, which increases component damage. For example, members made of ceramic materials are easily eroded by molten heavy metals and slag. On the other hand, molybdenum (Mo)-oxide cermet has good corrosion resistance against m@ffl metal and slag, and also has excellent thermal shock resistance. However, in an oxidizing or sulfiding atmosphere at still temperatures, molybdenum is oxidized or sulfided, causing damage. For this reason, when using a member made of molybdenum (MO)-oxide cermet, in order to reduce the time of exposure to an oxidizing atmosphere as much as possible, it is necessary to The problem arises in that it has to be inserted.

The present invention solves problems such as oxidation, sulfidation, corrosion, and reduction that occur when materials are exposed to oxidizing and reducing atmospheres at commercial temperatures. We provide a composite material that can be used for long periods of time even in such an atmosphere and atmosphere.More specifically, we provide a composite material that solves the problem of molten heavy metals and slag.

The composite material of the present invention has an alloy layer and an oxide ceramic layer obtained by thermal spraying on a molybdenum-oxide cermet material in sequence. The alloy of the alloy layer is an alloy represented by the formula (1) of NiCrAlX (wherein the formula represents at least one metal selected from yttrium, hafnium, scandium, and other rare earth metals). The composite material has reduction resistance and oxidation resistance at high temperatures, and is characterized by being an alloy represented by 1CrAI of the formula (2), or having a content of 5% or less of the alloy.

Furthermore, I? JC4 is a composite material that is formed by thermally spraying a mixture of an alloy and an oxide ceramic between an alloy layer and a direct oxide ceramic layer.

Molybdenum-oxide cermet used in the present invention Neo-Norconi 7r7. n+) full q
(Al2O)), chromia (Cr203) and titania ('Fj02).
It is m. Generally speaking, the ratio of molybdenum (MO) to these oxides can be varied.
The ratio is preferably 1:0.5 to 1:5. The cermet is a sintered composite of molybdenum (Mo) and an oxide, which may be formed by, for example, powder metallurgy methods known to those skilled in the art.

In the present invention, members for the reduction furnace refer to members that are directly exposed to the furnace atmosphere, such as thermocouple and thermometer protection tubes and nozzles.

In the present invention, the reduction furnace refers to fossil fuel and l'! It refers to a furnace that generates hydrogen and carbon oxide from air and water vapor, or a furnace that produces metal by reducing metal oxides with a reducing agent such as carbon.

The alloy used in the present invention is NiCrAlX (Xi±at least one selected from intrihum (Y), hafnium (Hf), scannowum (Sc) and other rare earth elements, and the content thereof is 5% by weight of the alloy. % or less) or NiCrAl. The compositions of both alloys are 10-35% Cr and 3-20% A1, with N1 being the balance.

Problems such as oxidation and corrosion cannot be solved only by an alloy layer obtained by thermally spraying the above alloy onto the surface of a Mo-oxide cermet material. The MO-oxide cermet material sprayed with this alloy layer has insufficient oxidation resistance in an oxidizing atmosphere at a high temperature of, for example, 1,300 to 1,400° C., and is likely to cause curvature and Ia comparison.

As a result of further studies, the present inventors found that by sequentially providing an alloy layer and an oxide ceramic layer on the Mo-oxide cermet material by thermal spraying, oxidation, sulfidation, corrosion, reduction, etc. It has been discovered that a composite material that can withstand long-term use without causing any problems can be obtained, and the present invention has been developed.

The oxide ceramic used in the present invention is alumina (
Al□oi) or norconia (ZrO2) on the alumina
, chromia (Cr20.), magnesia (MgO), calcia (CaO), and titania (TiOz). When oxides other than alumina are contained, the content of the other oxides is preferably 30% by weight or less. 30
If the weight percentage is exceeded, slag resistance tends to deteriorate. The above-mentioned ceramic IH powder may be commercially available, or may be obtained by firing each metal salt at a high temperature by a method known to those skilled in the art. The particle size of this thermal spray powder is 5 to 100
μm1 Preferably it is 5 to 30 μm.

A concrete example of the method for forming a sprayed film according to the present invention is as follows. A commercially available plasma spraying device can be used as the thermal spraying device. The surface of the MO-oxide cermet material is roughened by blasting with one abrasive material containing alumina as a main component. The Mo-oxide cermet material was fixed on a rotating '4AI, and while rotating it was heated with argon,
Thermal spray powder is inserted into a plasma flame obtained using a plasma gas such as hydrogen or helium to melt it, and then sprayed onto the cermet material to form a film. At this time, moving the plasma torch in the longitudinal direction of the cermet material helps to form a uniform film. The thickness of the film is not particularly specified, but it is 100 to 200 μm for the alloy layer, and 100 to 50 μm for the oxide ceramic layer (preferably 1 μm).If the 4jv is too thin, the corrosion resistance will be poor, and if it is too thin, it may cause peeling due to thermal strain. Easy to occur.

In the present invention, the coating may form a multi-layered layer in which an alloy layer and an oxide ceramic layer are formed separately and sequentially, or a powder containing a mixture of an alloy and a ceramic may be thermally sprayed between the alloy layer and the oxide ceramic layer. A mixed layer formed by the above method may also be provided. Providing a mixing tank further improves thermal shock resistance. Alternating alloy layers and ceramic layers! ET layered multilayer structure J
It's a company and it's 6 (ゝ.

In forming the sprayed layer, adjust the type and amount of plasma generation gas, the type and amount of powder feeding gas, arc current, voltage, spray distance 1, spray angle 7, relative movement speed, etc. It is essential to form a dense film.

The present invention will now be explained more specifically from Example 1.

Examples 1-10, Comparative Examples 1-3 A base material of molybdenum norconia thermeft (composition weight ratio 50:50) having 10 chains mφX3001I1 ml was coated with various thermal spray materials. This was installed in an atmospheric furnace and heated to 1300°C2 (heating rate = 200°C/hr).
After holding for a time, slowly cool down (temperature reduction rate = 200'C/I+
r). The high temperature oxidation resistance performance was evaluated based on the appearance of the composite at this time. Table 1 shows the test results for the Ill composition and film thickness of the thermal spraying materials used. The method for forming each layer by thermal spraying is as follows. N1-Cr-ALX alloy powder (particle size -10-88/jm) was inserted into a plasma flame generated with a mixed gas of Alfon and hydrogen using an argon carrier and melted, forming a Mo-ZrO2 cermet matrix. Material (M
o : l r○2 = 50:50 (heavy + J, )) to form an alloy no. The distance between the torch and the base material at this time was 100 μm. Next, the thermal spray powder was applied to alumina (A120.) or alumina-chromia (A120z).
-5CrzO*) (particle size 5 to 3() μm),
A ceramino shoe is formed on the film of the alloy layer of the base material in a similar manner. The distance between the torch and the base material at this time is 90mm.
Met.

Further, the thickness of the film was varied by changing the number of times the torch scanned the base material and the amount of spray powder supplied.

Examples 11-18 Next, composite materials were manufactured under the same conditions as in Example 4 except that only the type of ceramic layer was changed. That is, Mo-ZrO
2 Ni-16Cr-6Al-0,5 on the cermet base material
After plasma spraying Y to a thickness of about 100 μm, the ceramic was switched to ceramic powder having the composition shown in Table 2 and plasma sprayed to a thickness of about 300 μm to obtain a composite material. This was subjected to a high temperature oxidation resistance test under the same conditions as in Examples 1 to 10, and the results are shown in Table 2.

:□1. i Yu.

Example 19 Alumina-chromia (A I203-5 Cr2
0)) (ceramics τ4) with Ni-16Cr-6A
When adhering to the I-0,5Y layer (alloy layer), thermal shock resistance could be improved by providing a layer in which both were mixed (mixed layer).

First, N i-16Cr-6Al-0,5Y was thermally sprayed under the same conditions as in Example 4 to obtain a film with a thickness of 70 μm. Now, from another nozzle, A 120. -5 Cr2O3
into the plasma flame. At this time, Ni16Cr-6
While the amount of Al-0,5Y alloy powder fed was continuously decreased, the amount of alumina-chromia fed was increased until only alumina-chromia remained. As a result, the thicknesses of the mixed layer and the alumina-chromia layer (ceramic layer) were 80 μm and 250 μ(1), respectively.

In this way, in order to continuously change the ratio of alloy and ceramic in the thermal spray coating, it is necessary to change the thermal spraying conditions (7y spray amount, electric power,
(powder supply amount, thermal spraying distance, etc.) are preferably changed continuously.

When a high temperature oxidation resistance test was conducted in the same manner as in Example 1, no damage was observed.

On the other hand, the heat impact resistance test was conducted in accordance with 5-gun 5H8666.
A test piece (10 + ao + φ
The procedure of holding the sample (X300+nmL) for 10 minutes and administering it into cold water was repeated. The composite material obtained by mixed thermal spraying showed no damage such as peeling of the film even after 50 cycles. On the other hand, in the hr: composite material obtained in Example 4, part of the film peeled off after 5 cycles.

According to the experimental results obtained here, the thermal shock resistance of the mixed sprayed coating is excellent, but in the normal operation of a reduction furnace, there are no conditions of drastic temperature rise or fall used in this test, so Example 4 was used. The use of the resulting composite material does not depart from the objectives of the present invention. However, in the case of a mixed thermal spray coating, for example, the insertion speed of the thermocouple temperature J into the furnace can be increased.

Example 20 Molybdenum-alumina cermet (composition weight ratio 60:40) was used as the Mo-oxide cermet. In the isothermal oxidation resistance test conducted in the same manner as in Example 1, no precipitation of Moo or powder was observed.

Example 21 Molybdenum-chromina cermet (m molding amount ratio 60:40) was used as the Mo-I'll compound cermet, and till - was applied to the above base material in the same manner as in Example 2.
The alloy layer and the ceramic layer were provided so as to have the same thickness and the same thickness. In the isothermal oxidation resistance test conducted in the same manner as in Example 1, no precipitation of -6MoOz powder was observed.

Example 22: A demonstration test was conducted in an actual plant based on the results of the experimental examples that have been exemplified so far. That is, the outer diameter is 28+
++m, inner diameter +5+oa+, [sa9 (,) Omn+
Cylindrical Mo-2r O2 Therme >) (50:5
0 (heavy fi 1.)) was subjected to plasma spraying in the same manner as in Example 4 on the surface of a thermoelectric lamp thermometer protection tube with one end heated to obtain a composite.

The original electric lamp thermometer protection tube was inserted into a coal gasification furnace that generates hydrogen and carbon oxide at room temperature before the start of operation. Thereafter, propane gas was used as fuel to raise the temperature of the furnace, and when the temperature inside the furnace reached 1200'C or higher, the fuel was switched to coal, and continuous operation of sintering started.

The temperature of the gasifier in steady state is 1400°C, and the gas composition is water;! 35-40%, -carbon oxide 39-43
%, carbon dioxide 18-24% hydrogen sulfide 1.0-1.7%
Met. The thermoelectric lamp thermometer protection tube used under these conditions was 9
It worked without any problems for 0 days.

Comparative Example 4 The same thermoelectric lamp thermometer protection tube as in Example 20 was used without plasma spraying treatment. In this case, in order to avoid oxidation, the furnace was installed at a predetermined location during preheating (approximately 1000°C), and then continuous operation was started under the same conditions as in Example 22. However, it became unusable after 15 days. became.

Effects of the invention*- As mentioned above, the composite material of the present invention has extremely excellent oxidation resistance at high temperatures, and also has both an oxidizing atmosphere and a reducing atmosphere at high temperatures, and is free from the presence of slag, sulfur, etc. It can withstand long-term use even in reduction furnaces.
This brings great benefits to the operation of a reduction furnace (v'), for example, in a manufacturing industry under such an atmosphere.

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Claims (1)

[Claims] 1. An alloy layer obtained by thermal spraying and an oxide ceramic layer are successively provided on a molybdenum-oxide cermet material, and the alloy of the alloy layer is NiCrAlX of the formula (1) (in the formula (X represents at least one metal selected from yttrium, hafnium, scandium and other rare earth metals), where X is 5% by weight or less of the alloy, or NiCrAl of formula (2) A composite material having reduction resistance and oxidation resistance at high temperatures, characterized by being an alloy of the following. 2. The composite material according to claim 1, wherein the composite material is a member for a reduction furnace using fossil fuel. 3. The composite material according to claim 1, wherein the composite material is a member for a reduction furnace for reducing metal oxides. 4. The composite material according to claim 1, wherein the oxide in the cermet material is at least one selected from the group consisting of zirconia, alumina, chromia, and titania. 5. The composite material according to claim 1, wherein the oxide ceramic is alumina or the alumina contains at least one selected from zirconia, chromia, magnesia, calcia, and titania. 6. Claim 1, characterized in that there is a mixed layer formed by thermal spraying a mixture of the alloy and the oxide ceramic between the alloy layer and the oxide ceramic layer. composite material.