JPH04231453A - Thermal spray material and sprayed heat-resistant and corrosion-resistant member - Google Patents

Abstract

PURPOSE:To manufacture a thermal spray material excellent in heat resistance, thermal impact resistance and corrosion resistance by blending 2CaO.SiO2 with MgO.4ZrO2 in a specified ratio. CONSTITUTION:A thermal spray material of 2CaO.SiO2-MgO.4ZrO2 series oxide constituted of, by weight, 50<=2CaO.SiO2<=90 and 10<=MgO.4ZrO2<=50 as well as 2CaO.SiO2+MgO.4ZrO2=100 is prepd. Furthermore, the grain size of the above oxide material is regulated to 5 to 500mum, and its average grain size is preferably regulated to 0.1 to 100mum in particular. In this way, a thermal spray material excellent in heat resistance, thermal impact resistance and corrosion resistance is obtd., and by applying plasma spraying to the surface of a substrate, a member having excellent thermal shielding effect and corrosion resistance can be manufactured.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a thermal spray coating material with heat resistance and excellent heat insulating properties, which is used for thermal spray coating to improve the surface of ceramics, metals, etc., and high temperature durability of heat resistant parts. In particular, the present invention relates to heat-resistant and corrosion-resistant parts coated with these thermal spray coating materials by an optimal plasma spraying method, particularly as parts of gas turbines and the like.

0002

2. Description of the Related Art The high-temperature characteristics required for heat-resistant and thermal shock-resistant members are becoming more severe year by year. Among them, gas turbines exhibit higher efficiency as they are operated at higher temperatures, so there is a constant demand for higher operating temperatures. For this reason, fine ceramics such as SiC and Si3N4 are being considered as materials that have both heat resistance and thermal shock resistance, but at present gas turbine parts are basically made of metal materials due to problems with impact strength. Manufactured in

However, use of heat-resistant metal materials such as Ni-based and Co-based materials is limited to temperatures below 1000°C. Therefore, when they are applied to gas turbine parts,
Various methods of cooling or heat shielding have been investigated. Heat shielding is the process of forming a ceramic layer on the surface of the metal (hereinafter referred to as base material) of high-temperature heat-resistant parts such as gas turbines to lower the base material temperature. Ceramic powders with high efficiencies are used as coating materials.

[0004] Examples of materials that have been used for the above-mentioned purposes include, for example, ZrO2 to which a rare earth oxide such as Y2 O3 is added as a stabilizer. however,
Even with thermal spray coatings obtained using this currently best thermal spray material, the coating layer peels off from the base material and loses its function in gas turbines that are subjected to intense thermal cycles of rapid cooling and rapid heating. In addition, since these materials use expensive rare earth oxides, the manufactured thermal spray materials are also very expensive, and using large quantities for structural material components for industrial purposes is quite problematic in terms of cost. There is.

Generally, when thermal spray coating materials are used under intense thermal cycles of rapid heating and cooling, thermal distortion occurs between the base material and the coating, which cannot follow the thermal expansion of the base material, resulting in cracks and peeling. It is not possible to obtain sufficient durability. For this reason, various efforts have been made to develop thermal spray materials that not only have low thermal conductivity but also have an expansion coefficient close to that of the base material. Also,
A layer made of a mixture or composite of the metal and ceramic layers, which is the main cause of peeling, is provided (for example, in Japanese Patent Laid-Open No. 55
-113880 etc.) or ceramic layer.
Fine cracks are formed by high temperature and long heat treatment (
Various proposals have also been made, such as parts with a ceramic layer formed and then rapidly cooled to form fine cracks in the layer (for example, JP 58-87273, etc.). There is.

[0006]

[Problems to be Solved by the Invention] However, although each of the above-mentioned conventional means has been improved, their effects have been limited based on the results of thermal cycle tests and the like. Taking these current circumstances into consideration, the present invention provides ZrO2 -Y2 O3
A material for thermal spray coating that has heat resistance, thermal shock resistance, and corrosion resistance, and has a very low cost, high product yield, economical, and extended life compared to other materials, and thermal spray coating heat resistant materials such as gas turbine parts that are coated with this material. The purpose is to provide corrosion-resistant members.

[0007]

[Means for Solving the Problems] The inventors have conducted extensive research in order to find a material that has heat resistance, thermal shock resistance, and corrosion resistance. As a result, we have discovered that by using calcium silicate, which is also a natural resource, as a starting material, we can create a completely new thermal spraying material that does not use rare earth oxides and is inexpensive and has heat resistance, thermal shock resistance, and corrosion resistance. That is, the present invention has the following features: 1. 2CaO・SiO2 -MgO・4ZrO2
system oxide, the composition is 50≦2CaO・Si in weight%
O2 ≦90, 10≦MgO・4ZrO2 ≦50, and 2CaO・SiO2 +MgO・4ZrO2 =10
A material for thermal spray coating, characterized in that it consists of 0. 2. In a component made of a heat-resistant metal material, the component has a metal coating layer provided on its surface that is equivalent to or has higher high-temperature corrosion resistance than the heat-resistant material, and is further provided on the metal coating layer according to claim 1. A thermal spray-coated heat-resistant and corrosion-resistant member characterized by being thermally sprayed with a thermal spray coating material. 3. A material for thermal spray coating, wherein each of the oxide materials described in item 1 above is particles of a compound, a composite, or a mixture. 4. The particle size of the oxide material described in item 1 above is 5 to 500μ.
m, especially when the average particle diameter is 10 to 100 μm.
A thermal spray coating material characterized by: 5. A thermal spray-coated heat-resistant and corrosion-resistant member, characterized in that the thermal spray coating material described in item 2 above is the thermal spray coating material described in item 3 above. It is.

The present invention will be explained in detail below. We attempted to develop a ceramic material that is stable at high temperatures, has a high heat resistance effect, has a relatively large coefficient of thermal expansion, and can be manufactured at low cost, that is, a thermal spray material using calcium silicate as a starting material. Calcium silicate contains “CaO
・SiO2” “2CaO・SiO2” “3CaO・
"SiO2", "3CaO.2SiO2", etc. are known. As a result of conducting various studies on these calcium silicate thermal spray materials, it was found that 2CaO.SiO2 is superior. CaO.SiO2 contains a high amount of SiO2, and when thermally sprayed, a large amount of glass phase is generated in the coating, resulting in a significant decrease in thermal shock resistance. With 3CaO.SiO2, CaO is generated in the coating by thermal spraying and causes a dusting phenomenon due to moisture absorption. In addition, with the aim of improving the synergistic effect of heat insulation and thermal shock resistance of the coating, as a result of studies in the MgO/ZrO2 system, we found that
gO.4ZrO2 was selected and a plurality of these were used in the thermal spray coating material of the present invention. This is because using a plurality of these heat-resistant and heat-insulating materials exhibits better heat-resistance and heat-insulating properties than conventional heat-insulating materials, and can be expected to form a highly reliable coating layer. 2CaO・SiO2 has various crystal systems, and any of them can be used, but considering the slaking property, etc., we use γ-type 2CaO・SiO2.
is preferred.

[0009] Also, 2CaO.SiO2 and MgO.4
ZrO2 may be used as the thermal spray material of the present invention by simply mixing the powders of both. In this case, the fineness is preferably set to an average particle size of 10 to 100 μm. Alternatively, the powder mixture may be further granulated and composited to form the thermal spray material of the present invention. To obtain this granulated composite, 2CaO・SiO2
and MgO.4ZrO2 are ground to an average particle size of 1 to 3 μm using a ball mill, for example, and 2 to 5% by weight of polyvinyl alcohol is added as a binder, and granulated to an average particle size of 10 to 100 μm using a spray dryer. Also, 2CaO・SiO2 and MgO・4ZrO2 are
This can also be used as a thermal spraying material of the present invention as an electrofusion compound. For example, in order to make an electric fusion compound, 14
The thermal spray material of the present invention is obtained by melting at a temperature of 00 to 1,600°C, then cooling it, and pulverizing the cooled material to an average particle size of 10 to 100 μm.

As described above, there are three types of thermal spray materials of the present invention: a mixture, a granulated composite, and an electrofused compound. Among these, the granulated composite is the most preferred, followed by a mixture and an electrofused compound. In turn, they are excellent in terms of thermal shock resistance. Further, the thermal spraying material of the present invention has a particle size adjusted to 5 to 500 μm,
Particularly preferred is one whose average particle size is adjusted to 10 to 100 μm.

Furthermore, the composition range of the thermal spray material of the present invention is limited as described above for the following reasons. 2CaO・
If the SiO2 content is more than 90% by weight, the high temperature stabilization effect will decrease, which is not preferable. When MgO.4ZrO2 is more than 50% by weight, the coefficient of thermal expansion is so small that it cannot follow the coefficient of thermal expansion of the base material, resulting in cracking and peeling. If the particle size of the material of the present invention is smaller than 5 .mu.m, the flow of the powder supplied to the thermal spray gun will be poor and not only will a good coating not be obtained, but the thermal spraying yield will also decrease. On the other hand, if the particle size is larger than 500 μm, unmelted particles will form a film, resulting in a decrease in adhesion and function of the sprayed film.

The thermal spray material of the present invention is characterized in that two types of materials are combined, composited, or mixed in various proportions. This ensures durability. In other words, the coating sprayed with this material not only has excellent heat resistance and heat insulation properties, but also
Since it exhibits hot expansion behavior similar to that of the base material, peeling damage to the coating can be significantly suppressed. In addition, the thermal spray coating absorbs corrosive gas components such as V compounds and suppresses their diffusion into the base material, and CaO reacts with the V compounds to convert them into high melting point compounds (for example, the melting point of V2 O5 is 690°C). ,3CaO
・V2 O5 also has the function of lowering its corrosivity by changing the temperature to 1016°C. The present thermal sprayed material and thermal sprayed member having these characteristics have great industrial significance.

Various embodiments of the present invention will be described below. Peeling of the ceramic layer, which is the main cause of reduced service life, is caused by thermal stress due to the difference in coefficient of expansion between metal and ceramic. To alleviate this, various ceramics with relatively large coefficients of thermal expansion are selected and subjected to thermal shock. A test was conducted. The base material is a Ni-based alloy (IN939:
After blasting with alumina powder using a Ni-Co-Cr-W alloy, CoCrAIY alloy, which is a metal with excellent high-temperature corrosion resistance, is first applied by low-pressure plasma spraying to a thickness of 100 μm, and then various ceramics shown in Table 1 are sprayed on top using a spray dryer. The spray material was sprayed and granulated to have an average particle diameter of about 30 μm, and then plasma sprayed. The obtained test piece was heated at 1200°C for 15 minutes and cooled at room temperature for 15 minutes.
The material was subjected to a cyclic thermal shock test, and the number of thermal cycles until cracking was investigated. The results are shown in Table 1. From this test result, No. 9-2CaO・SiO2 -10wt%M
gO・4ZrO2 ~No. 15 2CaO・SiO2
-50 wt% MgO.4ZrO2 was found to have good thermal shock resistance, showing durability over 10 thermal shocks.

[0014]

[Table 1]

[0015] Furthermore, 2CaO.SiO2 -MgO.4
Regarding ZrO2-based raw materials, it was found in this test that composites had the best thermal shock resistance, followed by mixtures and compounds in that order. No. 1 showed good thermal shock resistance.
10 2CaO・SiO2 -25wt%MgO・4Z
The cross section of the film was observed using rO2 as a representative example. The results are shown in Figure 1. It was confirmed that there were many fine vertical cracks within the coating. It is presumed that this vertical crack improved the thermal shock resistance.

Next, a corrosion resistance test was conducted. Samples were prepared using the same procedure as in the thermal shock resistance test. Corrosion resistance tests were carried out using 85% V2O5 as the corrosive medium on thermally sprayed samples.
-Apply 40mg of 15% Na2SO4 and
After firing at ℃ for 4 hours, a sample was taken out from the furnace and the presence or absence of peeling of the coating and the thickness of the reaction layer were investigated. The results are shown in Table 2. No. 1 ZrO2 -8wt% Y2O3, No.
2 of 2CaO・SiO2, No. 3 MgO・4Zr
O2, No. 7-2CaO・SiO2 -60wt%
MgO・4ZrO2, No. 8-2CaO・SiO2
-75wt%MgO.4ZrO2 causes peeling of the sprayed coating due to reaction with corrosive media, and cannot be put to practical use. Also No. 4-2CaO・SiO2 -3wt%MgO
・4ZrO2, No. 5-2CaO・SiO2 -5
wt%MgO・4ZrO2, No. 6-2CaO・S
iO2 55wt%MgO.4ZrO2 had a thicker reaction layer than other materials.

[0017]

[Table 2]

From the above results, it was found that a heat-resistant and corrosion-resistant member characterized by being thermally sprayed coated with an oxide raw material consisting of 10 to 50 wt% MgO.4ZrO2 and the balance 2CaO.SiO2 has high durability. .

[0019]

[Example] Example 1 1 to 2% sulfur as a corrosive component, V: 10 to 18 ppm
CoCrAIY was sprayed under reduced pressure to a thickness of 0.1 mm on the first and second stage stator blades of power generation gas turbines that use fuel containing Na: 3 to 10 ppm.
The thermal spray coating material of the present invention, 2CaO・Si adjusted to m
O2 -25wt%MgO・4ZrO2 (composite raw material)
, 2CaO・SiO2 -40wt%MgO・4ZrO
2 (composite raw material) was thermally sprayed to a thickness of 0.2 mm each and used at a turbine inlet temperature of 1,100° C. for about one year, but the coating of the present invention remained in good condition with no cracks or peeling.

Example 2 CoCrAlY was sprayed under reduced pressure to a thickness of 0.15 mm on the inner surface of the combustor of the power generation gas turbine of Example 1 as an underlay layer, and test piece No. 1 shown in Table 1 was coated thereon. 2-2CaO・SiO2
, No. No. 3 MgO・4ZrO2 and No. 2 of 10
CaO・SiO2 -25wt%MgO・4ZrO2
The combustor inner cylinders each having a thickness of 0.3 mm plasma sprayed in the atmosphere were used for one year at a combustion chamber temperature of 1150 to 1300°C. All of the coatings in No. 10 were healthy and progressing well. In addition, No. 1 was used as a comparative material in this example.
2.No. All of the coatings No. 3 developed hexagonal cracks and peeling within 3 to 6 months, and no durability was observed.

[0021]

As is clear from the above results, the thermal spray coating material of the present invention has high resistance to heat and thermal shock, and is also excellent in corrosion resistance. By using the coating sprayed layer of the present invention, it is possible to obtain a highly reliable and efficient turbine blade that has excellent heat shielding effect and heat resistance, and
In addition, since rare earth oxides are not used, it has the effect of greatly contributing to cost reduction.

[Brief explanation of the drawing]

[Figure 1] Figure 1 shows 2CaO・SiO2 -25wt%M
It is a cross-sectional photograph showing the crystal structure of gO.4ZrO2 (composite raw material) thermal spray coating.

Claims (5)

[Claims] [Claim 1] 2CaO.SiO2 -MgO.4Z
An rO2-based oxide, the composition is 50≦2Ca in weight%.
O・SiO2 ≦90, 10≦MgO・4ZrO2 ≦
50, and 2CaO・SiO2 +MgO・4ZrO2
=100. 2. A component made of a heat-resistant metal material, the component having a metal coating layer provided on its surface that is equivalent to or has higher high-temperature corrosion resistance than the heat-resistant material, and further comprising a metal coating layer on the metal coating layer. A heat-resistant and corrosion-resistant member for thermal spray coating, characterized in that the material for thermal spray coating according to item 1 is thermally sprayed. 3. A material for thermal spray coating, wherein each oxide material according to claim 1 is a particle of a compound, a composite, or a mixture. 4. The particle size of the oxide material according to claim 1 is adjusted to 5 to 500 μm, particularly, the average particle size is 10 μm.
A material for thermal spray coating, characterized in that the particle diameter is 100 μm. 5. A thermal spray-coated heat-resistant and corrosion-resistant member, characterized in that the thermal spray coating material according to claim 2 is the thermal spray coating material according to claim 3.