JP5489519B2 - Coating material, coating method, and blade with shroud - Google Patents

Description

  The present invention relates to a coating material for a wear-resistant coating formed on a blade with a shroud.

  A tip shroud structure is employed for the rear stage blades of the gas turbine for the purpose of vibration damping. FIG. 1 is a partial perspective view showing a moving blade with a shroud. A Z-type shroud 2 is formed at the tip of the moving blade 1 to prevent fluid leakage and restrain the torsion of the moving blade 1, and further, a contact that is a surface in contact with the shroud 2 of the adjacent moving blade 1. It has surface 3. Further, since various vibrations due to drift, stationary blade nozzle passing, flutter, and the like occur in the moving blade 1, the contact surface 3 of the shroud 2 is usually subjected to wear resistance treatment. . Conventionally, a coating film of Trivalloy 800 (T-800: cobalt-based wear resistant material) is applied by APS spraying (atmospheric pressure plasma spraying).

  However, the APS spraying has a problem in that the contact with the base material on the contact surface 3 of the shroud 2 is low and is easily peeled off. Therefore, Patent Document 1 discloses a coating method in which a trivalloy coating film is formed on the shroud contact surface 3 of the turbine rotor blade 1 by high-speed flame spraying (HVOF), low-pressure plasma spraying (LPPS) or atmospheric plasma spraying, and subjected to diffusion heat treatment. Has been proposed.

JP 2001-152803 A (Claims 1 to 3)

  The T-800 coating film is excellent in ductility and has high wear resistance. However, in recent high-temperature gas turbines, significant oxidation thinning occurs and wear resistance decreases.

Although a cermet coating of Cr ₃ C ₂ (75% by mass) -NiCr (25% by mass) is also used as a coating film on the contact surface, it is inferior in impact resistance and has a problem that chipping occurs during use of the gas turbine. It was.

  The present invention provides a coating material which has a high wear resistance and can be a coating film excellent in oxidation resistance at high temperatures, a coating method using the coating material, and a rotor blade with a shroud. Objective.

In order to solve the above problems, the present invention provides molybdenum (Mo) of 18% by mass to 34% by mass, chromium (Cr) of 11% by mass to 18% by mass, and 0.5% by mass to 4% by mass. % Of silicon (Si), 1.5% by mass or less of cobalt (Co) and 0.08% by mass or less of carbon (C) are allowed to be contained, and 0.01% by mass. more than 3 mass% of yttrium (Y), contains at least one additive component selected from Ranaru group Toka 0.01 mass% to 10 mass% of aluminum (Al), balance nickel (Ni) and A coating material comprising inevitable impurities is provided.

The base material having the above composition is excellent in high-temperature oxidation resistance as compared with Co-based T-800. When the base material having the above composition is a coating film, high-temperature oxidation resistance can be improved while maintaining wear resistance equivalent to T-800. Furthermore, in the present invention, the base material further contains at least one additive component of Y and Al .

The reasons for limiting the amount of each additive component added will be described below.
Y has a peg effect to prevent the generated oxide scale from dropping in the coating film using the coating material of the present invention, and improves the oxidation resistance of the coating film. Since the measurement error of the oxide scale thickness is 1 to 2%, the amount of Y added is 0.01% by mass or more in order to obtain the peg effect. Further, in order to obtain a coating film having good wear resistance, the film needs to have an appropriate hardness. The greater the amount of Y added, the higher the hardness of the coating film. However, if the added amount of Y exceeds 3% by mass, the segregation of Y becomes remarkable and the hardness becomes high. Therefore, mechanical characteristics such as ductility are impaired, and problems such as easy cracking during construction occur. The addition amount of Y is more preferably 0.1% by mass or more and 1.5% by mass or less.

By adding Al to the base material having the above composition, dense Cr ₂ O ₃ can stably exist on the surface, and a protective film against oxidation inside the metal can be obtained. Thereby, the oxidation resistance of the coating film can be improved. Considering that the measurement error of the oxide scale thickness is 1 to 2%, the additive amount of Al for obtaining the oxidation resistance improvement effect is set to 0.01% by mass or more. Further, the greater the amount of Al added, the higher the hardness of the coating film. When the amount of Al added exceeds 10% by mass, the coating film becomes extremely hard and cracks are likely to occur during construction. The addition amount of Al is more preferably 0.2% by mass or more and 5.0% by mass or less.

Fe has the effect of improving the oxidation resistance of the coating film. This is thought to be due to the fact that the base materials Ni and Fe are solid-dissolved and the proportion of Mo having poor oxidation resistance is reduced. Considering that the measurement error of the oxide scale thickness is 1 to 2%, the addition amount of Fe for obtaining the oxidation resistance improvement effect is set to 0.1 % by mass or more. Moreover, when Fe is added, the hardness decreases and the wear resistance decreases. In order to ensure good wear resistance, the amount of Fe added is 10% by mass or less. The addition amount of Fe is more preferably 0.3% by mass or more and 5.0% by mass or less.

In the present invention, the coating material may contain a plurality of types of additive components. Thereby, the high temperature oxidation resistance of a coating film can be improved more.
In addition, in this invention, each component amount is represented by the mass percentage when the mass of the whole material is set to 100.

Moreover, this invention provides the coating method which forms a coating film on the heat-resistant-alloy base material surface by thermal spraying using the powder which consists of the said coating material.
In this case, it is preferable to perform a thermal diffusion treatment after forming the coating film.

  According to the coating method of the present invention, a dense coating film having high wear resistance and high temperature oxidation resistance can be formed. Furthermore, by performing the thermal diffusion treatment, the film quality of the coating film can be improved, and the adhesion between the coating film and the base material can be improved.

  The present invention relates to a blade with a shroud in which a shroud is provided at the tip of a turbine blade, and the shroud is in contact with another shroud provided at the tip of another blade that is adjacently disposed in use. And a shroud blade having a coating film formed by the above-described coating method.

  The rotor blade with a shroud of the present invention has a coating film having a long life that can withstand continuous use at high temperatures because the contact surface is provided with a coating film having excellent wear resistance and high temperature oxidation resistance.

  The coating film obtained by the coating material of the present invention has high wear resistance and excellent high-temperature oxidation resistance. In particular, when a coating film is formed on the contact surface of the shroud of the rear stage rotor blade in the high-temperature gas turbine using the coating material and the coating method of the present invention, the life of the contact surface can be improved.

It is a partial perspective view of a moving blade with a shroud. It is a graph which shows the oxide scale thickness of the coating film in the test piece of an Example and a comparative example.

  In the coating material of the present embodiment, the base material contains Mo: 18% by mass to 34% by mass, Cr: 11% by mass to 18% by mass, Si: 0.5% by mass to 4% by mass, The balance is Ni and inevitable impurities. The base material is allowed to contain Co: 1.5 mass% or less, Fe: 1.5 mass% or less, and C: 0.08 mass% or less. The coating material of this embodiment is 0.01 mass% or more and 3 mass% or less Y, 0.01 mass% or more and 10 mass% or less Al, and 0.1 mass% or more and 10 mass% with respect to the said base material. % At least one additional component selected from the group consisting of Fe or less.

  The coating film of this embodiment is formed by spraying the powder of the above coating material composition on the contact surface of a shroud whose base material is a refractory metal such as IN738LC. Examples of the thermal spraying method include high-speed flame spraying (HVOF), reduced pressure plasma spraying (LLPS), and atmospheric pressure plasma spraying (APS).

Since the coating material having the above composition contains an active metal element such as Cr or Al, the thermal spraying powder is produced by a gas atomizing method. Since the powder produced by the gas atomization method instantaneously transforms the molten alloy melt uniformly into droplets and cools, a spherical powder having a uniform microstructure is obtained. Moreover, since droplets are continuously formed from the same molten metal, the compositional difference between the particles is extremely small, and the compositional difference due to the size of the particles is also small.
The produced thermal spraying powder is classified using a sieve. The particle size of the powder to be used is appropriately selected depending on the type of thermal spraying. For example, the particle size is 53 μm or less for high-speed flame spraying, 10 to 44 μm for low-pressure plasma spraying, and 103 μm or less for atmospheric pressure plasma spraying.

Coating film formation by high-speed flame spraying is performed by the following steps. Since high-speed flame spraying is performed in the atmosphere, it is low in cost and applicable to large parts.
The thermal spraying powder is supplied to the thermal spray gun in a powder state. Oxygen and kerosene are supplied to the spray gun and burned. As a result, the thermal spraying powder is heated and melted and injected onto the contact surface of the shroud to form a coating film. The film thickness of the coating film is about 0.2 mm.

Examples of specific high-speed flame spraying conditions are as follows.
Combustion pressure: 0.7 MPa
Kerosene flow rate: 20 L / h
Oxygen flow rate: 54 m ³ / h
Thermal spray distance: 500mm
Gun movement speed: 500 mm / sec
Gun movement pitch: 6mm
Used thermal spraying device: JP5000 manufactured by Praxair

  According to high-speed flame spraying, the thermal spraying powder is collided with the surface of the base material at a relatively high temperature (1600 ° C. or lower) at a high speed of about Mach 1 (300 m / s to 500 m / s). Thereby, a dense coating film having the above composition can be formed in the atmosphere.

Note that the coating film formed by high-speed flame spraying has few pores, and since the spraying temperature is low and it is difficult to oxidize, peeling may occur because there are few oxides at grain boundaries in the film. Therefore, for the purpose of improving the film quality, a thermal diffusion treatment may be performed after the film formation. By subjecting the base material and the component derived from the sprayed particles in the coating film to the thermal diffusion treatment, the base material and the coating film can be integrated and the adhesion can be improved.
The thermal diffusion treatment is, for example, a treatment in which a solution heat treatment at 1121 ° C. for 2.5 hours, a cooling process in nitrogen, an aging heat treatment at 850 ° C. for 24 hours, and a cooling process in nitrogen are sequentially performed. The thermal diffusion treatment can be performed together with the heat treatment for the rotor blade.

Coating film formation by low-pressure plasma spraying is performed by a cleaning process in which deposits on the surface of an object are blown off by reverse polarity arc discharge in a vacuum chamber, a preheating process in which the base material is heated to 200 to 300 ° C., and a plasma spraying process. To be implemented. Table 1 shows an example of spraying conditions using a vacuum spraying system manufactured by Sulzer Metco.

Since the low-pressure plasma spraying is performed in a reduced-pressure atmosphere, no oxide is formed in the film, so that the film is dense and has excellent adhesion to the base material.
In addition to the low pressure plasma spraying, atmospheric plasma spraying can also be used.

Table 2 shows the compositions of the coating materials of Examples and Comparative Examples.

Using high-speed flame spraying, a heat-resistant alloy substrate (IN-738LC, chemical composition: Ni-16Cr-8.5Co-1.75Mo-2.6W-1.75Ta-0.9Nb-3.4Ti-3.4Al (Mass%)) A thermal spraying powder having the composition shown in Table 2 was sprayed thereon to form a coating film. The thickness of the coating film was 0.2 mm. After the film formation, the above thermal diffusion treatment was performed.
The test piece on which the coating film was formed was heated in an air atmosphere at 1000 ° C. for 300 hours using an electric furnace. The coating film cross section of the test piece after heating was observed using a scanning electron microscope, and the thickness of the oxide scale was measured.

FIG. 2 shows the oxide scale thickness of the coating film in the test pieces of Examples 1, 3 , 4, 6, 7 and Reference Examples 1, 3 and Comparative Examples 1 and 2. In the figure, the vertical axis shows the thickness ratio of the oxide scale when the oxide scale thickness of the test piece of Comparative Example 2 is 1. Compared to Co-based Comparative Example 1 (T-800 composition), Ni-based Comparative Example 2 was able to reduce the oxide scale thickness to about ½. Further, in all of the examples, the high-temperature oxidation resistance was improved as compared with Comparative Example 2. In particular, Y is effective in improving oxidation resistance. In Example 1, the oxide scale thickness was about ½ that of Comparative Example 2.

The Vickers hardness measurement of the coating film of each test piece was performed with a load of 1 kg. Table 3 shows the results.

Abrasion resistance falls that the hardness of a coating film is less than Hv500. On the other hand, when it becomes higher than Hv900, since ductility falls, a crack arises.
Examples 1-7 and Reference Examples 1-3 were all in the range of Hv500 or more and 900 or less. In particular, in Examples 1, 3, 6 and 7, and Reference Examples 1 and 3 to which 0.5% by mass of Y, Al and Fe were added, Comparative Example 1 and Comparative Example 2 (T-800 composition) which are base materials ) And almost the same hardness.
In Comparative Examples 2, 3, 5, and 6 in which the added amount of Y or Al was excessive, the Vickers hardness exceeded 900, and cracking of the film was confirmed. In Comparative Example 4 in which the Fe addition amount was excessive, it was expected that the wear resistance was low because the Vickers hardness was low.

Claims (4)

18% by mass or more and 34% by mass or less of molybdenum (Mo);
11 mass% or more and 18 mass% or less of chromium (Cr),
Containing 0.5 mass% or more and 4 mass% or less of silicon (Si),
Up to 1.5% by weight of cobalt (Co);
0.08% by mass or less of carbon (C) is allowed,
0.01% by mass or more and 3% by mass or less of yttrium (Y);
The coating material contains at least one additive component, the balance being nickel (Ni) and unavoidable impurities selected from 0.01 wt% to 10 wt% of aluminum (Al) Toka Ranaru group.   A coating method for forming a coating film on the surface of a heat resistant alloy substrate by thermal spraying using the powder comprising the coating material according to claim 1.   The coating method according to claim 2, wherein a thermal diffusion treatment is performed after the coating film is formed. A blade with a shroud provided with a shroud at the tip of the turbine blade,
The shroud has a contact surface that comes into contact with another shroud provided at the tip of another moving blade adjacently disposed in use;
A rotor blade with a shroud, wherein the contact surface includes a coating film formed by the coating method according to claim 2.

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