JPH0819497B2 - Turbine blade manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a method for manufacturing a turbine blade, and more particularly to a corrosion-preventing piece (erosion shield) attached to the front edge of the turbine blade. The present invention relates to a turbine blade manufacturing method in which the characteristics such as ductility and toughness and the hardness of the adhered portion after the anticorrosion piece is adhered are further improved as compared with conventional methods.

(Prior art) In steam turbines, there is a demand for higher power output that makes full use of steam energy, and inevitably turbine blades tend to have longer blades in order to make full use of that energy. is there.

Conventionally, 12Cr steel was applied to this type of material,
Since the 12Cr steel is heavy in weight, the centrifugal force generated when the turbine blades rotate is extremely high, and a strict design is required in terms of strength. In addition, steam may have fine water droplets appearing as it flows toward the wake stage of the turbine blade, and the corrosion-preventing piece (erosion shield) that functions to prevent erosion at the leading edge of the turbine blade.
Was wearing.

However, in consideration of the above centrifugal force, 12Cr steel that has been conventionally applied as a turbine blade material is not necessarily preferable in terms of design, and a titanium alloy that is much lighter in weight than conventional materials and has high corrosion resistance has been reviewed. Investigation into application is in progress.

However, even titanium alloys cannot withstand steam containing fine water droplets in terms of corrosion resistance due to long-term use, and studies are still underway to apply anticorrosive pieces to the leading edges of turbine blades. In this case, the anticorrosion piece (hardness Hv is approximately 500
However, there is a problem in the conventional deposition method because the characteristics of the alloy steel are different from each other even when the Co-based alloy is deposited.

Therefore, as for the material of the anticorrosion piece for a titanium alloy turbine blade, a β-type titanium alloy that can be hardened by heat treatment in the same titanium alloy, for example, Ti-15Mo-5Z.
We are considering the application of r.

(Problems to be Solved by the Invention) Although the above β-type titanium alloy is convenient for heat treatment, it is far inferior to the conventionally applied anticorrosion piece in terms of hardness and corrosion resistance. Moreover, when the anticorrosion piece is applied to the leading edge of the turbine blade, the ductility and toughness of the applied portion after hardening by heat treatment are extremely reduced, and there is a slight concern that it will be applied to the leading edge of the turbine blade. There is.

Therefore, in consideration of the characteristics of the anticorrosion piece itself and the above-mentioned inconveniences associated with the attachment of the anticorrosion piece to the turbine blade, the present invention has a much higher hardness and is rich in corrosion resistance, and also has ductility.
It is an object of the present invention to provide a method for manufacturing a turbine blade that also has toughness.

[Structure of Invention]

(Means and Actions for Solving Problems) In order to achieve the above object, the present invention provides titanium carbide powder containing Cr7 to 25%, Ni1 to 10%, and Co1 to 15% by weight.
%, Mo0.5-10%, Al0.5-2.5%, Ti0.5-2.5%, Cu0.5-2.
Argon atomized powder of matrix alloy consisting of 5%, C 0.1-1.5%, balance Fe and incidental impurities was mixed,
At the time of mixing, the above-mentioned titanium carbide powder is mixed in a volume ratio of 30-
60%, the mixture of argon atomized powder of the above matrix alloy adjusted to be 40-70% in the total volume ratio is sintered, and then the anticorrosion piece of the turbine blade formed by the hot isostatic pressing process is Apply to the front edge, and then apply the applied temperature range 500
Characterized by heat treatment at ~ 800 ° C.

In the turbine blade manufacturing method according to the present invention, the titanium carbide powder is mixed with the argon atomized powder of the matrix alloy, in which case the powder of the titanium carbide is 30 to 60% by total volume ratio, and the argon atomized powder of the matrix alloy is used. Is adjusted to a total volume ratio of 40 to 70% and sintered, and the corrosion-resistant piece obtained by molding the sintered body is applied to the front edge of the turbine blade, and then the applied part is subjected to the temperature range. 500
Since it is heat-treated at ~ 800 ° C, the anticorrosion piece itself is richer in ductility and toughness than before, while the hardness of the adhered part after the anticorrosion piece is attached to the turbine blade is also improved compared to the conventional one.

(Example) Hereinafter, each constituent reason of the composition components of the anticorrosion piece in the method for manufacturing a turbine blade according to the present invention, its mixing, the processing after the mixing, and the processing after the anticorrosion piece is attached to the turbine blade will be described, and The specific implementation means will be described.

First, titanium carbide (hereinafter referred to as TiC) is a powder itself having a hardness of Hv320, but 30% to 60% by volume is the most preferable range for uniform dispersion in a sintered body. . This is because if the total volume ratio is less than 30%, it is difficult to obtain the hardness Nv500 or more of the conventionally applied anticorrosion piece, and if it exceeds 60%, the hardness as a sintered body becomes brittle, This is because it cannot be used for a long time.

Next, the matrix alloy to be mixed with TiC has a total volume ratio of 40 to 70% in the most preferable range in consideration of ductility and toughness.

By the way, the matrix alloy contains Cr7-25% by weight,
Ni1-10%, Co1-15%, Mo0.5-10%, Al0.5-2.5%, Ti0.5
〜2.5%, Cu0.5〜2.5%, C0.1〜1.5%, balance Fe and incidental impurities.

Here, the reason for limiting the weight ratio of each composition is as follows.

Cr is an element necessary for corrosion resistance, and if it is less than 7%, the corrosion resistance in wet steam is insufficient, and if it exceeds 25%, the ductility of the matrix alloy is impaired, so this range is set.

Ni is an element that increases the ductility of the matrix alloy. If it is less than 1%, the effect of ductility is not obtained, but if it exceeds 10%, the effect remains constant and remains within this range.

Co has the same effect as Ni, but if it exceeds 15%, it rather embrittles the matrix alloy. If it is less than 1%, no effect is produced.

Mo is a useful element that solidifies and strengthens in the matrix.
The effect appears at 0.5% or more. However, if it exceeds 10%, embrittlement occurs.

Al and Ti both form an intermetallic compound with Ni and Co and contribute significantly to the hardening, but if they are less than 0.5% each, they hardly contribute to the hardening, and if they exceed 2.5% respectively, the ductility of the matrix alloy becomes an inclusion as an inclusion. Spoil.

Cu is an element necessary as a binder during sintering, 0.5%
The above effect is exhibited, but if it exceeds 2.5%, nonmetallic inclusions are formed and the matrix alloy becomes brittle.

C is a component that contributes to strengthening and precipitation strengthening of the matrix. If it is less than 0.1%, its effect is not exerted, and if it exceeds 1.5%, the ductility is remarkably reduced, so it is within this range.

Then, TiC and the matrix alloy are usually mixed as a powder produced by an argon atomizing treatment, and after molding, they are sintered at high temperature / high vacuum or in an inert gas. Since the sintered body thus formed usually has several percent of pores as a whole, it is fragile by itself and cannot be practically used.

Therefore, a hot isostatic press (hereinafter referred to as HIP) treatment step is performed to squeeze the pores to make them uniform. In this HIP processing step, first, the sample is placed in a stainless steel container, and then the periphery thereof is filled with boron nitride (BN) powder, and further heated to a temperature of 1100 to 1200 ° C. with argon gas, and 1000 atm. It is a process of pressurizing, holding for 1 hour, and then cooling.

After the HIP treatment, the molded anticorrosion piece is adhered to the leading edge of the turbine blade, which is a welding method that has been conventionally applied.

However, the strength and corrosion resistance of the turbine blade are
In spite of the anticorrosion piece that can be sufficiently guaranteed, in its application, in the anticorrosion piece in the border line, after being attached to the turbine blade,
Heat treatment is required in the temperature range 500-800 ° C.
By such heat treatment, precipitation of intermetallic compounds containing Ti and Al as the main components is observed from the matrix alloy, and in combination with hardening by TiC particles, an even higher hardness can be obtained as an anticorrosion piece. Here, the heat treatment temperature was selected to be 500 to 800 ° C because if it is less than 500 ° C, sufficient precipitates for curing cannot be obtained, and if it is 800 ° C or higher, the precipitates become coarse and do not contribute to hardening. Because.

Next, the characteristics of the anticorrosion piece produced based on the above-mentioned specific implementation means and the characteristics of the adhered portion after the anticorrosion piece is attached to the turbine blade will be described.

TiC powder with an average particle size of 20 μm and Cr-Ni-Co-Mo-Al-Ti
An argon atomized powder (100 mesh) of a -Cu-Fe matrix alloy was mixed to prepare a sample having a composition ratio shown in Table 1.

In Table 1 above, Samples 1, 2, 3, 4, 5 and 6 are samples of anticorrosion pieces obtained according to the present invention, and Samples 7 and 8 are samples deviated from those according to the present invention. After mixing each sample,
6Ton / cm ^{2 A} load is applied to form a brace and the temperature is 1200 to 1300 ° C.
It was vacuum sintered at. Each sample was partially subjected to a tensile test and a hardness test at this stage. The remaining sample was subjected to HIP treatment at a hydrostatic pressure of 4000 kg / cm ² and a temperature of 1000 to 1100 ° C. for 1 hour each. A part thereof was subjected to a tensile test, a hardness test and a corrosion resistance (erosion) test. Furthermore, each sample was subjected to appropriate heat treatment (aging) at 400 to 900 ° C., and then each of the above tests was performed. As an erosion test, a cavitation erosion test based on the Japan Society for the Promotion of Science (established by the 97th Committee of the Japan Society for the Promotion of Science) was performed. Test conditions are liquid temperature 24 ° ± 1 ° C, test time 180
Min, vibration frequency 6.5 KHz, vibration amplitude 100 μm. As a comparative material, a Co-based alloy steel (Stellite), which is a material as a conventional anticorrosion piece, was simultaneously subjected to various tests. Its composition is shown in Table 1.

FIG. 1 shows the relationship between hardness and tensile elongation at break of each sample, and the hardness at the time of sintering is equal to or more than that of Stellite alloy which is the material of the conventional anticorrosion piece except for the test 7, The elongation at break is the same or less except for Test 7. When the HIP treatment is applied, the hardness does not change in each test, but the tensile elongation at break improves and exceeds that of the conventional stellite alloy except for sample 4. It is considered that the main cause of this improvement is that the pores during sintering were squeezed by the HIP process, and the cycloporosity, which was the source of tensile fracture, disappeared. Further aging treatment (600 ℃ x 3
When h) was applied, the hardness of each sample except sample 7 increased and the tensile elongation at break decreased somewhat, but except sample 4 and 8, each sample had higher tensile elongation at break than the stellite alloy. There is. In Sample 7, the hardness at the time of sintering and after aging treatment is low because the amount of the strengthening element does not reach the range of the present invention, and in Samples 4 and 8, the tensile elongation at break is small because of the TiC amount and the matrix. This is because the strengthening element of the alloy exceeds the scope of the present invention. Samples 1, 2, 3, 5, and 6 within the scope of the present invention have higher hardness and tensile elongation at break than conventional stellite alloys both after HIP treatment and after aging treatment.

Fig. 2 shows the changes in hardness due to various aging treatments of the adhered part after being adhered to the turbine blade, based on samples 2, 5, 6 and 7, except for sample 7 at 500 ° C. Substantially effective hardening was obtained between ~ 800 ° C, and the hardness of the comparative Stellite alloy was as high as about Hv500 or higher. Since diffusion is slower at temperatures lower than 500 ° C, heating at a temperature of 500 ° C or higher requires heating for more than 100 hours, which is not economically suitable.

FIG. 3 shows the test results after the corrosion-preventing piece was attached to the turbine blade, and compared with the erosion amount of the conventional stellite alloy,
Each sample within the scope of the present invention shows the same or less erosion amount even if it is HIP-treated, and has good erosion resistance, but by performing an aging treatment, much higher corrosion resistance can be obtained.

As described above, it can be easily understood that in the turbine blade manufacturing method according to the present invention, the corrosion resistance of the adhered portion after the anticorrosion piece is adhered to the turbine blade is superior to the conventional one. In the above examples, the HIP treatment was described as an example for compressing the pores in the sintered body.
The same effect can be achieved by plastic working such as rolling and forging in hot and cold.

〔The invention's effect〕

As described above, according to the present invention, the hardness of the adhered portion of the anticorrosion piece after being adhered to the turbine blade is coupled with the toughness and ductility of the anticorrosion piece as compared with those conventionally applied. Corrosion resistance is further enhanced by the increased corrosion resistance.

Incidentally, in the turbine blade manufacturing method according to the present invention,
Although the erosion countermeasures of the turbine blade provided with the anticorrosion piece affected by the water droplets in the steam have been described, the sand contained in the working fluid is not limited to this implementation,
The present invention is also effective for solid particle erosion due to dust, oxide scale, and the like.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the hardness of the anticorrosion piece obtained by the present invention and the adhered portion of the anticorrosion piece after being attached to a turbine blade and the tensile elongation at break, and FIG. 2 is obtained by the present invention. Fig. 3 is a diagram showing the relationship between the hardness of the adhered part of the anticorrosion piece after being adhered to the turbine blade and the aging treatment. Fig. 3 is a test of the corrosion resistance of the adhered part of the anticorrosion piece after being adhered to the turbine blade. It is a figure which shows a result.

Claims (1)

[Claims] 1. A titanium carbide powder containing Cr7 to 2 in a weight ratio.
5%, Ni1-10%, Co1-15%, Mo0.5-10%, Al0.5-2.5%, T
i 0.5 to 2.5%, Cu 0.5 to 2.5%, C 0.1 to 1.5%, the balance of the argon atomized powder of the matrix alloy consisting of Fe and incidental impurities was mixed, and when mixing, the titanium carbide powder as a whole was mixed. A turbine blade anticorrosion piece formed by a hot isostatic press treatment step after sintering a mixture prepared by adjusting the volume ratio of the argon atomized powder of the above matrix alloy to 30 to 60% and the total volume ratio to 40 to 70%. Is adhered to the front edge of the turbine blade, and then the adhered portion is heat-treated in a temperature range of 500 to 800 ° C., a method of manufacturing a turbine blade.