JP2013053327A - Ni-BASED SUPERALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Ni-based superalloy having both heat-resistant high strength and oxidation resistance equivalent to or higher than a conventional alloy at high temperature even if the content of an expensive Re is substantially cut off.SOLUTION: The Ni-based superalloy contains as essential elements, by weight, 7.0-11.0% Cr, 6.0-10.0% W, 4.5-6.5% Al, 0.2-5.0% Nb, 6.0-11.0% (Nb+Ta), 0.1 to <2.5% Re, 0.03-1.0% Si, the balance Ni with inevitable impurities, but does not contain Co, Mo and Hf. Besides, an effective oxidation resistance is obtained by contriving an alloy composition so that an OP (oxidation parameter) value becomes ≥130, provided that the OP value is 5.5×[Cr(wt.%)]+15.0×(1+2.0[Si(wt.%)])×[Al(wt.%)].

Description

  The present invention relates to a Ni-base superalloy, which is a heat-resistant alloy used in high-temperature equipment such as jet engines and industrial gas turbines. More specifically, the present invention relates to excellent heat resistance at high temperatures as well as excellent oxidation resistance at high temperatures and The present invention relates to a Ni (nickel) -based superalloy having corrosion resistance.

Ni-base superalloys are widely used as materials for high-temperature equipment because of their excellent structure stability and creep properties at high temperatures, and many patent applications have been filed. In particular, since Ni-based single crystal superalloys have remarkable heat resistance as shown in Patent Documents 1 to 10, in recent years, Ni-based superalloys suitable for high-temperature equipment such as jet engines and industrial gas turbines are used. Some Ni-base superalloys described in these patent documents are widely used.
More specifically, the Ni-based single crystal superalloy reinforces high temperature characteristics by depositing Al (aluminum) and Ni3Al type precipitates on Ni, such as Cr (chromium), W (tungsten), Ta (tantalum), etc. It is a superalloy that is alloyed and single-crystallized by mixing refractory metals. Among these series of Ni-based single crystal superalloys, there are first generation alloys that do not contain Re (rhenium). It has been known. As alloys having excellent heat resistance at higher temperatures, second-generation alloys containing about 3 wt% Re and third-generation alloys containing 5-6 wt% Re have been developed. For example, CMSX-4 (manufactured by Canon Muskegon) is known for the second generation Ni-based single crystal superalloy, and CMSX-10 (manufactured by Canon Muskegon) is known for the third-generation Ni-based single crystal superalloy. (Patent Documents 1-10). The heat resistance is improved by increasing the content of Re, the second generation alloy, the third generation alloy, and Re, but even if only Re is increased further, the solid solution limit (γ phase) is exceeded, A so-called TCP phase is precipitated, and the heat resistance cannot be further improved. Therefore, new heat-resistant superalloy systems called fourth-generation alloys and fifth-generation alloys to which Ru (ruthenium) is added together with Re have been proposed.
Recently, from the viewpoint of soaring fuel or reducing carbon dioxide emissions, it is excellent in heat resistance, corrosion resistance and oxidation resistance at high temperatures in equipment such as jet engines and industrial gas turbines for the purpose of improving energy efficiency. The use of Ni-based single crystal superalloys has attracted attention, and the practical use of second-generation alloys and third-generation Ni-based single crystal superalloys containing expensive metals such as Re has been advanced. In addition, Ni + single crystal superalloys of 4th generation alloys and 5th generation alloys containing Re + Ru, which have excellent heat resistance at higher temperatures, are also suitable materials for improving energy efficiency at a higher level. Development for practical use is being promoted.

  On the other hand, however, rare metals such as Re and Ru tend to have higher raw material prices with the rapid increase in usage in recent years. In some cases, it is difficult to obtain these rare metal raw materials. It has become like this. Therefore, in Ni-based single crystal superalloys containing Re, even if the amount of Re used is greatly reduced without impairing mechanical properties at high temperatures, it is inferior to the currently used Ni-based single crystal superalloys. Development of a Ni-based single crystal superalloy having no heat resistance is strongly desired in industries such as jet engines and industrial gas turbines.

Since Co has an excellent function of increasing the solid solubility limit at high temperatures for gamma matrix phases such as Al and Ta, and dispersing and precipitating fine gamma prime phases by heat treatment to improve the high temperature strength. It has been considered as an indispensable component for the Ni-base superalloy used in the above. However, Co has a tendency to rapidly increase the amount used worldwide in new applications such as lithium ion battery materials and electronic materials. Since Co has a limited amount of resources compared to Ni, it is an expensive metal compared to Ni, and a Ni-base superalloy containing as little Co as possible is desired. In addition, since Co has a long half-life, the maintenance of the Ni-base superalloy containing Co becomes radioactive when it is contaminated with radioactivity. When using it as a component for high temperature equipment, it is desired to realize a Ni-base superalloy having creep strength characteristics equivalent to or higher than those containing Co, even if it does not contain Co with a long half-life. .

Mo (molybdenum) is generally known as an element that dissolves in an alloy substrate to increase the high-temperature strength and contributes to the high-temperature strength by precipitation hardening. On the other hand, if the content is too high, There is a disadvantage that it has a tendency to deteriorate the oxidization characteristics and corrosion resistance characteristics. Therefore, it is desired to realize a Ni-based superalloy that can maintain the same or higher high-temperature strength by an appropriate combination of refractory metals other than Mo.

  Hf (hafnium) has an effect of improving corrosion resistance and oxidation resistance at high temperatures, and is widely used in many heat-resistant Ni-based superalloys. However, Hf is an expensive rare metal element, which is one factor that pushes up the raw material price of Ni-base superalloys. Therefore, an alternative to a cheaper element that can improve corrosion resistance and oxidation resistance at high temperatures is also desired. .

  In view of the above-described circumstances, the present invention has a Ni-based superstructure that does not contain Co, Mo, and Hf, and has sufficient heat resistance and oxidation resistance even at high temperatures while suppressing the amount of expensive Re used as much as possible. An object is to provide an alloy.

The Ni-base superalloy of the invention 1 is a Ni-base superalloy that does not contain Co, Mo, and Hf, contains Cr, W, Al, Nb, Ta, Re, and Si as essential elements, and the composition range of the essential elements Cr: 7.0 wt% or more and 11.0 wt% or less, W: 6.0 wt% or more and 10.0 wt% or less, Al: 4.5 wt% or more and 6.5 wt% or less, Nb: 0.00 wt% or less. 2% by weight or more and 5.0% by weight or less, Nb + Ta: 6.0% by weight or more and 11.0% by weight or less, Re: 0.1% by weight or more and less than 2.5%, Si: 0.03% by weight or more. It is characterized by containing 0% by weight or less, with the balance being composed of Ni and inevitable impurities.

Invention 2 is the Ni-base superalloy of Invention 1, Cr: 8.0 wt% or more and 11.0 wt% or less, W: 6.0 wt% or more and 10.0 wt% or less, Al: 4.8 wt% More than 6.0% by weight, Nb: 0.5% to 4.0% by weight, Nb + Ta: 6.0% to 11.0% by weight, Re: 0.1% to 2.0% Less than, Si: 0.05 weight% or more and 0.5 weight% or less are contained, It is characterized by the above-mentioned.

Invention 3 is the Ni-base superalloy of Invention 1, Cr: 8.0 wt% or more and 10.0 wt% or less, W: 6.0 wt% or more and 10.0 wt% or less, Al: 4.8 wt% More than 6.0% by weight, Nb: 1.0% to 4.0% by weight, Nb + Ta: 6.0% to 10.0% by weight, Re: 0.1% to 2.0% Less than, Si: 0.05 weight% or more and 0.4 weight% or less are contained, It is characterized by the above-mentioned.

Invention 4 is the Ni-base superalloy of Invention 1, wherein Cr: 8.0 wt% or more and 10.0 wt% or less, Al: 4.8 wt% or more and 6.0 wt% or less, Nb + Ta: 6.0 wt% More than 9.0% by weight, Nb: 1.0% by weight or more and 4.0% by weight or less, Ta: 4.0% by weight or more and less than 6.0% by weight, Re: 0.1% by weight or more. It is characterized by containing less than 0% and Si: 0.05 wt% or more and 0.4 wt% or less.

Invention 5 is characterized in that the Ni-base superalloys of Inventions 1 to 4 contain C: 0.0001 wt% or more and 0.01 wt% or less, and S: 0.005 wt% or less.

Invention 6 is characterized in that the Ni-base superalloys of Inventions 1 to 3 contain C: 0.0005 wt% or more and 0.005 wt% or less, and S: 0.002 wt% or less.

Invention 7 is the Ni-base superalloy according to any one of Inventions 1 to 6, further comprising at least one of Y: 0.2% by weight or less, La: 0.2% by weight or less, and Ce: 0.2% by weight or less. It is characterized by containing.

Invention 8 is the Ni-base superalloy according to Inventions 1 to 7, wherein OP (Oxidation Parameter) = 5.5 × [Cr (wt%)] + 15.0 × (1 + 2.0 [Si (wt%)]) × [Al ( wt%)], the OP value is 130 or more.

Invention 9 is characterized in that in the Ni-base superalloy of Invention 8, the OP value is 135 or more.

Invention 10 is characterized in that in the Ni-base superalloy of Invention 9, the OP value is 140 or more.

Invention 11 is a member composed of a Ni-base superalloy, wherein the Ni-base superalloy is any of the Ni-base superalloys of Inventions 1 to 10.

Invention 12 is a method for producing a Ni-base superalloy member according to Invention 11, wherein the Ni-base superalloy according to any one of Inventions 1 to 10 is cast by a normal casting method, a unidirectional solidification method, or a single crystal solidification method. It is characterized by being manufactured.

  In view of the above-described circumstances, the present invention has sufficient heat resistance at high temperatures while minimizing the content of expensive Re, and also has oxidation resistance and corrosion resistance at high temperatures even without Hf. In order to provide an excellent Ni-base superalloy, sincere examination was conducted, Ni containing substantially no Co, Mo and Hf and containing Cr, W, Al, Nb, Ta, Re and Si as essential elements We were able to find a base superalloy. The Ni superalloy of the present invention has excellent heat resistance and excellent oxidation resistance at high temperature by controlling the Ni-base superalloy to a specific element and an optimal elemental composition while suppressing the amount of expensive Re used as much as possible. The present invention provides a Ni-base superalloy having both properties and corrosion resistance.

  The present invention has the features as described above, and an embodiment thereof will be described in detail below.

For the A3 alloy and A6 alloy as the alloys of the present invention and the R1 alloy, R2 alloy and R4 alloy as the comparative alloys, the sample was repeated at a high temperature of 1100 ° C. for 1 hour in air at a maximum temperature of 250 cycles, and the mass before the test. It is the figure which showed the change of the mass of the sample after the exposure with respect to. It is a SEM photograph of a cut surface microstructure about a sample after completion of a cycle test of A3 alloy and A6 alloy which is an alloy of the present invention, and R1 and R4 alloys which are comparative alloys. A comparison of the creep life under the creep life test conditions of 800 ° C.-735 MPa, 900 ° C.-392 MPa, 1000 ° C.-245 MPa, 1100 ° C.-137 MPa for the A3 alloy and A6 alloy which are the alloys of the present invention and the comparative R2 alloy. It is.

  Co has a function of increasing the solid solubility limit at a high temperature with respect to a gamma matrix phase such as Al and Ta, and dispersing and precipitating a fine gamma prime phase by heat treatment to improve the high temperature strength. Further, Mo dissolves in the alloy base to increase the high temperature strength and contributes to the high temperature strength by precipitation hardening. Therefore, it has been conventionally considered that both are indispensable components for a Ni-base superalloy having excellent structure stability and creep characteristics at high temperatures. However, in the invention of the present application, essential elements such as Cr, W, Al, Nb, Ta, etc. can be added without adding Co, Mo and Hf, which have been considered to be essential in high strength Ni-base superalloys. It has been found that by using Re and Si in a specific composition range, a Ni-base superalloy having both high creep strength and excellent oxidation resistance and corrosion resistance at high temperatures can be realized. If the Co content is less than 1.0% by weight and the Mo content is not more than 0.1% by weight, the excellent oxidation resistance and corrosion resistance of the alloy of the present invention will not be impaired.

That is, Cr: 7.0 wt% or more and 11.0 wt% or less, W: 6.0 wt% or more and 10.0 wt% or less, Al: 4.5 wt% or more and 6.5 wt% or less, Nb: 0 2% by weight or more and 5.0% by weight or less, Nb + Ta: 6.0% by weight or more and 11.0% by weight or less, Re: 0.1% by weight or more and less than 2.5%, Si: 0.03% by weight or more 1 It was found that a Ni-based single crystal alloy having a composition containing 0.0% by weight or less and the balance of Ni and inevitable impurities has excellent heat resistance and oxidation resistance. The alloy of the present invention is a first generation Ni-based single crystal alloy containing Co, Mo, and Hf widely used as a commercially available alloy (for example, PWA1480, CMSX-3, which are well known as existing alloys manufactured by Canon Maskegon) Etc.) and has excellent heat resistance. In addition, the alloy of the present invention is less than half the expensive Re content compared with the existing alloy CMSX-4 manufactured by Canon Maskegon, which can be said to be a representative example of the second generation Ni-based single crystal alloy. It is a Ni-based single crystal alloy that has excellent heat resistance and superior oxidation resistance at high temperatures.

  In the Ni-base superalloy of the present invention, quantitative control of trace elements C and B may be an important factor, and Y: 0.2% by weight or less, La: 0.2% by weight It is possible to further improve the physical properties of products according to various uses by adding at least one element of not more than% and Ce: not more than 0.2% by weight.

  The Ni-base superalloy of the present invention has excellent structure stability at high temperatures, creep characteristics, and oxidation / corrosion resistance, and is particularly suitable for the production of turbine blades or turbine vane parts.

  The optimum content range of the components of the Ni-base superalloy of the present invention will be described below.

  Cr (chromium) is an element excellent in oxidation resistance, and improves the high temperature corrosion resistance of the Ni-base superalloy. If the Cr content is too small, the effect is small. If the Cr content is too large, the balance with other heat-resistant strengthening elements deteriorates and the performance deteriorates, which is not preferable. The Cr content is preferably in the range of 7.0 wt% to 11.0 wt%, more preferably Cr: 8.0 wt% to 11.0 wt%, and Cr: 8.0 wt% to 10 wt%. 0.0% by weight or less is most preferable.

  W (tungsten) has the effects of solid solution strengthening and precipitation hardening, and improves the high temperature strength of the Ni-base superalloy. If the W content is too small, the effect of improving the high-temperature strength is small, and if it is too large, a harmful phase is precipitated, which is not preferable. Further, an increase in the amount of W is not preferable because the specific gravity of the entire alloy increases and the alloy cost also increases. The W content is preferably in the range of 6.0 wt% to 10.0 wt%.

Al (aluminum) is formed at a high temperature by forming an intermetallic compound represented by Ni ₃ Al constituting a gamma prime phase that combines with Ni and precipitates in a gamma matrix at a volume fraction of 50 to 70%. Improve strength. If the Al content is too small, the effect of precipitation strengthening of the gamma prime phase will not be sufficiently exhibited, and if it is added too much, the ductility of the alloy will be lowered, which is not preferable. Another important role of Al is that it contributes to the formation of a strong and dense oxide film for maintaining oxidation resistance at high temperatures. From this viewpoint, it is necessary to determine an appropriate Al content. is there. The content of Al is preferably in the range of 4.5% by weight to 6.5% by weight, and more preferably 4.8% by weight to 6.0% by weight.

Ta (tantalum) and Nb (niobium) are both effective elements for strengthening the gamma prime phase and improving the creep strength. Nb is effective for improving the creep strength and is effective for lowering the density of the alloy by substituting some alloy elements such as Ta. When the composition of Ta + Nb is small, the effect of precipitation strengthening of the gamma prime phase does not sufficiently appear, and when too much is added, the ductility of the alloy is lowered, which is not preferable. If the total content of Nb + Ta elements exceeds 11% by weight, the formation of harmful phases tends to be promoted, so Nb + Ta is used as 11.0% by weight or less.
The composition range of Nb and Ta is preferably Nb: 0.2 wt% or more and 5.0 wt% or less, and Nb + Ta: 6.0 wt% or more and 11.0 wt% or less. As the composition range of Nb and Ta, Nb: 0.5 wt% or more and 4.0 wt% or less, Nb + Ta: 6.0 wt% or more and 11.0 wt% or less are more preferable, and the composition range of Nb and Ta is Nb: More preferably, the content is 1.0% by weight or more and 4.0% by weight or less, and Nb + Ta: 6.0% by weight or more and 11.0% by weight or less. Moreover, Ta increases the density of the alloy, so Ta: 4.0 wt% or more and less than 6.0 wt%, Nb: 1.0 wt% or more and 4.0 wt% or less, Nb + Ta: 6.0 wt% It is most preferable to use in the range of not less than% and less than 10.0% by weight.

Re (rhenium) has the effect of improving the corrosion resistance as well as improving the high temperature strength by solid solution strengthening in the gamma phase. If the content of Re is extremely small, the effect of improving the high temperature strength and corrosion resistance is not remarkably observed. On the other hand, if the content of Re is too large, the TCP phase may precipitate at high temperatures and the high temperature strength may be lowered. In addition, it is not preferable to use a large amount of expensive Re because it increases the alloy cost. Accordingly, the Re content is preferably 0.1% by weight or more and less than 2.5%, and Re: 0.1% by weight or more and less than 2.0%. More preferred.

By adding a small amount of Si (silicon), a stable oxide film is formed on the alloy surface in a state where the base alloy surface is exposed to high-temperature oxidation conditions. The oxide film formed in the presence of Si is dense and homogeneous, and this oxide film is excellent in adhesion to the alloy surface. Since the amount of Si added is about one-tenth that of Al, Si shows a catalytic effect in the initial oxide film formation process rather than forming a strong and dense oxide film. This is considered to contribute to the formation of a strong and dense oxide film at high temperatures. However, if an excessive amount of Si is present in the alloy, it is not preferable because the solid solubility limit of other elements in the alloy is lowered and the heat resistance strength of the alloy at high temperatures is lowered. Therefore, it is desirable to determine the amount of Si added while considering the balance between heat resistance and oxidation resistance at high temperatures. Si: 0.03% by weight or more and 1.0% by weight or less is preferable, Si: 0.05% by weight or more and 0.5% by weight or less is more preferable, Si: 0.05% by weight or more and 0.4% by weight or less Most preferably, it is used at a weight percent or less.

  Cr, Al, and Hf are generally known as the main elements that have a significant effect on the oxidation resistance at high temperatures, and the oxidation resistance characteristics of OP (Oxidation Parameter) parameters that take into account the contribution of these elements. As a guide. The present inventors have found that it is effective to design an alloy in consideration of the OP parameter represented by the following formula including the Si content that greatly affects the oxidation resistance at high temperatures. When OP (Oxidation Parameter) = 5.5x [Cr (wt%)] + 15.0x (1 + 2.0 [Si (wt%)]) x [Al (wt%)], the OP value is 130 or more. It is desirable that the OP value be 135 or more, and it is most desirable that the OP value be 140 or more.

  C (carbon) contributes to grain boundary strengthening. However, excessive content may impair the ductility of the alloy, and it is desirable to carefully control the C content in the alloy. C: 0.0001% by weight or more and 0.01% by weight or less is preferable, and C: 0.0005% by weight or more and 0.005% by weight or less is more preferable.

  S (sulfur) not only lowers the high-temperature strength when it is contained to some extent in the Ni-base superalloy, but also significantly reduces the oxidation resistance at high temperatures, so it is sufficient for mixing from the stage of the alloy raw material used. Consideration is necessary. The S content contained in the alloy is preferably 0.005% by weight or less, and more preferably 0.002% by weight or less.

  B (boron), like C, contributes to grain boundary strengthening. However, an excessive content is preferably 0.2% by weight or less because it impairs ductility.

  Y (yttrium), La (lanthanum), and Ce (cerium) improve the adhesion of a protective oxide film that forms alumina, chromia, and the like during use of a Ni-based superalloy at high temperatures. However, excessive content will lower the solid solubility limit of other elements, so that Y: 0.2% by weight or less, La: 0.2% by weight or less, Ce: 0.2% by weight or less It is preferable to use in a range.

  The Ni-base superalloy of the present invention having the above elemental composition can be cast. In this casting, for example, a Ni-base superalloy can be manufactured as a polycrystalline alloy, a unidirectionally solidified alloy, or a single crystal alloy by a normal casting method, a unidirectional solidification method, or a single crystal solidification method. The ordinary casting method basically uses an ingot prepared to have a desired composition, but the mold temperature is heated to a solidification temperature of the alloy of about 1500 ° C. or higher, and after casting the superalloy, for example, a heating furnace In this method, a large number of crystals are grown in one direction by giving a temperature gradient gradually away from the substrate. The single crystal solidification method is almost the same as the unidirectional solidification method, but a zigzag or spiral type selector unit is provided before the desired product is solidified, and many crystals that have solidified in one direction are converted into one crystal in the selector unit. To produce the desired item.

The Ni-base superalloy of the present invention can have high creep strength by heat treatment after casting. In the standard heat treatment, after preliminary heat treatment at 1260 to 1300 ° C. for 20 minutes to 2 hours, 1300 to 1350 ° C. is heated in the temperature range of 1050 to 1150 ° C. for 2 to 8 hours and air-cooled. This treatment can be combined with a coating treatment for heat resistance and oxidation resistance. After air cooling, a secondary aging treatment for the purpose of stabilizing the gamma prime phase is subsequently performed at 800 to 900 ° C. for 10 to 24 hours, followed by air cooling. Each air cooling may be replaced with an inert gas. High temperature parts such as a turbine blade of a gas turbine or a turbine vane are realized by the Ni-base superalloy produced by this manufacturing method.

Table 1 shows the relationship between the alloy composition of the present invention alloy and the OP parameter. Alloys A1 to A7 are invention alloys of the present application. The R1 alloy is a comparative alloy obtained by removing Si element from the alloy of the present invention. In addition, R2 alloy to R4 alloy show PWA1480, CMSX-3, and CMSX-4, which are existing alloys, as comparative alloys.

In order to evaluate the oxidation resistance properties of Ni-based single crystal alloys such as the alloys A3 and A6 of the present invention, each sample specimen was exposed in air at 1100 ° C. for 1 hour in an electric furnace, and then removed from the electric furnace. An oxidation resistance cycle test at a high temperature was performed by a method of cooling for 1 hour. FIG. 1 shows the history of weight change in the cycle test of the four alloys shown in Table 1 in addition to the alloy of the present invention. The R1 alloy to which Si was not added in the alloy of the present invention and PWA1480 (R2 alloy) and CMSX-4 (R4 alloy), which are representative commercially available alloys, were evaluated as comparative examples under the same conditions.
The alloys of the present invention (A3 and A6 alloys) were accompanied by a slight increase in weight due to surface oxidation at the beginning of the cycle, but no significant decrease in mass was observed after 250 cycles. On the other hand, the commercially available alloys R2 alloy and R4 alloy showed a remarkable tendency to decrease the mass before reaching 100 cycles. Further, in the comparative alloy R1 to which no Si was added, a rapid decrease in mass was observed after 20 cycles. As is clear from these test results, it was found that the alloy of the present invention has superior oxidation resistance characteristics as compared with typical commercial alloys of the first generation and second generation alloys.

The excellent characteristics of the alloy of the present invention are made possible by optimizing the balance of the composition of alloy elements contributing to high temperature heat resistance and the composition of alloy elements contributing to oxidation resistance at high temperatures. In particular, in the latter case, it has been found that it is extremely effective for alloy design to use the OP parameter represented by the following formula focusing on each element of Cr, Al, and Si, which has a high contribution to the OP (Oxidation Parameter) parameter. It was.
OP (Oxidation Parameter) = 5.5x [Cr (wt%)] + 15.0x (1 + 2.0 [Si (wt%)]) x [Al (wt%)]
The rightmost column of Table 1 shows the OP values calculated using the above formulas for the alloys of the present invention and the comparative alloys. As is apparent from this table, the OP value is preferably 130 or more, more preferably 135 or more, and most preferably 140 or more. The comparative alloys R3 and R4 in Table 1 contain Hf element, and OP (Oxidation Parameter) = 5.5x [Cr (wt%)] + 15.0x (1 + 2.0 [Si ( wt%)]) x [Al (wt%)] + 9.5x [Hf (wt%)] was used.

  The characteristics of the oxide film formed on the surface of the sample subjected to the high-temperature cycle test under the conditions described in FIG. 1 were examined. FIG. 2 shows the cross-sectional microstructure of the A3 and A6 alloys, which are the alloys of the present invention, and the R1 alloy, which is the comparative alloy, after 250 cycles, and the R4 alloy, which is the comparative alloy, after the 200-cycle test. It is a SEM photograph. It is observed that the oxide layer after cycling of the A3 alloy and A6 alloy, which is the alloy of the present invention, is composed of at least three dense layers and that the adhesion between these layers is very good. It was done. The alloy of the present invention is considered to exhibit excellent cycle characteristics that hardly cause peeling of the oxide layer after 250 cycles by forming such a dense and homogeneous oxide layer at the beginning of the high temperature cycle. . On the other hand, the surface oxide layer of the comparative alloy has poor homogeneity and adhesion of the oxide layer produced compared to the alloy of the present invention. In the R1 alloy, a gap was observed between the alloy base and the oxide layer compared to the A3 and A4 alloys, and the cycle life was short because the adhesion of the oxide layer was insufficient. Further, as apparent from the SEM photograph of the R4 alloy, the oxide film layer formed on the R4 alloy was inhomogeneous lacking in density. It is considered that a part of the oxide film peeled off during the high-temperature cycle, and the formation of a heterogeneous oxide film layer was repeated, resulting in an oxide film surface with many irregularities.

  FIG. 3 shows the results of measuring the creep rupture life of the alloys of the present invention (A3 and A6 alloys) and commercially available alloys (R2). In the creep test, the lifetime was defined as the time until the sample creep ruptured under the conditions of 800 ° C.-735 MPa, 900 ° C.-392 MPa, 1000 ° C.-245 MPa, 1100 ° C.-137 MPa. Under any of the creep test conditions, the alloy of the present invention had a heat resistance superior to that of the R2 alloy. In other words, it can be concluded that the alloy of the present invention is an alloy having excellent properties with a good balance in both the oxidation cycle and creep rupture properties at high temperatures as compared with the R2 alloy.

  The heat resistance strength of the present invention alloy A3 alloy and the commercially available alloy R4 alloy were compared. Under the same conditions of 1100 ° C. and 137 MPa, 1% creep strength and creep rupture life were measured. It was 118 hours and 120 hours for the A3 alloy, and 118 hours and 155 hours for the R4 alloy, respectively. Although the content of expensive Re effective for improving heat resistance is less than half that of the R4 alloy, the A3 alloy has almost the same heat resistance as the R4 alloy, and as shown in FIG. It can be said that it is an excellent Ni-base superalloy having high temperature cycle characteristics significantly superior to those of the R4 alloy.

  The alloy compositions of the alloys A3 and A6 of the present invention are shown in Table 1. When trace elements other than Table 1 were analyzed, C (carbon) and S (sulfur) were detected as trace components. When these trace elements were analyzed a plurality of times, C: 0.0016 wt% or more and 0.0028 wt% or less for A3 alloy, S: 0.0002 wt%, C: 0.0007 wt% or more for A6 alloy It was found that 0.0036% by weight or less and S: 0.0001% by weight or more and 0.0004% by weight or less were present. These trace elements often affect the heat resistance and oxidation resistance at high temperatures, and it is important to control the amount of impurities within an appropriate range.

As is clear from the above examples, the alloy of the present invention is a Ni-based superalloy that does not contain Co, Mo, and Hf and contains Cr, W, Al, Nb, Ta, Re, and Si as essential elements. Thus, it can be said that the Ni-based superalloy has a very good balance of performance and has excellent heat resistance at high temperatures and cycle characteristics while minimizing the content of expensive Re.

  According to the present invention, it is possible to provide an excellent alloy that is very balanced in heat resistance and oxidation resistance at high temperatures. It is also possible to provide a cheaper Ni-based superalloy in which the amount of expensive metal such as expensive Re used is significantly reduced compared to existing alloys. Therefore, according to the present invention, it is possible to provide a suitable alloy that is well balanced from the middle temperature portion to the high temperature portion as a turbine blade or turbine vane such as a jet engine or a power generation gas turbine.

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Claims (12)

A Ni-based superalloy containing Cr, W, Al, Nb, Ta, Re, and Si as essential elements without containing Co, Mo, and Hf, and a composition range of the essential elements Cr: 7.0 wt. %: 11.0% by weight or less, W: 6.0% by weight or more, 10.0% by weight or less, Al: 4.5% by weight or more, 6.5% by weight or less, Nb: 0.2% by weight or more, 5.0% Nb + Ta: 6.0% by weight or more and 11.0% by weight or less, Re: 0.1% by weight or more and less than 2.5%, Si: 0.03% by weight or more and 1.0% by weight or less A Ni-base superalloy characterized in that the balance has a composition composed of Ni and inevitable impurities. 2. The Ni-base superalloy according to claim 1, wherein Cr: 8.0 wt% or more and 11.0 wt% or less, W: 6.0 wt% or more and 10.0 wt% or less, Al: 4.8 wt% or more 6.0% by weight or less, Nb: 0.5% by weight or more and 4.0% by weight or less, Nb + Ta: 6.0% by weight or more and 11.0% by weight or less, Re: 0.1% by weight or more and less than 2.0% Si: 0.05% by weight or more and 0.5% by weight or less, a Ni-base superalloy having a composition consisting of Ni and inevitable impurities. In the Ni-base superalloy according to claim 1, Cr: 8.0 wt% or more and 10.0 wt% or less, W: 6.0 wt% or more and 10.0 wt% or less, Al: 4.8 wt% or more 6.0% by weight or less, Nb: 1.0% by weight or more and 4.0% by weight or less, Nb + Ta: 6.0% by weight or more and 10.0% by weight or less, Re: 0.1% by weight or more and less than 2.0% Si: 0.05% by weight or more and 0.4% by weight or less, a Ni-base superalloy having a composition comprising Ni and inevitable impurities in the balance. In the Ni-base superalloy according to claim 1, Cr: 8.0 wt% or more and 10.0 wt% or less, W: 6.0 wt% or more and 10.0 wt% or less, Al: 4.8 wt% or more 6.0 wt% or less, Nb + Ta: 6.0 wt% or more and less than 9.0 wt%, Nb: 1.0 wt% or more and 4.0 wt% or less, Ta: 4.0 wt% or more 6.0 Less than wt%, Re: 0.1 wt% or more and less than 2.0%, Si: 0.05 wt% or more and 0.4 wt% or less, with the balance being composed of Ni and inevitable impurities Characteristic Ni-base superalloy. 5. The Ni-base superalloy according to claim 1, wherein the Ni-base superalloy contains C: 0.0001 wt% or more and 0.01 wt% or less and S: 0.005 wt% or less. 5. The Ni-base superalloy according to claim 1, wherein the Ni-base superalloy contains C: 0.0005 wt% or more and 0.005 wt% or less, and S: 0.002 wt% or less. The Ni-base superalloy according to claim 1, further comprising at least one of Y: 0.2 wt% or less, La: 0.2 wt% or less, Ce: 0.2 wt% or less. Characteristic Ni-base superalloy. The Ni-base superalloy according to any one of claims 1 to 7, wherein OP (Oxidation Parameter) = 5.5x [Cr (wt%)] + 15.0x (1 + 2.0 [Si (wt%)]) x [Al (wt %)], A Ni-base superalloy having an OP value of 130 or more.   The Ni-base superalloy according to claim 8, wherein the OP value is 135 or more. The Ni-base superalloy according to claim 8, wherein the OP value is 140 or more.   A Ni-based superalloy member comprising a Ni-based superalloy, wherein the Ni-based superalloy is the Ni-based superalloy according to any one of claims 1 to 10. A method for producing a Ni-base superalloy member according to claim 11, wherein the Ni-base superalloy according to any one of claims 1 to 6 is produced by a normal casting method, a unidirectional solidification method, or a single crystal solidification method. A method for producing a Ni-based superalloy member, characterized by being produced by casting using the above method.