JPH0255493B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to metal casting technology, and more particularly to novel products manufactured by low pressure, high speed plasma spray casting. Such products exhibit a unique microstructure and therefore have a novel combination of physical properties that are superior to those of products of the same alloy composition made by conventional methods. Examples of products of the invention that are useful for special applications due to their superior physical properties (e.g. high temperature strength, ductility and thermal fatigue resistance) include:
Mention may be made of vanes and discs for gas turbine engines made of superalloys based on nickel, cobalt or iron. In addition, products such as flywheels, which operate under lower temperature conditions than gas turbine engine components but require special physical properties, are problematic due to their geometry, material composition, or both. These include products that cannot be easily manufactured using conventional methods. Since the introduction of various forms of gas turbines as important power generation and propulsion machines decades ago, it has been widely accepted that their operation and performance are limited by the available materials of construction. . In such applications, the combination of relatively high tensile strength, good ductility in the range from room temperature to gas turbine combustion chamber operating temperatures, and good thermal fatigue resistance is highly desirable. As a result of extensive research and development efforts that have continued to this day, so-called "superalloys" have become available. Particularly superior are heat-resistant alloys based on nickel, cobalt, iron and chromium, such as Rene 80 (nominal composition C0.17%, Cr14%, Co9.5
%, Mo4.0%, W4.0%, Ti5.0%, Al3.0%,
B0.015%, Zr0.03%, Ni residual), Rene 95 (nominal composition C0.15%, Cr14%, Co8.0%, Mo3.5%, W3.5
%, Cb3.5%, Ti2.5%, Al3.5%, B0.01%,
Zr0.05%, Ni residual), IN738 (nominal composition C0.17%,
Mn0.2% (upper limit), Si0.3% (upper limit), Cr16%,
Co8.5%, Mo1.75%, W2.6%, Cb0.9%, Ti3.4
%, Al3.4%, B0.01%, Zr0.10%, Fe0.5% (upper limit), Ta1.75%, Ni residual (however, keep Fe, Mn, S and Si as small as possible),
IN617 (nominal composition C0.1%, Mn0.5%, Si0.5%,
Cr22.0%, Ni52.0%, Co12.5%, Mo9.0%,
Ti0.3%, Al1.2%, Fe1.5%, Cu0.2%), IN671
(Nominal composition C0.05%, Cr46.0%, Ni53.5%, Ti0.4
It is commercially available under the trade name %). While the first four of the above alloys are used for vane and disk manufacturing, due to the importance of strength requirements, especially in the low-temperature region of gas turbine operation, IN671 is primarily used for its environmental resistance. It is used. In such applications, IN671 is typically used as a wrought sheet, but it has also been proposed to be applied directly as a plasma sprayed coating onto the component to be protected. However, in order to use the other four alloys as blades and other high-temperature parts of gas turbines, they must be melted and then cast into a predetermined shape and size, or they must be cast or sintered. It is common to deform it mechanically. Regardless of the processing method, however, parts made of these alloys may require corrosion protection measures. Currently, thermally sprayed coatings are often used consisting of some type of MCrAlY alloy. As noted above, although considerable progress has been made in the development of materials in response to the special requirements of gas turbine engines, there are still important material performance gaps. To date, superalloys used in the manufacture of gas turbine high temperature components have been a compromise taking into account the various physical properties, operating conditions, and manufacturing operations described above. especially,
This is evident in the case of parts that are directly cast into a predetermined shape. Prior to this invention,
No new superalloys have emerged that eliminate the need for such compromises in the manufacture of cast parts for gas turbine engines, nor have other alternatives been proposed that would enable the elimination of such compromises. It should be noted that in the method described in U.S. Pat. Mechanical deformation processes such as forging are essential to manufacturing blades and other gas turbine engine components from ingots. The inventors have now discovered that it is possible to eliminate the need for compromises between materials of construction and operating conditions of components for gas turbine engines, as well as the need for forging and similar machining operations, and thus to eliminate the need for forging and similar machining operations. It has now been discovered that the long desired combination of properties in superalloy cast parts can now be achieved. The inventors have also discovered that the above results can be consistently achieved without modifying the superalloy composition or creating new superalloys, and without significantly increasing manufacturing costs. These results are based on the surprising discovery that, in a novel form, a superalloy traditionally used for casting parts for gas turbine engines has a nearly ideal combination of physical properties. It is. More specifically, in a morphology consisting of an extremely fine and uniform microstructure, such superalloys exhibit physical properties that are distinct from and significantly superior to the same alloy compositions exhibiting previously known morphologies. It was discovered that it has. These new morphologies cannot be obtained by conventional melt casting methods, but they can be achieved by forming parts of near theoretical density from fine superalloy particles near the melting temperature. Consistent results can be obtained by the plasma spray casting method carried out. Some conventional methods that fail to produce superalloy products with the unique combination of physical properties of this invention include, for example, Metals Engineering
Quarterly (Metals Engineering Quarterly)
Conventional plasma arc spraying methods include those described in the article by Mash & Brown entitled "Structure and Properties of Plasma Cast Materials" published in the February 1964 issue of . The strength properties of the independent members produced by Matsushi and Brown are limited by the achievable density (85-92%) and layered structure. The method selected for the production of superalloy products with unique physical properties of the present invention is ``Method and Apparatus for High-Energy Mechanical Coating of Substrates.''
No. 3,839,618 to Muehlberger, issued October 1, 1974. In fact, it was during the process of forming a superalloy coating using the low-pressure, high-speed plasma spray casting method of the aforementioned patent that the inventors made the important discovery that forms the basis of the present invention. Inspection and evaluation of the coatings thus obtained using nickel-based superalloys revealed unusual microstructures and physical properties attributable to them. Applying this knowledge, we fabricated a test piece using the plasma spray casting method and conducted a comparative test with a test piece made using the normal melt casting method. The novel idea has been established that the excellent physical properties of alloy coatings can be readily obtained even in bulk, ie components consisting entirely of plasma spray cast superalloys. Based on the above findings, plasma spray casting of superalloys in general, as well as other high-temperature alloys and alloys with high tensile strength in temperature ranges below the maximum operating temperature of gas turbine engines, can be It may be believed that components for turbine engines and other rotating machinery requiring severe tensile and fatigue loading conditions (eg flywheels) could be obtained. To illustrate typical operating conditions, the rotating disk of a gas turbine engine is 12.0 x ¹⁰³ at 538-649°C (1000-1200〓).
Tensile load up to Kg/ ^cm2 (170ksi) and 399~649
8.4×10 ³ Kg/cm ² (120ksi) at °C (750-1200〓)
Normally, it is subjected to a fatigue load of Similarly, fixed vanes and nozzles in such engines typically experience creep loads at engine operating temperatures and also require thermal fatigue cracking resistance under fluctuating temperature conditions ranging from ambient to engine operating temperatures. . In view of all the foregoing descriptions, and in particular the above discoveries, in accordance with the present invention, briefly described is a plasma sprayed superalloy selected from the group consisting of nickel-based superalloys, cobalt-based superalloys and iron-based superalloys. In the cast product, as plasma spray cast, oxygen content of less than about 1000 ppm, density greater than about 97% of theoretical, grain size of about 0.2 to about 0.5μ,
and a plasma spray cast product characterized in that it has a chemically homogeneous microstructure that is substantially free of microsegregation. When subjected to heat treatment, such products have densities in excess of about 98% of the theoretical value and exhibit less microsegregation due to the homogenization that occurs during heat treatment. The grain size of the product after heat treatment is generally greater than the grain size of the as-cast product, but the extent depends on the type of superalloy and the time and temperature of the heat treatment. However, for superalloys that are strengthened by the precipitation of one or more phases, the grain size after heat treatment may be limited to a small range of about 0.5 to about 5.0 microns. These products, whether flywheels, blades for gas turbine engines, disks for attaching blades to impellers, or other high-temperature components, are produced in solid form by low-pressure, high-velocity plasma spray casting. Alternatively, it can be manufactured as a hollow member by depositing the superalloy on a core and then selectively dissolving the core. The use of more complex core molds also allows for independent and self-supporting plasma sprayed cast parts having multiple hollow regions after melting. Furthermore, it is also possible to divide the heart shape into segments. That is, plasma spray casting a first superalloy onto a portion of the core to form a first portion of the final product, assembling such portion of the core with the remaining portions of the core, and then casting a first superalloy onto a portion of the core. The part can also be completed by plasma spray casting the second superalloy onto a complete core containing portions of the core. The invention will now be described in more detail with reference to the accompanying drawings. The gas turbine engine blade 10 shown in FIG.
1 is illustrative of the types of products that can be manufactured by plasma spray casting. A vane 10 of generally conventional size and shape is mounted on a platform 11.
and the simulated disk 50 of FIG. 5 and Example 5 described below.
It has a base 12 for rigid attachment in a conventional manner to a gas turbine disk such as a gas turbine disk. However, both vane 10 and disc 50 differ significantly from their conventional counterparts. That is, even if it is made of the same alloy composition as its conventional counterpart,
Vanes 10 and discs 50 have significantly different physical properties and therefore exhibit significantly different performance characteristics during normal engine operation. This fundamental and important difference stems from the different methods of manufacturing these new parts. That is, instead of using the usual melt casting method or the plasma arc spray casting method of Matsushi and Brown mentioned above, fine particles of a superalloy at a temperature slightly higher than the melting point are introduced into the plasma stream, and then cast in a low-pressure chamber with a neutral atmosphere. By projecting at high speed onto a placed substrate, the blade 1
0 and disk 50 are manufactured. Specifically, when manufacturing parts such as the vane 10 and disk 50, the particle size is -400 mesh (i.e., substantially all particles have a diameter of about
(less than 38μ), and the atmosphere in the spraying room is 30~
Argon at 60 Torr. Note that the term "gas turbine engine" used in this specification,
This includes gas turbines for power generation and jet engines for aircraft propulsion. Using the same low-pressure, high-velocity plasma spray manufacturing method as described above, the hollow blades 20 of Figures 2 and 3 are manufactured as shown in Example 4, and have the microstructure as summarized above. and physical properties are obtained. The major structural difference between vanes 10 and 20 is the use of a selectively dissolvable core assembly 40 of FIG. This provides the necessary internal clearance for the formation of the wall 21, so that the interior of the vane is divided into independent channels 22 and 23 for the flow of coolant. Flywheel 60, shown in perspective view in FIG. 6, is also manufactured by the same low pressure, high velocity plasma spray casting process described above. For such purposes, any nickel-based, cobalt-based or iron-based superalloy that, when plasma spray cast, can meet the tensile and fatigue loading conditions required for long-term service in such applications may be suitably used. Can be used for
Those skilled in the art will appreciate that such cast flywheels can be manufactured as a single plasma spray casting, or they can be manufactured in sections and then assembled together by suitable means. . In order to enable those skilled in the art to understand the invention more clearly, examples of the invention are presented below. These examples were conducted in the course of testing designed to obtain comparative data regarding key physical properties of plasma spray cast products of the present invention and prior art melt cast products. Therefore, these examples are merely illustrative of the practice of the invention and are not intended to limit the scope of the invention as defined by the claims. The data obtained in the following examples are presented in the usual manner. Thus, in Tables 1, 2 and 3, UTS stands for ultimate tensile strength in units of 10 ³ pounds per square inch and YS stands for 0.2% yield strength in the same units. Similarly, E _ML is the elongation at maximum load, E _FAIL is the elongation at break, and
RA is the cross-sectional reduction ratio, and all of these parameters are expressed in percentages. Example 1 A length of about 15 mm made of nickel-based superalloy IN738 was made by the low-pressure, high-speed plasma spray casting method as described above.
A plate member having a width of about 6.4 cm (2.5 inches) and a thickness of about 0.64 cm (0.25 inches) was manufactured. A steel plate that had been previously polished with No. 600 silicon carbide abrasive paper was used as the substrate. To achieve adhesion to the substrate (core) and control of IN738 density and microstructure, the substrate was preheated to approximately 1650°C (900°C). The pressure in the spraying chamber was 30 to 60Torr, the power of the plasma gun was 68KW, and the spraying time was 4 minutes and 30 seconds. After the thus coated substrate was cooled in a thermal spray chamber, the IN738 parts were separated by tapping the edge of the steel plate with a hammer. It takes
The total length is 2.54 cm (1.0 cm) from IN738 parts.
inch), width 1.0cm (0.4 inch) and thickness 0.16cm
A specimen with dimensions of (0.063 inch) was machined. The width of the gauge portion was 0.08 inch and was uniform over 0.25 inch. The test results obtained in this way were determined by the ordinary melt casting method.
Shown in Table 1 with typical data for specimens of the same size and shape made from IN738. Specimens formed by conventional melt casting were subjected to typical heat treatments used commercially. That is, prior to testing, the specimens were heated in argon at 2050° (1120°C) for 2 hours and then rapidly cooled, then heated in argon at 1550° (845°C) for 2 hours and then rapidly cooled. This represents the typical conditions under which IN738 components are used in today's gas turbine engines. In addition, for test pieces shaped by plasma spray casting method,
A simulated commercial heat treatment consisting of heating at 2100°C (1150°C) for 2 hours was performed. The data for 0.2% yield strength and elongation at break in Table 1 are graphically represented in Figures 7 and 8, respectively. As you can see from Figure 7,
When considering yield strength, it is approximately 1350〓 (735℃)
If:
Significantly stronger than IN738 parts. In addition,
The ultimate tensile strength shows a similar behavior. Approximately 1450〓
(790°C) and 1650°C (900°C), the yield strength of parts obtained by plasma spray casting is only 420 kg lower than the yield strength of parts obtained by ordinary melt casting. /cm ² (6ksi) smaller. Next, as you can see from Figure 8, approximately 1290〓
(up to 700°C) parts obtained by plasma spray casting are more ductile than the same IN738 parts obtained by conventional melt casting.
At approximately 2000 °C (1090°C), the member of this example exhibits complete superplasticity, possibly due to the ultrafine grain size inherent in this member. In order to prove that such superplastic behavior is due to the ultrafine grain size, several specimens were
The crystal grains were grown by heat treatment at ℃). Two heat-treated specimens were tested at room temperature and 1832°C (1000°C), respectively.
After heat treatment at 2300〓(1260℃), 1832〓
The elongation at break of the specimen tested at (1000℃) is 12
%, thus confirming that the superplastic behavior is due to the ultrafine grain size inherent in plasma spray cast parts. On the other hand, 2300〓(1260
The yield strength of the specimens tested at room temperature increased by 1.8×10 ³ Kg/cm ² (26 ksi) to 12.4×10 ³ Kg/cm ² (176 ksi) and
The yield strength of the specimen tested at 1000℃ (1832〓) increased by 700Kg/cm ² (10ksi) to 1.74×10 ³
Kg/cm ² (24.8ksi).

[Table] Example 2 A simulated disk 50 for a gas turbine engine, shown in FIG. 5, made of Rene 80 was manufactured by the low-pressure, high-speed plasma spray casting method as described above. By spraying the superalloy onto a substrate 51 consisting of a steel tube with a diameter of 4.2 cm, a structure having an annular cross-section when viewed along the longitudinal or perpendicular direction to the axial direction was obtained. Note that since the thickness of the accumulated superalloy layer was varied along the longitudinal direction of the structure, the cross section along the axial or longitudinal direction had a parabolic shape.
The nominal diameter of such a structure was approximately 10 cm. Specifically, as in Example 1, the surface of the substrate was first cleaned, grit blasted, and then preheated to about 1650°C (900°C). Throughout the work, the pressure in the spray chamber was 30-60 Torr (argon) and the power of the plasma gun was 68 KW, as in Example 1. After cooling in the spray chamber, the Rene 80 ring was separated from the steel tube 51 and machined into the shape shown in FIG. Thereafter, specimens for physical testing were obtained by cutting out the columns as indicated by the plurality of holes 52 in the disk 50. 1145°C for 2 hours and 870°C for specimens of standard shape and dimensions.
After heat treatment at ℃ for 2 hours, the test was carried out according to the usual method. The results obtained in this way are the second
Shown in the table. Also shown in Table 2 is comparative data for Rene 80, which was subjected to a typical commercial five-stage heat treatment operation after melt casting. As can be seen from Table 2, in Example 1
Similar to the results seen for IN738, the physical properties of Rene 80 parts obtained by plasma spray casting are superior to those of Rene 80 obtained by conventional melt casting.
The physical properties are better than those made of 80%.

[Table] Example 3 During an experiment designed to investigate the thermal fatigue behavior of a product of the present invention, a nickel-based superalloy, Rene
80 was plasma spray cast onto a Rene 80 substrate.
Specifically, by chill-casting a melt of nominal Rene 80 composition in a mold made of copper plate,
Two plates were obtained having dimensions of 4 inches x 1.5 inches x 0.25 inches. One end surface of each plate (10 cm x 0.64 cm [4 inches x 0.25 inches]) was grit blasted and degreased. Next, by the low-pressure, high-speed plasma spray casting method of Example 1, a plasma spray casting structure was formed on the treated end face. In this case, a powder of nominal Rene 80 composition with a particle size of -400 mesh was used. The resulting layer of plasma spray cast structure was approximately 0.150 inches thick.
A double wedge-shaped thermal fatigue specimen 70 as shown in FIG. 9 was machined from such a plate. One wedge 71 of such a specimen has a normal cast structure, whereas the other wedge 72 (finally 0.20
cm (0.08 inch) thick) had a plasma spray cast structure. By suspending such a test piece in the hole 73, it was exposed to a fluidized bed maintained at 1787〓 (975°C) for 4 minutes and 75〓 (24°C).
The samples were exposed to alternating periods of 2 minutes in a fluidized bed maintained at 10°C. Perform such operations 10, 30, 100,
Specimens 70 were inspected after 300, 600, and 1000 cycles. The plasma spray cast side wedge 72 showed no cracks after 1000 cycles, while the conventionally cast side wedge 71 showed cracks after 10 cycles. For the latter wedge 71, 30
After cycling the crack grows to a length of over 0.10 cm (0.04 inch), and after 1000 cycles it grows to a length of 0.572
cm (0.225 inch). EXAMPLE 4 A vane similar to that of FIGS. 2 and 3 except without the base 12 was produced by using the copper core assembly 40 of FIG. 4 and performing the plasma spray casting process described above. did. The spray chamber conditions were the same as in Example 1. In the first step, copper core segments 41 and 4
2 was plasma spray cast with IN738 to a thickness of approximately 0.38 mm (15 mils). Then, the heart segment 4
1 and 42 were assembled with the rest of the core assembly to form core assembly 40 as shown in FIG. Hole 43 in core segment 44 was filled with wire of nichrome composition. In the second step, the copper core assembly 40 of FIG. 4 and the IN738 formed in the first step are
A composite laminate structure was formed in areas such as area 24 by plasma spray casting Rene 80, 0.38-0.76 mm (15-30 mils), onto wall 21 of 1. After cooling in the spray chamber,
The blade 20 was obtained by immersing this structure in an aqueous nitric acid solution to dissolve and remove the copper core segment. When viewed in the position of FIG. 2, the height of the vane 20 was approximately 5 cm (2 inches) and the distance between the leading and trailing edges was approximately 3.8 cm (1.5 inches). As can be seen from FIG. 3, the internal wall 21 is
It consists of IN738, which is the outer shell 2 of Rene 80.
5 to form a blade 20. The outer peripheral surface 26 of the outer shell 25 made of Lune 80 defines the shape of the blade 20. In addition, the inner peripheral surface 27
surrounds aisles 22 and 23 and IN738
It is adhered to at least a part of the outer periphery of the wall body 21 and structurally joins it. The wire previously placed in the hole 43 is now an integral part 45 of the vane 20.
A hollow passage 2 at the trailing edge of the blade 20
3 serves to stir the coolant flowing through it.
The wall thickness of the vane 20 is about 15 to about 30 mils in the region consisting only of Lune 80.
In addition, the wall thickness in the area forming the laminated structure is approximately 1.14
cm (45 mil) or more, of which 0.38
cm (15 mil) consists of IN738. Example 5 Using the same plasma spray casting method and parameters as in Example 1, a thin walled tubular member or casing consisting of Rene 80 was manufactured. To be more specific, the inner diameter is 10cm (4 inches) and the length is 30cm.
A 0.51 cm (20 mil) thick Rene 80 was plasma spray cast onto a (12 inch) steel tube. Attempts to cast the thin-walled tubular member of this embodiment around a core material using conventional casting techniques often result in a product that is severely cracked. Other conventional techniques (eg, casting thick-walled tubular members and then machining them to size) are expensive. In any case, for example about 0.2
The thin-walled tubular member of this example, which has unique properties including a grain size of ~0.5 microns and a chemically homogeneous microstructure with substantially no microsegregation, can be manufactured by any conventional technique. Example 6 By repeating the procedure of Example 1, a plate made of cobalt-based superalloy (Co-29Cr-6Al-1Y), which is commonly used as a coating for gas turbine engine blades made of nickel-based superalloy, was obtained. The parts were manufactured by plasma spraying. The grain size of the as-produced plasma sprayed part was measured by transmission electron microscopy and was about 0.1 to about 0.3 microns. Example 7 By repeating the procedure of Example 1 again, a plate member made of an iron-based superalloy (19.5Cr-9.5CAl-balance Fe) was plasma spray cast. The grain size of the as-sprayed part was measured using a transmission electron microscope and was about 0.15 to about 0.25 microns. Room temperature, 1110〓(600℃) and 1380〓(750℃)
The mechanical properties of the commercially available iron-based superalloy MA956 (20Cr−4.5Al−0.5Ti−0.5Y−balance Fe) were melted and cast as shown in Table 3.
compared with the case of Plasma spray cast iron-based alloys are quite comparable to MA956, although they are less strong. Furthermore, since MA956 additionally contains titanium and yttrium as reinforcing elements, it is not surprising that such results were obtained.

【table】

Table: The plasma spray cast parts of Examples 1-4, 6 and 7 all exhibited essentially the same microstructural properties. That is, in the as-plasma spray cast state, the grain size is typically about 0.2 to about 0.5μ.
Moreover, the microstructure was chemically homogeneous with virtually no microsegregation. Although no test was conducted, Rene 80 of Example 5
The microstructure of the thin-walled tubular member is also expected to be the same as in other embodiments. The microstructure of a Rene 80 plate member plasma spray cast according to the method and procedure of Example 1 is shown in Figure 10, which is similar to the microstructure of the superalloy as it was plasma spray cast. This is a typical example. If you look at Figure 10, which is a transmission electron micrograph (40000X) of a thin plate specimen, it is approximately 0.2
Ultra-fine grain sizes in the range ~0.5μ are evident. Fig. 10 also shows that the grain boundaries and the interior of the grains are substantially free of precipitates and segregation, and therefore the microstructure is chemically homogeneous with virtually no microsegregation. I also understand.
Unfused particles may occasionally be found in the microstructure of the as-cast superalloy components of the present invention due to thermal spray equipment or powder disturbance. However, after heat treatment at 2100° C. (1150° C.) for 2 hours, no such particles remain. Note that in order to inspect the plasma spray cast member, it is necessary to use an electron microscope instead of a normal optical microscope. This is because the crystal grain size of such a member is extremely fine and exceeds the resolution of an optical microscope. To demonstrate the chemical homogeneity and absence of microsegregation in the plasma spray cast Rene 80 of FIG. 10, electron microprobe X-ray fluorescence data were determined as shown in Table 4. In Table 4, plasma spray cast Rene 80 is compared to conventionally melt cast Rene 80 having an average grain size of about 60 mils (1525 microns). The data in Table 4 were determined by stepwise scanning a beam of diameter 1-3μ across the sample, with scan intervals of 50μ for conventionally melt-cast Rene 80 and For spray cast Rene 80 it was 1μ. In both cases, the beam intersected both grains and grain boundaries. Especially in the case of Rene 80, which was cast by plasma spraying, this was natural considering that the beam diameter was about four times the crystal grain size. Cobalt is an essentially non-segregating element in nickel, so variations in cobalt concentration can be used as an indicator of the degree of dispersion in such data. For plasma spray cast Rene 80, the variation in Ti, Al, and Cr concentrations (ie, the degree of microsegregation or chemical heterogeneity) is only about 2-3% higher than normal variation. For Rene 80 which was melt cast as usual, the variation in Cr and Al concentrations was about 11% higher than the normal variation, and the variation in Ti concentration was about 70% higher than the normal variation. Therefore, the data in Table 4 shows that spray cast Rene 80 exhibits substantially no microsegregation or chemical heterogeneity compared to conventionally melt cast Rene 80.

[Table] Figure 11 is a transmission electron micrograph (20000X) of a thin plate specimen of Rene 80 that was subjected to plasma spray casting in the same manner as in Figure 10 and then heat treated at 2190°C (1200℃) for 2 hours. It is. Crystal grain size is approximately 5μ
However, this is still smaller than the average grain size of Rene 80, which is melt-cast as usual. Precipitates of γ′ phase are observed inside the crystal grains. Heat treatment at lower temperatures, e.g.
According to the heat treatment for several hours, the growth of crystal grains is less, and the obtained crystal grain size is about 2.0 to about 3.0μ. Theoretically speaking, microsegregation will also be even lower due to the homogenizing effect of the high temperature heat treatment. Given that Rene 80 is strengthened by precipitation of the γ' phase, the stability of this superalloy to grains at elevated temperatures was expected. Let us now compare the behavior of the nickel-based superalloy IN617, which is not strengthened by the γ′ phase. Example 1
IN617 plasma spray cast according to the procedure of
had the same ultrafine grain size (0.2-0.5μ) as parts made from other superalloys by plasma spray casting. Also, the tensile properties of plasma spray cast IN617 at room temperature were significantly better than those of conventionally melt cast IN617. For example, UTS is 7.80×
9.98×10 ³ Kg/cm ² for 10 ³ Kg/cm ² (111ksi)
(142ksi) and E _FAIL is 54% vs. 34%
It was hot. However, IN617 is melt cast as usual and plasma spray cast
IN617 exhibited approximately the same tensile properties when tested at 1650°C (600°C). The fact that the two exhibited almost equal behavior is due to the fact that crystal grains grew during the test. 2280〓(1250
When subjected to heat treatment at temperatures (℃), the grains of plasma spray cast IN617 grew significantly. After such heat treatment, the temperature at room temperature and 1650〓(900〓
The tensile properties of plasma spray cast IN617 were almost the same as those of conventional melt cast IN617 when tested at any temperature (°C). Before heat treatment, the plasma sprayed cast member of the present invention has a theoretically possible value of about 97 to about 97%.
It consistently had a high density of 100%. Components manufactured by conventional thermal spray casting methods are characterized by having gaps, pores, or voids between individual particles uniformly, irregularly, or both over their entire area. . If such gaps or voids exist, the member will have a sufficiently high density or
It is not possible to reach 100% density. After heat treatment, for example at 2100° C. (1150° C.) for 2 hours as described in Example 1, the plasma sprayed cast parts of the present invention are more than 1% higher and therefore have a minimum density of approximately It became 98%.
Note that the oxygen content of the test piece did not change due to the heat treatment. However, at levels below about 1000 ppm, oxygen content is not a significant factor in the strength properties of the plasma spray cast parts of the present invention. However, excess oxygen content beyond that level can have a detrimental effect on superalloy properties such as ductility. Thus, keeping the oxygen content below about 1000 ppm ensures that the superalloy exhibits higher tensile strength, good ductility, and thermal fatigue resistance for use as components in gas turbines. Furthermore, as is clear from the mechanical properties of the plasma sprayed cast parts of the present invention, the plasma sprayed cast parts for rotating machinery of the present invention can withstand long-term use as rotor and stator parts of gas turbine engines. Especially in the case of aircraft engines,
Approximately 1.8×10 ³ Kg/cm ² at 816-982℃ (1500-1800〓)
It is useful as a rotating vane that typically experiences pitch line (centerline) stresses of (25 ksi). In fact, the superalloy rotor blade of the present invention for a gas turbine engine,
The stationary vanes, nozzles, transition members and disks can be expected, based on our experience and the data above, to have a much longer service life than their counterparts manufactured according to the prior art. As can be seen from the foregoing description, the plasma spray cast products of the present invention do not require mechanical deformation during the manufacture of components such as gas turbine engine components. For example, hollow vanes such as those shown in FIGS. 2 and 3 can also be cast with the outer wall and inner portion having the desired thickness, and also the superior microstructure inherent in the products of the present invention as described above. and physical properties can also be obtained. in this way,
The present invention is particularly useful in applications to relatively small, thin-walled components. However, the present invention can also be applied to large, thick-walled components with substantial benefits, given that no mechanical deformation of the casting (e.g., by forging) is required. The grain sizes shown herein are values determined from transmission electron micrographs (eg, Figures 10 and 11) using a method known as the linear crossover method. When viewed parallel to the sprayed surface, crystal grains usually have an equiaxed appearance as shown in Figures 10 and 11, but the grain size is defined as the "diameter" of the crystal grains. It has been reported. Embodiment Aspect 1 A plasma spray cast product comprising a superalloy selected from the group consisting of nickel-based superalloys, cobalt-based superalloys and iron-based superalloys, wherein said superalloy in the as-plasma spray cast state is about
Oxygen content less than 1000ppm, density greater than about 97% of theoretical value, grain size within the range of about 0.2 to about 0.5μ,
and a plasma spray cast product characterized by having a chemically homogeneous microstructure that exhibits substantially no microsegregation. 2. In a plasma spray cast product comprising a superalloy selected from the group consisting of nickel-based superalloys, cobalt-based superalloys, and iron-based superalloys, said superalloy has an oxygen content of less than about 1000 ppm, a theoretical value of about 98
%, a grain size within the range of about 0.5 to about 5.0 microns, and a chemically homogeneous microstructure exhibiting substantially no microsegregation. 3. In a plasma spray casting product for rotating machinery made of a superalloy selected from the group consisting of a nickel-based superalloy, a cobalt-based superalloy, and an iron-based superalloy, the superalloy in a state as it is plasma sprayed and cast is about 1000 ppm. Oxygen content less than the theoretical value of approx.
A plasma sprayed cast part for rotating machinery characterized by having a density greater than 97%, a grain size within the range of about 0.2 to about 0.5 microns, and a chemically homogeneous microstructure exhibiting substantially no microsegregation. 4. A plasma spray cast product for rotating machinery comprising a superalloy selected from the group consisting of a nickel-based superalloy, a cobalt-based superalloy, and an iron-based superalloy, wherein said superalloy has an oxygen content of less than about 1000 ppm;
Density exceeding about 98% of the theoretical value, about 0.5 to about 5.0μ
Plasma sprayed cast parts for rotating machinery characterized by having a grain size in the range of , and a chemically homogeneous microstructure exhibiting substantially no microsegregation. 5. The plasma sprayed cast part for a rotating machine according to item 3 or 4, which is a gas turbine rotor part, a gas turbine stator part, or a flywheel 60. 6. The plasma spray cast part for a rotating machine according to claim 5, wherein the gas turbine rotor part is a rotating blade 10, 20 or a gas turbine disc 50 made of a nickel-based superalloy. 7. The plasma spray cast part for a rotating machine according to item 5, wherein the gas turbine stator part is a fixed blade. 8. Plasma spray cast part for a rotating machine according to claim 6, wherein the vane 20 is a hollow structure having at least one passage 22, 23 for the flow of coolant during use. 9 consisting of at least a first and a second superalloy selected from the group consisting of a nickel-based superalloy, a cobalt-based superalloy, and an iron-based superalloy, the first superalloy having a different composition from the second superalloy; and wherein a first layer of said first superalloy is located adjacent to a second layer of said second superalloy, said plasma spray cast as-cast composite article The first and second superalloys have an oxygen content of less than about 1000 ppm, a density of greater than about 97% of theoretical, about 0.2 to about
A plasma spray cast composite product characterized by having a grain size in the range of 0.5μ and a chemically homogeneous microstructure that is substantially free of microsegregation. 10 consisting of at least a first and a second superalloy selected from the group consisting of a nickel-based superalloy, a cobalt-based superalloy and an iron-based superalloy, the first superalloy having a different composition from the second superalloy; and wherein a first layer of said first superalloy is located adjacently on a second layer of said second superalloy. The superalloy has an oxygen content of less than about 1000 ppm, a density exceeding about 98% of the theoretical value, about
A plasma spray cast composite product characterized by having a grain size in the range of 0.5 to about 5.0 microns and a chemically homogeneous microstructure that is substantially free of microsegregation. 11 said second layer 21 of said second superalloy where said plasma spray cast composite product is a vane 20 having a plurality of hollow passages 22, 23;
is shaped to define at least one of the hollow passageways, and the first layer 25 of the first superalloy surrounds the hollow passageways and has an inner circumferential surface 27 and an outer circumferential surface 26. 11. The outer circumferential surface defines the shape of the vane, and at least a portion of the inner circumferential surface is located adjacently on at least a portion of the second layer of the second superalloy. plasma spray casting composite products.

[Brief explanation of drawings]

Figure 1 is an elevational view of a vane manufactured from a nickel-based superalloy by a low-pressure, high-velocity plasma spray casting method and comprising a solid structure entirely made of the nickel-based superalloy, and Figure 2 is an elevational view of a blade made of a copper core. FIG. 3 is a partial cross-sectional elevation view of a vane which, unlike the vane of FIG. 1, is hollow due to plasma spray casting on the assembly and subsequent removal of the core assembly by selective chemical dissolution. Line 3 in Figure 2 shows the internal passageway created by removing the copper core assembly after forming the vane by plasma spray casting.
Figure 4 is a perspective view of a copper core assembly for producing the blades of Figures 2 and 3 by plasma spray casting; Figure 5 is a low-pressure, high-velocity plasma spray casting. FIG. 6 is a perspective view of a flywheel manufactured by low-pressure, high-speed plasma spray casting method, and FIG. 7 is a schematic perspective view of a simulated gas turbine disk manufactured by the method described in Example 1. A graph plotting the 0.2% yield strength of the IN738 test piece obtained by plasma spray casting against the test temperature. Figure 8 shows the IN738 test piece obtained by plasma spray casting as described in Example 1. Figure 9 is a schematic diagram of a double wedge specimen for thermal fatigue testing; Figure 10 is a diagram of a Rene 80 sheet specimen as plasma spray cast. Transmission electron micrograph (40,000X), and Figure 11 is a transmission electron micrograph (20,000X) of a thin plate specimen of Rene 80 that was heat treated at 2190°C (1200°C) for 2 hours after plasma spray casting. In the figure, 10 is a solid blade, 11 is a platform, 12 is a base, 20 is a hollow blade, 21 is an internal wall, 22 and 23 are coolant passages, 25 is an outer shell, 26 is an outer peripheral surface, 27 is an inner peripheral surface, 40 is a core assembly, 41, 42 and 44 are core segments, 50 is a simulated disk, 51 is a base body, and 60
represents a flywheel.

Claims (1)

[Scope of Claims] 1. A low-pressure, high-velocity plasma spray casting product comprising a superalloy selected from the group consisting of a nickel-based superalloy, a cobalt-based superalloy, and an iron-based superalloy, the product comprising: a plasma spray casting product; The product's superalloy has a density greater than 97% of its theoretical value in its as-assembled state and a density greater than 98% of its theoretical value in its heat-treated state; Then, the grain size within the range of 0.2~0.5μ,
In addition, the heat-treated state has a grain size in the range of 0.5-5.0μ, an oxygen content of less than 1000ppm,
and a product characterized in that it has a chemically homogeneous microstructure that exhibits substantially no microsegregation. 2. The product according to claim 1, which is a rotating machine part. 3. The product according to claim 2, wherein the rotating mechanical component is a gas turbine rotor component. 4. The product according to claim 2, wherein the rotating mechanical component is a gas turbine stator component. 5. The product according to claim 3, wherein the gas turbine stator component is a rotating blade made of a nickel-based superalloy. 6. The product of claim 4, wherein the gas turbine stator component is a fixed blade. 7. The product of claim 5, wherein the rotary vane is a hollow structure having at least one passageway for the flow of coolant during use. 8. The article of claim 3, wherein the gas turbine rotor component is a gas turbine engine disk. 9. The product according to claim 2, wherein the rotating mechanical part is a flywheel. 10 A composite product having a bonded structure in which at least a second low-pressure high-velocity plasma spray-cast deposit layer overlaps at least a portion of the first low-pressure high-velocity plasma spray-cast deposit layer, the first and at least second The superalloys forming the deposited layer are selected from the group consisting of nickel-based superalloys, cobalt-based superalloys, and iron-based superalloys, but have different compositions from each other.
a grain size in the range of 0.2 to 0.5μ, with a grain size in the range of 0.5 to 5.0μ after further heat treatment, an oxygen content of less than 1000ppm, and a chemical composition that shows virtually no microsegregation. Composite products with a homogeneous microstructure and a density greater than 97% of the theoretical value in the as-sprayed state and a density greater than 98% of the theoretical value after further heat treatment. 11 said article is in the form of a rotating vane having a plurality of hollow passages, said first deposited layer comprising at least one
the second deposited layer defining two hollow passageways and surrounding the hollow passageways has an inner circumferential surface and an outer circumferential surface;
The product according to claim 10, wherein the outer circumferential surface defines the shape of the rotating blade, and at least a portion of the inner circumferential surface is adjacent to at least a portion of the first deposited layer to form a bonded structure. .