JPH0463148B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention forms an oxidation-resistant film of Al ₂ O ₃ on the surface of the intermetallic compound of TiAL by selectively oxidizing only Al without oxidizing Ti, and is inexpensive, lightweight, The purpose of the present invention is to provide a material with high temperature and oxidation resistance equivalent to or higher than the Ni-based superalloy Inconel 713C. The intermetallic compound TiAL or TiAL-based material is mainly used as a structural material for steam turbines or gas turbines for power generation, jet engine materials, or materials for automobile turbochargers, etc., which are used as equipment components that are exposed to temperatures of 900°C or higher. When alloys are used, they are subjected to surface treatment to improve their oxidation resistance to form an oxidation-resistant film. (Prior Technology) Conventionally, Ni-based superalloys such as Inconel 713C have often been used as high-temperature, heat-resistant, oxidation-resistant device components, but in order to increase thermal efficiency and output, the operating temperatures of the various engines mentioned above have increased. As the temperature rises, materials that can withstand even higher temperatures are required. In addition, in engines that rotate at high speeds such as jet engines or gas turbines,
In order to reduce the force that acts as an external force that causes the creep phenomenon, that is, the centrifugal force due to rotation, a material with a lower specific gravity is desired. Under these circumstances, considering the intermetallic compound TiAL or its alloy, its melting point is approximately 1460.
It has properties such as being more than 100°C hotter than normal Ni-based superalloys, and having a specific gravity of approximately 3.8, which is less than half that of normal superalloys. As an alternative material for
Furthermore, it is currently attracting a lot of attention and expectations as one of the most promising candidates for next-generation materials to be used in harsher environments than before. However, several problems have been pointed out with this intermetallic compound TiAL, and the two biggest obstacles to its practical application are its lack of ductility at room temperature and its lack of oxidation resistance at high temperatures of 800°C or higher. It is becoming. As seen in many research publications both domestically and internationally, the problem of lack of ductility at room temperature is being resolved, but so far there have been no reports of particularly effective means of improving oxidation resistance at high temperatures. Not talked about. (Problem to be Solved by the Invention) Generally, methods for improving the oxidation resistance of metals include alloying metal elements such as Cr that are effective in improving oxidation resistance, and surface treatments such as plating or diffusion infiltration. There are known methods of forming a surface layer with good oxidation properties through treatment, but alloying the intermetallic compound TiAL with a third element impairs its greatest advantage, the low density. , a surface treatment method with relatively little increase in density is considered to be promising here. However, for surface treatment of the intermetallic compound TiAL, diffusion infiltration treatment or vacuum evaporation treatment of Cr, Si or Al has been considered, but vacuum evaporation treatment of Cr, Si or Al is not particularly effective, and diffusion infiltration treatment Except for Al, no particular improvement in high-temperature oxidation resistance has been observed. In addition, some problems have been pointed out regarding the diffusion treatment of Al, such as the properties of the diffusion film, and there is a desire to develop a more effective surface treatment method. (Means for Solving the Problems) The present invention provides an intermetallic compound of TiAL with an oxygen partial pressure of 1×
10 ^-2 ~ 1 x 10 ^-5 Pa at a temperature of 900℃ ~
Hold at 1050℃ for 30 minutes to 100 hours
An oxidation-resistant film is formed on the surface of the intermetallic compound of TiAl, which is characterized by selectively oxidizing only Al without oxidizing the TiAl, thereby forming an oxidation-resistant Al ₂ O ₃ film on the surface of the intermetallic compound in advance. This is a method of forming. (Function) Put the untreated intermetallic compound TiAL in the atmosphere.
It is known that when oxidized at a temperature of 900°C or higher, an oxide film with a three-layer structure is formed, that is, an oxide film with a structure consisting of _two layers of TiO, _three layers of Al ₂ O, and a mixture of both from the outermost layer. There is. Among these especially
It is believed that the preferential growth of the _TiO2 layer as the oxidation time progresses is the cause of the deterioration of TiAL's oxidation resistance. The thickness of the oxide film is approx.
Grows up to 200μm. However, the intermetallic compound TiAL that has been heat-treated under low oxygen partial pressure has a very thin layer of Al ₂ O ₃ on its surface.
It was confirmed by X-ray diffraction and an X-ray microanalyzer that only a film of TiO 2 was formed, and no formation of a TiO ₂ layer was observed. In addition, when the treated specimen was subjected to repeated oxidation tests at 900°C in static air, the Al ₂ O ₃ film was oxidized with the growth of a TiO ₂ layer as observed in the untreated specimen. It was found that it has the effect of suppressing the progression of. In this heat treatment, only the Al ₂ O ₃ film is
The reason why TiO ₂ is formed preferentially to TiO 2 is because the heat of oxidation of Al is negatively larger than that of Ti, and the amount of oxygen that can be dissolved in Al is smaller than that of Ti. It can be explained that Al binds preferentially to oxygen atoms deficient in an atmosphere with an oxygen partial pressure, and only Al ₂ O ₃ is produced. Among metal oxides, Al ₂ O ₃ is chemically extremely stable and known to be one of the slowest self-diffusing metal elements, making it an excellent choice for intermetallic compounds.
It is thought that by forming a dense film with few defects on the surface of TiAL, its oxidation resistance can be significantly improved. Furthermore, it is already well known that the diffusion of each element for growing an Al ₂ O ₃ film is mainly carried out via Al ₂ O ₃ grain boundaries. Therefore, it can be said that the growth rate of the Al ₂ O ₃ film depends on the area of grain boundaries serving as diffusion paths, or in other words, the grain size. By the way, due to oxidation under low oxygen partial pressure, Al ₂ O ₃
Felten et al., who studied the growth of Al ₂ O ₃ films on Pt-Al alloys, found that when a film is formed and grows, the oxide crystal grains become coarser than in the case of oxidation at atmospheric pressure. clarified by. Regarding this, when oxidation begins under low oxygen partial pressure,
It is thought that because the number of nucleation positions of oxides is smaller than that under atmospheric pressure, an oxide film with relatively coarse grains is formed as a result. It is thought that the Al ₂ O ₃ film formed on the surface of the substrate by the heat treatment under low oxygen partial pressure of the present invention also becomes coarse grained, and the effect of this treatment on improving oxidation resistance is also unknown. It is thought that this is the case, but if the heating temperature is low, the heating time should be selected to be long, and if the heating temperature is high, the heating time should be selected to be short. Moreover, if the oxygen partial pressure is small, the heating time must be increased. Moreover, if the oxygen partial pressure is large, the heating time may be short.
From the above viewpoint, the range of oxygen partial pressure is 1×10 ^-2 to 1×
10 ^-5 Pa, temperature 900℃~1050℃ and heating time
The duration ranged from 30 minutes to 100 hours. (Example) Examples of heat treatment under low oxygen partial pressure of the present invention will be described below. Example 1 The sample used in this example was Al with a purity of 99.99%.
99.6% sponge Ti is blended into the stoichiometric composition of the intermetallic compound TiAL, and approximately
It was melted into a 280g rod-shaped ingot.
These were homogenized and annealed at 100° C. for 168 hours, and then a test piece with dimensions of 10 x 5 x 2 mm was cut out using a discharge wire cutter and a fine vine cutter, and the surface of the test piece was polished with emery paper up to #1000.

[Table] Table 1 shows the compositions of intermetallic compounds TiAL and TiAL-based alloys that were heat-treated under low oxygen partial pressure. This test piece was subjected to heat treatment under low oxygen partial pressure under various conditions as shown in Table 2, and then an oxidation test was conducted to examine the heat treatment conditions that exhibited the best oxidation resistance. The pressures in the table indicate air pressure.

[Table] As is clear from the second table, Sample No. 1 has a low oxygen partial pressure in the atmosphere, so even if the treatment time is short, there is a lot of oxygen in the atmosphere, and in addition to Al ₂ O ₃ , TiO ₂ is also present. Since this is a condition where it is possible, the effect is relatively small. In addition, sample No. 3 has an oxygen partial pressure of 6.7 in the processing atmosphere.
×10 ^-4 , and the degree of vacuum was high, so there was little oxygen in the processing atmosphere, and it would have taken a long time to form Al ₂ O ₃ , but the processing time was shortened to 4 hours, so the effect was small. . In this case processing time is 10-20
It was confirmed that, like time, it is effective if left long enough. In the oxidation test, each test piece was inserted into a horizontal tubular electric furnace previously maintained at 900°C and oxidized in still air. After a predetermined period of time, the specimen was removed from the furnace and the mass change was measured and the surface was observed. This was carried out intermittently by returning the material to the furnace and continuing oxidation. The oxidation layer was also analyzed using a scanning microscope (SEM), an X-ray microanalyzer (XMA), and an X-ray diffractometer as necessary.
As a comparison material, Ni-based superalloy Inconel 713C was also subjected to oxidation tests. The composition of this comparative material is shown in Table 3.

[Table] Figure 1 shows the untreated intermetallic compound TiAL and the Ni-based superalloy Inconel used as a comparison material.
This figure shows the change in mass due to oxidation tests of 713C and pure Ti plates. This figure shows that untreated intermetallic compound TiAL has better oxidation resistance than pure Ti, but is several steps inferior to Inconel 713C. Next, FIG. 2 shows the results of an oxidation test on samples in which the intermetallic compound TiAL was subjected to the heat treatment under the low oxygen partial pressure shown in Table 2. Both specimens No. 1 and No. 3 have considerably improved oxidation resistance compared to the TiAL specimen (TA) without heat treatment, but No. 2A
and No. 2B have much less mass increase due to oxidation than those, and are two orders of magnitude smaller than the untreated TiAL specimen (TA). Their oxidation resistance exceeds that of Inconel 713C. In addition, it was observed that sample No. 1 and sample No. 3 showed almost zero oxidation weight gain after cumulative oxidation treatment for 50 to 100 hours, and were superior to Inconel (Ni-based alloy). . The film on the untreated TiAL specimen (TA) after oxidation for 150 hours was white in appearance and had a thickness of approximately 100 μm. From XMA and X-ray diffractometer analysis, this oxide film consists of _two layers of TiO and two layers of Al ₂ O ₃ from the outside.
It was observed that a Ti ₃ AL layer with a thickness of several μm was formed between the oxide film and the TiAL base material. In general, TiAL's poor oxidation resistance is due to the growth of _two TiO layers.
This is because the second Al ₂ O ₃ layer is non-uniform and discontinuous, making it impossible to prevent the outward diffusion of Ti.
It is thought that the outer TiO ₂ grew as oxidation progressed. Among the test pieces subjected to the heat treatment of the present invention, Nos. 1 and 3, which had a relatively large oxidation weight gain, partially formed a white oxide film (TiO ₂ ) similar to the untreated TiAL test piece (TA). However, No.2B is 250
Even when the test was continued for hours, the dense gray-black oxide film (Al ₂ O ₃ ) remained and no change was observed. Figure 3 shows an optical micrograph and the results of XMA analysis of the cross section of No. 2A as it was heat-treated under low oxygen partial pressure. A uniform film is formed on the surface of the base material, although it is very thin and only a few micrometers thick. It was identified as Al ₂ O ₃ by X-ray analysis. The dramatic improvement in oxidation resistance caused by heat treatment under low oxygen partial pressure is thought to be due to this Al ₂ O ₃ film. In other words, this Al ₂ O ₃ film was denser than the oxide film produced by normal oxidation of TiAL, so it is presumed that it prevented outward diffusion of Ti during the oxidation test and suppressed the growth of the oxide film. It is thought that under the treatment conditions such as No. 1, the continuity of this Al ₂ O ₃ film was still insufficient, so the growth of the TiO ₂ layer progressed from the incomplete parts of the film. Particularly in No. 3, which had a moderately large oxidation weight gain, it was found that hemispherical white oxides with a diameter of about 1 mm were sparsely dispersed over the entire surface. This can be thought of as the oxide film starting to grow from the incomplete part of the Al ₂ O ₃ film. As described above, when TiAL is heat-treated at 1000℃ under low oxygen partial pressure, it becomes thin and looks gray-black in appearance.
It was discovered that it forms an Al ₂ O ₃ film and dramatically suppresses the formation and growth of an oxide film (TiO ₂ ) during normal oxidation. This effect was maintained even after intermittent oxidation at 900°C for up to 250 hours. (Comparative example) After homogenizing and annealing the two types of samples shown in Table 1 above at 1000°C in a vacuum of 10 ^-3 Pa for 168 hours,
A test piece was cut out from a plate with dimensions of 10 x 5 x 2 mm, the surface was polished with #1000 emery paper, and various surface treatments were applied. The surface treatments tested in this experiment were conventional diffusion infiltration treatment and vacuum evaporation treatment, and were compared with the low oxygen partial pressure heat treatment of the present invention. Among them, test specimens with relatively good surface conditions or with improved oxidation resistance were subjected to oxidation tests at 900°C in a static atmosphere for 25 to 150 hours. In addition, Ni-based superalloy Inconel 713C was used as a comparison material.
SUS430 stainless steel was also subjected to oxidation tests at the same time. The composition of Inconel 713C used is the same as shown in Table 3. The composition of SUS430 stainless steel is shown in Table 4.

[Table] The results of this oxidation test do not show an increase in oxidation due to continuous oxidation, but are based on an intermittent method in which the oxidation test is carried out by taking it out of the furnace after a predetermined period of time, measuring the mass change, and then returning it to the furnace to continue oxidation. This is due to oxidation. The mass of the peeled film was also measured. The effects of each treatment on oxidation resistance were evaluated by observing the test pieces and measuring the oxidation weight increase per unit surface area after the oxidation test, and also using an X-ray diffractometer, XMA, etc. . First, untreated TiAL (TA), 1.5% Mn−
TiAl (TAM), nickel-based superalloy (Inconel)
713C) and stainless steel (SUS430) are shown in Figure 4. As already known, Mn addition
TiAL has a higher degree of oxidation than when no additive is added. TiAL (TA) oxide film is white, Mn added
TiAL (TAM) was black. Also, at this temperature, peeling of both TA and TAM films was observed, and they showed a much larger oxidation weight gain than Inconel 713C, which maintains a stable film. Next, the results of oxidation tests for each surface treatment will be explained. First, we decided to use the powder pack method for the diffusion and penetration treatment. For this purpose, a test piece is filled in a stainless steel tube together with a powder pack material having a particle size of 200 mesh or less, and then treated in a Kanthal wire furnace under the conditions shown in Table 5.

[Table] These methods have already been established for superalloys, and are expected to be effective for TiAl as well. Cr as a diffusion material,
Although attempts were made to use three types, Si and Al, it was difficult to obtain a sufficient diffusion film for Cr and Si within the scope of the inventor's efforts. Regarding the diffusion and penetration treatment of Al, we varied the treatment temperature and treatment time within the range shown in Table 5, and tried two types of pack material formulations to find the optimal conditions. It was found that a diffusion film with excellent properties could be obtained. At this time, the diffusion film had a thickness of approximately 100 μm, was dense, and had a good appearance. The composition of this film was identified as TiAL ₃ based on the results of an X-ray diffractometer. When the treatment conditions were changed, in general, many cracks were observed in the structure of the film at high temperatures for short periods of time, while dense films with good adhesion were obtained at low temperatures for long periods of time.

[Table] We also prepared samples that had been subjected to vacuum heat treatment as shown in Table 6 after Al diffusion and penetration, and also conducted oxidation tests. The results of the oxidation test are shown in FIG. It was found that compared to untreated TiAl, the one treated with Al diffusion infiltration has superior oxidation resistance and is comparable to Inconel 713C. It was also found that the material subjected to vacuum heat treatment had even better oxidation resistance, surpassing Inconel 713C. By the way, there is a problem that occurs under any processing conditions. As shown in FIG. 6a, large cracks occur in the diffusion film near the edges of the test piece. The test piece for this test had a rectangular parallelepiped shape with sharp edges, so when we prepared a test piece with rounded edges and applied diffusion penetration treatment, cracks were evident as shown in Figure 6b. became smaller. Therefore, it is assumed that this problem can be solved by further finding an optimal shape, and it is considered that this problem can be dealt with industrially as well. Now, the present inventors have learned about vacuum evaporation treatment of Cr,
Four types were tried: Si, Ni, and Al. Vapor deposition itself is difficult for Cr and Si, but Ni and Al can be vapor-deposited, so after vapor deposition, heat treatment was performed at 1000-1050℃ for 4 hours in a vacuum of 10 ^-3 Pa for diffusion. After that, an oxidation test was conducted. The results are shown in FIG. As shown in Figure 7
Regarding Ni vapor deposition, no significant improvement in oxidation resistance was observed. Furthermore, although some effect was observed for Al, the effect was lost in a relatively short period of time, and even when observed with an optical microscope, sufficient diffusion did not occur as shown in Figure 8 below. This is clear, and we believe that sufficient effects can be expected if more appropriate Al deposition and diffusion conditions are used in the future. Example 2 The same intermetallic compounds TiAL and Mn-added TiAL shown in Table 1 were subjected to heat treatment under low oxygen partial pressure under a wide range of conditions, and repeated oxidation tests were conducted at 900° C. in still air. Table 7 shows the treatment conditions for heat treatment under low oxygen partial pressure applied to the intermetallic compound TiAL. The parameters that were changed as processing conditions in this heat treatment were processing air pressure (degree of vacuum), processing temperature, and processing time, and the actual heat treatment was performed by heating the sample in an atmosphere with the conditions shown in Table 7. It is held for a predetermined period of time.

[Table] Regarding intermetallic compound TiAL or TiAL-based alloy test pieces heat-treated under the conditions shown in Table 7
Repeated oxidation tests were conducted at 900°C in still air to examine the relationship between each treatment condition and oxidation resistance. The graphs from FIG. 9 to FIG. 11 show the increase in mass of each test piece when an oxidation test was conducted. The horizontal axis of these graphs shows the cumulative oxidation time, and the vertical axis shows the change in mass of the test piece as a value per unit surface area. Oxidation of each test piece when the intermetallic compound TiAL is heat-treated under low oxygen partial pressure according to the present invention, with the treatment air pressure and treatment time constant at 6.7×10 ^-3 Pa and 10 hours, respectively, and the treatment temperature varied. The increase is shown in Figure 9. It is clear that the oxidation resistance is improved by the heat treatment under low oxygen partial pressure compared to the untreated case shown in FIG. 1 shown above. For this effect, the processing temperature
In the range from 900°C to 1000°C, it was observed that the weight gain due to oxidation decreases as the temperature approaches 1000°C, and the effect of improving oxidation resistance is particularly greatest near 1000°C. It should be noted that among the samples of the present invention, those shown in the D curve in Figure 9 seem to have a large oxidation weight gain, but up to 100 hours, the oxidation weight gain is less than 4 g m ² and has sufficient oxidation resistance effect than Inconel 713C. was confirmed. Figure 10 shows processing air pressure 6.7×10 ^-3 Pa and processing temperature.
The oxidation resistance of an intermetallic compound TiAL test piece heat-treated under low oxygen partial pressure at 1000°C for 10 hours was compared with that of Inconel 713C through repeated oxidation tests over a long period of time. It is found that the oxidation resistance exceeds that of Inconel 713C in the range of cumulative oxidation time up to 500 hours. FIG. 11 shows the oxidation curve J of a sample of a TiAL-based alloy containing 1.5% Mn, which was subjected to the heat treatment under low oxygen partial pressure according to the present invention. The oxidation curve K of the same sample without the same treatment is also shown. It is recognized that the heat treatment under low oxygen partial pressure according to the present invention is effective in improving the oxidation resistance of this Mn-containing sample TiAL alloy as well. Table 8 summarizes the evaluation of oxidation resistance improvement by repeated oxidation tests as described above, according to treatment conditions. The symbol ○ in the table indicates that oxidation resistance equal to or higher than that of Inconel 713C was obtained, the symbol △ indicates that the effect was better than Inconel 713C, and the symbol × indicates that oxidation resistance was greater than that of Inconel 713C. This indicates that the

[Table] FIG. 12 is a characteristic diagram showing that the TiAL shown in Example 1 was treated at a high degree of vacuum (6.7×10 ⁻⁴ Pa) at 1000° C., and shows that the longer the time, the better the effect. As is clear from this, a sufficient effect can be obtained by processing material No. 3 shown in Table 2 for a longer time, from 4 hours to 10 hours, even at the same degree of vacuum. Figure 13 shows TiAL6.7×10 ^-3 Pa shown in Example 1.
FIG. 2 is a characteristic diagram showing that the longer the time, the more effective the treatment is when treated at a low temperature (900° C.). In addition, in Figures 9 and 11, even if the weight increase is large after oxidation for 100 hours or more, the weight will increase at 1000℃.
From 2 hours in an atmosphere with an oxygen partial pressure of 6.7×10 ^-4 Pa
A sufficient effect can be obtained by increasing the treatment time to 10 hours. This indicates that a sufficient oxidation-resistant film of Al ₂ O ₃ could be formed by extending the treatment time. Figure 14 shows the intermetallic compound TiAL at 1000℃, 6.7×
This is a characteristic diagram showing that when treated at 10 ^-3 Pa, the longer the treatment time, the greater the effect.When the temperature is relatively high at 1000℃ under an appropriate oxygen partial pressure, the treatment time is 2 hours, The longer the time is 4 hours, 10 hours, and 16 hours, the more complete the formation of the Al ₂ O ₃ film is, indicating that the effect is sufficient. FIG. 15 is a characteristic diagram showing that when using the same sample with the same processing time and vacuum degree, the best effect is obtained at around 1000°C. This means that the processing temperature,
This shows that there is a correlation between processing time and degree of vacuum. In other words, if the degree of vacuum is high, it is better to increase the treatment temperature and process for a long time.If the treatment time and temperature are appropriate for the degree of vacuum, Al ₂ O ₃ will be completely generated and will have sufficient oxidation resistance. The effect can be obtained. FIG. 16 is a characteristic diagram showing that even for the same sample as in FIG. 15, if the treatment temperature is high (1050° C.) and the treatment time is long, there is no effect. This shows that the shorter the treatment time, the better the effect in the case of high-temperature treatment at 1050°C for a vacuum degree of 6.7×10 ^-3 Pa. As described above, in the present invention, the intermetallic compound TiAL
As a surface treatment method to improve the oxidation resistance of
It was confirmed that heat treatment under low oxygen partial pressure has a remarkable effect. By applying the treatment of the present invention, the oxidation resistance of the intermetallic compound TiAL (TA) is improved,
The most excellent of these was confirmed to have superior oxidation resistance to the Ni-based superalloy Inconel 713C. (Effect of the invention) By applying the treatment of the present invention, intermetallic compounds
The oxidation resistance of TiAL (TA) has been improved, the best of which is Ni-based superalloy Inconel 713C
It has a great industrial effect in that it can provide a lightweight, inexpensive oxidation-resistant material that has superior oxidation resistance, has heat resistance at high temperatures of 900°C or higher, and
It is extremely useful as a material for internal combustion engines and spacecraft used in aircraft and ships, a structural material for steam turbines or gas turbines for power generation, a material for jet engines, and a material for turbochargers for automobiles.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the results of a comparative oxidation test on the untreated intermetallic compound TiAL and comparative materials (pure Ti material and Inconel 713C).
Figure 2 shows test pieces No. 1 and No. 1 treated according to the present invention.
2A, No. 2B, No. 3, untreated material (TA), and Inconel 713C are compared and subjected to an oxidation test. Microscopic metallographic diagram and XMA diagram of a cross section of a TiAL specimen heat-treated in a partial pressure atmosphere,
Figure 4 is an oxidation resistance characteristic diagram showing the oxidation test results comparing TiAL (TA) and TiAL (TAM) with Inconel 713C and stainless steel SUS430.
Inconel 713C heat-treated and non-heat-treated TiAL with diffusion penetration treatment film.
Figure 6a and b show the state of coating cracks in the steep corners and gentle corners of the test piece (TiAL) with the Al diffusion treatment coating. A metallographic diagram obtained by microscopy. Figure 7 is an oxidation resistance characteristic diagram showing the oxidation test results of specimens TA and TAM with Ni evaporated on the surface and specimen TA with Al evaporated. Figure 8 is TiAL. Al
Microscopic metallographic diagram of the film deposited with
Figures and Figure 10 are intermetallic compound TiAL (D, E, F curves) subjected to heat treatment under low oxygen partial pressure according to the present invention.
Comparative test characteristic diagram showing the results of oxidation test compared with Inconel 713C (G, H curve), No. 11
The figure shows the results of an oxidation test in which a TiAL-based alloy with 1.5% Mn added and heat treated under low oxygen partial pressure was compared with an untreated material.
Figure 2 shows the intermetallic compound TiAL alloy of the present invention.
Characteristic diagram showing the relationship between processing time and oxidation weight gain when processing at ℃ and high vacuum degree (6.7 × 10 ^-4 Pa), Part 1
Figure 3 is a characteristic diagram showing the relationship between treatment time and oxidation weight gain when the intermetallic compound TiAL alloy of the present invention is treated at low temperature (900°C) and low vacuum (6.7 × 10 ^-3 Pa). The figure is a characteristic diagram showing the relationship between oxidation time and oxidation weight gain when the intermetallic compound TiAL alloy of the present invention is treated at 1000°C and vacuum degree (6.7 × 10 ^-3 Pa). Figure 16 is a characteristic diagram showing the relationship between the treatment temperature, oxidation time, and oxidation weight gain when the intermetallic compound TiAL alloy was treated at a vacuum level (6.7 × 10 ^-3 Pa) for 4 hours. Compound
It is a characteristic diagram showing the effect of treatment temperature and treatment time on oxidation weight gain of TiAL alloy at vacuum degree (6.7×10 ^-3 Pa) and 1050°C.

Claims (1)

[Claims] 1 TiAL intermetallic compound at oxygen partial pressure 1×10 ^-2 ~
Temperature 900℃~1050℃ under oxygen atmosphere of 1×10 ^-5 Pa
The method is characterized by holding for 30 minutes to 100 hours to selectively oxidize only Al without oxidizing Ti, thereby forming an oxidation-resistant Al ₂ O ₃ film on the surface of the intermetallic compound TiAl in advance. A method of forming an oxidation-resistant film on the surface of TiAl intermetallic compounds.