Single crystal blade heat treatment method based on oxidation vacuum reduction control

Abstract

The invention relates to a single-crystal blade heat treatment method based on oxidation vacuum reduction control, and belongs to the technical field of single-crystal high-temperature alloy blade preparation. The heat treatment method comprises the following steps: carrying out solution treatment on the single crystal blade; the solution treatment comprises first-stage heating, first-stage heat preservation and cooling; the first-stage heat preservation is carried out in an inert atmosphere containing trace oxygen. In the solid solution heat treatment process, the inert atmosphere containing trace oxygen is used for heat preservation, so that metal knots caused by decomposition of oxides on the surface of the blade casting can be avoided, meanwhile, the risk of recrystallization in the heat treatment process can be reduced, and the procedure of treating the surface of the casting with alkali liquor is omitted.

Description

Technical Field

[0001] The present invention belongs to the technical field of single crystal high temperature alloy blade preparation, and more specifically, relates to a single crystal blade heat treatment method based on oxidation vacuum reduction control. Background Art

[0002] In order to obtain excellent comprehensive performance, single crystal high temperature alloys usually adopt a high solution temperature and a long-term heat preservation solution treatment system. Under such circumstances, the surface of the single crystal blade has sufficient time to undergo surface reaction. The single crystal blade is prepared by directional solidification. During the directional solidification process, the mold shell is heated to a high temperature. After the directional solidification is completed, the blade precision casting is taken out of the directional solidification furnace together with the mold shell that wraps the blade. When it is out of the furnace, the single crystal blade is still at a high temperature and exposed to the atmospheric environment. The surface of the blade reacts with the oxygen in the atmosphere and the surface is oxidized. At the same time, due to the heat preservation effect of the high temperature mold shell, oxidation will continue for a period of time. After the directional solidification is completed, there is usually an oxide layer on the surface of the blade casting. Studies have shown that the oxide layer is mainly the oxide of the base metal nickel.

[0003] In the prior art, before the solution treatment, the surface oxide and other sticky layers formed on the blade surface during the casting process are usually removed. However, the pre-solidification treatment of the blade not only increases the process, but also easily causes recrystallization defects. In the prior art, there is also a situation where heat treatment is directly performed after casting. If the single crystal blade is directly heat treated after casting, due to the lack of oxygen in the vacuum heat treatment atmosphere, for the single crystal blade directly heat treated after casting, the oxide layer formed on the surface during the casting process will decompose during the heat treatment process. At the same time, due to the complexity of the oxide layer composition, the melting point of the decomposition product is lower than that of the single crystal alloy at the solution treatment temperature to become a liquid alloy. The liquid alloy generated on the surface of the oxide layer cannot be directly dissolved into the blade matrix due to the isolation of the oxide layer. Under the combined action of gravity and surface tension, the liquid alloy generated by the decomposition reaction gradually gathers at the bottom of the blade. After the oxide layer on the surface of the single crystal blade casting is completely decomposed during the casting solution process, the alloy liquid contacts the base metal to form a metallurgical bond, and a metal nodule is formed on the blade surface after heat treatment. Summary of the invention

[0004] The purpose of the present invention is to provide a single crystal blade heat treatment method based on oxidation vacuum reduction control, which is used to directly perform solid solution heat treatment on the blade surface without any treatment after directional solidification, and to avoid the decomposition of oxides on the surface of the blade casting to form metal nodules by controlling the heat treatment process conditions. The present invention provides the following technical solutions:

[0005] A single crystal blade heat treatment method based on oxidation vacuum reduction control comprises: subjecting the single crystal blade to solid solution treatment;

[0006] The solution treatment includes a first stage of heating, a first stage of heat preservation, and cooling;

[0007] The first stage of heat preservation is carried out under an inert atmosphere containing a trace amount of oxygen.

[0008] Furthermore, the inert atmosphere containing trace amounts of oxygen satisfies one or more of the following conditions:

[0009] (1) The volume of trace oxygen in the inert atmosphere accounts for 0.05%-0.1%;

[0010] (2) The pressure of the inert atmosphere is 10-100 Pa; the oxygen partial pressure in the inert atmosphere is 0.005-0.1 Pa.

[0011] Optionally, the volume of trace oxygen in the inert atmosphere is 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095% or 0.1%.

[0012] Optionally, the pressure of the inert atmosphere is 10Pa, 20Pa, 30Pa, 40Pa, 50Pa, 60Pa, 70Pa, 80Pa, 90Pa or 100Pa.

[0013] Optionally, the oxygen partial pressure in the inert atmosphere is 0.005Pa, 0.01Pa, 0.015Pa, 0.02Pa, 0.03Pa, 0.04Pa, 0.05P, 0.07Pa, 0.08Pa, 0.09Pa or 0.1Pa.

[0014] Among them, according to the oxidation-reduction tendency of single crystal high-temperature alloys under vacuum conditions, the activity of trace oxygen in the vacuum atmosphere is utilized, and the stability of the oxide layer on the surface of the single crystal blade casting is achieved through an inert protective atmosphere with a specific oxygen content concentration, thereby avoiding the vacuum reduction and aggregation of the oxide layer to form surface defects.

[0015] Among them, this method can be applied to all current nickel-based single crystal high-temperature alloy blades, such as DD6 single crystal alloy blades and DD9 single crystal alloy blades.

[0016] Furthermore, after the first stage of heat preservation, multiple stages of heating-heat preservation are also included;

[0017] Optionally, after the first stage of heat preservation, it also includes a second stage of temperature rise-second stage of heat preservation, a third stage of temperature rise-third stage of heat preservation... and an Nth stage of temperature rise-Nth stage of heat preservation, where N is an integer greater than one.

[0018] Furthermore, the first stage of heating includes: placing the single crystal blade into a heat treatment furnace, evacuating the furnace, and controlling the heating rate to heat the temperature to a first target temperature.

[0019] Furthermore, the vacuum degree of the vacuum extraction is 0.1-0.01Pa.

[0020] Optionally, the vacuum degree of the vacuum extraction is 0.01Pa, 0.02Pa, 0.03Pa, 0.04Pa, 0.05Pa, 0.06Pa, 0.07Pa, 0.08Pa, 0.09Pa or 0.1Pa.

[0021] Furthermore, the heating rate of the first stage of heating is 2-10°C / min.

[0022] Optionally, the heating rate is 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min.

[0023] Further, the first target temperature is 1250-1370°C;

[0024] Optionally, the first target temperature is 1250°C, 1260°C, 1270°C, 1280°C, 1290°C, 1300°C, 1310°C, 1320°C, 1330°C, 1340°C, 1350°C, 1360°C or 1370°C.

[0025] Further, the insulation temperature of the first stage insulation is equal to the first target temperature;

[0026] Furthermore, the first stage of heat preservation has a heat preservation time of 1-20 hours;

[0027] Optionally, the insulation time of the first stage is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0028] Optionally, the second stage heating-second stage insulation is: heating to a second target temperature, and then performing a second stage insulation; the second target temperature is not lower than the first target temperature, and the second target temperature is 1250-1370°C; preferably, the second target temperature is 1270-1330°C; more preferably, the second target temperature is 1290-1310°C.

[0029] Optionally, the third stage heating-third stage insulation is: heating to a third target temperature, and then performing a third stage insulation; the third target temperature is not lower than the second target temperature, and the third target temperature is 1250-1370°C; preferably, the third target temperature is 1280-1350°C; more preferably, the third target temperature is 1300-1330°C.

[0030] Optionally, the Nth stage heating-Nth stage insulation is: heating to the Nth target temperature, and then performing the Nth stage insulation; the Nth target temperature is not lower than the (N-1)th target temperature, and the Nth target temperature is 1250-1370°C.

[0031] Optionally, the heating rates of the second stage, the third stage ... the Nth stage are 2-10°C / min; for example, 2°C / min, 5°C / min, 6°C / min, 8°C / min, 10°C / min.

[0032] Optionally, the insulation time of the second stage, the third stage ... the Nth stage is 1-20 hours, preferably 1-10 hours.

[0033] Furthermore, the inert atmosphere is argon or nitrogen.

[0034] Furthermore, the cooling is air-cooling quenching using an inert gas; the pressure of the air-cooling quenching is 1-4 bar; and the inert gas is argon or nitrogen.

[0035] The present invention realizes the stability of the oxide layer on the surface of the single crystal blade casting by using the activity of trace oxygen in the vacuum atmosphere based on the oxidation-reduction tendency of the single crystal high-temperature alloy under vacuum conditions, and avoids the oxide layer from being reduced and aggregated in vacuum to form surface defects through an inert protective atmosphere with a specific oxygen content concentration.

[0036] The formation of oxidation is a chemical reaction between gaseous oxygen and solid or liquid alloy to form solid oxide. This is a chemical reaction with reduced volume. According to the thermodynamics of chemical reactions, increasing the partial pressure of oxygen is conducive to the reaction. Since one of the reactants is oxygen, this is what we usually call an oxidation reaction. Reversibly, when the partial pressure of oxygen in the surrounding atmosphere is low to a certain extent, a reverse reaction can occur, that is, the solid oxide decomposes into solid or liquid alloy and gaseous oxygen. The lack of oxygen in the atmosphere of the furnace under vacuum can even be considered to provide the driving force for the decomposition reaction of the oxide. Since it is the decomposition of the oxide, this can be considered a reduction reaction under vacuum conditions.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] By adopting the present invention, on the one hand, it saves working steps and does not need to use alkali solution to treat the surface of the casting, but can directly carry out solid solution heat treatment. In the solid solution heat treatment process, the use of an inert atmosphere containing a trace amount of oxygen for heat preservation can avoid the decomposition of oxides on the surface of the blade casting and the formation of metal nodules; on the other hand, it can reduce the risk of recrystallization during the heat treatment process.

[0039] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the specific embodiments pointed out in the description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a photo of the blade structure with metal nodules on the surface of the blade casting after heat treatment in Comparative Example 1;

[0041] Figure 2 This is a photo of the blade structure after heat treatment of the single crystal blade in Example 2 of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present invention clearer, the implementation scheme of the present application will be described in detail below in conjunction with specific examples. The technical terms and scientific terms used in the present invention have the meanings generally understood by those of ordinary skill in the art to which the present invention belongs, without other definitions. Without departing from the concept of the present invention, those skilled in the art may make various improvements and changes to the specific implementation methods of the present invention specification, which all belong to the protection scope of the present invention. The raw materials used in the present invention are all commercially available unless otherwise specified.

[0043] A single crystal blade heat treatment method based on oxidation vacuum reduction control comprises: subjecting the single crystal blade to solid solution treatment;

[0044] The solution treatment includes a first stage of heating, a first stage of heat preservation, and cooling;

[0045] The first stage of heat preservation is carried out under an inert atmosphere containing a trace amount of oxygen.

[0046] Furthermore, the inert atmosphere containing trace amounts of oxygen satisfies one or more of the following conditions:

[0047] (1) The volume of trace oxygen in the inert atmosphere accounts for 0.05%-0.1%;

[0048] (2) The pressure of the inert atmosphere is 10-100 Pa; the oxygen partial pressure in the inert atmosphere is 0.005-0.1 Pa.

[0049] Furthermore, after the first stage of heat preservation, multiple stages of heating-heat preservation are also included;

[0050] Optionally, after the first stage of heat preservation, there is also a second stage of temperature rise-second stage of heat preservation, and a third stage of temperature rise-third stage of heat preservation.

[0051] Furthermore, the first stage of heating includes: placing the single crystal blade into a heat treatment furnace, evacuating the furnace, and controlling the heating rate to heat the temperature to a first target temperature.

[0052] Furthermore, the vacuum degree of the vacuum extraction is 0.1-0.01Pa.

[0053] Furthermore, the heating rate of the first stage of heating is 2-10°C / min.

[0054] Furthermore, the first target temperature is 1250-1370°C.

[0055] Furthermore, the first stage of heat preservation has a heat preservation temperature of 1250-1370°C;

[0056] Furthermore, the insulation temperature of the first stage insulation is equal to the first target temperature.

[0057] Furthermore, the insulation time of the first stage is 1-20 hours.

[0058] Optionally, the second stage heating-second stage heat preservation is: heating to a second target temperature, and then performing a second stage heat preservation; the second target temperature is not lower than the first target temperature. In a specific embodiment, the second target temperature is 1290-1310°C.

[0059] Optionally, the third stage heating-third stage heat preservation is: heating to a third target temperature, and then performing a third stage heat preservation; the third target temperature is not lower than the second target temperature. In a specific embodiment, the third target temperature is 1300-1330°C.

[0060] Optionally, the insulation time of the second stage and the third stage is 1-20 hours; in a specific embodiment, the insulation time of the second stage and the third stage is 1-6 hours.

[0061] Optionally, the heating rate of the second stage and the third stage is 2-10°C / min; in a specific embodiment, the heating rate of the second stage and the third stage is 5-10°C / min.

[0062] Furthermore, the inert atmosphere is argon.

[0063] Furthermore, the cooling is air-cooling quenching using an inert gas; the pressure of the air-cooling quenching is 1-4 bar; and the inert gas is argon.

[0064] The following is further described in conjunction with the embodiments:

[0065] Comparative Example 1

[0066] The DD6 single crystal blade was placed in a heat treatment furnace, the furnace door was closed, and the vacuum was evacuated to 0.01Pa. Then the temperature was raised to 1290℃ at a rate of 10℃ / min, and the temperature was kept at 1290℃ for 1h. In the second heating-keeping stage, the temperature was raised to 1300℃ at a rate of 5℃ / min and kept for 2h. In the third heating-keeping stage, the temperature was raised to 1310℃ at a rate of 5℃ / min and kept for 4h.

[0067] After the heat preservation is completed, argon gas is blown to cool to room temperature, and the pressure of the argon gas is 2 bar to obtain a single crystal blade; the general metallographic sample preparation method can be used here, and the sample organization is briefly described as follows: the single crystal blade is partially cut to obtain a sample, and then inlaid ( Figure 1 The black part on the left is the inlay material), ground, polished, and etched to show the tissue morphology, and the following is obtained: Figure 1 The blade structure photograph of the blade casting in Comparative Example 1 shown in the figure shows metal nodules appearing on the surface after heat treatment, wherein the nodules having flaky morphology are flaky metal nodules.

[0068] Example 1

[0069] A single crystal blade heat treatment method based on oxidation vacuum reduction control, comprising:

[0070] Place the DD6 single crystal blade into a heat treatment furnace, close the furnace door, evacuate to 0.01 Pa, and then heat up to 1290°C at a rate of 5°C / min in the first stage.

[0071] Subsequently, argon gas containing 0.1% oxygen was filled until the pressure in the furnace reached 100 Pa, and the first stage of heat preservation treatment was carried out at a temperature of 1290°C for 4 h;

[0072] After the heat preservation, argon gas is blown to cool to room temperature, and the pressure of the argon gas is 2 bar, and finally a single crystal blade with a smooth surface and no metal nodule defects is obtained.

[0073] Example 2

[0074] A single crystal blade heat treatment method based on oxidation vacuum reduction control, comprising:

[0075] Place the DD6 single crystal blade into a heat treatment furnace, close the furnace door, evacuate to 0.01 Pa, and then heat up to 1290°C at a rate of 10°C / min in the first stage.

[0076] Subsequently, argon gas containing 0.1% oxygen was filled in until the pressure in the furnace reached 100Pa, and the first stage of insulation treatment was carried out at 1290°C for 1h; the second stage of heating was carried out by raising the temperature to 1300°C at a rate of 5°C / min, and the second stage of insulation treatment was carried out for 2h; the third stage of heating was carried out by raising the temperature to 1310°C at a rate of 5°C / min, and the third stage of insulation treatment was carried out for 4h.

[0077] After the heat preservation is completed, argon gas is blown to cool to room temperature. The pressure of the argon gas is 2 bar, and finally a single crystal blade with a smooth surface and no metal nodule defects is obtained; the general metallographic sample preparation method can be used here. The sample organization is briefly described as follows: the single crystal blade is partially cut to obtain the sample, and then inlaid ( Figure 2 The black part on the upper left is the inlay material), ground, polished, and etched to show the tissue morphology, and the following is obtained: Figure 2 Shown is a photograph of the blade structure of the single crystal blade after heat treatment in Example 2 of the present invention.

[0078] By comparison, the single crystal blade of Example 1 obtained by conventional heat treatment has obvious sheet metal nodule defects, while the heat treatment method of the present invention as in Example 2 Figure 2 From the single crystal blade microstructure photograph shown, it can be found that metal nodule defects on the surface of the single crystal blade can be avoided.

[0079] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A single crystal blade heat treatment method based on oxidation vacuum reduction control, characterized in that: include: The single crystal blade is subjected to a solution treatment; The solution treatment includes a first stage of heating, a first stage of heat preservation, and cooling; The first stage of heat preservation is carried out under an inert atmosphere containing a trace amount of oxygen.

2. A single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 1, characterized in that: The inert atmosphere containing trace amounts of oxygen satisfies one or more of the following conditions: (1) The volume of trace oxygen in the inert atmosphere accounts for 0.05%-0.1%; (2) The pressure of the inert atmosphere is 10-100 Pa; the oxygen partial pressure in the inert atmosphere is 0.005-0.1 Pa.

3. The single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 1 is characterized in that: After the first stage of heat preservation, there are also multiple stages of heating-up and heat preservation.

4. The single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 1 is characterized in that: The first stage of heating includes: placing the single crystal blade into a heat treatment furnace, evacuating the furnace, and controlling the heating rate to raise the temperature to a first target temperature.

5. The single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 4 is characterized in that: The vacuum degree of the vacuum pumping is 0.01-0.1Pa.

6. The single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 4 is characterized in that: The heating rate of the first stage of heating is 2-10°C / min.

7. The single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 4 is characterized in that: The first target temperature is 1250-1370°C.

8. The single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 1 is characterized in that: The first stage of heat preservation has a heat preservation time of 4-20 hours.

9. The single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 1 is characterized in that: The inert atmosphere is argon or nitrogen.

10. The single crystal blade heat treatment method based on oxidation vacuum reduction control according to claim 1, characterized in that: The cooling is air-cooling quenching using an inert gas.

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