CN112410616B - Low-cost and low-macrosegregation-tendency high-temperature alloy for large isothermal forging die - Google Patents
Low-cost and low-macrosegregation-tendency high-temperature alloy for large isothermal forging die Download PDFInfo
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- CN112410616B CN112410616B CN202011213699.1A CN202011213699A CN112410616B CN 112410616 B CN112410616 B CN 112410616B CN 202011213699 A CN202011213699 A CN 202011213699A CN 112410616 B CN112410616 B CN 112410616B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
- C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
- C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
- C22C19/057—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being less 10%
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J13/00—Details of machines for forging, pressing, or hammering
- B21J13/02—Dies or mountings therefor
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T50/00—Aeronautics or air transport
- Y02T50/60—Efficient propulsion technologies, e.g. for aircraft
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Abstract
The invention relates to a high-temperature alloy for a large isothermal forging die with low cost and low macrosegregation tendency, which comprises the following components in percentage by mass: 0.5-1.8% of Cr, 7-12% of Co, 14-18% of W, 1.5-3% of Mo, 0.5-2% of Nb, 5.5-6.5% of Al, 1-1.5% of Ti, 0.001-0.048% of C, 0.01-0.03% of B, 0.05-0.15% of Zr, and the balance of Ni; the high-temperature alloy for the isothermal forging die has good processing performance, low cost without containing precious metal elements, low macrosegregation tendency of thick and large sections, very high mechanical property and excellent local oxidation resistance, and is a high-performance isothermal forging die material for large-size turbine discs with low cost and low macrosegregation tendency.
Description
Technical Field
The invention relates to a high-temperature alloy for a large isothermal forging die with low cost and low macrosegregation tendency, belonging to the technical field of high-temperature structural materials.
Background
The nickel-based high-temperature alloy is mainly used for aviation and industrial gas turbines, and is also used for key materials such as isothermal forging dies for turbine disks of aircraft engines. At present, most advanced gas turbines adopt powder metallurgy high-temperature alloy with higher performance level to prepare turbine disc parts, isothermal forging is not required to be carried out on the turbine disc, and the performance and the service life of isothermal forging die materials become key factors for preparing the turbine disc. The isothermal forging die material for the turbine disc generally contains main elements such as Ni, Co, Cr, W, Mo, Nb, Ta, Hf, Al, Ti and the like, meanwhile, C is generally considered as an indispensable trace alloying element for polycrystalline casting high-temperature alloy, and the alloy composition generally needs to be precisely designed due to the high degree of compound alloying and the interaction of multiple elements. However, when the alloy is used for preparing a large isothermal forging die with the weight per ton, the cost factor is the first factor, and the alloy cost is greatly increased by noble elements such as Ta and Hf in the alloy. In addition, the mechanical properties of the tonnage large isothermal forging die are often far lower than the test bar properties due to the large size and the slow solidification cooling speed. Further analysis shows that the performance degradation is related to the occurrence of macro segregation of refractory elements such as tungsten and the like in the forging die preparation process, the tungsten content of the high-tungsten area and the low-tungsten area is 50 percent higher and 30 percent lower than the average composition of the alloy, the design composition is greatly deviated, and the macro segregation causes the large isothermal forging die to have a low performance area. Besides the reduction of mechanical properties, the oxidation resistance of a macrosegregation area is obviously reduced, and the service life of a forging die is influenced by the massive peeling of oxide skin in the area at the high temperature of 1100 ℃. In the past, the theory is that the macrosegregation caused by the density difference is caused by the uneven distribution of heavy elements in the melt, which may occur in the master alloy ingot, but the macrosegregation of the elements of the detected master alloy ingot is uniform. Therefore, macrosegregation should be generated during the preparation of large isothermal forging dies. One possibility is that the solidification speed of a large-size forging die is too slow, which leads to too long solidification time and causes segregation of melt elements, but generally, such segregation is only a microsegregation scale and is not a direct cause of macrosegregation. Therefore, it is difficult to eliminate such macro-segregation by adjusting the solidification cooling rate through the casting process in the isothermal forging die manufacturing process. In order to solve the problems, firstly, the real reason of macrosegregation is found, measures are taken to reduce the macrosegregation tendency of the alloy so as to improve the performance and the service life of the alloy and simultaneously reduce the alloy cost, and the high-temperature alloy for the large isothermal forging die with low cost and low macrosegregation tendency is formed.
Disclosure of Invention
The invention aims to design and provide a large isothermal forging die high-temperature alloy with low cost and low macrosegregation tendency, aiming at reducing the content of trace additive element carbon to reduce the macrosegregation tendency of refractory elements in thick large-section high-temperature alloy, simultaneously adjusting the content of noble metal elements to reduce cost and improve the performance and service life of the alloy and excellent uniform oxidation resistance of the forging die on the basis of determining the macrosegregation of tungsten caused by carbon segregation as a main cause of macrosegregation, and meeting the requirement of isothermal forging forming of large-size powder metallurgy high-temperature alloy turbine discs in China.
The purpose of the invention is realized by the following technical scheme:
the high-temperature alloy for the large isothermal forging die with low cost and low macrosegregation tendency is characterized in that: the high-temperature alloy comprises the following chemical components in percentage by weight: 0.5-1.8% of Cr, 7-12% of Co, 14-18% of W, 1.5-3% of Mo, 0.5-2% of Nb, 5.5-6.5% of Al, 1-1.5% of Ti, 0.001-0.048% of C, 0.01-0.03% of B, 0.05-0.15% of Zr and the balance of Ni.
In one implementation, the weight percentages of the C elements in the superalloy are: 0.001 to 0.02%.
The technical scheme of the invention is based on finding the reason of the macrosegregation of the nickel-based superalloy. For this reason, a great deal of research and experimentation was conducted prior to the determination of the technical solution of the present invention, and the specific process thereof is illustrated by the following steps:
(1) performing metallographic polishing on the cut isothermal forging die high-temperature alloy sample;
(2) putting the polished sample into a heating furnace, heating to 1100 ℃, preserving heat for 5-10min, and then discharging and cooling, wherein in the step, a macrosegregation area rich in harmful phases is displayed through high-temperature short-time oxidation;
(3) the normal matrix area is flat when observed under a microscope at the magnification of 100-times and 200-times, and the macrosegregation area is locally bulged and raised on the surface due to poor oxidation resistance and is cracked with the matrix boundary, so that the macrosegregation area can be conveniently and quickly determined by utilizing the characteristic;
(4) the components of a macrosegregation region are analyzed by adopting an electronic probe, the high-temperature alloy for the large isothermal forging die is a nickel-based high-temperature alloy, and for the alloy material, the macrosegregation region mainly contains refractory tungsten elements and trace carbon elements which are far higher than the average components of the elements in the alloy, so that the component characteristics in the macrosegregation region are determined;
(5) in order to further verify the cause of macro segregation, in addition, a cut isothermal forging die high-temperature alloy sample is heated to 1385 ℃ and then is quenched into water, and the main refractory element tungsten and the trace element carbon in the alloy are uniformly distributed without macro segregation; the alloy is heated to 1370 ℃ and then is quenched into water, the refractory element tungsten is inverse segregation, the content of the refractory element tungsten in interdendritic and postsolidification regions is lower than the average content of the alloy, the trace element carbon is positive segregation, the concentration of interdendritic and postsolidification liquid phases is increased, tungsten-rich carbide is easily formed by the interdendritic and postsolidification liquid phases, the density of the tungsten-rich carbide is 35% higher than that of an alloy matrix, the tungsten-rich carbide is settled in a melt to form macro segregation, the macro segregation is different from the macro segregation of heavy elements such as tungsten in the melt by the aid of the fact that the heavy elements such as tungsten are subjected to the macro segregation in the melt according to the traditional theory, and finally the macro segregation caused by the formation of compounds with tungsten after the macro segregation of carbon is proved.
(6) In order to overcome and improve the macrosegregation, the technical scheme of the invention provides a new alloy component, and the design idea is to reduce the content of trace element carbon until the state of ultralow carbon so as to reduce the macrosegregation tendency of refractory elements in a large-size isothermal forging die high-temperature alloy with a large thickness and a large cross section, and simultaneously remove precious metal elements such as Ta and Hf so as to reduce the cost.
The characteristics and beneficial technical effects of the technical scheme of the invention are specifically analyzed as follows:
the major amount of strengthening element macrosegregation is controlled by reducing trace element carbon, when the alloy composition enters the preferable range of 0.001-0.02% of ultralow carbon, the carbon concentration factor in the forming condition of tungsten-rich carbide causing macrosegregation is deprived, the precipitation and macrosegregation of the harmful carbide phase are effectively inhibited, and the casting process performance of the alloy is improved;
secondly, the cost is low, and the alloy composition of the invention does not contain noble metals Ta and Hf contained in the existing isothermal forging die material. One of the main functions of the elements Ta and Hf is to form an MC type carbide strengthened alloy. Once harmful-phase tungsten-rich carbide in the isothermal forging die material is formed in a high-temperature region in the solidification process, Ta and Hf-rich MC type carbide formed at a lower temperature cannot be formed due to the reduction of carbon concentration, and the strengthening effect cannot be achieved actually. In order to eliminate macro segregation, the alloy adopts an ultra-low carbon scheme, and Ta and Hf-rich MC type carbide strengthening phases are not formed or are rarely formed, so Ta and Hf do not need to be added. After the ultra-low carbon, because a harmful carbide phase rich in tungsten is not formed, more metal matrixes can be used for strengthening the alloy by the tungsten, so that the performance is improved;
thirdly, because harmful phase generation is eliminated, the alloy saturation tolerance is improved, the Co content can be further reduced, and the cost is further reduced;
fourthly, eliminating macro segregation, thereby eliminating severe local oxidation peeling of the area;
fifthly, breaking through the concept that the traditional high-temperature alloy can not lack carbon, and improving the performance through careful balance of an ultra-low carbon scheme and other major elements;
sixth, the structure stability is good, secondary harmful phases cannot be formed when the alloy is used at high temperature for a long time, and the secondary harmful phases can be separated out and distributed in a chain shape after the existing alloy is used at the temperature of 1000-1100 ℃ for a long time, so that the existing alloy often becomes a crack expansion channel;
seventh, an alternative material is provided for large isothermal forging dies that are suitable for thick large cross-sectional sizes.
Detailed Description
The technical solution of the present invention will be further described with reference to the following examples:
example 1
The steps for preparing the high-temperature alloy for the large isothermal forging die with low cost and low macrosegregation tendency are as follows:
(1) melting raw materials such as Ni, Co, Cr, W, Mo, Nb, Al, Ti, C, B, Zr and the like by vacuum induction melting according to the proportion of 0.5-1.8% of Cr, 7-12% of Co, 14-18% of W, 1.5-3% of Mo, 0.5-2% of Nb, 5.5-6.5% of Al, 1-1.5% of Ti, 0.001-0.048% of C, 0.01-0.03% of B, 0.05-0.15% of Zr and the balance of Ni to prepare the high-temperature alloy master alloy;
(2) remelting a master alloy ingot in vacuum induction melting equipment, pouring the master alloy ingot into a shell mold, and solidifying and forming, wherein the alloy comprises the following analysis components:
1.34Cr-9.71Co-16.02W-2.07Mo-0.86Nb-6.04Al-1.13Ti-0.045C-0.029B-0.05 Zr-residual Ni (mass percent);
(3) the endurance life of the test alloy is 40.5h under the conditions of 1100 ℃ and 118MPa stress;
(4) because of the low carbon content, no macrosegregation, harmful phase precipitation and local severe oxidation zone are found in the alloy. And because the alloy does not contain noble metal elements such as Ta, Hf and the like, the alloy cost is obviously reduced.
Example 2
The steps for preparing the high-temperature alloy for the large isothermal forging die with low cost and low macrosegregation tendency are as follows:
(1) melting raw materials such as Ni, Co, Cr, W, Mo, Nb, Al, Ti, C, B, Zr and the like by vacuum induction melting according to the proportion of 0.5-1.8% of Cr, 7-12% of Co, 14-18% of W, 1.5-3% of Mo, 0.5-2% of Nb, 5.5-6.5% of Al, 1-1.5% of Ti, 0.001-0.048% of C, 0.01-0.03% of B, 0.05-0.15% of Zr and the balance of Ni to prepare the high-temperature alloy master alloy;
(2) remelting a master alloy ingot in vacuum induction melting equipment, pouring the master alloy ingot into a shell mold, and solidifying and forming, wherein the alloy comprises the following analysis components:
1.45Cr-9.00Co-15.2W-1.92Mo-1.69Nb-5.42Al-1.18Ti-0.018C-0.019B-0.09 Zr-residual Ni (mass percent);
(3) the endurance life of the test alloy is 30.2h under the conditions of 1100 ℃ and 118MPa stress;
(4) because of the adoption of the ultra-low carbon content, macrosegregation, precipitation of harmful phases and local severe oxidation zones are not found in the alloy. And because the alloy does not contain noble metal elements such as Ta, Hf and the like, the alloy cost is obviously reduced.
Example 3
The steps for preparing the high-temperature alloy for the large isothermal forging die with low cost and low macrosegregation tendency are as follows:
(1) melting raw materials such as Ni, Co, Cr, W, Mo, Nb, Al, Ti, C, B, Zr and the like by vacuum induction melting according to the proportion of 0.5-1.8% of Cr, 7-12% of Co, 14-18% of W, 1.5-3% of Mo, 0.5-2% of Nb, 5.5-6.5% of Al, 1-1.5% of Ti, 0.001-0.048% of C, 0.01-0.03% of B, 0.05-0.15% of Zr and the balance of Ni to prepare the high-temperature alloy master alloy;
(2) remelting a master alloy ingot in vacuum induction melting equipment, pouring the master alloy ingot into a shell mold, and solidifying and forming, wherein the alloy comprises the following analysis components:
1.47Cr-9.16Co-15.16W-1.93Mo-1.70Nb-5.52Al-1.21Ti-0.008C-0.019B-0.091Z r-residual Ni (mass percent);
(3) the endurance life of the test alloy under the conditions of 1100 ℃ and 118MPa stress is 35.0 h;
(4) because of the low carbon content, no macrosegregation, harmful phase precipitation and local severe oxidation zone are found in the alloy. And because the alloy does not contain noble metal elements such as Ta, Hf and the like, the alloy cost is obviously reduced.
Claims (1)
1. A method for testing the macrosegregation tendency of high-temperature alloy for a large isothermal forging die is characterized by comprising the following steps: the method comprises the following steps:
step one, performing metallographic polishing on a cut large isothermal forging die by using a nickel-based high-temperature alloy sample;
step two, placing the polished sample into a heating furnace, heating to 1100 ℃, preserving heat for 5-10min, and then discharging and cooling, wherein in the step, a macrosegregation area rich in harmful phases is displayed through high-temperature short-time oxidation;
thirdly, observing under a microscope at the magnification of 100-200 times, wherein the normal matrix region is flat, the surface of the macrosegregation region locally bulges and protrudes due to the oxidation resistance difference, and the macrosegregation region and the matrix boundary can crack, and the macrosegregation region can be conveniently and quickly determined by utilizing the characteristic;
analyzing the components of a macrosegregation area by adopting an electronic probe, wherein the macrosegregation area mainly contains refractory tungsten elements and carbon elements, and the contents of the elements are far higher than the average components of the elements in the alloy, and the component characteristics in the macrosegregation area are determined in the step;
fifthly, in order to further confirm the cause of the macrosegregation, the cut sample is heated to 1385 ℃ and then is quenched into water, and the main refractory elements tungsten and the element carbon in the alloy are distributed uniformly without macrosegregation;
and heating the sample to 1370 ℃, then quenching the sample into water, wherein the refractory element tungsten is inverse segregation, the content of the refractory element tungsten in interdendritic and postsolidification regions is lower than the average content of the refractory element tungsten in the alloy, the element carbon is positive segregation, the concentration of interdendritic and postsolidification liquid phases is increased, the interdendritic and postsolidification liquid phases are easy to form tungsten-rich carbide, the density of the tungsten-rich carbide phase is 35% higher than that of an alloy matrix, the tungsten-rich carbide phase is precipitated in the melt to form macro-segregation in a phase form, and finally the macro-segregation caused by the compound formed by the tungsten after the carbon segregation is proved to be the cause of the macro-segregation.
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