Preparation method of low-oxide-inclusion high-performance powder metallurgy nickel-based high-temperature alloy
Technical Field
The invention belongs to the field of metal materials, and relates to a preparation method of a low-oxide inclusion high-performance powder metallurgy nickel-based high-temperature alloy.
Background
The high-temperature alloy has good oxidation resistance, corrosion resistance, excellent tensile property, durability, fatigue property and long-term structure stability, is developed for meeting the requirements of modern aerospace technology under various high-temperature use conditions, and shows strong vitality in the field of advanced aerospace engines. The powder metallurgy high-temperature alloy is prepared by adopting a powder metallurgy method, has the advantages of uniform structure, no macrosegregation, high yield strength, good fatigue performance and the like compared with the traditional cast forging high-temperature alloy, overcomes the segregation (nonuniformity) generated by the conventional process, ensures that each particle of the used pre-alloying powder is a 'micro steel ingot', ensures that the alloy segregation can only occur in a tiny range of the powder particle, can improve the comprehensive performance of the alloy, can reduce the cutting processing amount and improve the utilization rate of the alloy. Particularly, as the components of the high-temperature alloy become more complex and the size of parts is increased, the powder metallurgy high-temperature alloy shows greater superiority.
The basic preparation process of the powder superalloy is that spherical powder is prepared by adopting an air atomization or plasma rotary atomization process, then hot pressing or hot isostatic pressing sintering densification treatment is carried out on the powder, and finally deformation and heat treatment are carried out on a dense sintering blank to obtain the required material or component. The performance of the powder superalloy is closely related to the components, the granularity and the oxygen content of raw material powder, generally, finer powder is helpful for sintering densification to obtain high performance, but when the powder is finer, the oxygen content adsorbed on the surface of the powder is higher, the high oxygen content is easy to form oxide inclusions or oxide films with strengthening elements such as Ti, Nb, Hf and the like in the alloy on the surface of the powder, and is very unfavorable for the low-cycle fatigue performance and the high-temperature endurance performance of the superalloy, so on the basis of optimizing the component design, how to reduce the oxygen content of the powder metallurgy superalloy to obtain high performance is a difficult point and a hot point in the current powder superalloy preparation.
Disclosure of Invention
The invention provides a method for preparing a powder metallurgy high-temperature alloy material with high endurance strength and low cycle fatigue strength by optimizing components and reducing oxygen content.
A preparation method of a low-oxide-inclusion high-performance powder metallurgy nickel-based high-temperature alloy is characterized in that nine elements of C, Cr, W, Mo, Al, B, Zr and Ni are prepared into spherical pre-alloy powder according to a certain mass ratio through a vacuum gas atomization powder preparation technology, then the pre-alloy powder with a certain particle size is selected to be mixed with elements of Ti, Ta and Hf, and the elements of Ti, Ta and Hf are respectively TiH2TaH and HfH2Adding the powder in a form, filling the uniformly mixed powder into a rubber sheath for cold isostatic pressing, removing the rubber sheath, placing a formed blank into a high vacuum hot pressing furnace for hot pressing sintering densification according to a certain sintering process, forging or rolling the densified sintered blank according to requirements to obtain a blank part, and finally performing aging treatment on the part to obtain the nickel-based alloy part with high endurance strength and high and low cycle fatigue strength.
Further, the preparation method comprises the following specific steps:
(1) firstly, preparing spherical pre-alloy powder by adopting a vacuum gas atomization powder preparation technology, wherein the mass ratio of the powder is as follows: c: 0.16-0.19%, Cr: 9.8-12%, Co: 16.5-17.5%, W: 7.7-8.8%, Mo: 0.65-0.88%, Al: 5.75-6.30%, B: 0.025-0.033%, Zr: 0.055-0.087 percent and the balance of Ni, wherein the atomization atmosphere adopts high-purity argon, and the atomization temperature is 1650-1700 ℃.
(2) Sieving the prealloying powder obtained by atomization, and taking the prealloying powder with the grain size range of 10-180 mu m and TiH2TaH and HfH2Mixing the three powders, wherein TiH2The granularity of the powder is 1-5 mu m, and the mass ratio of the powder after mixing is 4.1-4.6%; the particle size of the TaH powder is 1-3 μm, and the mass ratio of the TaH powder in the mixed powder is 2.6-2.85%; HfH2The granularity of the powder is 1-3 mu m, and the mass ratio of the powder after mixing is 1.6-1.85%; packaging the mixed powderPutting the mixture into a rubber sheath for cold isostatic pressing forming, wherein the forming pressure is 200 MPa; and then removing the sheath to obtain a pressed green body.
(3) And placing the green body in a vacuum hot-pressing sintering furnace for sintering and heat preservation, and then cooling to room temperature at a certain rate to obtain a compact sintered green body.
(4) Forging the sintered blank into a required shape by forging deformation, wherein free forging or die forging can be adopted for forging; if the forging does not meet the forming requirements, the rolling needs to be continued.
(5) And carrying out aging heat treatment on the formed part, cooling along with a furnace to obtain a high-temperature alloy material part blank with high endurance strength and fatigue strength, and then carrying out machining treatment according to the surface requirement to finally obtain a finished part.
Further, the sintering heat preservation parameters in the step (3) are as follows: firstly, heating the blank to 295-plus-305 ℃ at 15 ℃/min, preserving the heat for 19-21min, then heating to 690-plus-710 ℃ at 1 ℃/min, preserving the heat for 29-31min, heating to 1340-plus-710 ℃ at 10 ℃/min, preserving the heat for 85-95min, and applying axial pressure of 30-50MPa while preserving the heat. The cooling rate is 50-80 deg.C/min.
Further, the forging temperature in the step (4) is 1200-1250 ℃. The rolling temperature is 1150-1200 ℃.
Further, the aging temperature of the aging heat treatment in the step (5) is 750-800 ℃, and the temperature is kept for 4-6 hours.
By adopting the process, the oxygen content of the prepared high-temperature alloy material is lower than 50ppm, the endurance strength of the prepared high-temperature alloy material at 650 ℃ and 100 hours exceeds 1150MPa, the endurance strength of the prepared high-temperature alloy material at 750 ℃ and 100 hours exceeds 780MPa, and the low-cycle fatigue strength at 650 ℃ (frequency is 1Hz, and cycle number is 2 × 104) Over 1150MPa, the comprehensive performance is higher than that of the existing nickel-based high-temperature alloy material.
The high-temperature alloy material prepared by the process has the main advantages that: (1) the strengthening elements Ti, Ta and Hf are added in the form of hydride powder, hydrogen can be released to become Ti, Ta and Hf within the temperature range of 300-700 ℃, the released hydrogen has the reduction effect on the prealloying powder, and the oxygen content of the final alloy can be reduced to be below 50ppm, so that higher fatigue strength is obtained; (2) the hydrogen releasing process increases the sintering activity of the powder, is beneficial to the Ti, Ta and Hf to be completely dissolved in the nickel matrix, and simultaneously improves the density of the sintered body to more than 99.8 percent, which is close to the level of the hot isostatic pressing sintering process widely adopted at present, but the cost of the invention is far lower than the cost level of adopting the hot isostatic pressing sintering; (3) by adopting the alloy components and adding Ti, Ta and Hf in the form of powder, the size of a precipitated gamma ' phase in the alloy is reduced, the precipitation temperature of the gamma ' phase is improved, and the lattice mismatch degree between the gamma ' phase and a substrate is increased, so that the high-temperature performance of the alloy is better.
Detailed Description
Example 1
Preparation of high fatigue strength and durable strength nickel-based powder superalloy rod
Firstly, preparing prealloying powder by adopting a vacuum gas atomization powder preparation technology, wherein the mass ratio of the powder is as follows:
c: 0.19%, Cr: 12%, Co: 17.5%, W: 8.8%, Mo: 0.88%, Al: 6.30%, B: 0.033%, Zr: 0.087 percent and the balance of Ni, wherein the atomization atmosphere adopts high-purity argon, and the atomization temperature is 1700 ℃. Then sieving the prealloy powder obtained by atomization, and taking the alloy powder with the particle size range of 10-180 mu m and TiH2TaH and HfH2Mixing the three powders, wherein TiH2The granularity of the powder is 1-5 mu m, and the mass ratio of the powder after mixing is 4.6%; the particle size of the TaH powder is 1-3 μm, and the mass ratio of the TaH powder in the mixed powder is 2.85%; HfH2The granularity of the powder is 1-3 mu m, and the mass ratio of the powder after mixing is 1.85%; and filling the mixed powder into a rubber sheath for cold isostatic pressing at a forming pressure of 200MPa, and removing the sheath to obtain a pressed green body. And (2) placing the blank body in a vacuum hot-pressing sintering furnace for sintering, firstly heating the blank body to 300 ℃ at a speed of 15 ℃/min, preserving heat for 20min, then heating to 700 ℃ at a speed of 1 ℃/min, preserving heat for 30min, then heating to 1350 ℃ at a speed of 10 ℃/min, preserving heat for 90min, applying axial pressure of 50MPa while preserving heat, and then cooling to room temperature at a cooling rate of 80 ℃/min to obtain a compact sintered blank body. The sintered blank is forged and deformed,the forging temperature is 1250 ℃, the forged blank is rolled at 1200 ℃, the blank is rolled into a bar with required size, then aging heat treatment is carried out, the aging temperature is 800 ℃, heat preservation is carried out for 6 hours, furnace cooling is carried out, a high-temperature alloy material bar blank with high endurance strength and fatigue strength is obtained, machining treatment is carried out according to the surface requirement, and finally a bar finished product is obtained4) Reaching 1190MPa and the comprehensive performance higher than that of the prior nickel-based high-temperature alloy material.
Example 2
Preparation of high fatigue strength and durable strength nickel-base superalloy disk
Firstly, preparing prealloy powder by adopting a vacuum gas atomization powder preparation technology, wherein the mass ratio of the powder is as follows:
c: 0.17%, Cr: 10%, Co: 17%, W: 8%, Mo: 0.7%, Al: 6%, B: 0.03%, Zr: 0.06 percent and the balance of Ni, wherein the atomization atmosphere adopts high-purity argon, and the atomization temperature is 1650 ℃. Secondly, sieving the prealloy powder obtained by atomization, taking the alloy powder with the particle size range of 10-180 mu m, and then mixing with TiH2TaH and HfH2Mixing the three powders, wherein TiH2The granularity of the powder is 1-5 mu m, and the mass ratio of the powder after mixing is 4.1%; the particle size of the TaH powder is 1-3 μm, and the mass ratio of the TaH powder in the mixed powder is 2.6%; HfH2The granularity of the powder is 1-3 mu m, and the mass ratio of the powder after mixing is 1.6%; the mixed powder is filled into a rubber sheath for cold isostatic pressing forming, and the forming pressure is 200 MPa; and then removing the sheath to obtain a pressed green body. Thirdly, placing the blank body in a vacuum hot-pressing sintering furnace for sintering, firstly heating the blank body to 300 ℃ at a speed of 15 ℃/min, preserving heat for 20min, then heating to 700 ℃ at a speed of 1 ℃/min, preserving heat for 30min, heating to 1350 ℃ at a speed of 10 ℃/min, preserving heat for 90min, applying axial pressure to 30MPa while preserving heat, and then cooling at a speed of 50 ℃/minReducing the speed to room temperature to obtain a compact sintered blank, carrying out free forging deformation on the sintered blank at the forging temperature of 1200 ℃ to forge the sintered blank into a disc-shaped blank with the required size, carrying out aging heat treatment on the formed blank at the aging temperature of 750 ℃, keeping the temperature for 4 hours, cooling the blank along with a furnace, and carrying out machining treatment according to the surface requirement to finally obtain a disc-shaped finished part, wherein the prepared high-temperature alloy disc part has the oxygen content of 43ppm, the endurance strength of 650 ℃, 100 hours reaches 1170MPa, 750 ℃, the endurance strength of 100 hours reaches 788MPa, and the low-cycle fatigue strength of 650 ℃ (frequency 1Hz and cycle number 2 × 104) Up to 1160MPa, and the comprehensive performance is higher than that of the prior nickel-based high-temperature alloy material.