阅读说明：本技术 一种优异高温拉伸性能的γ′相强化钴基高温合金 (Gamma' phase reinforced cobalt-based high-temperature alloy with excellent high-temperature tensile property ) 是由 王磊 刘杨 王宏伟 宋秀 于 2021-07-21 设计创作，主要内容包括：本发明公开了一种优异高温拉伸性能的γ’相强化钴基高温合金,所属钴基高温合金领域。其成分质量百分含量为：C 0.02-0.1,Cr 5-9,Ni 24-28,Mo 2-6,Ti 1-3,Al 2.5-5,B 0.005-0.01,Ta 4-8,W 2-6,Zr 0.05-0.2,Co为余量。本发明的一种优异高温拉伸性能的γ’相强化钴基高温合金的密度在传统Co-Al-W三元体系合金中有着明显的优势。本发明合金在800℃-900℃温度区间内有着高于先进多晶镍基高温合金Mar-M247的高温强度及一定的高温塑性,且在室温至800℃温度区间内本发明合金无明显屈服异常及中温脆性,保证了合金在使用过程中的安全性及稳定性。此外,本发明的合金在900℃以下200小时以内的抗高温氧化能力属于完全抗氧化级。最后,本发明的合金适用于航空发动机和工业燃气轮机燃气轮机涡轮叶片合金材料。(The invention discloses a gamma' phase reinforced cobalt-based high-temperature alloy with excellent high-temperature tensile property, belonging to the field of cobalt-based high-temperature alloys. The weight percentage of the components is as follows: 0.02-0.1 part of C, 5-9 parts of Cr, 24-28 parts of Ni, 2-6 parts of Mo, 1-3 parts of Ti, 2.5-5 parts of Al, 0.005-0.01 part of B, 4-8 parts of Ta, 2-6 parts of W, 0.05-0.2 part of Zr and the balance of Co. The density of the gamma' phase strengthened cobalt-based high-temperature alloy with excellent high-temperature tensile property has obvious advantages in the traditional Co-Al-W ternary system alloy. The alloy has high-temperature strength and certain high-temperature plasticity higher than that of the advanced polycrystalline nickel-based high-temperature alloy Mar-M247 at the temperature of 800-900 ℃, has no obvious yield abnormality and medium-temperature brittleness at the temperature of room temperature-800 ℃, and ensures the safety and stability of the alloy in the using process. In addition, the high-temperature oxidation resistance of the alloy of the invention within 200 hours at the temperature of 900 ℃ is of a complete oxidation resistance level. Finally, the alloy of the invention is suitable for turbine blade alloy materials of aeroengines and industrial gas turbines.)

1. The gamma' phase reinforced cobalt-based high-temperature alloy with excellent high-temperature tensile property is characterized by comprising the following chemical components in percentage by mass: 0.02-0.1 part of C, 5-9 parts of Cr, 24-28 parts of Ni, 2-6 parts of Mo, 1-3 parts of Ti, 2.5-5 parts of Al, 0.005-0.01 part of B, 4-8 parts of Ta, 2-6 parts of W, 0.05-0.2 part of Zr and the balance of Co.

2. The gamma prime phase strengthened cobalt-based high-temperature alloy with excellent high-temperature tensile property as claimed in claim 1, wherein the alloy can be directly used in a cast state, and the heat treatment schedule is 1200-1280 ℃ solid solution for 4-12h +900-950 ℃ aging for 16-100h +750 ℃ aging for 16-50 h.

3. The gamma prime strengthened cobalt-based superalloy with excellent high temperature tensile properties as claimed in claim 1, wherein the heat treatment schedule is 1200 ℃ solutionized for 12h +900 ℃ aging for 72h +750 ℃ aging for 24 h.

4. The gamma prime phase strengthened cobalt-based superalloy with excellent high temperature tensile properties as claimed in claim 1, wherein the alloy is a cast polycrystalline alloy with a dendritic microstructure and phase composition of gamma-Co matrix and gamma' -Co₃(Al, Me), MC type carbide, eutectic (gamma + gamma'), wherein Me is W, Ta, Ti, Mo, and has no other harmful phase.

5. The gamma prime strengthened cobalt-based superalloy with excellent high temperature tensile properties of claim 1, wherein the density of the alloy is 8.58g/cm³。

6. The gamma prime strengthened cobalt-based superalloy with excellent high temperature tensile properties of claim 1, wherein the gamma prime temperature of the alloy is 1030 ℃.

7. The gamma prime phase strengthened cobalt-based superalloy with excellent high temperature tensile property as claimed in claim 1, wherein the alloy has an elongation of 7-12% after tensile failure at 800-1000 ℃ and an elongation of 15.6% after tensile failure at room temperature.

8. The gamma prime phase strengthened cobalt-based superalloy with excellent high temperature tensile properties according to claim 1, wherein the alloy is applied to high temperature components of aircraft engines and gas turbines.

Technical Field

The invention belongs to the field of cobalt-based high-temperature alloys, and particularly relates to a gamma' phase reinforced cobalt-based high-temperature alloy with excellent high-temperature tensile property.

Background

Cobalt-based superalloys are of great interest for their excellent thermal fatigue resistance, thermal corrosion resistance, oxidation resistance and high structural stability. However, the conventional cobalt-based superalloy relies on carbide strengthening, and lacks an effective strengthening phase to cause low high-temperature strength, and is often used as an alloy material for guide vanes of turbine engines and gas turbines.

γ′-Co₃The discovery of the (Al, W) phase compensates for the deficiency, and the phase has long-term structure stability at 900 ℃, so that the high-temperature performance of the cobalt-based high-temperature alloy is remarkably improved. This means that cobalt-based superalloys can replace nickel-based superalloys as alloying materials for turbine blades of turbine engines and gas turbines.

Over a decade of research by researchers, gamma prime strengthened cobalt-based superalloys have evolved from the original ternary Co-Al-W alloys to multi-element alloys by the addition of alloying elements to achieve superior alloy properties, such as Ti, Ta, Nb, V, Fe, B, Si, Ni, Cr, Mo, etc. As more and more alloying elements are added into the alloy, the melting point and the gamma' phase re-dissolving temperature of the alloy are influenced to a certain degree. Different combinations of alloying elements have different effects on the high temperature properties of the alloy. At present, the main problem of the gamma' -phase strengthened cobalt-based high-temperature alloy is insufficient high-temperature strength and high-temperature plasticity.

Disclosure of Invention

The invention aims to obtain the cobalt-based high-temperature alloy which integrates excellent high-temperature strength, oxidation resistance and certain high-temperature plasticity in a temperature range of 800-900 ℃. The alloy utilizes submicron gamma' -Co₃The (Al, W) phase is the main strengthening phase, the carbide strengthening and the solid solution strengthening are carried out to obtain good high-temperature strength, and the Cr element is added to obtain excellent oxidation resistance so as to meet the severe service conditions of turbine blades of turbine engines and gas turbines. The alloy not only has high-temperature strength superior to that of the traditional cobalt-based high-temperature alloy, but also has high-temperature yield with the advanced nickel-based high-temperature alloy within the temperature range of 800-1000 DEG CThe strength ratio also has obvious advantages. In addition, the density of the alloy of the invention has obvious advantages in the traditional Co-Al-W ternary system alloy, and the alloy has excellent structure stability at 900 ℃.

The gamma' phase strengthened cobalt-based high-temperature alloy with excellent high-temperature tensile property comprises the following chemical components in percentage by weight: 0.02-0.1 part of C, 5-9 parts of Cr, 24-28 parts of Ni, 2-6 parts of Mo, 1-3 parts of Ti, 2.5-5 parts of Al, 0.005-0.01 part of B, 4-8 parts of Ta, 2-6 parts of W, 0.05-0.2 part of Zr and the balance of Co.

The alloy can be directly used in a cast state, and the heat treatment system is solid solution at 1280 ℃ for 4-12h +900 + 950 ℃ for 16-100h +750 ℃ for 16-50 h.

The density of the alloy is 8.58g/cm³。

The gamma prime temperature of the alloy was 1030 ℃.

The elongation of the alloy after tensile fracture at 800-1000 ℃ is 9-12 percent, and the elongation after tensile fracture at room temperature is 15.6 percent

The alloy elements selected by the gamma' phase strengthened cobalt-based high-temperature alloy with excellent high-temperature tensile property have different purposes:

nickel: the Ni element is added to promote the stability of the gamma/gamma ' phase, improve the redissolution temperature of the gamma ' phase and reduce the lattice mismatching degree of the gamma/gamma ' two phases.

Tungsten: the stability of the gamma 'phase is improved by adding the W element, the re-dissolving temperature of the gamma' phase is improved, and the solid solution strength of the gamma-Co is increased.

Aluminum: by adding Al element as the constituent element of gamma' phase, the oxidation resistance of the alloy is improved, and the continuous diffusion of O element into the alloy is hindered.

Titanium: the volume fraction of the gamma ' phase and the stability of the gamma ' phase are improved by adding Ti element, and the precipitation of the gamma ' phase is promoted.

Molybdenum: by adding Mo element to replace W element, the solid solution strength of gamma-Co is increased, the content of rare earth elements in gamma-Co is improved, and the coarsening of gamma' phase is delayed.

Chromium: the high-temperature oxidation resistance of the alloy is improved by adding the Cr element, and the cracking sensitivity of the alloy during solidification is reduced.

Tantalum: the Ta element is added to improve the stability of the gamma 'phase and the volume fraction of the gamma' phase, and the stacking fault energy is increased.

Zirconium: by adding Zr element, the crystal boundary defect is reduced, the vacancy on the crystal boundary is filled, the crystal boundary binding force is improved, and the crystal boundary is strengthened.

Carbon: by adding C element to form carbide, dislocation movement is hindered, and tensile, fatigue and creep properties are improved.

Boron: the B element is added to improve the bonding force of the grain boundary, improve the plasticity of the alloy and strengthen the grain boundary.

The gamma' phase reinforced cobalt-based high-temperature alloy with excellent high-temperature tensile property mainly comprises dendritic crystals in microstructure and comprises the following phase components: gamma-Co, gamma' -Co₃(Al, Me), MC, and eutectic crystal (gamma + gamma'), wherein Me is W, Ta, Ti or Mo.

The invention takes the submicron gamma' phase as the main strengthening phase, and the excellent high-temperature performance is obtained by the combined action of carbide strengthening and solid solution strengthening; cr is added to enhance the oxidation resistance of the alloy; b, Zr is added to force the bonding force of grain boundary, so that the alloy integrates excellent high-temperature strength and certain high-temperature plasticity.

Drawings

FIG. 1 is an as-cast dendrite structure of alloy 3 in an example of the present invention.

FIG. 2 is a graph comparing the densities of alloy 3 in the examples of the present invention.

FIG. 3 is an XRD phase analysis of alloy 3 in an example of the invention.

FIG. 4 shows the grain boundary morphology of alloy 3 in the example of the present invention.

FIG. 5 shows the eutectic morphology of alloy 3 in the example of the present invention.

FIG. 6 is the carbide morphology of alloy 3 in the examples of the invention.

FIG. 7 shows the γ' phase morphology of alloy 3 in the example of the present invention.

FIG. 8 is a graph of the 1200 deg.C/12 h solution +900 deg.C aging for alloy 3 of the examples of the present invention.

FIG. 9 is a graph of stress-strain curves for alloy 3 at various temperatures in an example of the present invention.

FIG. 10 is a graph comparing the high temperature tensile yield strength of alloy 3 in examples of the invention.

FIG. 11 is the post fracture elongation for alloy 3 at different temperatures in the example of the present invention.

FIG. 12 shows high-temperature tensile fracture of alloy 3 in example of the present invention.

FIG. 13 is a graph of the oxidation kinetics of alloy 3 at 900 deg.C and 1000 deg.C for 200 hours in an example of the present invention.

FIG. 14 shows the cross-sectional profile of the oxide layer of alloy 3 in an embodiment of the present invention.

Detailed description of the preferred embodiments

The present invention will be further described with reference to the following specific embodiments, but the present invention is not limited to the following three embodiments, and the scope of the present invention is not limited thereto.

Compared with the traditional cobalt-based high-temperature alloy and the advanced polycrystalline nickel-based high-temperature alloy, the high-temperature strength, the perfect oxidation resistance and certain high-temperature plasticity of the high-temperature alloy in the temperature range of 800-900 ℃ are highlighted.

The heat treatment system of the embodiment is solid solution at 1200 ℃ for 12h +900 ℃ aging for 72h +750 ℃ aging for 24 h. Three gamma' -phase strengthened cobalt-based superalloy ingots were prepared, the chemical compositions of which are shown in table 1.

Table 1 shows the chemical compositions (in weight percent) of examples and comparative examples

Alloy 1, alloy 2 and alloy 3 of the present example all contain 0.012% Y and 0.004% Mg; DZ40M contains 0.95 Fe%, 0.6% Si and 0.44% Mn; Mar-M247 contains 1.50% Hf.

In the embodiment, three kinds of gamma' -phase strengthened cobalt-based high-temperature alloy master alloys are prepared by a vacuum induction smelting furnace, and are secondarily smelted and cast into alloy test bars. In this embodiment, alloy 3 is taken as an example, and the microstructure, alloy density, XRD phase analysis, and γ' phase after solution aging treatment are shown in the drawings, and the experimental process is not described in detail.

In this example, the comparative analysis of the high temperature tensile property and the high temperature oxidation resistance of alloy 3 and the comparative example includes the following steps:

(1) high temperature tensile test

High temperature tensile properties test according to national standard GB/T228.2-2015 part 2 of tensile test for metallic materials: high temperature test methods. The detection apparatus was an electronic universal tester model AG-Xplus100KN, manufactured by Shimadzu corporation, Japan, and the tensile strain rate was 0.001/s.

The detailed size of the tensile sample is shown in figure 3, the sample is heated by an accessory heating system of an electronic universal testing machine in high-temperature tensile of 800-1000 ℃, and the temperature control precision is +/-2 ℃. In the experimental process, the sample is heated along with the furnace, the heating rate is 20 ℃/min, and the temperature is preserved for 15 minutes after the sample is heated to the target temperature, so as to ensure that the interior of the sample also reaches the target temperature. In the heating process, the thermocouple is tightly attached to the sample so as to ensure that the temperature shown by the thermocouple is the surface temperature of the sample. And selecting three parallel samples under each temperature deformation condition, and calculating the average value as a final result to ensure the accuracy of experimental data.

(2) High temperature cyclic oxidation experiment

The high-temperature cyclic oxidation experiment is carried out according to the national standard GB/T38231-2019 thermal cycle exposure oxidation test method of corrosive metal materials of metals and alloys under the high-temperature corrosion condition. The heating equipment is a Shenyang Kejing 1400K heat treatment furnace, which is used for the cyclic oxidation heating experiment of alloy at 800-900 ℃, and the furnace takes a silicon carbide rod as a heating body.

High temperature cycle oxidized samples were prepared by wire electrical discharge machining with sample sizes of 10 x 3 mm. And sequentially polishing and flattening by SiC sand paper 240#, 800# and 1500 #. The length, width and height of the sample are accurately measured by using a micrometer screw with the precision of 0.01 mm. The sample surface was cleaned in a JP-040ST type ultrasonic cleaner using analytically pure absolute ethanol. Five parallel samples are selected under each temperature condition, and the average value is calculated as a final result so as to ensure the accuracy of experimental data.

The results of the above tests lead to the following conclusions:

(1) the alloy is a polycrystalline casting alloy, and has the advantages of simple production process, few preparation procedures and low production cost;

(2) the strengthening phase of the alloy mainly comprises gamma ' phase and MC type carbide, and the microstructure of the as-cast alloy consists of gamma-Co (matrix), gamma ' -Co3(Al, Me), MC and eutectic (gamma + gamma ') (the eutectic can be completely dissolved in a solid solution treatment). No other harmful precipitated phases.

(3) The alloy of the invention has excellent structure stability within 200 hours at the temperature of 900 ℃ or below.

(4) The alloy of the present invention has high initial melting temperature and precipitation temperature of gamma' phase and low density.

(5) The alloy of the invention has excellent high-temperature strength within the temperature range of 800-900 ℃.

(6) The alloy of the invention has no obvious yield abnormality and plasticity abnormality in the temperature range of 800-900 ℃.

(7) The alloy of the invention has excellent high-temperature oxidation resistance below 900 ℃.

By combining the characteristics, the alloy has excellent high-temperature strength and oxidation resistance within the temperature range of 800-900 ℃. The alloy has a good future application prospect, realizes the autonomous localization of the alloy and breaks the dependence on foreign alloy import.