阅读说明：本技术 一种钴基变形高温合金及其制备方法 (Cobalt-based wrought superalloy and preparation method thereof ) 是由 安宁 牛永吉 田建军 郭文东 万克军 刘长源 曹青 张�荣 李振瑞 于 2019-09-25 设计创作，主要内容包括：一种钴基变形高温合金及其制备方法,属于高温合金技术领域。其合金化学成分按重量百分比为：Cr 9～13％,Ni 20～25％,W 13～18％,Al0.5～4％,Ti 0.5～2.5％,Mo 1～2％,V 0.2～0.8％,C 0.05～0.2％,RE 0.05～0.15％,Mn 0.5～1.5％,Si 0.3～0.8％,B 0.002～0.015％,Zr 0.01～0.12％,余量Co；Al+Ti+V≤6％,其中RE为Ce、La和Y中任一种稀土元素。该合金的制备工艺为将原材料按照比例配料熔炼,锻造电极棒进行重熔,重熔合金锭进行均匀化退火,而后进行锻造,制备成合金棒材,合金棒材进行固溶和时效热处理。优点在于,所制备合金棒材具有高的高温强度、良好的热加工和抗氧化性能。(A cobalt-based wrought superalloy and a preparation method thereof belong to the technical field of superalloys. The alloy comprises the following chemical components in percentage by weight: 9-13% of Cr, 20-25% of Ni, 13-18% of W, 0.5-4% of Al, 0.5-2.5% of Ti, 1-2% of Mo, 0.2-0.8% of V, 0.05-0.2% of C, 0.05-0.15% of RE, 0.5-1.5% of Mn, 0.3-0.8% of Si, 0.002-0.015% of B, 0.01-0.12% of Zr and the balance of Co; al + Ti + V is less than or equal to 6 percent, wherein RE is any one rare earth element of Ce, La and Y. The preparation process of the alloy comprises the steps of proportioning and smelting raw materials according to a proportion, remelting a forged electrode bar, carrying out homogenizing annealing on a remelted alloy ingot, then forging to prepare an alloy bar, and carrying out solid solution and aging heat treatment on the alloy bar. The method has the advantages that the prepared alloy bar has high-temperature strength and good hot working and oxidation resistance.)

1. The cobalt-based wrought superalloy is characterized by comprising the following chemical components in percentage by weight: 9-13% of Cr, 20-25% of Ni, 13-18% of W, 0.5-4% of Al, 0.5-2.5% of Ti, 1-2% of Mo, 0.2-0.8% of V, 0.05-0.2% of C, 0.05-0.15% of RE, 0.5-1.5% of Mn, 0.3-0.8% of Si, 0.002-0.015% of B, 0.01-0.12% of Zr0.01 and the balance of Co; and Al + Ti + V is less than or equal to 6 percent, wherein RE is any one rare earth element of Ce, La and Y.

2. A method of preparing a cobalt-based wrought superalloy according to claim 1, comprising the steps of:

1) mixing Ni, Cr, Co, W, Mo, Al, Ti, V, C, RE, Mn, Si, B and Zr according to a proportion, putting the mixture into a smelting furnace for smelting, wherein the refining temperature is 1550-1650 ℃, the refining time is 15-30 min, and casting the mixture into an alloy ingot;

2) forging the alloy ingot to form an electrode bar, remelting the electrode bar, and crystallizing the remelted alloy ingot;

3) carrying out homogenizing annealing on the heavy-fusion alloy ingot, and then forging to prepare an alloy bar;

4) and carrying out solid solution and aging heat treatment on the alloy bar.

3. The method for preparing the cobalt-based wrought superalloy according to claim 2, wherein the melting is vacuum induction furnace melting;

forging the electrode bar into an electrode bar at the temperature of 1200-1280 ℃, wherein the forging ratio is 3-5;

remelting is vacuum arc furnace remelting or vacuum electroslag remelting;

and homogenizing annealing, namely slowly heating to 1150-1280 ℃, and preserving heat for 10-40 hours.

4. The method for preparing the cobalt-based wrought superalloy according to claim 2, wherein the alloy bar is forged into an alloy billet 1 by cogging forging at a temperature of 1200-1280 ℃, and the forging ratio is 3-5; after surface grinding and defect flaw detection treatment, forging the alloy square billet 1 into an alloy billet 2 at the temperature of 1200-1280 ℃, wherein the forging ratio is 5-8, tempering the alloy billet 2 at the temperature of 1200-1280 ℃ for 25-30 min, rounding the alloy billet 2 at the forging ratio of 1-5 to obtain a square billet 3, tempering the alloy billet 3 at the temperature of 1200-1280 ℃ for 25-30 min, and rinsing the alloy billet into a round bar at the forging ratio of 1-5.

5. The preparation method of the cobalt-based wrought superalloy according to claim 2, wherein the solution heat treatment process comprises heating to 1000-1120 ℃, preserving heat for 1-2 hours, continuing heating to 1150-1280 ℃, preserving heat for 1-4 hours, and air cooling to obtain a solution alloy.

6. The preparation method of the cobalt-based wrought superalloy according to claim 2, wherein an aging system is that the temperature is kept at 700-800 ℃ for 5-20 hours, and air cooling is performed.

Technical Field

The invention belongs to the technical field of high-temperature alloys, and relates to a cobalt-based wrought high-temperature alloy and a preparation method thereof.

Background

The high-temperature alloy is generally used at the temperature of over 600 ℃, bears larger complex stress and has extremely harsh use environment. The high-temperature-resistant hot-end component has high-temperature strength, good oxidation and corrosion resistance, excellent creep resistance and fatigue resistance, good long-term structure stability, good use reliability and other comprehensive properties, and is widely applied to key hot-end components of aircraft engines and industrial ground gas turbines. Cobalt-based superalloys based on solid solution strengthening and carbide strengthening were developed during the thirties to the fifties of the last century and were first applied to hot end components of aircraft engines. Compared with the nickel-based superalloy, the cobalt-based superalloy has the following advantages: high melting point, better oxidation resistance, corrosion resistance, thermal fatigue resistance and welding performance. However, the conventional cobalt-based superalloy only relies on solid solution strengthening and carbide strengthening, and the high-temperature strength and temperature-bearing capacity of the conventional cobalt-based superalloy are significantly lower than those of the nickel-based superalloy strengthened by a gamma' precipitation phase, so that the application of the cobalt-based superalloy is greatly limited. Especially in the case of cobalt-based wrought superalloys, the choice of material can be made to a degree that is comparable.

Until 2006, Sato et Al discovered a gamma' precipitation strengthening phase similar to that of nickel-based superalloys in a Co-Al-W ternary cast alloy system, with a dissolution temperature of 990 ℃ indicating that the high temperature strength and temperature capability would be significantly improved, which is not available in conventional cobalt-based superalloys [ Sato J, Omori T, Oikawa K, et Al cobalt-base high temperature alloys [ J ]. Science,2006,312(5770):90-91 ]. Subsequently, other scholars' studies showed that: the creep properties of Co-Al-W based polycrystalline and single crystal alloys at 850 ℃ and 900 ℃ are comparable to those of the nickel-based polycrystalline alloy IN100 and the first generation nickel-based single crystal superalloy Ren N4, respectively. Therefore, the novel cobalt-based alloy has great development potential and is likely to become a new generation of high-temperature structural material, thereby rapidly becoming a research hotspot of the international high-temperature alloy community. However, up to now, the existing novel cobalt-based high temperature alloys mainly comprise simple components of low principal elements (3-5 elements), and only the german s.neumeier project group, the british d.dye project group, the Carpenter Technology company in the united states, and the peyronie and von willpower project group have reported multi-element cobalt-based wrought high temperature alloy components. The total content of gamma 'strengthening phase forming elements such as Al, Ti and Ta in the cobalt-based wrought high-temperature alloy of Neumeier project group is 4.8-9.1% [ Neumeier S, free L P, M.novel zero gamma/gamma' cobalt superalloys with high strength and improved hardness resistance [ J ]. Scripta material, 2015,109: 104-. The composition of cobalt-based wrought superalloy of the British D.dye group is characterized by high Ni, Al, Cr contents, where Ni content corresponds to Co content, the total of Al and Cr exceeds 17.7%, and the total content of γ' strengthening phase forming elements such as Al and Ta is 7.8% [ Knop M, Mulvey P, IsmailF, et al.A. new polycrystalline Co-Ni superalloy [ J ]. JOM,2014,66(12): 2495-. The cobalt-based wrought Superalloy of Carpenter Technology, Inc. in the United states has the composition characteristics of high Ni, Al, Ti, low Cr, and antioxidant elements such as Al and Cr accounting for 13.5%, and a total content of gamma' strengthening phase forming elements such as Al and Ti approaching 7.0% [ formula S A J, Rosas A O P, Wang T, et Al, high-Temperature oxidation behavior of a Novel Co-Base superior [ J ]. metallic and Materials transformations A,2018,49(9):4058 and 4069 ]. The cobalt-base wrought alloy of the Zhanwan subject group is characterized by emphasizing the action of an alloy element Mo, replacing a part of W element with Mo for reducing the alloy density, but Mo is known to be unfavorable for the high-temperature oxidation resistance of the alloy [ Zhanwan, Xiexin, Zhanyi, a cobalt-base superalloy with low density and high structure stability and a preparation method thereof ]. The cobalt-based wrought superalloy of the Von-Strong subject group is characterized in that on the premise of ensuring the stability of an alloy structure, the alloy strength is improved by increasing the content of Al and Cr and increasing the content of Al, Ti, Ta and Nb gamma' strengthening phase forming elements, and the sum of the content of Al, Ti, Ta and Nb elements is 4.5-19.5% [ CN 109321786A ], and the cobalt-based wrought superalloy and the preparation method thereof.

Although some multi-component cobalt-based wrought superalloy compositions have been reported, these alloy compositions are more focused on a single property, resulting in less than optimal overall properties of these alloys. The reported components of the cobalt-based wrought superalloy are all characterized in that the content of Al, Ti and Ta alloying elements is continuously improved, and the improvement of the alloying strength inevitably brings about the problems of serious component segregation and narrow hot processing window, which causes the cobalt-based wrought superalloy to be difficult to deform. In addition, these alloys have low production yield and high cost, and cannot be applied in engineering. Therefore, reasonable addition proportion of alloy elements, and a processing preparation process and a heat treatment process matched with the addition proportion are particularly important, and the components of the cobalt-based wrought superalloy need to be optimized, and the process preparation technology needs to be improved and innovated, so that the engineering application of the cobalt-based wrought superalloy can be promoted.

Disclosure of Invention

The invention aims to provide a cobalt-based wrought superalloy and a preparation method thereof, and the cobalt-based wrought superalloy with high strength, good hot workability and good oxidation resistance is prepared. Through proper addition of alloy strengthening elements, reasonable hot working and solution aging heat treatment process schedule, the high-temperature strength of the obtained novel cobalt-based wrought high-temperature alloy at 700-900 ℃ is obviously superior to that of traditional wrought high-temperature alloys such as GH605 and GH5188 under the condition of keeping good hot working performance. Therefore, the key technology for solving the problems is selection and dosage of alloy elements, optimization of a processing and preparation process and selection of a solution aging heat treatment process.

The cobalt-based wrought superalloy comprises the following chemical components in percentage by weight: 9-13% of Cr, 20-25% of Ni, 13-18% of W, 0.5-4% of Al, 0.5-2.5% of Ti, 1-2% of Mo, 0.2-0.8% of V, 0.05-0.2% of C, 0.05-0.15% of RE, 0.5-1.5% of Mn, 0.3-0.8% of Si, 0.002-0.015% of B, 0.01-0.12% of Zr and the balance of Co; al + Ti + V is less than or equal to 6 percent, wherein RE is any one rare earth element of Ce, La and Y.

The novel cobalt-based wrought superalloy and the preparation method thereof comprise the following steps:

1) mixing Ni, Cr, Co, W, Mo, Al, Ti, V, C, RE, Mn, Si, B and Zr according to a proportion, putting the mixture into a smelting furnace for smelting, wherein the refining temperature is 1550-1650 ℃, the refining time is 15-30 min, and casting the mixture into an alloy ingot;

2) forging the alloy ingot to form an electrode bar, remelting the electrode bar, and crystallizing the remelted alloy ingot;

3) carrying out homogenizing annealing on the heavy-fusion alloy ingot, and then forging to prepare an alloy bar;

4) and carrying out solid solution and aging heat treatment on the alloy bar.

The smelting is vacuum induction furnace smelting;

the forged electrode bar is forged into an electrode bar at the temperature of 1200-1280 ℃, and the forging ratio is 3-5;

the remelting is vacuum arc furnace remelting or vacuum electroslag remelting;

the homogenizing annealing is slowly heating to 1150-1280 ℃, and preserving heat for 10-40 hours;

the forging alloy bar is formed by cogging forging at the temperature of 1200-1280 ℃ to form an alloy square billet 1, and the forging ratio is 3-5. After surface grinding and defect flaw detection treatment, forging the alloy square billet 1 into an alloy billet 2 at the temperature of 1200-1280 ℃, wherein the forging ratio is 5-8, tempering the alloy billet 2 at the temperature of 1200-1280 ℃ for 25-30 min, rounding the alloy billet 2 at the forging ratio of 1-5 to obtain a square billet 3, tempering the alloy billet 3 at the temperature of 1200-1280 ℃ for 25-30 min, and rinsing the alloy billet into a round bar at the forging ratio of 1-5.

The solid solution heat treatment process comprises the steps of firstly heating to 1000-1120 ℃, preserving heat for 1-2 hours, continuously heating to 1150-1280 ℃, preserving heat for 1-4 hours, and air cooling to obtain a solid solution alloy;

the aging system is to perform heat preservation for 5-20 hours at 700-800 ℃ and perform air cooling.

The alloy of the invention comprehensively considers the influence of alloy elements on the high-temperature mechanical property, the hot working property and the oxidation resistance of the alloy during component design, and the specific consideration factors are as follows:

cr: mainly enter a gamma matrix to play a role in solid solution strengthening, and can also precipitate granular M on a grain boundary₂₃C₆Carbide strengthens the grain boundaries and another important function of Cr is to protect the alloy surface from O, S, salt action, which causes oxidation and hot corrosion. The existing alloy with better corrosion resistance generally has higher Cr content. However, Cr is an element that promotes the formation of a brittle sigma-type harmful phase, and since an excessively high Cr content deteriorates the structural stability of the alloy, the Cr content is 9 to 13%.

Ni: the gamma ' phase forming element obviously expands the two-phase area of gamma/gamma ', improves the stability of alloy structure and improves the complete dissolving temperature of the gamma ' phase to a certain extent. However, if the Ni content is too high, the chemical composition of the gamma' phase is closer to Ni3Al, and the coarsening rate is increased, so that the Ni content is 20-25%.

W and Mo: w and Mo have strong solid solution strengthening effect on both gamma phase and gamma' phase. Meanwhile, the two elements are carbide forming elements and play an important role in improving the high-temperature performance of the alloy. However, W and Mo are elements promoting formation of harmful μ brittle phases, and excessive addition thereof is disadvantageous in structural stability of the alloy. In addition, the excessive Mo content is very unfavorable for the oxidation resistance and the hot corrosion resistance of the alloy, so that the W content is 13-18%, and the Mo content is 1-2%.

Al and Ti: al and Ti are main elements forming gamma' phase, and can greatly improve the precipitation strengthening effect of the alloy. Meanwhile, the addition of Al element can form Al on the surface of the alloy₂O₃The protective film is beneficial to improving the oxidation resistance of the alloy, and the Ti is beneficial to improving the corrosion resistance. However, too high Al and Ti precipitate harmful beta phases, which is disadvantageous for the structure stabilization. In addition, Ti can obviously lower the solidus temperature, reduce the hot working window and is not beneficial to the hot working performance of the alloy, so that Al is 0.5-4.0%, and Ti is 0.5-2.5%.

V: very strong carbide and gamma' phase forming elements can effectively improve the creep property of the alloy, but the over-high V is not beneficial to the oxidation resistance of the alloy, so that the V is 0.2-0.8%.

C: the grain boundary strengthening element is also a strong deoxidizer, is beneficial to deoxidation in the alloy smelting process, improves the purity of the alloy and improves the processability of the alloy. Meanwhile, C can react with partial refractory element performance carbide, so that the supersaturation degree of a matrix is reduced, and the structure stability is facilitated. However, the content of C is too high, which forms continuous and network-distributed carbide on the crystal boundary and is not beneficial to the mechanical property of the alloy, so that the content of C is 0.05-0.2%.

RE: ce. The addition of the La and Y rare earth elements can play good roles of deoxidation, desulfurization and degassing in the alloy smelting process, purify and strengthen the grain boundary and improve the processing performance of the alloy; the product can also be used as a microalloying element to be segregated in a grain boundary, and plays a role in strengthening the grain boundary; in addition, Ce, La and Y are used as active elements to improve the oxidation resistance of the alloy and improve the surface stability. However, too high rare earth elements can form a large amount of large-particle oxides on grain boundaries, which is not favorable for the processability of the alloy, so that the RE is 0.05-0.15%.

Mn: the alloy is beneficial to the oxidation resistance and the welding performance of the alloy, but the mechanical property of the alloy is not facilitated due to the excessively high Mn content, so that the Mn content is 0.5-1.5%.

Si: is favorable for the oxidation resistance of the alloy. However, the Si content is too high, which is not favorable for the stability and mechanical property of the alloy structure, so that the Si content is 0.3-0.8%.

B and Zr: and B is a crystal boundary strengthening element, can increase the plasticity of the alloy, is beneficial to the coordinated deformation of the crystal boundary in the hot working process, and can improve the oxidation resistance and creep resistance of the alloy. However, if the content of B is too high, large block boride is easy to form in the grain boundary, which is not favorable for the mechanical property of the alloy. Zr is also a crystal boundary strengthening element, has an important effect on purifying crystal boundaries, and improves the plasticity and creep resistance of the alloy. However, too high Zr content is not favorable for the mechanical properties of the alloy. Therefore, B is 0.002 to 0.015% and Zr is 0.01 to 0.12%.

Al + Ti + V: al, Ti and V are all gamma 'phase forming elements, and the content of the elements directly influences the volume fraction and the complete dissolution temperature of the gamma' phase, so that the high-temperature mechanical property of the alloy is determined. However, the too high contents of Al, Ti and V are not good for the processability of the alloy, so that the Al + Ti + V is controlled to be less than or equal to 6 percent.

The alloy has reasonable component proportion, wide hot processing window and heat treatment system, and the prepared alloy bar has high-temperature strength, good hot processing and oxidation resistance, and is a candidate material for hot end parts of aircraft engines and industrial gas turbines

The invention has the following beneficial effects:

1) the alloy has high strength. 9-13% of Cr and 13-18% of W play strong solid solution strengthening effects; in addition, three gamma 'phase forming elements of Al, Ti and V are added, so that the alloy has a stable gamma' phase at 700-800 ℃ to play a role in precipitation strengthening, and the high-temperature mechanical property of the alloy is obviously improved;

2) the alloy has good hot workability. The alloy has a wider hot working window of 320-470 ℃, and has less surface cracks, good plasticity and high yield in the alloy forging process. By controlling Al + Ti + V to be less than or equal to 6 percent, the alloy is ensured to have good hot workability while the aging strengthening effect is fully achieved, and the amount of the gamma' phase is controlled not to exceed 50 percent. By adding RE rare earth elements, the grain boundary is purified, and the hot processing performance of the grain boundary is improved;

3) the alloy has good oxidation resistance. Cr production on alloy surface by adding 9-13% of Cr₂O₃The oxidation resistance is improved; in addition, the oxidation resistance of the alloy is further improved by adding RE, Mn and Si elements;

4) the alloy has the advantages of less harmful impurity elements, high purity, less internal defects and good uniformity of component structure. Through reasonable addition of C, RE alloy elements, better effects of deoxidation, denitrification and desulfurization are achieved. The high vacuum refining is adopted to further reduce the gas content and improve the purity and the hot workability of the alloy. By adopting a smelting and remelting duplex smelting mode, the contents of non-metallic inclusions, gas and sulfur in the alloy are reduced, the segregation of alloy components is reduced, the uniformity of component structures is ensured, and the mechanical property of the alloy is further improved.

5) The alloy does not contain noble metals such as Ta, Nb, Re and the like, has low cost and low density, is lower than most of the existing other cobalt-based high-temperature alloys, is equivalent to the advanced nickel-based wrought high-temperature alloy, can be used as a candidate material for high-temperature components of aero-engines and industrial gas turbines, and has good application prospect.

Detailed Description

Table 1 shows the alloy compositions of the examples and some of the reference alloy compositions (in weight percent). It is apparent that the embodiments described below are only a part of the embodiments of the present invention, and not all of them. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

TABLE 1 chemical composition

Alloy (I)	Cr	Ni	W	Al	Ti	Mo	V	C	Ce	La	Y	Mn	Si	B	Zr	Co
																	1	13	25	13	0.5	2.5	4.0	0.8	0.05	0.05	-	-	0.5	0.8	0.015	0.01	Surplus
2	11.5	20	15	4.0	0.5	2.0	0.2	0.06	0.09	-	-	0.9	0.4	0.01	0.08	Surplus
																	3	9	22	18	2.5	1.8	1.0	0.5	0.2	0.15	-	-	1.5	0.3	0.002	0.12	Surplus
4	9.2	21	13.2	2.0	0.5	2.0	0.2	0.10	0.08			0.6	0.4	0.003	0.012	Surplus
																	5	9.5	20	18	0.6	2.5	1.0	0.8	0.2	-	0.05	-	1.5	0.8	0.015	0.08	Surplus
6	11	23	16	2.6	1.6	3.0	0.3	0.11	-	0.07	-	0.8	0.5	0.012	0.12	Surplus
																	7	12.8	25	13	4.0	0.9	4.0	0.2	0.05	-	0.14	-	0.5	0.3	0.002	0.01	Surplus
8	11.8	22.1	14.6	2.8	1.5	3.0	0.2	0.1		0.08	-	0.5	0.3	0.003	0.012	Surplus
																	9	9	20	18	4.0	1.3	1.0	0.4	0.08	-	-	0.05	1.5	0.8	0.015	0.08	Surplus
10	10	21	15	2.9	0.5	3.1	0.6	0.12	-	-	0.1	1.3	0.4	0.009	0.01	Surplus
																	11	13	25	13	0.5	2.5	4.0	0.8	0.2	-	-	0.15	0.5	0.3	0.002	0.12	Surplus
12	14	25	15	3.5	2.2	4.0	0.2	0.013	-	-	0.08	0.5	0.3	0.002	0.01	Surplus
																	GH605	20	10	15	-	-	-	-	0.1	-	-	-	1.5	-	-	-	Surplus
GH5188	22	22	14.5	-	-	-	-	0.1	-	0.07	-	1.0	0.3	-	-	Surplus
																	GH738	19.5	Surplus	-	1.4	3.0	4.2	-	0.08	-	-	-	-	-	0.007	0.05	13.5