A method for preparing a niobium carbide reinforced cobalt-based wear-resistant material

Abstract

The application belongs to the field of material science, and specifically discloses a preparation method of high-uniformity niobium carbide reinforced cobalt-based wear-resistant material. The high-uniformity niobium carbide reinforced cobalt-based composite material is prepared by adopting vacuum induction melting, gas atomization powdering and hot-pressing sintering processes. The alloy composition is homogenized by adopting the method, and the niobium carbide reinforced phase can be uniformly and diffusely distributed in the alloy from the metallographic structure. The alloy composition of different parts is detected, and the composition is uniform and stable. The process stability is good, and the method is suitable for high-end aviation single crystal blade matched wear-resistant material.

Description

TECHNICAL FIELD

[0001] The application relates to the alloy manufacturing technical field, in particular to a preparation method of a niobium carbide reinforced cobalt-based wear-resistant material. BACKGROUND

[0002] Aircraft engine blades are prone to wear under high-temperature and high-speed rotation, and the niobium carbide reinforced cobalt-based composite material can be used as a wear-resistant sheet material to reduce the wear of the single-crystal blade body caused by high-temperature and high-speed rotation. The wear-resistant material contains a large amount of refractory metal elements such as tungsten, molybdenum and niobium and 1.5-2.5% of carbon elements, and a large amount of carbide strengthening phases are formed in the smelting process, thereby improving the wear resistance of the alloy.

[0003] However, the vacuum induction smelting method has large composition segregation and many shrinkage holes, resulting in low yield of the alloy and poor actual use effect. Therefore, a corresponding solution needs to be developed for the problem. SUMMARY

[0004] The application provides a preparation method of a niobium carbide reinforced cobalt-based wear-resistant material.

[0005] The application provides a preparation method of a niobium carbide reinforced cobalt-based wear-resistant material, and the niobium carbide reinforced cobalt-based material is a high-carbon alloy containing 1.8-3% of carbon and niobium, molybdenum and tungsten.

[0006] The preparation method comprises the following steps.

[0007] Step 1, the following raw materials are distributed: metal cobalt, cobalt-carbon alloy, metal molybdenum, cobalt-tungsten alloy, cobalt-niobium alloy, metal chromium, pure iron and aluminum ingot; vacuumizing, starting heating, heating to 1600-1650 DEG C after the alloy raw material is melted, cooling and maintaining at 1600-1620 DEG C, refining, casting after refining, the casting temperature is controlled at 1620-1640 DEG C, the casting power is 20-30 kW, and the alloy ingot is cast.

[0008] Step 2, the alloy ingot is loaded into a smelting device, vacuumized to below 10 Pa, preheated by power, heated to alloy melting, refined for 10-20 minutes after the alloy is melted, then cast and atomized; the refining power is 60-80 kW, the temperature is controlled at 1680 DEG C, the casting temperature is controlled at 1620-1660 DEG C; the atomization pressure is controlled at 2.5-3.5 MPa, the atomization time is 3-7 min, and the alloy powder after atomization is obtained.

[0009] Step 3, the alloy powder is placed in a graphite mold, leveled, and sintered in a vacuum hot-pressing sintering furnace for 8-12 hours. The sintering vacuum is 0.1 Pa or less, and the sintering pressure is 30-35 MPa.

[0010] Specifically, the alloy composition of the niobium carbide reinforced cobalt-based material is: Nb: 16-18%, Cr: 22-24%, W: 12-14%, Mo: 2-3%, Fe: 2-5%, Al: 2-3%, C: 1.8-3%, and Co: the balance.

[0011] Specifically, the cobalt-niobium alloy contains 60-80% niobium, the cobalt-tungsten alloy contains 30-50% tungsten, and the cobalt-carbon alloy contains 1-5% carbon. The reason for controlling the element content of the above intermediate alloy is that directly adding metallic tungsten and niobium will cause incomplete melting of tungsten in the alloy and uneven distribution of tungsten and niobium elements in the alloy. Directly adding high-purity graphite, carbon will float on the melt, and it is difficult to distribute uniformly in the melt, which cannot form a uniform niobium carbide reinforcement phase, affecting the use effect of the alloy. The composition ratio of cobalt-niobium and cobalt-tungsten alloy is designed near the eutectic point of binary alloy, which is more conducive to the uniformity of the intermediate alloy composition. Further optimization, in the cobalt-niobium alloy, the niobium content is 70-75%; in the cobalt-tungsten alloy, the tungsten content is 40-45%.

[0012] Specifically, in step 1, the specific process of heating is: vacuum to less than 15 Pa, power 10-30 kW, vacuum degree less than 5 Pa, power 30-50 kW, material red, power increased to 40-60 kW, spatter in the melting process, appropriately reduce the power, after melting clean, heat to 1600-1650 degrees Celsius.

[0013] Specifically, in step 1, the refining is 5-10 minutes, and the refining vacuum is 2 Pa.

[0014] Further, in step 1, the material arrangement sequence is preferably Fe-Mo-CoC-CoW-CoNb-Cr-Al. The reason for arranging the materials in this order is that arranging refractory metals and alloys in the area with high inductive melting energy helps the refractory metals to melt.

[0015] Specifically, in step 2, preheat with power 7-12 kW, continue to increase the power to 40-60 kW after 20-50 minutes, refine for 10-20 minutes after the alloy is melted, refine with power 60-80 kW, temperature control at 1680°C, and pouring temperature control at 1620-1660°C.

[0016] Specifically, in step 2, the refining power is 60-80 kW, the temperature is controlled at 1680℃, and the casting temperature is controlled at 1620-1660℃. The atomization pressure is controlled at 2.5-3.5 MPa, and the atomization time is 3-7 min.

[0017] Specifically, in step 3, the sintering process is as follows: room temperature-600℃ for 1h, 600℃ for 0.5h, 600℃-950℃ for 1-2h, 950℃ for 2-3h, 950-1000℃ for 0.5-1h, 1050-1150℃ for 3-4h, and then in-furnace cooling to room temperature and out of the furnace.

[0018] Beneficial effects: The method adopts vacuum induction melting, gas atomization powder preparation, and hot-pressing sintering process to prepare the tungsten carbide reinforced cobalt-based composite material. The product prepared by the preparation method has stable and uniform composition, and the high melting point elements and carbon elements are not segregated.

[0019] The method realizes the homogenization of alloy composition through vacuum induction melting, powder preparation, and hot-pressing sintering three-in-one process. As can be seen from the metallographic structure, the niobium carbide strengthening phase can be uniformly and dispersedly distributed in the alloy. After detecting the alloy composition of different parts, the composition is uniform and stable. The process has good stability and is suitable for use in high-end aviation single crystal blade matching wear-resistant materials. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Metallographic photo of the master alloy prepared in Example 1.

[0021] Figure 2 Physical photo of the wear-resistant alloy prepared in Example 1.

[0022] Figure 3 Metallographic photo of the wear-resistant alloy prepared in Example 1.

[0023] Figure 4 Metallographic photo of the master alloy prepared in Comparative Example 1. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be described in detail below through examples, but the protection scope of the present application is not limited to the examples.

[0025] Example 1:

[0026] The designed value of the alloy composition of the present embodiment is: Nb: 16.5%, Cr: 21.5%, W: 12.3%, Mo: 2.0%, Fe: 2.5%, Al: 2.5%, C: 2.2%, and Co: balance.

[0027] The preparation steps are as follows:

[0028] Step 1: Place pure iron, molybdenum, cobalt-carbon alloy, cobalt-tungsten alloy, cobalt-niobium alloy, chromium, and aluminum ingots into a crucible in a vacuum induction furnace. Vacuum the furnace. When the vacuum is less than 10 Pa, apply 20 kW of power. When the vacuum is less than 5 Pa, apply 50 kW of power. The material turns red. Increase the power to 50 kW. Sputtering occurs during the melting process. After the melt is clear, heat to 1650°C, turn off the power, cool to 1620°C, and refine for 8 minutes at a refining vacuum of 2 Pa. The casting temperature is controlled at 1620°C and the casting power is 25 kW. After the alloy cools, samples are taken from different parts for chemical analysis. The results are shown in the following table (in percentage):

[0029]

[0030] From the table above, we can see that although the smelting process has adopted the form of master alloy to reduce segregation, the alloy composition produced by induction melting is still uneven, especially the high melting point and high content metals niobium and tungsten have segregation.

[0031] like Figure 1 As shown in the figure, it can be seen that the blocky niobium carbide strengthening phase is unevenly distributed in the matrix and agglomerated in large pieces. Such uneven structure will have a great impact on the wear resistance of the material. The large agglomerated carbides are also easy to fall off during the friction process, and the material without the carbide strengthening phase is prone to wear and oxidation.

[0032] Step 2: The alloy ingot is powdered using a vacuum induction argon atomization process. The specific steps are: the alloy is placed in a crucible, evacuated to below 10 Pa, and preheated at 10 kW. After 30 minutes, the power is increased to 60 kW. Once the alloy is melted, it is refined for 20 minutes at 80 kW, with the temperature controlled at 1650°C and the casting temperature at 1660°C. The atomization pressure is controlled at 2.5 MPa, and the atomization time is 5 minutes. After cooling, the powder is removed and sieved. A powder of 50-150 microns is selected as the target powder. The target powder is placed in a mixer and mixed for 0.5-2 hours. Multiple samples are then tested for composition.

[0033]

[0034] The test results are as follows: From the above results, it can be seen that the powder composition uniformity is good.

[0035] Step 3: Place the prepared powder in a graphite mold, flatten it, and sinter it in a vacuum hot-pressing furnace for 8-12 hours. The sintering process parameters are: room temperature to 600°C: 1 hour, 600°C: 0.5 hour; 600°C to 950°C: 1 hour; 950°C: 3 hours; 950°C to 1000°C: 0.5 hour; 1100°C: 3 hours.

[0036] Cooling to room temperature in the furnace, out of the furnace. Sintering vacuum 0.1 Pa, sintering pressure 30 MPa.

[0037] The prepared alloy photos are shown as Figure 2 .

[0038] The surface of the sintered block is processed, and after removing the surface layer of 2-3 mm and the graphite mold contact, multi-point sampling is performed for composition analysis, and the test results are as follows:

[0039]

[0040] From the composition, the standard deviation of different test points of the alloy is less than 0.5%, which proves that the composition of each element is stable and there is no segregation. As shown in Figure 3 , it can be seen from the figure that compared with the master alloy produced by vacuum induction melting and casting, the carbide distribution is more uniform, and there is no large block of carbide, but is dispersed and uniformly distributed in the structure, which is consistent with the uniformity of the chemical composition test.

[0041] Example 2:

[0042] The suitable composition design value of the scheme is: Nb: 15.5%, Cr: 20.5%, W: 11.5%, Mo: 2.2%, Fe: 3.0%, Al: 2.0%, C: 2.0%, Co balance.

[0043] Step 1: Put pure iron, metal molybdenum, cobalt-carbon alloy, cobalt-tungsten alloy, cobalt-niobium alloy, metal chromium and aluminum ingots into the crucible in the vacuum induction furnace, and vacuumize the furnace. When the vacuum degree is less than 10 Pa, send power 30 kW, the vacuum degree is less than 5 Pa, send power 50 kW, the material is red, the power is increased to 50 kW, the melting process has spatter, after melting, heat to 1650℃, power off to 1670℃, refine for 5 minutes, refine the vacuum degree to 5 Pa. The pouring temperature is controlled at 1650℃, and the pouring power is 30kW. After the alloy is cooled, different part samples are taken for chemical analysis.

[0044] Step 2: The alloy ingot is powdered by vacuum induction argon atomization process, the specific steps are as follows: the alloy is loaded into the crucible, vacuumized to below 10 Pa, preheated with power 15 KW, 30 minutes later, continue to increase the power to 70 kW, when the alloy is melted, refine for 15 minutes, refine the power to 80 kW, the temperature is controlled at 1670℃, the pouring temperature is controlled at 1670℃. The atomization pressure is controlled at 2.5 MPa, and the atomization time is 6 min. After cooling, the powder is taken out for screening, and the powder of 50-150 microns is selected as the target powder. The target powder is put into a mixer for 3h, and multiple sample composition tests are performed to verify the uniformity.

[0045] Step 3: Put the prepared powder into a graphite mold, flatten, and sinter in a vacuum hot-pressing sintering furnace for 8-12 hours to form a shape. The sintering process parameters are: room temperature-600℃: 1h, 600℃: 0.5h; 600℃-950℃ 1h; 950℃ 3h; 950-1050℃ 0.5h; 1150℃ 4h.

[0046] Cool the furnace to room temperature and discharge. The sintering vacuum is within 0.1 Pa, and the sintering pressure is 33 MPa.

[0047] Process the surface of the sintered block, remove the 3mm surface layer in contact with the graphite mold, and then take samples for analysis to verify the uniformity of the material.

[0048] Comparative Example 1

[0049] The master alloy is prepared using pure metals instead of intermediate alloys. The alloy composition design values of this example are: Nb: 16.5%, Cr: 21.5%, W: 12.3%, Mo: 2.0%, Fe: 2.5%, Al: 2.5%, C: 2.2%, Co: balance.

[0050] The preparation steps are as follows:

[0051] Step 1: Put pure iron, high-purity carbon (wrapped), metallic cobalt, metallic molybdenum, metallic tungsten, cobalt-niobium alloy, metallic chromium, and aluminum ingots into the crucible in the vacuum induction furnace, vacuumize, when the vacuum degree is less than 10 Pa, send power 20 kW, vacuum degree less than 5 Pa, send power 50 kW, material red, power increased to 50 kW, melting process with spatter, after melting clean, heat to 1650 degrees Celsius, add the remaining carbon package, power off to 1620℃, refine for 8 minutes, refining vacuum degree 2 Pa. The pouring temperature is controlled at 1620℃, and the pouring power is 25 kW. After the alloy cools down, take samples from different parts for chemical analysis, and the test results are shown in the following table (unit is percentage %):

[0052]

[0053] As can be seen from the above table, although the smelting process does not use intermediate alloy to add refractory metal to produce the material, the composition is very uneven, and from the metallographic photo, it can be seen that the carbide is in large block aggregation, and there are regions of aggregation and regions of little distribution. The metallographic photo is shown in Figure 4 .

[0054] Comparative Example 2

[0055] The main steps of Comparative Example 2 are substantially the same as those of Example 1, except that the sintering process parameters in step 3 are: room temperature-600℃: 1h, 600℃: 0.5h; 600℃-950℃ 1 h; 950℃ 3h; 950-1000℃ 0.5h; 1000℃ 3h.

[0056] Comparative Example 3:

[0057] The main steps of Comparative Example 3 are substantially the same as those of Example 1, except that the sintering process parameters in step 3 are: room temperature-600℃: 1h, 600℃: 0.5h; 600℃-950℃ 1 h; 950℃ 3h; 950-1050℃ 0.5h; 1050℃ 4h.

[0058] Comparative Example 4:

[0059] The main steps of Comparative Example 4 are substantially the same as those of Example 1, except that the sintering process parameters in step 3 are: room temperature-600℃: 1h, 600℃: 0.5h; 600℃-950℃ 1 h; 950℃ 3h; 950-1100℃ 0.5h; 1100℃ 4h.

[0060] The effects of different sintering temperatures and times on sintering density in Comparative Example 2, Comparative Example 3 and Comparative Example 4 are tested. The results are shown in the following table:

[0061]

[0062] From the above data comparison, it can be seen that when the sintering temperature reaches 1100℃, the sintering time is 3 hours, and the sintering density can reach more than 99%. If the sintering temperature continues to increase to 1150℃ and the sintering time is 4 hours, the sintering density does not increase significantly. When the sintering temperature is 1050℃, the sintering density is only 94.77%. Therefore, 1100℃ and 3 hours are the best sintering temperature and time.

[0063] The above only describes the preferred embodiments of the present application and is not intended to limit the present application.

Claims

1. A method of producing a niobium carbide reinforced cobalt-based wear resistant material, characterized in that, The cobalt-based material reinforced by niobium carbide is a high-carbon alloy containing 1.8-3% carbon and niobium, molybdenum and tungsten, and the preparation steps are as follows: Step 1, the following raw materials are arranged: metal cobalt, cobalt-carbon alloy, metal molybdenum, cobalt-tungsten alloy, cobalt-niobium alloy, metal chromium, pure iron, aluminum ingot, the arrangement sequence is Fe-Mo-CoC-CoW-CoNb-Cr-Al; vacuumize, start heating with power, after the alloy raw materials are melted and cleaned, heat to 1600-1650℃, cool down and maintain at 1600-1620℃, carry out refining, after refining, carry out casting, the casting temperature is controlled at 1620-1640℃, the casting power is 20-30kW, and the alloy ingot is cast; The cobalt-niobium alloy contains 60-80% niobium; the cobalt-tungsten alloy contains 30-50% tungsten; and the cobalt-carbon alloy contains 1-5% carbon. Step 2, the alloy ingot is loaded into a smelting device, vacuumized to below 10Pa, preheated with power, and heated to the alloy melting point; after the alloy is melted, refine for 10-20 minutes, and then carry out casting and atomization; the refining power is 60-80kW, the temperature is controlled at 1680℃, the casting temperature is controlled at 1620-1660℃, the atomization pressure is controlled at 2.5-3.5MPa, the atomization time is 3-7min, and the alloy powder after atomization is obtained; Step 3, the alloy powder is placed in a graphite mold, flattened, and sintered in a vacuum hot-pressing sintering furnace for 8-12 hours to form a shape, the sintering vacuum degree is below 0.1Pa, and the sintering pressure is 30-35Mpa. The alloy composition of the cobalt-based material reinforced by niobium carbide is: Nb: 16-18%, Cr: 22-24%, W: 12-14%, Mo: 2-3%, Fe: 2-5%, Al: 2-3%, C: 1.8-3%, and Co: the balance; In step 1, the specific heating process is as follows: vacuumize to less than 15Pa, send power of 10-30kW, vacuum degree less than 5Pa, send power of 30-50kW, the material is red, the power is increased to 40-60kW, there is spatter in the melting process, the power is appropriately reduced, and after the material is melted and cleaned, heat to 1600-1650℃; In step 2, preheat with power of 7-12kW, continue to increase the power to 40-60kW after 20-50 minutes, refine for 10-20 minutes after the alloy is melted, the refining power is 60-80kW, the temperature is controlled at 1680℃, and the casting temperature is controlled at 1620-1660℃; In step 3, the sintering process is as follows: room temperature-600℃ for 1h, 600℃ for 0.5h, 600℃-950℃ for 1-2h, 950℃ for 2-3h, 950-1000℃ for 0.5-1h, 1050-1150℃ for 3-4h, and then cool to room temperature in the furnace.

2. The method of producing a niobium carbide reinforced cobalt-based wear resistant material according to claim 1, characterized in that, In step 1, the refining is carried out for 5-10 minutes, and the refining vacuum degree is 2Pa.

3. The method of making a niobium carbide reinforced cobalt- based wear resistant material according to claim 1, wherein, In step 3, the final sintering temperature is 1100℃ for 3-4h.

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