Methods for improving high temperature performance of selective laser melting in718plus alloy and in718plus alloy

Abstract

The application relates to a method for improving the high-temperature performance of selective laser melting IN718Plus alloy, which comprises the following steps: preparing an IN718Plus alloy sample by using selective laser melting, homogenizing treatment, solid solution treatment and double aging treatment. According to the method, the cooling mode after the solid solution treatment is controlled, so that the gamma prime phase of the IN718Plus alloy monopole and dipole is regulated. The application also provides the IN718Plus alloy prepared by the method. After the air cooling after the solid solution treatment, the alloy has the dipole gamma prime phase, the high-temperature stability of the gamma prime phase is greatly improved, and therefore the high-temperature mechanical performance of the IN718Plus alloy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature alloy performance, and specifically to a processing method for improving the high-temperature performance of additively manufactured high-temperature alloys and a high-temperature alloy. Background Art

[0002] IN718Plus alloy is a polycrystalline nickel-based high-temperature alloy. As an improved alloy of the widely used IN718 alloy, it increases its operating temperature from 650°C to 704°C. At the same time, IN718Plus alloy is an improved alloy of IN718 alloy. By adding W and Co elements and changing the ratio of Al and Ti elements, the main strengthening phase is successfully transformed from IN718~γ" phase to IN718Plus~γ'. This also increases the operating temperature of IN718Plus alloy by nearly 55°C compared to IN718 alloy, while retaining its excellent hot working properties. Therefore, it is widely used in aerospace and other fields.

[0003] The γ' phase is an intermetallic compound with an L12 face-centered cubic structure. It is the primary strengthening phase in IN718Plus alloy. Its primary components are Ni, Al, and Ti. Its chemical formula can be approximated as Ni³(Al,Ti), and its morphology is spherical. The γ' phase in IN718Plus alloy is small, typically not exceeding 100 nm. This finely dispersed γ' phase contributes to its exceptionally excellent high-temperature mechanical properties.

[0004] Currently, the production process for IN718Plus alloy is still primarily based on casting and forging. Cast alloys often suffer from shortcomings such as low density, numerous porosity defects, and severe element segregation, limiting their use and development. While wrought alloys offer superior performance compared to cast alloys, their complex structures are difficult to mass-produce and result in significant raw material waste. These issues not only limit the potential use of IN718Plus alloy but also reduce its service performance.

[0005] At the same time, by controlling the various parameters of selective laser melting technology, it is now possible to control the microstructure and grain size, achieving mass production of complex parts. However, due to its unique forming method, the microstructure is relatively special, making the performance of the deposited alloy lower than that of forgings. Appropriate heat treatment will greatly improve its defects and achieve the control of microstructure and performance. Currently, the selective laser melting of IN718Plus alloy still uses the standard forging heat treatment method, but its performance is not ideal. Therefore, it is necessary to improve the heat treatment steps and methods on this basis to improve performance and provide help and basis for future applications. Summary of the Invention

[0006] The object of the present invention is to overcome the shortcomings of the prior art and provide a treatment method for improving the high-temperature performance of IN718Plus alloy and an IN718Plus alloy, which achieves the regulation of the microstructure of the unipolar and bipolar strengthening phases by controlling the cooling rate after heat treatment, and proves in tensile tests that better high-temperature performance is obtained.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a method for improving the high temperature performance of IN718Plus alloy processed by selective laser melting, comprising the following steps:

[0008] Step 1: Prepare IN718Plus alloy specimens using selective laser melting:

[0009] On the selective laser melting platform of BLT S210, selective laser melting forming experiments were carried out on IN718Plus alloy powder prepared by gas atomization method under the conditions of laser power 85-185W, scanning rate 300-1350mm / s, layer thickness 0.02-0.03mm, and overlap spacing 0.06-0.2mm to obtain deposited IN718Plus alloy samples.

[0010] Step 2: Homogenization:

[0011] The deposited IN718Plus alloy sample was subjected to a first heat treatment at a furnace temperature of 1050-1150°C for 1-1.8 hours, and then water-cooled to room temperature at a rate of 1200-1400°C / s to obtain a homogenized IN718Plus alloy sample.

[0012] Step 3: Solution treatment:

[0013] The homogenized IN718Plus alloy sample was subjected to a second heat treatment at a furnace temperature of 960-980°C for 1-1.5 hours, and then water-cooled to room temperature at a rate of 1200-1400°C / s.

[0014] Step 4: Cooling and double aging treatment:

[0015] Under the condition of furnace temperature of 780-796℃, keep it warm for 8h-9h, then cool it to 696-712℃ at a cooling rate of 56℃ per minute, keep it warm for another 8h-9h, that is, complete the third heat treatment, and finally, air cool it to room temperature at a rate of 200-300℃ / s;

[0016] That is, the improvement of the high temperature performance of the selective laser melted IN718Plus alloy is completed.

[0017] Furthermore, the step 3, solution treatment is as follows:

[0018] After the second heat treatment is completed, the material is air-cooled to room temperature at a rate of 200-300°C / s.

[0019] Furthermore, the particle size of the IN718Plus alloy powder in step 1 is 15 μm to 45 μm.

[0020] Furthermore, the density of the IN718Plus alloy sample in step 1 is 8.236 g / cm3, the relative density is 99.83%, and the columnar grain size in the IN718Plus alloy sample is 5 to 50 μm.

[0021] Furthermore, the grains in the IN718Plus alloy sample after the homogenization treatment in step 2 are equiaxed grains with a grain size of 28 to 30 μm.

[0022] Furthermore, in step 3, the IN718Plus alloy sample after homogenization is subjected to a second heat treatment at a furnace temperature of 960° C. and a holding time of 1 hour.

[0023] Furthermore, in step 1, a selective laser melting forming experiment was performed on IN718Plus alloy powder using the selective laser melting parameters of 135W laser power, 900mm / s scanning rate, 0.02mm layer thickness, and 0.08mm overlap spacing to obtain deposited IN718Plus alloy;

[0024] In the second step, the deposited IN718Plus alloy sample is subjected to a first heat treatment at a furnace temperature of 1100° C. and a heat preservation time of 1.5 hours.

[0025] The present invention also provides an IN718Plus alloy obtained by treating the method for improving the high-temperature performance of the selective laser melted IN718Plus alloy. The IN718Plus alloy is an IN718Plus alloy with a unipolar distribution of the γ' phase. The unipolar γ' phase is uniformly distributed, has a size of 17 to 42 nm, and a content of approximately 28% to 32%; and an appropriate amount of needle-shaped η phase is precipitated at the grain boundaries.

[0026] Or the IN718Plus alloy is an IN718Plus alloy with a bipolar distribution of the γ' phase, that is, the size of the strengthening phase γ' in the alloy is graded, wherein the large-sized γ' phase has a size of 88 to 110 nm and a content of about 4.4% to 6%; the small-sized γ' phase has a size of 11 to 37 nm and a content of about 18.2% to 21.2%; and an appropriate amount of needle-shaped η phase precipitates at the grain boundaries.

[0027] The present invention has the following beneficial effects: The present invention uses IN718Plus alloy as the research object and uses selective laser melting technology to prepare IN718Plus alloy. The present invention achieves the regulation of the unipolar and bipolar γ' phase of IN718Plus alloy by controlling the post-solution cooling method.

[0028] At the same time, the IN718Plus alloy with bipolar γ' phase was obtained by this method, which greatly improved the high-temperature stability of the γ' phase, thereby improving the high-temperature mechanical properties of the IN718Plus alloy, which is of great significance for the future production and use of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a microstructural characterization diagram of the deposited structure of the present invention;

[0030] Figure 2 This is a microstructural characterization diagram of the sample after homogenization treatment of the present invention;

[0031] Figure 3 The microscopic characterization diagrams of two heat-treated samples of the present invention - WQ and AC samples;

[0032] Figure 4 The room temperature tensile properties of the WQ specimen, AC specimen, and forging standard and measured values ​​are shown in the figure.

[0033] Figure 5 This is a diagram showing the high-temperature tensile properties of the WQ and AC samples of the present invention at 704°C. DETAILED DESCRIPTION

[0034] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0035] In order to achieve the above object, the present invention provides the following specific implementation methods:

[0036] Example 1: Figures 1 to 5 As shown, a method for improving the high temperature performance of IN718Plus alloy processed by selective laser melting includes the following steps:

[0037] Step 1: Prepare IN718Plus alloy specimens using selective laser melting:

[0038] On a BLT S210 selective laser melting platform, selective laser melting experiments were conducted on IN718Plus alloy powder prepared by gas atomization under the conditions of laser power 85-185W, scanning rate 300-1350mm / s, layer thickness 0.02-0.03mm, and overlap spacing 0.06-0.2mm. The powder particle size ranged from 15μm to 45μm. The deposited IN718Plus alloy specimens were obtained. The density of the deposited IN718Plus alloy specimens was 8.236g / cm3, the relative density was 99.83%, and the columnar grain size in the specimens was 5-50μm.

[0039] Step 2: Homogenization:

[0040] The deposited IN718Plus alloy sample was subjected to a first heat treatment at a furnace temperature of 1050-1150°C and a holding temperature of 1-1.8 hours. After the treatment, it was water-quenched to room temperature at a rate of 1200-1400°C / s to obtain the homogenized IN718Plus alloy sample. The grains in the homogenized IN718Plus alloy sample were equiaxed grains with a grain size of 28-30 μm.

[0041] Step 3: Solution treatment:

[0042] The homogenized IN718Plus alloy sample was subjected to a second heat treatment at a furnace temperature of 960-980°C for 1-1.5 hours, and then water-cooled to room temperature at a rate of 1200-1400°C / s.

[0043] Step 4: Cooling and double aging treatment:

[0044] Under the condition of furnace temperature of 780-796℃, keep it warm for 8h-9h, then cool it to 696-712℃ at a cooling rate of 56℃ per minute, keep it warm for another 8h-9h, that is, complete the third heat treatment, and finally, air cool it to room temperature at a rate of 200-300℃ / s;

[0045] That is, the improvement of the high temperature performance of the selective laser melted IN718Plus alloy is completed.

[0046] Example 2: The same as Example 1, except that in step 3, the IN718Plus alloy sample after homogenization is subjected to a second heat treatment at a furnace temperature of 960° C. and a holding time of 1 h.

[0047] Example 3: The same as Example 1, except that: in step 1, a selective laser melting forming experiment was performed on IN718Plus alloy powder using the selective laser melting parameters of 135W laser power, 900mm / s scanning rate, 0.02mm layer thickness, and 0.08mm overlap spacing to obtain deposited IN718Plus alloy;

[0048] In step 2, the deposited IN718Plus alloy sample is subjected to the first heat treatment at a temperature of 1100° C. and a heat preservation time of 1.5 h.

[0049] Due to the excellent high-temperature mechanical properties and stability of IN718Plus alloy, it has a large market in many fields including aerospace. Traditional production methods have problems such as long production cycle and serious waste of resources. Therefore, this embodiment adopts the process parameters of laser power 135W, scanning rate 900mm / s, layer thickness 0.02mm, overlap spacing 0.08mm to selectively laser melt IN718Plus alloy with high density and good metallurgical bonding. The density of the sample is 8.236g / cm3 and the relative density is 99.83%. Figure 1 The figure shows the microscopic characterization of the deposited sample. The sample is mainly composed of Laves phase and cellular substructure. The grain composition is coarse and uneven columnar grains along the deposition direction, and the grain size is 5 to 50 μm.

[0050] Due to the additive manufacturing process of stacking layers, each deposited layer of the material has experienced extremely hot and cold processes, so the uniformity of the structure is very poor and it needs to be homogenized. The homogenization method selected in this example is to keep the temperature at 1100℃ for 1.5 hours and then cool it with water. The structure morphology of the sample after homogenization is as follows: Figure 2 After homogenization, the molten pool line and Laves phase of the sample have completely dissolved back, and the average grain size is 28μm. At this time, the recrystallization of the alloy has reached the level of complete recrystallization, and the grains have completely changed from columnar crystals to equiaxed crystals.

[0051] Example 4: The present invention also provides an IN718Plus alloy obtained by processing the method for improving the high-temperature performance of the selective laser melted IN718Plus alloy provided in Examples 1 to 3. The IN718Plus alloy is an IN718Plus alloy with a unipolar distribution of the γ' phase. The unipolar γ' phase is uniformly distributed, has a size of 17 to 42 nm, and a content of approximately 28% to 32%; an appropriate amount of needle-shaped η phase is precipitated at the grain boundaries.

[0052] Example 5: The same as Example 1, except for the solution treatment in step 3, specifically: after the second heat treatment, air cooling to room temperature is performed at a rate of 200-300°C / s.

[0053] Example 6: The same as Example 5, except that the homogenized IN718Plus alloy sample is subjected to a second heat treatment at a furnace temperature of 960° C. and a holding time of 1 hour.

[0054] Example 7: The present invention also provides an IN718Plus alloy obtained by being treated with the method for improving the high-temperature performance of the selective laser melted IN718Plus alloy provided in Examples 5 and 6. The IN718Plus alloy is an IN718Plus alloy with a bipolar distribution of the γ' phase, that is, the size of the strengthening phase γ' in the alloy is graded, wherein the size of the large-size γ' phase is 88 to 110 nm, and the content is about 4.4% to 6%; the size of the small-size γ' phase is 11 to 37 nm, and the content is about 18.2% to 21.2%; and an appropriate amount of needle-shaped η phase is precipitated at the grain boundaries.

[0055] In order to further describe the present invention, the present invention provides the following experimental description: Figures 1 to 5 As shown,

[0056] like Figure 1 As shown in the figure, the deposited microstructure is mainly composed of matrix γ, Laves phase and cellular substructure. There are a large number of melt pool lines perpendicular to the deposition direction, and the grain morphology is coarse and uneven columnar grains. After homogenization treatment, the cellular substructure, Laves phase and melt pool boundary lines are completely dissolved, and the phase composition is only matrix γ phase.

[0057] like Figure 2 As shown in the figure, after homogenization treatment at 1100℃, the grain composition is small and uniform equiaxed grains, and the size and orientation of the grains are close to those of the forging material. Therefore, after homogenization treatment, two groups of heat treatments were carried out, namely the first group of heat treatment and the second group of heat treatment, which were water-cooled and cooled at 960℃ for 1h and double aging treatment at 960℃ for 1h and air-cooled and cooled respectively. WQ and AC samples were obtained respectively.

[0058] like Figure 3 As shown in Figure 2, microscopic characterization of the WQ sample revealed that a moderate amount of needle-shaped η phase precipitated at the grain boundaries of the alloy. In addition, due to the double aging process, a large amount of γ' phase precipitated in the alloy. Its size and distribution are relatively uniform, about 30nm. The cooling rate after solution treatment at 960℃ may affect the size and distribution of the precipitated phase.

[0059] like Figure 3 As shown in the figure, microscopic characterization of the AC sample revealed that needle-shaped η phase was also precipitated at the grain boundary; characterization of the main strengthening phase γ' phase revealed that the γ' phase in the AC sample showed a graded phenomenon, among which the large-sized γ' phase was about 93nm in size and the small-sized γ' phase was about 28nm in size.

[0060] It can be seen that after double aging, both samples precipitated a large amount of γ' phase. The size and distribution of the γ' phase in the WQ sample were very uniform, but the γ' phase in the AC sample showed a graded phenomenon. This shows that the cooling rate after 960°C is the key factor affecting whether the γ' phase is graded.

[0061] Then, the WQ and AC specimens were subjected to room temperature tensile tests and compared with the forgings. The results are shown in Figure 2. Figure 4 As shown, the room temperature tensile properties all exceed the forging standards, with a yield strength of 0.958 GPa, a tensile strength of 1.338 GPa, and an elongation of 15%.

[0062] Next, control tests were conducted on WQ and AC samples at 704℃, and the results are as follows: Figure 5 As shown in Figure 3, the experimental results show that the yield strength of the AC specimen decreased by less than 2% compared with room temperature tensile strength. This shows that the high-temperature stability of the γ' phase with a bimodal distribution in the AC specimen is higher than that of the uniformly distributed γ' phase in the WQ specimen (strength decreased by 9.6%).

[0063] The present invention provides a heat treatment method for regulating the size distribution of the γ' phase of the selective laser melted IN718Plus alloy. By changing the cooling method after the 960°C solution treatment, a WQ sample with a unipolar distribution of the γ' phase and an AC sample with a bipolar distribution of the γ' phase can be obtained. By comparing the room temperature tensile property test results of the two samples with the high-temperature tensile property test results of 704°C, it is found that the high-temperature stability of the γ' phase with a bipolar distribution in the AC sample is higher than that of the unipolar distribution in the WQ sample.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for improving the high temperature performance of IN718Plus alloy by selective laser melting, characterized in that: The steps include: Step 1: Prepare IN718Plus alloy specimens using selective laser melting: On the selective laser melting platform of BLT S210, selective laser melting forming experiments were carried out on IN718Plus alloy powder prepared by gas atomization method under the conditions of laser power 85-185W, scanning rate 300-1350mm / s, layer thickness 0.02-0.03mm, and overlap spacing 0.06-0.2mm to obtain deposited IN718Plus alloy samples. Step 2: Homogenization: The deposited IN718Plus alloy sample was subjected to a first heat treatment at a furnace temperature of 1050-1150 °C for 1-1.8 h, and then water-cooled to room temperature at a rate of 1200-1400 °C / s to obtain a homogenized IN718Plus alloy sample. Step 3: Solution treatment: The homogenized IN718Plus alloy sample was subjected to a second heat treatment at a furnace temperature of 960-980 °C for 1-1.5 h, and then water-cooled to room temperature at a rate of 1200-1400 °C / s. Step 4: Cooling and double aging treatment: Under the condition of furnace temperature of 780-796 °C, keep it warm for 8-9 hours, then cool it to 696-712 °C at a cooling rate of 56 °C per minute, keep it warm for another 8-9 hours, thus completing the third heat treatment. Finally, air cool it to room temperature at a rate of 200-300 °C / s. That is, the improvement of the high temperature performance of the selective laser melted IN718Plus alloy is completed.

2. The method for improving the high temperature performance of selective laser melted IN718Plus alloy according to claim 1, characterized in that: The solution treatment in step three is as follows: the homogenized IN718Plus alloy sample is subjected to a second heat treatment at a furnace temperature of 960-980°C for 1-1.5 hours, and then air-cooled to room temperature at a rate of 200-300°C / s.

3. The method for improving the high temperature performance of selective laser melted IN718Plus alloy according to claim 1, characterized in that: The particle size of the IN718Plus alloy powder in step 1 is 15 μm to 45 μm.

4. The method for improving the high temperature performance of selective laser melted IN718Plus alloy according to claim 1, characterized in that: The density of the IN718Plus alloy sample in step 1 is 8.236 g / cm 3 , the relative density is 99.83%, and the columnar grain size in the IN718Plus alloy sample is 5 to 50 μm.

5. The method for improving the high temperature performance of selective laser melted IN718Plus alloy according to claim 1, characterized in that: The grains in the IN718Plus alloy sample after the homogenization treatment in step 2 are equiaxed grains with a grain size of 28 to 30 μm.

6. The method for improving the high temperature performance of selective laser melted IN718Plus alloy according to claim 1, characterized in that: In step 3, the IN718Plus alloy sample after homogenization is subjected to a second heat treatment at a furnace temperature of 960° C. and a holding temperature of 1 h.

7. The method for improving the high temperature performance of selective laser melted IN718Plus alloy according to claim 2, characterized in that: In the step 3, the IN718Plus alloy sample after homogenization is subjected to a second heat treatment at a furnace temperature of 960° C. and a holding time of 1 h.

8. The method for improving the high temperature performance of selective laser melted IN718Plus alloy according to any one of claims 1 to 7, characterized in that: In the step 1, a selective laser melting forming experiment is performed on IN718Plus alloy powder using the selective laser melting parameters of 135W laser power, 900mm / s scanning rate, 0.02mm layer thickness, and 0.08mm overlap spacing to obtain deposited IN718Plus alloy; In the second step, the deposited IN718Plus alloy sample is subjected to a first heat treatment at a furnace temperature of 1100° C. and a holding time of 1.5 h.

9. The IN718Plus alloy obtained by the method for improving the high temperature performance of the selective laser melted IN718Plus alloy according to claim 1, 3, 4, 5, or 6 is characterized in that: The IN718Plus alloy is an IN718Plus alloy with a unipolar distribution of the γ' phase. The unipolar γ' phase is evenly distributed, has a size of 17 to 42 nm, and a content of 28% to 32%. An appropriate amount of needle-shaped η phase is precipitated at the grain boundary.

10. The IN718Plus alloy obtained by the method for improving the high temperature performance of the selective laser melted IN718Plus alloy according to claim 2 or 7 is characterized in that: The IN718Plus alloy is an IN718Plus alloy with a bipolar distribution of the γ' phase, that is, the size of the strengthening phase γ' in the alloy is graded, wherein the large-sized γ' phase has a size of 88 to 110 nm and a content of 4.4% to 6%; the small-sized γ' phase has a size of 11 to 37 nm and a content of 18.2% to 21.2%; and an appropriate amount of needle-shaped η phase precipitates at the grain boundaries.

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