Laser additive manufacturing method of nickel-based superalloy based on laser stereolithography

Abstract

The application provides a laser additive manufacturing method of a nickel-based high-temperature alloy based on laser stereoscopic forming, which comprises the following steps: respectively adding TiB2 powder and GH3536 powder mixed according to a mass ratio of 99.5:0.5, 99:1 and 98:2 into a planetary ball mill; completing the powder mixing operation of the planetary ball mill according to a first parameter to obtain a plurality of mixed powders, and drying each mixed powder, wherein the first parameter comprises a rotation speed of 300 r / min-500 r / min, an intermittent working mode of combining forward and reverse rotation is adopted during the powder mixing operation, the working time is 5 min-10 min, the pause time is 4 min-5 min, then the reverse rotation is continued, and the ball milling time of each group of powder is 4 h-5 h; respectively performing cross scanning on each dried mixed powder according to a second parameter to complete the laser additive manufacturing of the nickel-based high-temperature alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser additive manufacturing technology, and particularly relates to a laser additive manufacturing method for nickel-based superalloy based on laser stereolithography. BACKGROUND

[0002] Nickel-based superalloy is a kind of alloy with the widest application and the largest high-temperature strength in high-temperature alloy. In recent years, it has attracted more and more attention of laser additive manufacturing (LAM) researchers due to its good oxidation resistance, corrosion resistance, wear resistance and welding performance (540℃-1000℃) at high temperature. Among them, GH3536 is a high-Fe-content nickel-based superalloy with Cr and Mo as the main strengthening elements, and the corresponding American brand is Hastelloy X (HX). Compared with similar alloys (IN625 and IN718), it has more excellent high-temperature strength, ductility, oxidation resistance and corrosion resistance, and is mainly used for preparing combustion chamber parts of gas turbine engine, such as transition pipe, combustion chamber and flame stabilizer, etc.

[0003] The laser stereolithography of metal materials is often realized by point-by-point and layer-by-layer cladding deposition, and its characteristics of large temperature gradient and rapid melting and solidification have a great influence on the solid solubility, organizational structure and microsegregation of nickel-based superalloy, which often causes defects such as cracks, pores and anisotropy of mechanical properties of samples. In recent years, with the continuous pursuit of lightweight and high performance of aero-engine parts, researchers have made a lot of attempts and explorations in the field of laser additive manufacturing of nickel-based superalloy, mainly through the adjustment of processing parameters, pretreatment of substrate and post-heat treatment to realize the improvement of sample forming quality.

[0004] At present, many studies have confirmed that the optimization of process parameters, pretreatment of substrate and post-heat treatment can improve the quality of SLM formed samples of nickel-based superalloy, but the improvement effect is limited. Therefore, many scholars at home and abroad start from the material direction, and realize the further regulation of the performance by adjusting the alloy composition. In the laser additive manufacturing of nickel-based superalloy, the optimization of alloy composition is mainly realized by adjusting the element content of the powder itself-micro-alloying, and adding external nano-ceramic particles and rare earth oxides.

[0005] However, TiC has poor oxidation resistance and is not suitable for working in the high-temperature operating environment (usually greater than 600℃) of gas turbine. TiB2, as the most stable compound of boron and titanium, has a melting point as high as 1850℃, and can still maintain good oxidation resistance at high temperature of 1100℃, and its thermal expansion coefficient is also close to that of nickel-based alloy, which is more suitable for reinforcing HX alloy than TiC. SUMMARY

[0006] Based on this, the purpose of the present application is to provide a laser additive manufacturing method of nickel-based superalloy based on laser stereolithography to at least solve the deficiencies in the related art.

[0007] The present application provides a laser additive manufacturing method of nickel-based superalloy based on laser stereolithography, comprising:

[0008] The TiB2 powder and GH3536 powder are mixed in a mass ratio of 99.5:0.5, 99:1 and 98:2 respectively and then added to a planetary ball mill;

[0009] The planetary ball mill is operated with a first parameter to obtain a plurality of mixed powders, and each mixed powder is dried, wherein the first parameter includes a rotation speed of 300r / min-500r / min, an intermittent working mode of forward and reverse combination during powder mixing operation, a working time of 5min-10min, a pause time of 4min-5min, and then continue to work in reverse, and the ball milling time of each group of powder is 4h-5h;

[0010] Each mixed powder after drying treatment is cross-scanned based on a second parameter to complete the laser additive manufacturing of nickel-based superalloy.

[0011] Further, the second parameter includes a laser power of 100W-1200W, a scanning speed of 400mm / min-800mm / min, an overlap rate of 50%, a powder feeding disc rotation speed of 0.1r / min-0.6r / min, a Z-axis one-way stroke of 0.35mm-0.4mm, a spot diameter of 2mm-3mm, a constraint gas flow of 4L / min-6L / min, and the powder feeding gas is argon.

[0012] Further, the step of drying each mixed powder includes:

[0013] Each mixed powder and a metal substrate are placed in a powder drying furnace and vacuum dried with a third parameter, and the powder drying furnace is left at room temperature, wherein the metal substrate is selected from a steel plate.

[0014] Further, the third parameter includes a drying temperature of 100℃-120℃ and a drying time of 4h-5h, and the steel plate is a forged 316L steel plate with a size of 120mmx60mmx6mm.

[0015] Further, the oxygen content during cross-scanning is controlled within a range of 100ppm-200ppm.

[0016] Compared with the prior art, the beneficial effects of the present application are that by increasing the mass fraction of TiB2, the melt pool boundary in the as-deposited sample becomes shallower, the dendritic structure is coarsened, and the grain size is increased; the segregation of phases at the interdendritic and grain boundary positions of the as-deposited sample is intensified, and the morphology and composition of precipitated phases change significantly, and a high-performance GH3536 alloy material is formed by using laser stereoscopic forming technology, the tensile strength of the as-deposited sample of the prepared alloy material is lower, and the tensile strength of the solid solution sample is higher. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The flow chart of the laser additive manufacturing method of the nickel-based superalloy based on laser stereoscopic forming in the first embodiment of the present application is shown in

[0018] Figure 2 The tensile size diagram of the laser additive of the nickel-based superalloy in the first embodiment of the present application is shown in

[0019] Figure 3 The microstructure diagrams of the as-deposited sample of the GH3536 alloy laser additive of TiB2 at various concentrations in the first embodiment of the present application are shown in

[0020] The following specific embodiments will further illustrate the present application in conjunction with the above drawings. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the related drawings. Several embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0023] Embodiment one

[0024] Please refer to Figure 1 , which shows the laser additive manufacturing method of the nickel-based superalloy based on laser stereoscopic forming in the first embodiment of the present application, which specifically comprises steps S101 to S103:

[0025] S101, respectively, mix TiB2 powder and GH3536 powder according to the mass ratio of 99.5:0.5, 99:1 and 98:2, and then add them to a planetary ball mill;

[0026] In the embodiment, the GH3536 powder used is an alloy powder prepared by a rotating electrode method, with a particle size distribution of 30-150 μm, and the specific components are shown in Table 1:

[0027] Table 1 Chemical composition of GH3536 alloy powder (wt. %)

[0028]

[0029] Specifically, the TiB2 powder and the GH3536 powder are mixed in a mass ratio of 99.5:0.5, 99:1 and 98:2 respectively, and then added to a planetary ball mill.

[0030] S102, the planetary ball mill is operated at a first parameter to complete the powder mixing operation, to obtain a plurality of mixed powders, and each of the mixed powders is subjected to a drying treatment, wherein the first parameter includes a rotation speed of 300-500 r / min, an intermittent working mode of positive and negative rotation is adopted during the powder mixing operation, the working time is 5-10 min, the pause time is 4-5 min, and then the reverse working is continued, and the ball milling time of each group of powder is 4-5 h.

[0031] The step of drying each of the mixed powders includes:

[0032] Each of the mixed powders and the metal substrate are placed in a powder drying furnace, and a third parameter is used for vacuum drying, and the powder drying furnace is left at room temperature, wherein the metal substrate is selected as a steel plate.

[0033] Specifically, the third parameter includes a drying temperature of 100-120 °C and a drying time of 4-5 h, and the steel plate is a forged 316L steel plate with a size of 120 mm x 60 mm x 6 mm.

[0034] In the embodiment, a vertical planetary ball mill of XQM-0.4 type is used to complete the powder mixing operation at a rotation speed of 500 r / min. An intermittent working mode of positive and negative rotation is adopted during the powder mixing, i.e. working for 10 min, pausing for 5 min, and then continuing the reverse working, and the ball milling time of each group of powder is 5 h. After the powder mixing, the TiB2 clumps are successfully broken and uniformly dispersed on the surface of the GH3536 spherical powder. Then, the mixed powder is subjected to vacuum drying at 120 °C for 5 h in a powder drying furnace, and the furnace is cooled to room temperature. Considering the physical properties of the substrate such as the thermal expansion coefficient, the specific heat capacity, and the thermal conductivity, a forged 316L steel plate with a size of 120 mm x 60 mm x 6 mm is selected as the substrate.

[0035] S103, based on a second parameter, each of the mixed powders after the drying treatment is subjected to cross scanning to complete the manufacturing of the nickel-based superalloy laser additive.

[0036] Further, the oxygen content during the cross scanning is controlled in the range of 100 ppm to 200 ppm; the second parameters include laser power of 100 W to 1200 W, scanning speed of 400 mm / min to 800 mm / min, overlap rate of 50%, powder feeding disc rotation speed of 0.1 r / min to 0.6 r / min, Z-axis single stroke of 0.35 mm to 0.4 mm, spot diameter of 2 mm to 3 mm, and constraint gas flow of 4 L / min to 6 L / min, and the powder feeding gas is argon.

[0037] In the specific implementation, the whole cross scanning process is performed in the Ar atmosphere protection, the oxygen content in the protection box is controlled in the range of 200 ppm, in order to reduce the residual stress, the laser additive manufacturing of the nickel-based superalloy is performed by the cross scanning, the parameters used are laser power of 1200 W, scanning speed of 800 mm / min, overlap rate of 50%, powder feeding disc rotation speed of 0.6 r / min, Z-axis single stroke of 0.4 mm, spot diameter of 3 mm, and constraint gas flow of 6 L / min, and the powder feeding gas is also argon.

[0038] Further, after the laser additive manufacturing of the nickel-based superalloy is completed, two groups of samples are cut by a DK77550 type electric spark wire cutting machine, one group is in the deposited state, and the other group is subjected to a solid solution treatment scheme of 1150 ℃ for 2 h, and pure GH3536 and 0.5wt.%, 1wt.%, 2wt.% TiB2 / GH3536 alloys are heat treated by an SX2-5-12 box resistance furnace. After being inlaid by an XQ-1 type inlaying machine, each group of samples is polished, and the polished surface is corroded by a reagent with a proportion of 8g FeCl3+14ml HCl+20ml C2H5OH for 10-20s. Subsequently, the macro and micro structures of each group of samples are characterized by an MR 5000 type optical microscope (OM), an FEI Nova Nano SEM450 type scanning electron microscope (SEM) and an INCA 250X-Max 50 type energy dispersive spectrometer (EDS), and the element types and contents are analyzed and measured.

[0039] The microhardness and tensile properties of the samples in each group were measured by using a WT-401MVD microhardness tester and a NSTRON-5543 precision electronic tensile testing machine, respectively. The microhardness was measured on the longitudinal section of the sample: 10 data points were taken on each sample to be tested at intervals of 0.5 mm, and the sample was pressed for 10 s under a load of 200 g; the tensile sample was taken along the transverse section of the sample, and the size of the sample was as shown in Figure 2 The tensile strength σb and elongation δ of the sample at room temperature were measured at a tensile rate of 2 mm / min. The tensile fracture morphology of the samples in each group was observed by using a FEI Nova Nano SEM450 scanning electron microscope (SEM).

[0040] As shown in Figure 3 (a) shows the schematic diagram of the grain structure of the as-deposited sample of GH3536, (b) shows the schematic diagram of the grain structure of the as-deposited sample of the 0.5wt.% TiB2 / GH3536 alloy, (c) shows the schematic diagram of the grain structure of the as-deposited sample of the 1wt.% TiB2 / GH3536 alloy, and (d) shows the schematic diagram of the grain structure of the as-deposited sample of the 2wt.% TiB2 / GH3536 alloy. The molten pool of GH3536 in (a) is distributed in a stacked “fish scale” shape, and the boundary has a fine and narrow arc-shaped fusion line. By increasing the mass fraction of TiB2, the molten pool boundary line is “blurred” on both sides, and the clarity gradually decreases; in addition, the arc-shaped fusion line gradually tends to be flat, the included angle at the lap joint position increases, and the transition between the two fusion lines becomes smoother, and finally the size and morphology of the molten pool change: the “fish scale” becomes larger, denser, and clearer, as shown in (b)-(d). When the addition amount of TiB2 is 2wt.%, the molten pool boundary line is weakened and difficult to distinguish, and the “fish scale” feature almost disappears, as shown in (d).

[0041] In summary, in the laser additive manufacturing method of the nickel-based superalloy based on laser stereolithography in the above embodiments, by increasing the mass fraction of TiB2, the molten pool boundary in the as-deposited sample becomes shallow, the dendritic structure is coarsened, and the grain size is increased; the segregation of the phase at the dendritic interstice and the grain boundary position of the as-deposited sample is intensified, and the morphology and composition of the precipitated phase change significantly, and a high-performance GH3536 alloy material is formed by using the laser stereolithography technology. The tensile strength of the as-deposited sample of the prepared alloy material is lower, and the tensile strength of the solid solution sample is higher.

[0042] The technical features of the above embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered as within the scope of the present disclosure.

[0043] The above-described embodiments are merely illustrative of several embodiments of the present application, which are described in more detail and in a specific manner, but should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these are all within the scope of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims.

Claims

1. A laser additive manufacturing method for nickel-based superalloys based on laser stereolithography, characterized in that, include: TiB2 powder and GH3536 powder were mixed at a mass ratio of 99.5:0.5, 99:1, or 98:2 and then added to a planetary ball mill. The planetary ball mill was used to mix the TiB2 powder and GH3536 powder at a speed of 300 r / min to 500 r / min. During the mixing process, an intermittent working mode with a combination of forward and reverse rotation was adopted. The working time was 5 min to 10 min, the pause time was 4 min to 5 min, and then the reverse rotation was resumed. The ball milling time of TiB2 powder and GH3536 powder was 4 h to 5 h. After mixing, the TiB2 clumps were successfully broken up and evenly dispersed on the surface of GH3536 spherical powder, resulting in a variety of mixed powders. The mixed powders and metal substrates are placed in a drying oven and vacuum dried at a drying temperature of 100℃~120℃ for 4h~5h. The drying oven is then placed at room temperature. The metal substrate is a 120 mm × 60 mm × 6 mm forged 316L steel plate. Based on the second parameter, each mixed powder after drying is cross-scanned to complete the laser additive manufacturing of nickel-based superalloy. The second parameter includes laser power of 100W~1200W, scanning rate of 400mm / min~800mm / min, overlap rate of 50%, powder feeding tray speed of 0.1r / min~0.6r / min, Z-axis unidirectional stroke of 0.35mm~0.4mm, spot diameter of 2mm~3mm, and confinement gas flow rate of 4L / min~6L / min. Argon is used as the powder feeding gas.

2. The laser additive manufacturing method for nickel-based superalloys based on laser stereolithography according to claim 1, characterized in that, The oxygen content during the cross-scan was controlled within the range of 100ppm to 200ppm.

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