Grading powder for binder jet printing and printing method

Abstract

The invention discloses graded powder for binder jet printing and a printing method, and relates to the technical field of additive manufacturing, the graded powder adopts a mixed system of coarse powder (10-45 microns) and fine powder (smaller than or equal to 4.5 microns), the volume ratio of the coarse powder to the fine powder is 5: 1-1: 1, compared with the prior art, the particle size of the fine powder is further reduced, the volume ratio of the fine powder is increased, and the particle size of the fine powder is reduced. The fine powder not only can effectively fill pores among coarse powder particles, but also can separate the coarse powder, so that direct contact areas among the coarse powder are greatly reduced, the disadvantage of low sintering activity of the direct contact areas among the coarse powder is eliminated, the sintering activity of the mixed powder is greatly improved, and the service life of the mixed powder is prolonged. And important guarantee is provided for improvement of the final sintering density.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of additive manufacturing technology, in particular to a graded powder for binder jet printing and a printing method. BACKGROUND

[0002] Binder Jetting technology was first proposed by MIT in 1993, which is a kind of powder bed-based additive manufacturing technology. Through the selective jetting of the binder by the nozzle, the powder material (such as metal, ceramic, sand, etc.) is solidified layer by layer to form a green body, and then the final part is obtained after debinding and sintering. Its core advantages include high efficiency (the surface forming speed can reach 10 times that of laser powder bed fusion), high design freedom of support-free structure, and material utilization rate > 95%. It has been widely used in aerospace, medical, casting mold and other fields. With the promotion of enterprises such as HP and Desktop Metal, this technology is becoming an important solution for large-scale customized production.

[0003] The working process of binder jet printing technology can be divided into the following steps: first, design the model by CAD software and generate the printing instructions by slicing, then the powder laying mechanism lays a layer of uniform powder (metal / ceramic / sand, etc.) on the building platform; the inkjet printhead selectively sprays binder droplets to bind the powder particles according to the slicing data, and after completing each layer, the building platform is lowered, and the powder laying-jetting process is repeated to accumulate layer by layer; after printing, solidification, powder removal and other post-processing are required, and metal / ceramic parts also need to be sintered at high temperature to realize densification.

[0004] In the BJ printing process, the particle size distribution of the powder directly affects the powder laying quality. Fine powder less than 5 μm can improve the sintering efficiency and sintering density, but its flowability is poor and it is easy to agglomerate into irregular particles, resulting in an increase in powder bed porosity and a decrease in bulk density; while coarse powder larger than 10 μm has good flowability and uniform powder laying, but the porosity between particles is large, which significantly reduces the final density of the sintered part.

[0005] In the BJ printing process, when the powder in the powder bed comes into contact with the binder, particle rearrangement occurs. Optimizing the particle size distribution of the powder can significantly improve the stability of the powder, improve the powder laying quality, reduce the disordered pore distribution caused by particle rearrangement, and improve the filling effect between the powders, so that the pores are more uniformly filled. This process directly improves the bulk density of the powder bed, and ultimately promotes the increase of the green body density. The key to optimizing the powder laying quality lies in balancing the particle flowability and the packing tightness, thereby laying a foundation for the subsequent binder penetration and sintering. SUMMARY

[0006] In view of this, the application provides a graded powder for binder jet printing, which adopts a mixed system of coarse powder (10-45 μm) and fine powder (≤4.5 μm). The fine powder can effectively fill the pores between the coarse powder particles, significantly improving the powder bed bulk density. At the same time, the excellent fluidity of the coarse powder can drive the uniform dispersion of the fine powder, improving the agglomeration problem of the fine powder. Through the particle size complementary effect, especially the significant increase in the proportion of fine powder, the sintering efficiency and the final sintering density are significantly improved under the premise of ensuring the smooth progress of the powder laying process.

[0007] The specific technical solutions are as follows:

[0008] A graded powder for binder jet printing, comprising: coarse powder with a particle size of 10-45 μm and fine powder with a particle size of ≤4.5 μm; the volume ratio of the coarse powder to the fine powder is 5:1 to 1:1; the coarse powder is spherical particles, and the fine powder is spherical or spheroidal particles; the coarse powder is selected from at least one of metal, ceramic, and metal-ceramic composite material; the fine powder is selected from at least one of metal, ceramic, and metal-ceramic composite material; the melting point of the coarse powder is greater than or equal to the melting point of the fine powder.

[0009] Preferably, the coarse powder and the fine powder are made of the same material.

[0010] Preferably, the volume ratio of the coarse powder to the fine powder is 3.5:1 to 1.5:1.

[0011] Preferably, the metal includes at least one of Fe-based, Al-based, Mg-based, Cu-based, Ti-based, and Ni-based metal and alloy; or / and, the ceramic includes at least one of oxide ceramic, nitride ceramic, boride ceramic, carbide ceramic, silicate ceramic, phosphate ceramic, high-entropy ceramic, and glass; and the metal-ceramic composite material includes at least one of WC-based hard alloy and TiC-based hard alloy.

[0012] Preferably, the Fe-based metal includes at least one of 316L and 17-4PH stainless steel.

[0013] The application also provides a binder jet printing method, comprising the following steps:

[0014] S1, providing raw materials according to the graded powder described in the application, and mixing uniformly;

[0015] S2, laying powder, printing, curing, debinding, and sintering the uniformly mixed raw materials.

[0016] Preferably, the powder laying process is: material strength 50-80%, powder laying speed 5-30mm / s; or / and, the printing process is: powder layer thickness 10-300μm, binder saturation 10-90%, powder bed temperature room temperature-180℃; or / and, the curing process is: curing temperature 150-250℃, curing time 1-48h.

[0017] Preferably, the debinding process is: the heating rate during debinding is 2℃ / min-8℃ / min, the maximum debinding temperature is 300-800℃, and the holding time is 10-180min; the sintering process is: the heating rate during sintering is 2℃ / min-50℃ / min; when the coarse powder and the fine powder are made of different materials, the sintering temperature is higher than the melting point of the fine powder, but is 10-250℃ below the melting point of the coarse powder; when the coarse powder and the fine powder are made of the same material, the sintering temperature is 10-250℃ below the melting point of the powder; the holding time is 10-180min, and the sintering process is carried out in air, protective gas or vacuum.

[0018] Preferably, the protective gas during the sintering process is at least one of argon, hydrogen and nitrogen, the pressure is 0.1-40.2MPa, and the flow rate is 0.5-1L / min.

[0019] Beneficial effects:

[0020] 1) The coarse and fine powder grading can synergistically optimize the powder laying quality and sintering performance. The fine powder can effectively fill the pores between the coarse powder particles, significantly improving the powder bed bulk density; at the same time, the excellent flowability of the coarse powder can drive the uniform dispersion of the fine powder, improving the agglomeration problem of the fine powder; through the particle size complementary effect, especially the large proportion of fine powder, the sintering efficiency and the final sintering density are significantly improved under the premise of ensuring the smooth progress of the powder laying process.

[0021] 2) Through the coarse and fine powder grading ratio of 5:1 to 1:1, the fine powder not only can effectively fill the pores between the coarse powder particles, but also can separate the coarse powder, so that the direct contact between the coarse powder and the coarse powder is greatly reduced, and the sintering activity of the direct contact area between the coarse powder and the coarse powder is low, which greatly improves the sintering activity of the mixed powder and provides an important guarantee for the improvement of the final sintering density. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described in the present application. Obviously, the embodiments described in the present application are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0023] The present application provides a graded powder for binder jet printing, comprising: coarse powder with a particle size of 10-45 μm and fine powder with a particle size of ≤4.5 μm; the volume ratio of the coarse powder and the fine powder is 5:1 to 1:1; the coarse powder is spherical particles, and the fine powder is spherical or spheroidal particles; the coarse powder is selected from at least one of metal, ceramic, and cermet composite material; the fine powder is selected from at least one of metal, ceramic, and cermet composite material; the melting point of the coarse powder is greater than or equal to the melting point of the fine powder, and when the melting point of the coarse powder is equal to the melting point of the fine powder, the coarse powder and the fine powder can be made of the same material.

[0024] The metal includes at least one of Fe-based, Al-based, Mg-based, Cu-based, Ti-based, Ni-based metal and alloy; the ceramic includes at least one of oxide ceramic, nitride ceramic, boride ceramic, carbide ceramic, silicate ceramic, phosphate ceramic, high-entropy ceramic, and glass; the cermet composite material includes at least one of ceramic reinforced metal matrix composite material, such as WC-based hard alloy and TiC-based hard alloy. The Fe-based metal includes at least one of stainless steel powder, such as 316L and 17-4PH stainless steel.

[0025] The present application also provides a binder jet printing method, comprising the following steps:

[0026] S1, providing raw materials according to the graded powder described in the present application, and uniformly mixing in a ball mill;

[0027] The coarse powder and the fine powder are mixed and treated in a ratio of 5:1 to 1:1 in volume, and are mixed under room temperature dry conditions or wet mixed in an organic solvent or deionized water, with a powder mixing speed of 150-250 rpm; the powder mixing time is 1-5 h.

[0028] S2, uniformly mixing the raw materials, and performing binder jet printing, with a material strength of 50-80%, a powder laying speed of 5-30 mm / s; a powder laying layer thickness of 10-300 μm in printing, a binder saturation of 10-90%, and a powder bed temperature of room temperature-180°C; after completion, performing heat curing on the printed part, with a curing temperature of 150-250°C and a curing time of 1-48 h;

[0029] The solidified printing piece is subjected to debinding, and the heating rate range during the debinding process is 2-8°C / min, the highest debinding temperature is 300-800°C, and the holding time is 10-180 min.

[0030] The printing piece after debinding is subjected to sintering to obtain a printing-sintering piece, and the heating rate range during the sintering process is 2-50°C / min; when the coarse powder and the fine powder are made of different materials, the sintering temperature is higher than the melting point of the fine powder but is 10-250°C lower than the melting point of the coarse powder; when the coarse powder and the fine powder are made of the same material, the sintering temperature is 10-250°C lower than the melting point of the powder; the holding time is 10-180 min, and the sintering is carried out in a protective gas or vacuum; the protective gas during the sintering process is at least one of argon, hydrogen and nitrogen, the pressure is 0.1-40.2 MPa, and the flow rate is 0.5-1 L / min.

[0031] Performance characterization:

[0032] The printing-sintering piece is subjected to density testing, and the density is tested by the Archimedes drainage method.

[0033] In order to further illustrate the present application, the graded powder for binder jet printing and the printing method provided by the present application are described in detail in combination with examples and comparative examples.

[0034] Example 1

[0035] The 15-45 μm 316L stainless steel spherical powder and the 2-4.5 μm 316L stainless steel spherical powder are subjected to mixing treatment, and the volume ratio of the two is 1:1 to obtain the graded spherical or spherical-like powder corresponding to the 1:1 ratio.

[0036] a) The graded powder is subjected to BJ printing, and the green printing piece is subjected to heat curing treatment after printing to obtain a printing piece.

[0037] b) The printing piece is subjected to debinding treatment to obtain a printing-debinding piece.

[0038] c) The printing-debinding piece is subjected to sintering treatment, and the highest sintering temperature is 1370°C, and the holding time is 15 min to obtain a printing-sintering piece.

[0039] d) The printing-sintering piece is subjected to performance characterization.

[0040] Example 2

[0041] The 15-45 μm 316L stainless steel spherical powder and the 2-4.5 μm 316L stainless steel spherical powder are subjected to mixing treatment, and the volume ratio of the two is 2.5:1 to obtain the graded spherical or spherical-like powder corresponding to the 2.5:1 ratio.

[0042] a) BJ printing of the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0043] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0044] c) The printed-debinding part is subjected to sintering treatment, the highest sintering temperature is 1370℃, and the holding time is 15 min, to obtain a printed-sintering part.

[0045] d) The printed-sintering part is subjected to performance characterization.

[0046] Example 3

[0047] The 15-45 μm 316L stainless steel spherical powder and the 2-4.5 μm 316L stainless steel spherical powder are subjected to mixing treatment, the volume ratio of the two is 2.5:1, to obtain the graded spherical or spherical-like powder corresponding to the ratio of 2.5:1.

[0048] a) BJ printing of the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0049] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0050] c) The printed-debinding part is subjected to sintering treatment, the highest sintering temperature is 1370℃, and the holding time is 30 min, to obtain a printed-sintering part.

[0051] d) The printed-sintering part is subjected to performance characterization.

[0052] Example 4

[0053] The 15-45 μm 316L stainless steel spherical powder and the 2-4.5 μm 316L stainless steel spherical powder are subjected to mixing treatment, the volume ratio of the two is 5:1, to obtain the graded spherical or spherical-like powder corresponding to the ratio of 5:1.

[0054] a) BJ printing of the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0055] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0056] c) The printed-debinding part is subjected to sintering treatment, the highest sintering temperature is 1370℃, and the holding time is 15 min, to obtain a printed-sintering part.

[0057] d) The printed-sintering part is subjected to performance characterization.

[0058] Comparative Example 1

[0059] The 15-45 pm 316L stainless steel spherical powder and the 2-4.5 pm 316L stainless steel spherical powder are subjected to mixing treatment, and the volume ratio of the two is 7:1, to obtain a graded spherical or spherical-like powder corresponding to a 7:1 ratio.

[0060] a) BJ printing of the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0061] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0062] c) The printed-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1370°C, and the holding time is 15 min, to obtain a printed-sintered part.

[0063] d) The printed-sintered part is subjected to performance characterization.

[0064] Comparative Example 2

[0065] The 15-45 pm 316L stainless steel spherical powder and the 2-4.5 pm 316L stainless steel spherical powder are subjected to mixing treatment, and the volume ratio of the two is 7:1, to obtain a graded spherical or spherical-like powder corresponding to a 7:1 ratio.

[0066] a) BJ printing of the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0067] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0068] c) The printed-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1370°C, and the holding time is 30 min, to obtain a printed-sintered part.

[0069] d) The printed-sintered part is subjected to performance characterization.

[0070] Comparative Example 3

[0071] The 15-45 pm 316L stainless steel spherical powder and the 2-4.5 pm 316L stainless steel spherical powder are subjected to mixing treatment, and the volume ratio of the two is 9:1, to obtain a graded spherical or spherical-like powder corresponding to a 9:1 ratio.

[0072] a) BJ printing of the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0073] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0074] c) The printed-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1370°C, and the holding time is 15 min, to obtain a printed-sintered part.

[0075] d) The print-sintered part is subjected to performance characterization.

[0076] Comparative Example 4

[0077] The 15-45 pm 316L stainless steel spherical powder and the 2-4.5 pm 316L stainless steel spherical powder are subjected to mixing treatment, and the volume ratio of the two is 9:1, to obtain a graded spherical or spherical-like powder corresponding to a ratio of 9:1.

[0078] a) The graded powder is subjected to BJ printing, and the green print part is subjected to heat curing treatment after printing to obtain a print part.

[0079] b) The print part is subjected to debinding treatment to obtain a print-debinding part.

[0080] c) The print-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1370°C, and the holding time is 30 min, to obtain a print-sintered part.

[0081] d) The print-sintered part is subjected to performance characterization.

[0082] Comparative Example 5

[0083] a) The 15-45 pm 316L stainless steel spherical powder (coarse powder) is subjected to BJ printing, and the green print part is subjected to heat curing treatment after printing to obtain a print part.

[0084] b) The print part is subjected to debinding treatment to obtain a print-debinding part.

[0085] c) The print-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1370°C, and the holding time is 15 min, to obtain a print-sintered part.

[0086] d) The print-sintered part is subjected to performance characterization.

[0087] Comparative Example 6

[0088] a) The 15-45 pm 316L stainless steel spherical powder (coarse powder) is subjected to BJ printing, and the green print part is subjected to heat curing treatment after printing to obtain a print part.

[0089] b) The print part is subjected to debinding treatment to obtain a print-debinding part.

[0090] c) The print-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1370°C, and the holding time is 30 min, to obtain a print-sintered part.

[0091] d) The print-sintered part is subjected to performance characterization.

[0092] The sintering process and sintering density in the examples and comparative examples were compared, and the results are shown in Table 1:

[0093] Table 1 shows the experimental data and comparative data in Examples 1-4 and Comparative Examples 1-6 of the present application

[0094]

[0095] Table 1 shows that for 316L stainless steel, the optimal grading ratio of coarse (10-45 μm) and fine (2-4.5 μm) powder is 2.5:1, and a sintering density of more than 98% can be achieved at a sintering temperature of 1370°C for only 15 min, and when the sintering time reaches 30 min, the sintering density is already more than 99%; in contrast, the BJ prints with a grading ratio of 7:1 and above have generally lower density, even after 30 min of sintering, the density is lower than that of the BJ prints with a grading ratio of 2.5:1, especially the BJ prints with pure coarse powder, even if the sintering time is extended, the density cannot be improved, so the grading ratio of coarse (10-45 μm) and fine (2-4.5 μm) powder of 2.5:1 can significantly improve the sintering efficiency and sintering density of the BJ prints.

[0096] Example 5

[0097] The 10-40 μm pure copper spherical powder and the 1-4 μm pure copper spherical powder were mixed at a volume ratio of 1:1 to obtain the graded spherical or spherical-like powder corresponding to a ratio of 1:1.

[0098] a) BJ printing of the graded powder, followed by heat curing of the green printed part to obtain the printed part.

[0099] b) The printed part was subjected to debinding treatment to obtain the printed-debinding part.

[0100] c) The printed-debinding part was subjected to sintering treatment, the maximum sintering temperature was 1075°C, and the holding time was 15 min, to obtain the printed-sintered part.

[0101] d) Performance characterization of the printed-sintered part.

[0102] Example 6

[0103] The 10-40 μm pure copper spherical powder and the 1-4 μm pure copper spherical powder were mixed at a volume ratio of 1.5:1 to obtain the graded spherical or spherical-like powder corresponding to a ratio of 1.5:1.

[0104] a) BJ printing of the graded powder, followed by heat curing of the green printed part to obtain the printed part.

[0105] b) the printed piece is subjected to debinding treatment to obtain a printed-debinding piece.

[0106] c) the printed-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1075℃, and the holding time is 15 min, to obtain a printed-sintering piece.

[0107] d) the printed-sintering piece is subjected to performance characterization.

[0108] Example 7

[0109] The 10-40 pm pure copper spherical powder and the 1-4 pm pure copper spherical powder are subjected to mixing treatment, the volume ratio of the two is 3:1, to obtain a graded spherical or quasi-spherical powder corresponding to a 3:1 ratio.

[0110] a) the graded powder is subjected to BJ printing, and the green printed piece is subjected to heat curing treatment after printing to obtain a printed piece.

[0111] b) the printed piece is subjected to debinding treatment to obtain a printed-debinding piece.

[0112] c) the printed-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1075℃, and the holding time is 15 min, to obtain a printed-sintering piece.

[0113] d) the printed-sintering piece is subjected to performance characterization.

[0114] Comparative Example 7

[0115] The 10-40 pm pure copper spherical powder and the 1-4 pm pure copper spherical powder are subjected to mixing treatment, the volume ratio of the two is 7:1, to obtain a graded spherical or quasi-spherical powder corresponding to a 7:1 ratio.

[0116] a) the graded powder is subjected to BJ printing, and the green printed piece is subjected to heat curing treatment after printing to obtain a printed piece.

[0117] b) the printed piece is subjected to debinding treatment to obtain a printed-debinding piece.

[0118] c) the printed-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1075℃, and the holding time is 15 min, to obtain a printed-sintering piece.

[0119] d) the printed-sintering piece is subjected to performance characterization.

[0120] Comparative Example 8

[0121] The 10-40 pm pure copper spherical powder and the 1-4 pm pure copper spherical powder are subjected to mixing treatment, the volume ratio of the two is 9:1, to obtain a graded spherical or quasi-spherical powder corresponding to a 9:1 ratio.

[0122] a) BJ printing of the graded powder, and then heat curing the green printed part to obtain a printed part.

[0123] b) The printed part is subjected to debinding to obtain a printed-debinding part.

[0124] c) The printed-debinding part is subjected to sintering, with a maximum sintering temperature of 1075°C and a holding time of 15 min, to obtain a printed-sintering part.

[0125] d) The printed-sintering part is subjected to performance characterization.

[0126] Comparative Example 9

[0127] a) BJ printing of the 10-40 μm pure copper spherical powder (coarse powder), and then heat curing the green printed part to obtain a printed part.

[0128] b) The printed part is subjected to debinding to obtain a printed-debinding part.

[0129] c) The printed-debinding part is subjected to sintering, with a maximum sintering temperature of 1075°C and a holding time of 15 min, to obtain a printed-sintering part.

[0130] d) The printed-sintering part is subjected to performance characterization.

[0131] The sintering process and sintering density in the examples and comparative examples are compared, and the results are shown in Table 2:

[0132] Table 2: Experimental data and comparative data in Examples 5-7 and Comparative Examples 7-9 of the application

[0133]

[0134] Table 2 shows that for coarse (10-40 μm) and fine (1-4 μm) graded powders of pure copper, the optimal grading ratio is 1.5:1, and a sintering density of more than 98% can be achieved at a sintering temperature of 1075°C for only 15 min of holding time, showing the great advantages of the coarse and fine grading ratio of 1.5:1 in terms of sintering efficiency and sintering density.

[0135] Example 8

[0136] The 10-45 μm alumina irregularly shaped powder and the 1-4.5 μm alumina irregularly shaped powder are subjected to mixing treatment, with a volume ratio of 1:1, to obtain a graded spherical or spherical-like powder corresponding to a ratio of 1:1.

[0137] a) BJ printing of the graded powder, and then heat curing the green printed part to obtain a printed part.

[0138] b) the printed piece is subjected to debinding treatment to obtain a printed-debinding piece.

[0139] c) the printed-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1650℃, and the holding time is 45 min, to obtain a printed-sintering piece.

[0140] d) the printed-sintering piece is subjected to performance characterization.

[0141] Example 9

[0142] The 10-45 μm alumina irregular-shaped powder and the 1-4.5 μm alumina irregular-shaped powder are subjected to mixing treatment, the volume ratio of the two is 3.5:1, to obtain the graded spherical or spherical-like powder corresponding to the ratio of 3.5:1.

[0143] a) the graded powder is subjected to BJ printing, and the green printed piece is subjected to heat curing treatment after printing to obtain a printed piece.

[0144] b) the printed piece is subjected to debinding treatment to obtain a printed-debinding piece.

[0145] c) the printed-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1650℃, and the holding time is 45 min, to obtain a printed-sintering piece.

[0146] d) the printed-sintering piece is subjected to performance characterization.

[0147] Example 10

[0148] The 10-45 μm alumina irregular-shaped powder and the 1-4.5 μm alumina irregular-shaped powder are subjected to mixing treatment, the volume ratio of the two is 3.5:1, to obtain the graded spherical or spherical-like powder corresponding to the ratio of 3.5:1.

[0149] a) the graded powder is subjected to BJ printing, and the green printed piece is subjected to heat curing treatment after printing to obtain a printed piece.

[0150] b) the printed piece is subjected to debinding treatment to obtain a printed-debinding piece.

[0151] c) the printed-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1650℃, and the holding time is 120 min, to obtain a printed-sintering piece.

[0152] d) the printed-sintering piece is subjected to performance characterization.

[0153] Example 11

[0154] The 10-45 μm alumina irregular-shaped powder and the 1-4.5 μm alumina irregular-shaped powder are subjected to mixing treatment, the volume ratio of the two is 5:1, to obtain the graded spherical or spherical-like powder corresponding to the ratio of 5:1.

[0155] a) BJ printing of the graded powder, and then heat curing the green printed part to obtain a printed part.

[0156] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0157] c) The printed-debinding part is subjected to sintering treatment, the maximum sintering temperature is 1650℃, and the holding time is 45min, to obtain a printed-sintered part.

[0158] d) The printed-sintered part is subjected to performance characterization.

[0159] Comparative Example 10

[0160] The 10-45μm irregularly shaped alumina powder and the 1-4.5μm irregularly shaped alumina powder are subjected to mixing treatment, and the volume ratio of the two is 7:1, to obtain graded spherical or spherical-like powder corresponding to a 7:1 ratio.

[0161] a) BJ printing of the graded powder, and then heat curing the green printed part to obtain a printed part.

[0162] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0163] c) The printed-debinding part is subjected to sintering treatment, the maximum sintering temperature is 1650℃, and the holding time is 45min, to obtain a printed-sintered part.

[0164] d) The printed-sintered part is subjected to performance characterization.

[0165] Comparative Example 11

[0166] The 10-45μm irregularly shaped alumina powder and the 1-4.5μm irregularly shaped alumina powder are subjected to mixing treatment, and the volume ratio of the two is 7:1, to obtain graded spherical or spherical-like powder corresponding to a 7:1 ratio.

[0167] a) BJ printing of the graded powder, and then heat curing the green printed part to obtain a printed part.

[0168] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0169] c) The printed-debinding part is subjected to sintering treatment, the maximum sintering temperature is 1650℃, and the holding time is 120min, to obtain a printed-sintered part.

[0170] d) The printed-sintered part is subjected to performance characterization.

[0171] Comparative Example 12

[0172] The 10-45 pm irregular-shaped alumina powder and the 1-4.5 pm irregular-shaped alumina powder are mixed to obtain a graded spherical or spherical-like powder corresponding to a 9:1 ratio.

[0173] a) BJ printing is performed on the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0174] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0175] c) The printed-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1650°C, and the holding time is 45 min, to obtain a printed-sintered part.

[0176] d) The printed-sintered part is subjected to performance characterization.

[0177] Comparative Example 13

[0178] The 10-45 pm irregular-shaped alumina powder and the 1-4.5 pm irregular-shaped alumina powder are mixed to obtain a graded spherical or spherical-like powder corresponding to a 9:1 ratio.

[0179] a) BJ printing is performed on the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0180] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0181] c) The printed-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1650°C, and the holding time is 120 min, to obtain a printed-sintered part.

[0182] d) The printed-sintered part is subjected to performance characterization.

[0183] Comparative Example 14

[0184] a) BJ printing is performed on the 10-45 pm irregular-shaped alumina powder (coarse powder), and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0185] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0186] c) The printed-debinding part is subjected to sintering treatment, and the highest sintering temperature is 1650°C, and the holding time is 45 min, to obtain a printed-sintered part.

[0187] d) The printed-sintered part is subjected to performance characterization.

[0188] Comparative Example 15

[0189] a) BJ printing is performed on irregularly shaped alumina powder (coarse powder) with a particle size of 10-45 μm, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0190] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0191] c) The printed-debinding part is subjected to sintering treatment, and the maximum sintering temperature is 1650°C, and the holding time is 120 min, to obtain a printed-sintered part.

[0192] d) The printed-sintered part is subjected to performance characterization.

[0193] The sintering process and sintering density in the examples and comparative examples are compared, and the results are shown in Table 3:

[0194] Table 3: Experimental data related to examples 8-11 and comparative examples 10-15 of the present application and comparative data thereof

[0195]

[0196] Table 3 shows that for the coarse (10-45 μm) and fine (1-4.5 μm) alumina powders, when the grading ratio is 3.5:1, the sintering density of the BJ printed part reaches more than 97% in only 45 min of holding time, and when the holding time is extended to 120 min, the density reaches more than 99%; in sharp contrast, when the grading ratio is increased to 7:1 and above, the sintering density of the BJ printed part decreases significantly, and even if the holding time is extended to 120 min, the sintering density does not increase significantly, fully verifying the significant technical advantages of the coarse and fine powder grading ratio of 3.5:1 in terms of sintering efficiency and sintering density.

[0197] Example 12

[0198] The 10-45 μm zirconia-like spherical powder and the 1-4.5 μm zirconia-like spherical powder are mixed, and the volume ratio of the two is 1:1 to obtain a graded spherical or spherical-like powder corresponding to a ratio of 1:1.

[0199] a) BJ printing is performed on the graded powder, and after printing, the green printed part is subjected to heat curing treatment to obtain a printed part.

[0200] b) The printed part is subjected to debinding treatment to obtain a printed-debinding part.

[0201] c) The printed-debinding part is subjected to sintering treatment, and the maximum sintering temperature is 1500°C, and the holding time is 60 min, to obtain a printed-sintered part.

[0202] d) The printed-sintered part is subjected to performance characterization.

[0203] Example 13

[0204] The 10-45 pm zirconia-like spherical powder and the 1-4.5 pm zirconia-like spherical powder were mixed at a volume ratio of 2.5:1 to obtain a graded spherical or like-spherical powder corresponding to a ratio of 2.5:1.

[0205] a) BJ printing was performed on the graded powder, and the green printed part was heat-cured after printing to obtain a printed part.

[0206] b) The printed part was subjected to debinding treatment to obtain a printed-debinding part.

[0207] c) The printed-debinding part was subjected to sintering treatment, and the maximum sintering temperature was 1500°C, and the holding time was 60 min, to obtain a printed-sintered part.

[0208] d) The printed-sintered part was subjected to performance characterization.

[0209] Example 14

[0210] The 10-45 pm zirconia-like spherical powder and the 1-4.5 pm zirconia-like spherical powder were mixed at a volume ratio of 5:1 to obtain a graded spherical or like-spherical powder corresponding to a ratio of 5:1.

[0211] a) BJ printing was performed on the graded powder, and the green printed part was heat-cured after printing to obtain a printed part.

[0212] b) The printed part was subjected to debinding treatment to obtain a printed-debinding part.

[0213] c) The printed-debinding part was subjected to sintering treatment, and the maximum sintering temperature was 1500°C, and the holding time was 60 min, to obtain a printed-sintered part.

[0214] d) The printed-sintered part was subjected to performance characterization.

[0215] Comparative Example 16

[0216] The 10-45 pm zirconia-like spherical powder and the 1-4.5 pm zirconia-like spherical powder were mixed at a volume ratio of 7:1 to obtain a graded spherical or like-spherical powder corresponding to a ratio of 7:1.

[0217] a) BJ printing was performed on the graded powder, and the green printed part was heat-cured after printing to obtain a printed part.

[0218] b) The printed part was subjected to debinding treatment to obtain a printed-debinding part.

[0219] c) The printing-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1500°C, and the holding time is 60 min, to obtain a printing-sintering piece.

[0220] d) The printing-sintering piece is subjected to performance characterization.

[0221] Comparative Example 17

[0222] The 10-45 μm zirconia spherical powder and the 1-4.5 μm zirconia spherical powder are subjected to mixing treatment, the volume ratio of the two is 7:1, to obtain a corresponding 7:1 ratio of graded spherical or spherical powder.

[0223] a) The graded powder is subjected to BJ printing, and the green printing piece is subjected to heat curing treatment after printing, to obtain a printing piece.

[0224] b) The printing piece is subjected to debinding treatment, to obtain a printing-debinding piece.

[0225] c) The printing-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1500°C, and the holding time is 120 min, to obtain a printing-sintering piece.

[0226] d) The printing-sintering piece is subjected to performance characterization.

[0227] Comparative Example 18

[0228] The 10-45 μm zirconia spherical powder and the 1-4.5 μm zirconia spherical powder are subjected to mixing treatment, the volume ratio of the two is 1:2, to obtain a corresponding 1:2 ratio of graded spherical or spherical powder.

[0229] a) The graded powder is subjected to BJ printing, and it is found that due to the too high proportion of fine powder, the powder cannot be smoothly laid and printed.

[0230] Comparative Example 19

[0231] a) The 10-45 μm zirconia spherical powder (coarse powder) is subjected to BJ printing, and the green printing piece is subjected to heat curing treatment after printing, to obtain a printing piece.

[0232] b) The printing piece is subjected to debinding treatment, to obtain a printing-debinding piece.

[0233] c) The printing-debinding piece is subjected to sintering treatment, the maximum sintering temperature is 1500°C, and the holding time is 60 min, to obtain a printing-sintering piece.

[0234] d) The printing-sintering piece is subjected to performance characterization.

[0235] Comparative Example 20

[0236] a) BJ printing of zirconia spherical powder (coarse powder) with particle size of 10-45 μm, and then heat curing the green printed part to obtain a printed part.

[0237] b) performing debinding treatment on the printed part to obtain a printed-debinding part.

[0238] c) performing sintering treatment on the printed-debinding part, with the highest sintering temperature of 1500 ℃ and the holding time of 120 min, to obtain a printed-sintering part.

[0239] d) performing performance characterization on the printed-sintering part.

[0240] The sintering process and sintering density in the examples and comparative examples are compared, and the results are shown in Table 4.

[0241] The test results in Table 4 show that the optimal grading ratio of zirconia coarse powder (10-45 μm) and fine powder (1-4.5 μm) is 2.5:1, and the BJ printed part thereof obtains a density of more than 97% at a sintering temperature of 1500 ℃ only with a holding time of 60 min, while the BJ printed parts of other grading powders and pure coarse powders generally have lower sintering density, and even if the holding time is doubled at a sintering temperature of 1500 ℃, the density does not significantly increase, which fully verifies that the grading powder with a ratio of 2.5:1 can significantly improve the sintering efficiency and sintering density.

[0242] The experimental results in the above examples show that, in the case of using fine particle metal, alloy, ceramic powder with a particle size of 1-4.5 μm and coarse particle metal, alloy, ceramic powder with a particle size of 10-45 μm as raw materials, the sintering efficiency and density of the grading powder with a coarse-to-fine powder volume ratio in the range of 2.5:1-3.5:1 are better, and the grading powder with a ratio in the range of 1.5:1-3.5:1 is preferably used as the raw material for the BJ printing process of metal, alloy and ceramic.

[0243] Table 4 Related data and comparison data of experiments in examples 12-14 and comparative examples 16-20 of the present application

[0244]

[0245] The above cases are preferred embodiments of the present application, and any improvement and change made by any person skilled in the art within the claims of the present application is considered to be within the protection scope of the present application.

Claims

1. A graded powder for binder jet printing, characterized by: The coarse powder has a particle size of 10-45 μm and the fine powder has a particle size of ≤4.5 μm; the coarse powder and the fine powder have a volume ratio of 5:1 to 1:1; the coarse powder is a spherical particle and the fine powder is a spherical or spheroidal particle; the coarse powder is selected from at least one of a metal, a ceramic and a cermet composite material; the fine powder is selected from at least one of a metal, a ceramic and a cermet composite material; the melting point of the coarse powder is greater than or equal to the melting point of the fine powder.

2. The graded powder for binder jet printing according to claim 1, wherein: The coarse powder and the fine powder are made of the same material.

3. The graded powder for binder jet printing according to claim 1, wherein: The coarse powder and the fine powder have a volume ratio of 3.5:1 to 1.5:

1.

4. The graded powder for binder jet printing according to claim 1, wherein: The metal includes at least one of Fe-based, Al-based, Mg-based, Cu-based, Ti-based, Ni-based metal and alloy; or / and, the ceramic includes at least one of oxide ceramic, nitride ceramic, boride ceramic, carbide ceramic, silicate ceramic, phosphate ceramic, high-entropy ceramic and glass; the cermet composite material includes at least one of WC-based hard alloy and TiC-based hard alloy.

5. The graded powder for binder jet printing according to claim 4, wherein: The Fe-based metal includes at least one of 316L and 17-4PH stainless steel.

6. A binder jet printing method characterized by: The method comprises the following steps: S1, providing raw materials according to the graded powder of any one of claims 1-5, and mixing uniformly; S2, powder laying, printing, solidification, debinding and sintering the mixed raw materials.

7. The binder jet printing method of claim 6, wherein: The powder laying process is that the material strength is 50-80% and the powder laying speed is 5-30 mm / s; or / and, the printing process is that the powder layer thickness is 10-300 μm, the binder saturation is 10-90% and the powder bed temperature is room temperature-180 ℃; or / and, the solidification process is that the solidification temperature is 150-250 ℃ and the solidification time is 1-48 h.

8. The binder jet printing method of claim 6, wherein: The debinding process is that the heating rate range is 2 ℃ / min-8 ℃ / min, the highest debinding temperature is 300-800 ℃ and the holding time is 10-180 min; the sintering process is that the heating rate range is 2 ℃ / min-50 ℃ / min; when the coarse powder and the fine powder are made of different materials, the sintering temperature is higher than the melting point of the fine powder but 10-250 ℃ lower than the melting point of the coarse powder; when the coarse powder and the fine powder are made of the same material, the sintering temperature is 10-250 ℃ lower than the melting point of the powder; the holding time is 10-180 min and the sintering process is carried out in air, protective gas or vacuum.

9. The binder jet printing method of claim 8, wherein: The protective gas in the sintering process is at least one of argon, hydrogen and nitrogen, the pressure is 0.1-40.2 MPa and the flow rate is 0.5-1 L / min.

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