CN117282986B

CN117282986B - Printing method for regulating and controlling wear resistance of sole of robot through directional texture and workpiece

Info

Publication number: CN117282986B
Application number: CN202311405937.2A
Authority: CN
Inventors: 杨洋; 宋伟; 张宇; 聂大明; 孔令雨
Original assignee: Zhejiang Lab
Current assignee: Zhejiang Lab
Priority date: 2023-10-25
Filing date: 2023-10-25
Publication date: 2024-05-10
Anticipated expiration: 2043-10-25
Also published as: CN117282986A

Abstract

The application provides a printing method and a workpiece for regulating and controlling the wear resistance of the sole of a robot through directional texture. The printing method comprises the steps of constructing a three-dimensional model of a sample to be printed, and slicing the three-dimensional model to obtain contour boundaries of a plurality of slice layers; paving raw material powder in the contour boundary of a slice layer; scanning the raw material powder by a first energy beam to melt once, and solidifying to obtain a formed entity; scanning the forming entity by a second energy beam to carry out secondary melting, and obtaining a printed workpiece for preparing the sole of the robot after solidification; wherein the scanning interval of the second energy beam is smaller than the scanning interval of the first energy beam. The printing method provided by the application can improve the hardness of the printed workpiece and obviously improve the wear resistance and the service life of the printed workpiece.

Description

Printing method for regulating and controlling wear resistance of sole of robot through directional texture and workpiece

Technical Field

The application relates to the technical field of 3D printing, in particular to a printing method and a workpiece for regulating and controlling wear resistance of a sole of a robot through directional texture.

Background

3D printing is one of the rapid prototyping techniques, also known as additive manufacturing. It is a technology for constructing objects by using a bondable material such as powdered metal or plastic based on digital model files in a layer-by-layer printing manner. The powder bed fusion process is one of the most commonly used processes in additive manufacturing, and mainly utilizes the thermal energy of an energy beam to sinter raw material powders together to form a printed workpiece. The powder bed melting process has the greatest characteristic of being capable of forming any complex structure with high precision.

However, there is still a gap between the surface wear resistance of the printed workpiece and the actual industrial application requirements. For improving the wear resistance of the surface of the printed workpiece, the traditional post-treatment process still needs to be relied on. This means that more post-processing related technicians need to be invested in the production of the workpiece, greatly increasing the production cost and cycle time of printing the workpiece. In addition, many post-processing methods have low or no workability on structures such as irregular curved surfaces, inner holes and the like of complex workpieces due to the characteristics of the process, which also limits the design freedom of the printed workpieces, and greatly reduces the design and manufacturing flexibility of the printed workpieces. Therefore, how to improve the wear resistance of the printed workpiece in the printing process, so that the problem of insufficient wear resistance of the surface of the printed workpiece is solved, and the service life of the printed workpiece is prolonged.

Disclosure of Invention

The application provides a printing method and a workpiece for regulating and controlling the wear resistance of the sole of a robot through directional texture. The printing method can improve the wear resistance of the printing workpiece, and improve the working performance and the service life of the printing workpiece.

Specifically, the application is realized by the following technical scheme:

The application provides a printing method for regulating and controlling the wear resistance of the sole of a robot through directional texture, which comprises the following steps:

constructing a three-dimensional model of a sample to be printed, and slicing the three-dimensional model to obtain contour boundaries of a plurality of slice layers; paving raw material powder in the contour boundary of a slice layer;

Scanning the raw material powder by a first energy beam to melt once, and solidifying to obtain a formed entity; scanning the forming entity by a second energy beam to carry out secondary melting, and obtaining a printed workpiece for preparing the sole of the robot after solidification;

wherein the scanning interval of the second energy beam is smaller than the scanning interval of the first energy beam.

Optionally, the scan path of the second energy beam is parallel to the scan path of the first energy beam.

Optionally, the scan path of the second energy beam is perpendicular to the scan path of the first energy beam.

Optionally, the scanning interval of the second energy beam is 10-30 μm;

And/or the scanning interval of the first energy beam is 90-110 mu m.

Optionally, the primary melting and/or the secondary melting process is performed under inert atmosphere conditions.

Optionally, the power of the first energy beam and/or the second energy beam is 200-220 w; the scanning speed is 740-760 mm/s; the exposure time is 70-90 mu s, and the dot pitch is 50-70 mu m.

Optionally, the first energy beam and/or the second energy beam comprises any one of a laser beam, an electron beam, and a plasma beam.

Optionally, the raw material powder comprises the following elements in percentage by weight: 0-0.003% of C, 12.5-13% of Ni, 0-2.00% of Mn, 0-0.01% of S, 0-0.02% of P, 17.5-18% of Cr, 0-0.50% of Cu and 2.25-2.5% of Mo; the balance being Fe;

and/or the layer thickness of the raw material powder paved is 40-60 mu m.

The application also provides a workpiece which is printed by the printing method.

Optionally, the workpiece has a vickers hardness (HV 0.05) of 254-289; the wear resistance of the workpiece is 0.18-2.46 mm < 3 >/(N.m).

The technical scheme provided by the application can achieve the following beneficial effects:

The application provides a printing method and a workpiece for regulating and controlling wear resistance of a sole of a robot through directional texture. The printing method comprises the steps of scanning raw material powder by a first energy beam to melt once, and solidifying to obtain a formed entity; and secondly melting the formed entity through scanning of the second energy beam, and obtaining the printed workpiece for preparing the sole of the robot after solidification, wherein the scanning interval of the second energy beam is smaller than that of the first energy beam. Thus, a small pitch secondary scan by the second energy beam can change the grain orientation of the printed workpiece to form grains of a particular orientation. Under the action of external force, the crystal structure containing the crystal grains with specific orientation has smaller component force along the sliding direction, so that the atomic close-packed surface is more difficult to slide, namely, the external force which can be born by the material when the material slides is larger, thereby improving the capability of resisting plastic deformation of a printing workpiece, improving the hardness of the printing workpiece, and obviously improving the wear resistance and the service life of the printing workpiece.

Drawings

Fig. 1 is a method flowchart of a printing method according to an exemplary embodiment of the present application.

Fig. 2 is a schematic diagram of scanning paths of laser beams employed in example 1, example 5 and comparative example 1 of the present application.

Fig. 3 is a polar diagram of the printed workpiece processed in comparative example 1 and examples 1 to 8 to depict the spatial orientation of the texture.

Fig. 4 is a graph showing hardness test data of printed works processed in comparative example 1 and examples 1 to 8.

Fig. 5 is a graph showing wear rate test data of printed works processed in comparative example 1 and examples 1 to 8.

FIG. 6 is a graph of the scratch microscopic morphology of the printed workpiece processed according to comparative example 1, example 1 and example 5 of the present application.

Detailed Description

In order to further understand the present application, exemplary embodiments will be described in detail below, and it should be noted that the scope of the present application is not limited by the following embodiments. The technical features in the following examples and embodiments may be combined with each other without conflict.

As shown in fig. 1, the application provides a printing method for regulating and controlling wear resistance of a sole of a robot through directional texture, comprising the following steps:

S1, constructing a three-dimensional model of a sample to be printed, and slicing the three-dimensional model to obtain contour boundaries of a plurality of slice layers; paving raw material powder in the contour boundary of a slice layer;

S2, scanning the raw material powder by a first energy beam to melt once, and solidifying to obtain a formed entity; scanning the forming entity by a second energy beam to carry out secondary melting, and obtaining a printed workpiece for preparing the sole of the robot after solidification;

According to the application, the grain orientation of a printed workpiece can be changed by carrying out secondary scanning through the second energy beam, the growth direction of the grain depends on the preferential growth direction and the temperature gradient direction of the top end of the grain on the solid-liquid interface, the preferential growth of the grain is easy to occur in a bottom-up forming mode of the laser powder bed fusion technology (L-PBF), the scanning interval determines the positions of two adjacent laser centers, namely the angle of the temperature gradient, and when the scanning interval of the second energy beam is reduced, the difference between the preferential growth direction of the top end of the grain and the temperature gradient is reduced, so that the preferential growth of the grain is more favorable to form the grain with specific orientation, and the formation of textures is promoted. The crystal structure containing the crystal grains with the specific orientation is not easy to slide along the close-packed surface and the close-packed direction of atoms in the crystal under the action of external force, in other words, the crystal grains with the specific orientation can prevent the sliding movement of the internal atoms in the crystal structure to a certain extent, thereby improving the hardness of the printed workpiece and remarkably improving the wear resistance and the service life of the printed workpiece.

In the process of scanning, the energy beam is usually scanned in rows and columns, and the scanning interval refers to the distance between two adjacent rows or two adjacent columns. For example, as shown in fig. 2, the scanning paths of the first energy beam may be a first serpentine arrangement formed by sequentially connecting the first energy beam and the second energy beam may be a second serpentine arrangement formed by sequentially connecting the first energy beam and the second energy beam, and a distance between two adjacent paths in the second serpentine arrangement, that is, a scanning interval S2, is smaller than a distance between two adjacent paths in the first serpentine arrangement, that is, a scanning interval S1. In addition, in other embodiments, the printed workpiece prepared by the application is not limited to use in preparing the sole of a robot. For example: the method can also be used for preparing the parts such as the ankle and the palm of the robot, is not limited to the field of the robot, and can also be used for preparing any mechanical structure in any mechanical field.

The scanning pitch referred to above refers to "the distance between two adjacent scanning paths of the laser beam during scanning", which may also be referred to as the scanning line pitch.

In one embodiment, the forming apparatus may select an AM250 laser melting system (RENISHAW AM, 250). Specifically, the system comprises a laser and a powder spreading device, wherein the powder spreading device can spread raw material powder onto a substrate by a scraper, the laser emits laser and scans the raw material powder according to a preset track, and the raw material powder is melted and then condensed to obtain a printing workpiece. Of course, the type and model of the forming apparatus are not limited thereto.

In one embodiment, the scan path of the second energy beam is parallel to the scan path of the first energy beam. This promotes the dispersion of heat in the forming direction in the horizontal direction perpendicular to the scanning path of the first energy beam, and induces the preferential orientation <001> of the crystal grains to align in the forming direction and the horizontal direction, respectively, thereby promoting the formation of the plate texture.

In one embodiment, the scan path of the second energy beam is perpendicular to the scan path of the first energy beam. This promotes the dispersion of heat in the forming direction in the horizontal direction parallel to the scanning path of the first energy beam, and induces the alignment of the preferred orientation <001> of the crystal grains in the forming direction and the horizontal direction, respectively, thereby promoting the formation of the plate texture.

In one embodiment, the scanning interval of the second energy beam is 10-30 μm. In one embodiment, the scanning interval of the first energy beam is 90-110 μm. Therefore, heat accumulation in the raw material powder melting process caused by too small scanning interval can be avoided, holes caused by liquid metal splashing are avoided, and meanwhile, warping deformation of a printing workpiece caused by increased internal stress is also avoided; and the defect that the raw material powder is not completely melted due to overlarge scanning interval is avoided, so that microscopic defects such as breakage or holes and the like are easy to occur to a printed workpiece.

In one embodiment, the primary melting and/or the secondary melting process is performed under inert atmosphere conditions. Preferably, the inert atmosphere comprises at least one of argon and nitrogen. Therefore, the oxygen content in the environment can be reduced, oxidation in the forming process is prevented, the surface of the printed workpiece is smoother, the surface crack defect is reduced, and the tensile strength of the printed workpiece is improved.

In one embodiment, the power of the first energy beam and/or the second energy beam is 200-220 w; the scanning speed is 740-760 mm/s; the exposure time is 70-90 mu s, and the dot pitch is 50-70 mu m.

The application can ensure the void ratio in the printed workpiece to be in a lower range by limiting the power of the energy beam in the range so as to reduce the occurrence of microscopic defects such as fracture or holes. The phenomenon that a large number of air holes are left due to the fact that more gas is discharged when part of raw material powder is instantaneously melted and evaporated due to excessive power is avoided, so that the overall porosity is improved; meanwhile, the problem that the raw material powder cannot be melted in time due to too low power is avoided, the spheroidized raw material powder cannot be spread in time, larger pores exist among the raw material powder, and the overall porosity is still improved. In addition, the scanning speed is limited in the range, so that the problem that partial raw material powder cannot be completely melted due to the fact that larger pores exist between solid phases of unmelted raw material powder due to the fact that the scanning speed is too high is avoided, and meanwhile, the problem that the printing efficiency is affected due to the fact that the scanning speed is too low is also avoided.

Exposure time refers to the time that the energy beam stays at each point; by limiting the exposure time to the above range, it is possible to avoid the exposure time from being too long, easily causing evaporation of the liquid metal, and increasing the printing time; and the exposure time is too short, so that the raw material powder is not thoroughly melted, and microscopic defects such as fracture or holes and the like of a printed workpiece are easily caused. The point distance refers to the distance between the centers of two adjacent light spots; by limiting the dot distance to the above range, the defect that the adjacent two light spots are not overlapped due to the overlarge dot distance, so that raw material powder is not completely melted and microscopic defects such as fracture or holes and the like of a printed workpiece are easy to occur can be avoided; too small a spot pitch is avoided to reduce the scanning efficiency of the laser.

In one embodiment, the first energy beam and/or the second energy beam comprises any one of a laser beam, an electron beam, and a plasma beam.

In one embodiment, the raw material powder comprises the following elements in weight percent: 0-0.003% of C, 12.5-13% of Ni, 0-2.00% of Mn, 0-0.01% of S, 0-0.02% of P, 17.5-18% of Cr, 0-0.50% of Cu, 2.25-2.5% of Mo and the balance of Fe. Thereby facilitating printing out the alloy workpiece of 316L stainless steel.

The alloy workpiece has an austenitic structure at room temperature, including a face-centered cubic FCC crystal structure, the unit cells of which are cubic, and metal atoms distributed in the centers of the eight corners and six faces of the cubic unit cell. Under the action of external force, the sliding surface of metal atoms, namely the atomic close-packed surface, slides along the atomic close-packed direction in the crystal, so that macroscopic plastic deformation occurs.

In one embodiment, the layer thickness of the raw material powder is 40-60 μm. Therefore, the former layer of melted raw material powder can be soaked in the latter layer of raw material powder when the latter layer of raw material powder is melted, and the interlayer bonding strength between two adjacent layers is improved. The quality of a printed workpiece is prevented from being influenced by the fact that an energy beam cannot penetrate through raw material powder due to overlarge layer thickness.

In one embodiment, the workpiece has a Vickers hardness (HV 0.05) of 254-289; the wear resistance of the workpiece is 0.18-2.46 mm < 3 >/(N.m).

The raw material powders used in the following examples 1 to 8 and comparative example 1 comprise the following elements in percentage by weight: 0.001% of C, 12.78% of Ni, 1.54% of Mn, 0.01% of S, 0.01% of P, 17.64% of Cr, 0.16% of Cu, 2.39% of Mo and the balance of Fe.

Example 1

S1, constructing a three-dimensional model of a sample to be printed by using a computer, slicing the three-dimensional model by using layering slicing software to obtain contour boundary data of a plurality of slicing layers, and transmitting the contour boundary data of each slicing layer to a controller of a RENISHAW AM system; and loading the raw material powder prepared according to the weight percentage into a powder spreading device of RENISHAW AM-250 system, and spreading the raw material powder in the contour boundary of a certain slice layer by controlling a powder feeding mechanism through a controller.

S2, scanning the raw material powder by laser under the argon atmosphere to perform primary melting (the scanning path of the laser in the primary melting is shown in the S1 path in the Pa-30 of figure 2 in detail), and solidifying to obtain a formed entity; wherein the power of the laser is 200W, the distance between two adjacent scanning paths, namely the scanning distance, is 110 mu m, the scanning speed is 750 mm/s, the layer thickness is 50 mu m, the exposure time is 80 mu s, and the point distance is 60 mu m;

Scanning the forming entity by the same laser under argon atmosphere to perform secondary melting (the scanning path of the laser in the secondary melting is shown in the S2 path in the Pa-30 in the detail of fig. 2), and obtaining a printed workpiece after solidification; wherein the distance between two adjacent scanning paths of the laser in the secondary melting process, namely the scanning distance, is 30 mu m; the scanning path of the laser during the secondary melting is parallel to the scanning path of the laser during the primary melting.

And S3, printing all the slice layers layer by layer until a 316L stainless steel printing workpiece is obtained. The printed workpiece processed in this example is abbreviated as "Pa-30".

Example 2

The difference from example 1 is that: the scan pitch of the secondary melting process was 20 μm, and other preparation methods and preparation conditions were the same as in example 1. The printed workpiece processed in this example is abbreviated as "Pa-20".

Example 3

The difference from example 1 is that: the scan pitch of the secondary melting process was 15 μm, and other preparation methods and preparation conditions were the same as in example 1. The printed workpiece processed in this example is abbreviated as "Pa-15".

Example 4

The difference from example 1 is that: the scan pitch of the secondary melting process was 10 μm, and other preparation methods and preparation conditions were the same as in example 1. The printed workpiece processed in this example is abbreviated as "Pa-10".

Example 5

The difference from example 1 is that: the scanning path of the laser light during the secondary melting is perpendicular to the scanning path of the laser light during the primary melting (the scanning path of the laser light during the secondary melting is shown in detail as the S2 path in fig. 2 (Pe-30)), and other production methods and production conditions are the same as in example 1. The printed workpiece processed in this example is abbreviated as "Pe-30".

Example 6

The difference from example 5 is that: the scan pitch of the secondary melting process was 20 μm, and other preparation methods and preparation conditions were the same as in example 5. The printed workpiece processed in this example is abbreviated as "Pe-20".

Example 7

The difference from example 5 is that: the scan pitch of the secondary melting process was 15 μm, and other preparation methods and preparation conditions were the same as in example 5. The printed workpiece processed in this example is abbreviated as "Pe-15".

Example 8

The difference from example 5 is that: the scan pitch of the secondary melting process was 10 μm, and other preparation methods and preparation conditions were the same as in example 5. The printed workpiece processed in this example is abbreviated as "Pe-10".

Note that: the pole diagrams of the 316L stainless steel printed workpiece samples obtained by printing in examples 1-8 are shown in FIG. 3.

Comparative example 1

S1, constructing a three-dimensional model of a sample to be printed, slicing the three-dimensional model to obtain contour boundary data of a plurality of slice layers, and transmitting the contour boundary data of each slice layer to a RENISHAW AM system controller; and the raw material powder prepared according to the weight percentage is loaded into a RENISHAW AM and 250 system, and the controller controls RENISHAW AM and 250 system to lay the raw material powder in the contour boundary of a slice layer.

And S2, melting the paved raw material powder once by utilizing laser scanning in an argon atmosphere (the scanning path of the laser is shown in the S1 path in the (R) of fig. 2 in detail), and solidifying to obtain the 316L stainless steel printing workpiece. Wherein the power of the laser is 200W, the distance between two adjacent scanning paths, namely the scanning interval, is 110 mu m, the scanning speed is 750 mm/s, the layer thickness is 50 mu m, the exposure time is 80 mu s, and the point distance is 60 mu m. The 316L stainless steel printed workpiece processed by the comparative example is called R for short.

Note that: comparative example 1a pole figure of a sample "R" of a 316L stainless steel printed workpiece is shown in fig. 3.

Test case

And carrying out abrasion resistance test on the 316L stainless steel printed workpiece samples obtained by printing in examples 1-8 and comparative example 1 by adopting a nanometer automatic scratch tester. The diamond indenter used in this test had a radius of 200 μm, a test load of 1N, a scratch length of 5 mm, and a sliding speed of 10 mm/min.

The scratch morphology of the sample (scratch morphology graph is shown in fig. 6) is measured by using a confocal microscope, the abrasion rate of the sample is calculated from the total amount of the sample and the measured abraded sample (shown in fig. 5), and the vickers hardness of the sample is calculated from the test load and the surface area of the scratch (shown in fig. 4). Wherein, before and after the abrasion resistance experiment, an ultrasonic cleaner is used for ultrasonic cleaning of the sample.

Referring to the pole figures of the individual samples shown in fig. 3, the comparison of pole figure (a) with the standard pole figure reveals that the grain-oriented texture type of the printed workpiece "R" is <001> silk texture. The comparison result with the standard polar diagram shows that the grain orientation texture type of the printed workpiece Pa-30-Pa-10 is {001} <110>. The comparison result of the polar diagram (f-i) and the standard polar diagram shows that the grain orientation texture type of the printed workpiece 'Pe-30-Pe-10' is {110} <001>.

According to the application, after laser and a secondary small-space scanning strategy are adopted for secondary melting, the grain orientation of the crystal structure of the printed workpiece can be changed, and grains with specific orientation can be formed. The crystal structure containing the crystal grains with the specific orientation is not easy to slide along the close-packed surface and the close-packed direction of atoms in the crystal under the action of external force, in other words, the crystal grains with the specific orientation can block the sliding movement of the internal atoms in the crystal structure to a certain extent, so that the hardness (shown in fig. 4) of a printed workpiece is improved, and the wear resistance and the service life of the printed workpiece are remarkably improved.

As shown in FIG. 5, the abrasion rate of the 316L stainless steel printing workpiece R formed by solidification after only one time of melting by laser is 5.5X10-2 mm 3/(N.m), the abrasion rate of the 316L stainless steel printing workpiece Pa-10 formed by solidification after two times of melting by laser and adopting a parallel secondary small-space scanning strategy can be as low as 1.7X10-2 mm 3/(N.m), the abrasion rate is reduced by 67.8%, and the abrasion rate of the 316L stainless steel printing workpiece Pe-10 formed by solidification after two times of melting by laser and adopting an orthogonal secondary small-space scanning strategy can be as low as 0.18X10-2 mm 3/(N.m), and the abrasion rate is reduced by 96.7%. Therefore, the printed workpiece obtained by laser and adopting a secondary small-space scanning strategy for secondary melting has stronger plastic deformation resistance and greatly improved wear resistance.

As shown in fig. 6. The 316L stainless steel printing workpiece R processed in the comparative example 1 has a large number of sliding bands and cracks, which indicates that the printing workpiece R is easy to slide along the close-packed direction under the action of a certain external force, namely the crystal grain orientation of the crystal structure of the printing workpiece R is in a soft orientation, so that the hardness of the printing workpiece R is lower, and plastic deformation is easy to occur. The application passes laser and adopts a secondary small-space scanning strategy to carry out secondary melting to obtain the printed workpieces such as Pa-10 and Pe-10, wherein scratches of the printed workpieces show ploughed shapes, the interior of the printed workpieces is not damaged, and cracks are not generated. The crystal structure of the printing workpiece obtained by the application has strong capability of resisting sliding of materials under the action of a certain external force, namely, the grain orientation is presented as a hard orientation, so that the capability of resisting deformation of the printing workpiece is enhanced, and the wear resistance of the printing workpiece is improved.

The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather to enable any modification, equivalent replacement, improvement or the like to be made within the spirit and principles of the application.

Claims

1. A printing method for regulating wear resistance of a sole of a robot through directional texture, comprising the steps of:

Wherein the scanning interval of the second energy beam is smaller than the scanning interval of the first energy beam, and the scanning path of the second energy beam is perpendicular to the scanning path of the first energy beam; the scanning interval of the first energy beam is 90-110 mu m, and the scanning interval of the second energy beam is 10-30 mu m.

2. The printing method according to claim 1, wherein the primary melting and/or the secondary melting process is performed under an inert atmosphere.

3. The printing method according to claim 1, wherein the power of the first energy beam and/or the second energy beam is 200-220 w; the scanning speed is 740-760 mm/s; the exposure time is 70-90 mu s; the dot pitch is 50-70 μm.

4. The printing method according to claim 1, wherein the first energy beam and/or the second energy beam includes any one of a laser beam, an electron beam, and a plasma beam.

5. The printing method according to claim 1, wherein the raw material powder comprises the following elements in weight percent: 0-0.003% of C, 12.5-13% of Ni, 0-2.00% of Mn, 0-0.01% of S, 0-0.02% of P, 17.5-18% of Cr, 0-0.50% of Cu, 2.25-2.5% of Mo and the balance of Fe;

and/or the layer thickness of the raw material powder paved is 40-60 mu m.

6. A workpiece printed by the printing method according to any one of claims 1 to 5.

7. The workpiece according to claim 6, characterized in that the workpiece has a vickers hardness (HV _0.05) of 254-289; the wear resistance of the workpiece is 0.18-2.46 mm ³/(N.m).