Computed tomography (CT) detection reference block for powder bed molten part and manufacturing method of CT detection reference block

Abstract

The invention discloses a powder bed molten part CT (Computed Tomography) detection reference block and a manufacturing method thereof. The reference block comprises a reference block matrix and a defect unit, the test block base body is of a stepped shaft structure formed by two cylinders with different diameters and is used for a contrast test of CT detection on the thickness sensitivity of a powder bed molten part; and the defect unit consists of a plurality of flat-bottomed holes with different diameters, spherical defects and columnar defects which are formed in the test block base body, and is used for verifying the defect detection capability of CT detection on the powder bed molten part. After the reference block and the manufacturing method disclosed by the invention are adopted, recognizable defect unit details can be analyzed by using a CT image of the reference block, so that the influence of unmelted metal powder in the defect of a powder bed melted workpiece on CT detection sensitivity and defect recognition is determined; the reliability of the CT detection result of the powder bed molten part is improved; and defect evaluation is assisted.

Description

Technical Field

[0001] The invention belongs to the technical field of nondestructive testing of aircraft structural materials, and in particular relates to a powder bed fusion product CT testing comparison test block and a manufacturing method thereof. Background Art

[0002] The powder bed fusion additive manufacturing process forms metal parts by material accumulation. Due to the influence of factors such as raw materials, process parameters and forming chamber environment during the forming process, metallurgical defects such as micropores or unfused parts exist in the powder bed fusion parts. The pores or unfused defects between the cladding layers or cladding paths of the powder bed fusion parts often contain unmelted metal powder inside the unfused pores. This defect form of unmelted metal powder inside poses a great challenge to the defect detection and quantitative evaluation of powder bed fusion parts.

[0003] Existing X-ray and industrial CT detection technologies can effectively detect internal defects of traditional castings, forgings and welds, but it is usually difficult to accurately and reliably identify and evaluate defects when detecting unfused pores in powder bed fusion parts, especially in the layered or sharp-angled areas inside the unfused pores, and in the case of unmelted metal powder, it is often difficult to accurately determine the actual shape and size of the defects. In the application of non-destructive testing of additively manufactured structural materials, it is urgent to develop a comparison test block suitable for CT testing of powder bed fusion parts by combining specific defect characteristics and CT detection principles, which is used to verify the defect detection capabilities of CT detection devices and detection process parameters for powder bed fusion parts, improve the reliability of CT detection results of powder bed fusion parts, and assist in defect assessment. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a powder bed fusion product CT inspection comparison test block in view of the deficiencies of the above-mentioned prior art.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] A powder bed fusion product CT inspection comparison test block, the comparison test block comprising a test block matrix and a defect unit;

[0007] The test block base is a stepped shaft structure composed of two cylinders of different diameters, and is used for comparative testing of the thickness sensitivity of CT detection to powder bed fusion products;

[0008] The defect unit is composed of a number of flat-bottom holes, spherical defects and columnar defects of different diameters arranged on the test block substrate, and is used to verify the defect detection capability of CT detection for powder bed fusion products, improve the reliability of detection results and assist in defect assessment.

[0009] Preferably, the test block matrix comprises two test block matrix units, namely a first test block matrix unit and a second test block matrix unit; the two test block matrix units are cylinders with the same height and different diameters, and the cylinders of the two test block matrix units are coaxial and form a stepped shaft structure;

[0010] The cylindrical diameter of the first test block base unit is the same as the minimum thickness of the powder bed fusion product detected by CT, and the cylindrical diameter of the second test block base unit is the same as the maximum thickness of the powder bed fusion product detected by CT.

[0011] Preferably, the two test block base units are provided with the same number of defect units; the defect units are provided with flat-bottom holes, spherical defects and columnar defects with the same diameter, and the centers of the spherical defects with the same diameter are on the axes of the flat-bottom holes, and the axes of the flat-bottom holes and columnar defects are parallel to the axes of the test block base unit.

[0012] Preferably, the flat-bottom hole is a cylindrical hollow structure and is arranged in a vertical manner, one end of the flat-bottom hole is located on the upper surface of the test block base unit and the end is open to the outside, and the other end is a sealed end and is located inside the test block base unit;

[0013] The spherical defect is a spherical hole structure containing unmelted metal powder, and is arranged inside the test block matrix unit;

[0014] The columnar defect is a cylindrical hole structure containing unmelted metal powder inside, and is vertically arranged inside the test block base unit;

[0015] The flat-bottomed holes, spherical defects and columnar defects are arranged on the test block base unit at equal axial intervals and are located at the upper part, the middle part and the lower part thereof respectively.

[0016] Preferably, the flat-bottomed holes are provided in plurality, and the diameters of any two flat-bottomed holes on the same test block base unit are different, the plurality of flat-bottomed holes are arranged at equal circumferential intervals on the upper part of the test block base unit, and the distances from each flat-bottomed hole to the axis of the test block base unit are equal;

[0017] There are multiple spherical defects and the number is equal to that of the flat-bottom holes. The diameters of any two spherical defects on the same test block base unit are different and correspond one-to-one to the diameters of the flat-bottom holes. The distribution position of the spherical defects in the middle of the test block base unit is the same as that of the flat-bottom holes.

[0018] There are multiple columnar defects, and the diameter of each columnar defect on the same test block base unit is the same, the density inside each columnar defect is different, and the melting state of the metal powder inside the columnar defect decreases from completely melted to completely unmelted in sequence, and the distribution position of the columnar defects in the lower part of the test block base unit is the same as that of the flat-bottomed holes.

[0019] The present invention also discloses a method for manufacturing a powder bed fusion product CT inspection comparison test block, which is used to manufacture the comparison test block. The method comprises:

[0020] S1, test block design, according to the requirements of CT inspection of powder bed fusion products, the size of the test block matrix, the position and size of the defect unit on the test block matrix are designed, and a digital model is established to complete the test block design;

[0021] S2, test block forming, according to the digital model established in the test block design in S1, powder bed fusion forming of spherical defects and columnar defects in the test block matrix and defect units is performed, wherein the raw materials and process parameters for forming the test block matrix are the same as those for the product, the spherical defects are hollow spherical holes preset in the digital model, and the energy density at the spherical holes is set to zero during forming to obtain a spherical hole structure containing unmelted metal powder inside, and the energy density at each cylindrical hole in the columnar defect forming is set to 75%, 50%, 25% to 0% of the product forming energy density to obtain a cylindrical hole structure containing metal powder of different densities or in a molten state inside, and then the test block matrix blank is obtained through post-processing;

[0022] S3, test block screening, using X-ray or CT method to detect the test block base blank, determine the location and size of spherical defects and columnar defects in the defect unit, and screen out the test block base blank that meets the design requirements based on the X-ray or CT test results;

[0023] S4, test block processing, machining the test block base blank selected from the test block in S3 into a stepped shaft structure of a first test block base unit and a second test block base unit, and then machining a flat bottom hole in the defective unit, and then performing surface treatment to obtain a comparative test block;

[0024] S5, test block evaluation, uses X-ray, ultrasound or CT methods to test, evaluate and compare the comparison test blocks obtained from the test blocks in S4, and evaluate whether the shape, size and surface quality of the test block matrix, as well as the position and size of the defective unit meet the test block design requirements. If they meet the requirements, they will be accepted and marked, otherwise they will be remade.

[0025] The present invention has the following beneficial effects:

[0026] After adopting a powder bed fusion product CT detection comparison test block and a manufacturing method of the present invention, the comparison test block provided by the present invention can effectively simulate the pores and unfused defects of the powder bed fusion product. The CT images of the comparison test block matrix units with different diameters can be used for comparative tests on the thickness sensitivity of CT detection to the powder bed fusion product, verifying the defect detection capability of the CT detection process for specific sizes of internal details of the powder bed fusion product under different wall thicknesses, and at the same time verifying the defect detection capability of the CT detection process for different sizes of internal details of the powder bed fusion product under the same wall thickness.

[0027] By using the comparison test block of the present invention, by comparing the CT images of different types of defect units and analyzing the details of identifiable flat-bottom holes, spherical defects and columnar defects, it can be used to determine the influence of completely unmelted or partially unmelted metal powder inside the porosity and unfusion defects of powder bed fusion parts on CT detection sensitivity and defect identification, which helps to improve the reliability of CT detection results of powder bed fusion parts and assists in defect assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structural composition of a powder bed fusion product CT inspection comparison test block of the present invention.

[0029] Figure 2 It is a schematic circumferential cross-sectional view of a test block base unit of a powder bed fusion product CT inspection comparison test block of the present invention.

[0030] Figure 3 It is a schematic axial cross-sectional view of a test block matrix unit of a powder bed fusion product CT inspection comparison test block of the present invention.

[0031] In the figure: 1. test block matrix; 11. first test block matrix unit; 12. second test block matrix unit; 2. defect unit; 21. flat bottom hole; 21-1. first flat bottom hole; 21-2. second flat bottom hole; 21-3. third flat bottom hole; 21-4. fourth flat bottom hole; 22. spherical defect; 22-1. first spherical defect; 22-2. second spherical defect; 22-3. third spherical defect; 22-4. fourth spherical defect; 23. columnar defect; 23-1. first columnar defect; 23-2. second columnar defect; 23-3. third columnar defect; 23-4. fourth columnar defect. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0033] See also Figure 1-Figure 3 , a powder bed fusion product CT inspection comparison test block, the comparison test block comprising a test block matrix 1 and a defect unit 2;

[0034] The test block substrate 1 is a stepped shaft structure composed of two cylinders of different diameters, and is used for comparative testing of the thickness sensitivity of CT detection to powder bed fusion products;

[0035] The defect unit 2 is composed of a plurality of flat-bottom holes 21, spherical defects 22 and columnar defects 23 of different diameters arranged on the test block substrate 1, and is used to verify the defect detection capability of CT detection for powder bed fusion products, improve the reliability of detection results and assist in defect assessment.

[0036] In a specific implementation, the test block matrix 1 includes two test block matrix units, namely a first test block matrix unit 11 and a second test block matrix unit 12; the two test block matrix units are cylinders with the same height (30 mm can be selected in actual manufacturing) and different diameters, and the cylinders of the two test block matrix units are coaxial and form a stepped shaft structure;

[0037] The cylindrical diameter of the first test block base unit 11 (30 mm can be selected during actual manufacturing) is the same as the minimum thickness of the powder bed fusion product detected by CT, and the cylindrical diameter of the second test block base unit 12 (90 mm can be selected during actual manufacturing) is the same as the maximum thickness of the powder bed fusion product detected by CT.

[0038] In a specific implementation, the two test block base units are provided with the same number of defect units 2; the defect unit 2 is provided with a flat-bottom hole 21, a spherical defect 22 and a columnar defect 23 with the same diameter, and the center of the spherical defect 22 with the same diameter is on the axis of the flat-bottom hole 21, and the axis of the flat-bottom hole 21 and the columnar defect 23 is parallel to the axis of the test block base unit 11.

[0039] In a specific implementation, the flat-bottom hole 21 is a cylindrical hollow structure and is arranged in a vertical manner. One end of the flat-bottom hole 21 is located on the upper surface of the test block base unit (such as the first test block base unit 11), and the end is open to the outside, and the other end is a sealed end, which is located inside the test block base unit;

[0040] The spherical defect 22 is a spherical hole structure containing unmelted metal powder inside, and is arranged inside the test block matrix unit (such as the first test block matrix unit 11);

[0041] The columnar defect 23 is a cylindrical hole structure containing unmelted metal powder inside, and is vertically arranged inside the test block matrix unit (such as the first test block matrix unit 11);

[0042] The flat-bottomed holes 21, spherical defects 22 and columnar defects 23 are arranged at equal axial intervals on the test block base unit (such as the first test block base unit 11), and are located at the upper part, the middle part and the lower part thereof respectively.

[0043] In a specific implementation, a plurality of flat-bottom holes 21 are provided, and the diameters of any two flat-bottom holes 21 on the same test block base unit are different. The plurality of flat-bottom holes 21 are arranged at equal circumferential intervals on the upper part of the test block base unit, and the distance from each flat-bottom hole to the axis of the test block base unit is equal.

[0044] See also Figure 2 In a specific implementation, the flat-bottom hole 21 is composed of a first flat-bottom hole 21-1 (the diameter can be selected as 0.3mm in specific implementation), a second flat-bottom hole 21-2 (the diameter can be selected as 0.5mm in specific implementation), a third flat-bottom hole 21-3 (the diameter can be selected as 0.7mm in specific implementation) and a fourth flat-bottom hole 21-4 (the diameter can be selected as 0.9mm in specific implementation). The first flat-bottom hole 21-1, the second flat-bottom hole 21-2, the third flat-bottom hole 21-3 and the fourth flat-bottom hole 21-4 are arranged at equal circumferential intervals on the circular section A-A' parallel to the bottom surface of the upper part of the first test block base unit 11, and the distances from the first flat-bottom hole 21-1, the second flat-bottom hole 21-2, the third flat-bottom hole 21-3 and the fourth flat-bottom hole 21-4 to the axis of the first test block base unit 11 are all one-third of the diameter of the first test block base unit 11 (the distance can be selected as 10mm in actual implementation).

[0045] There are multiple spherical defects 22 and the number is equal to the flat-bottom holes. The diameters of any two spherical defects 22 on the same test block base unit are different and correspond one-to-one to the diameters of the flat-bottom holes 21. The distribution position of the spherical defects 22 in the middle of the test block base unit is the same as that of the flat-bottom holes 21.

[0046] See also Figure 2In a specific implementation, the spherical defect 22 is composed of a first spherical defect 22-1 (the diameter can be 0.3 mm in actual implementation), a second spherical defect 22-2 (the diameter can be 0.5 mm in actual implementation), a third spherical defect 22-3 (the diameter can be 0.7 mm in actual implementation) and a fourth spherical defect 22-4 (the diameter can be 0.9 mm in actual implementation). The first spherical defect 22-1, the second spherical defect 22-2, the third spherical defect 22-3 and the fourth spherical defect 22-4 are connected with the first flat-bottom hole 21-1, the second flat-bottom hole 21-2 and the third flat-bottom hole 21- 3 and the fourth flat-bottomed holes 21-4 are equal in number and diameter, the first spherical defect 22-1, the second spherical defect 22-2, the third spherical defect 22-3, and the fourth spherical defect 22-4 are arranged at equal circumferential intervals on the circular section BB' parallel to the bottom surface in the middle of the first test block matrix unit 11, and the distances from the first spherical defect 22-1, the second spherical defect 22-2, the third spherical defect 22-3, and the fourth spherical defect 22-4 to the axis of the first test block matrix unit 11 are all one-third of the diameter of the first test block matrix unit 11 (the optional distance is 10 mm in actual implementation).

[0047] In a specific implementation, the center of the first spherical defect 22-1 is on the axis of the first flat-bottom hole 21-1, the center of the second spherical defect 22-2 is on the axis of the second flat-bottom hole 21-2, the center of the third spherical defect 22-3 is on the axis of the third flat-bottom hole 21-3, and the center of the fourth spherical defect 22-4 is on the axis of the fourth flat-bottom hole 21-4.

[0048] There are multiple columnar defects 23, and the diameter of each columnar defect on the same test block base unit is the same, the density inside each columnar defect is different, and the melting state of the metal powder inside the columnar defect decreases from completely melted to completely unmelted. The distribution position of the columnar defects 23 at the lower part of the test block base unit is the same as that of the flat-bottomed hole 21.

[0049] See also Figure 2In a specific implementation, the columnar defect 23 is composed of a first columnar defect 23-1 (a diameter of 0.9 mm can be selected in actual implementation), a second columnar defect 23-2 (a diameter of 0.9 mm can be selected in actual implementation), a third columnar defect 23-3 (a diameter of 0.9 mm can be selected in actual implementation) and a fourth columnar defect 23-4 (a diameter of 0.9 mm can be selected in actual implementation); the density inside the first columnar defect 23-1, the second columnar defect 23-2, the third columnar defect 23-3 and the fourth columnar defect 23-4 decreases in sequence, and the metal powder inside the first columnar defect 23-1 is in a completely unmelted state, the metal powder inside the second columnar defect 23-2 is in a 75% unmelted state, and the metal powder inside the third columnar defect 23-3 is in a 75% unmelted state. The metal powder in the fourth columnar defect 23-4 is in a 50% unmelted state, and the metal powder in the fourth columnar defect 23-4 is in a 25% unmelted state, which is in contrast to the completely melted state of the metal powder after the first test block matrix unit 11 is formed; the first columnar defect 23-1, the second columnar defect 23-2, the third columnar defect 23-3 and the fourth columnar defect 23-4 are arranged at equal circumferential intervals on the circular section C-C' parallel to the bottom surface at the lower part of the first test block matrix unit 11, and the distances from the first columnar defect 23-1, the second columnar defect 23-2, the third columnar defect 23-3 and the fourth columnar defect 23-4 to the axis of the first test block matrix unit 11 are all one-third of the diameter of the first test block matrix unit 11 (the optional distance is 10 mm in actual implementation).

[0050] See also Figure 3 In a specific implementation, the axes of the flat-bottomed hole 21 and the columnar defect 23 are parallel to the axis of the first test block base unit 11. For example, the axis of the first flat-bottomed hole 21-1, the center of the first spherical defect 22-1, and the axis of the first columnar defect 23-1 are on the same straight line and are parallel to the axis of the first test block base unit 11.

[0051] The present invention also discloses a method for manufacturing a powder bed fusion product CT inspection comparison test block, which is used to manufacture the comparison test block. The method comprises:

[0052] S1, test block design, the size of the test block matrix 1 designed according to the CT inspection requirements of the powder bed fusion product (including dimensional tolerance and surface roughness, in actual manufacturing, the size can be selected as the height of the first test block matrix unit 11 is 30.05mm, the diameter is 30.05mm; the height of the second test block matrix unit 12 is 30.05mm, the diameter is 90.05mm, and the surface roughness Ra≤3.2 microns), the position and size of the defect unit 2 on the test block matrix 1, that is, the position and size of the flat-bottomed hole 21, the spherical defect 22 and the columnar defect 23 in the first test block matrix unit 11 and the second test block matrix unit 12 (in actual manufacturing, it can be selected to set a height of 5. 0mm, the first flat-bottom hole 21-1 has a diameter of 0.3mm; the second flat-bottom hole 21-2 has a diameter of 0.5mm; the third flat-bottom hole 21-3 has a diameter of 0.7mm; the fourth flat-bottom hole 21-4 has a diameter of 0.9mm; and they are respectively located on the upper part of the first test block matrix unit 11; at the same time, the positions and sizes of the first spherical defect 22-1, the second spherical defect 22-2, the third spherical defect 22-3 and the fourth spherical defect 22-4 and the first columnar defect 23-1, the second columnar defect 23-2, the third columnar defect 23-3 and the fourth columnar defect 23-4 are as described above), based on the design parameters of the test block matrix 1 and the defect unit 2 designed as above, a digital model is established to complete the test block design;

[0053] S2, test block forming, according to the digital model established in the test block design in S1, the test block matrix 1 (the material can be titanium alloy, aluminum alloy, nickel-based alloy, cobalt-chromium alloy or stainless steel and other metal materials) and the spherical defects 22 and columnar defects 23 in the defect unit 2 are formed by powder bed fusion, wherein the raw materials and process parameters for forming the test block matrix 1 are the same as those of the inspected workpiece of the powder bed fusion product, the spherical defect 22 is a hollow spherical hole preset in the digital model, and the energy density at the spherical hole is set to zero during the forming to obtain a spherical hole structure containing unmelted metal powder inside, and the columnar defect 23 is formed by the first The cylindrical holes of the first columnar defect 23-1, the second columnar defect 23-2, the third columnar defect 23-3 and the fourth columnar defect 23-4 are set to 75%, 50%, 25% to 0% of the workpiece forming energy density, and a cylindrical hole structure containing metal powders of different densities or molten states is obtained (the completely unmelted or partially unmelted metal powders inside the spherical defect 22 and the columnar defect 23 in the formed test block matrix 1 are of a single same material), and the formed test block matrix 1 is separated from the printed substrate after appropriate heat treatment, and then the test block matrix blank is obtained through post-processing;

[0054] S3, test block screening, using X-ray or CT method to detect the test block base blank, determine the position and size of the spherical defect 22 and the columnar defect 23 in the defect unit 2, and screen the test block base blank that meets the design requirements based on the X-ray or CT detection results;

[0055] S4, test block processing, machining the test block base blank selected from the test block in S3 into a stepped shaft structure of the first test block base unit 11 and the second test block base unit 12, and then machining the flat bottom hole 21 in the defective unit, and then performing surface treatment to obtain a comparative test block;

[0056] S5, test block evaluation, uses X-ray, ultrasound or CT methods to test, evaluate and compare the comparison test blocks obtained from the test blocks in S4, and evaluate whether the shape, size and surface quality of the test block matrix, as well as the position and size of the defective unit meet the test block design requirements. If they meet the requirements, they will be accepted and marked, otherwise they will be remade.

[0057] The operation process is as follows:

[0058] The comparison test block is subjected to industrial computer tomography (CT) detection. By recording and analyzing the CT image grayscale values ​​of the first test block matrix unit 11 and the second test block matrix unit 12 of different diameters, it can be used for comparative testing of the sensitivity of CT detection devices and detection process parameters to the thickness of powder bed fusion products.

[0059] By comparing the CT images of the flat-bottom holes 21 of the same size on the first test block matrix unit 11 and the second test block matrix unit 12 of different diameters, the details of the identifiable flat-bottom holes 21 are analyzed, which can be used to verify the CT detection sensitivity of the CT detection process for flat-bottom holes 21 of specific sizes of powder bed fusion products under different wall thicknesses; by comparing the CT images of flat-bottom holes 21 of different sizes (including the first flat-bottom hole 21-1, the second flat-bottom hole 21-2, the third flat-bottom hole 21-3 and the fourth flat-bottom hole 21-4) on the first test block matrix unit 11 of the same diameter, the details of the identifiable flat-bottom holes 21 are analyzed, which can be used to verify the CT detection sensitivity of the CT detection process for flat-bottom holes 21 of different sizes of powder bed fusion products under the same wall thickness.

[0060] By comparing the CT images of spherical defects 22 of the same size on the first test block matrix unit 11 and the second test block matrix unit 12 of different diameters, the details of the identifiable spherical defects 22 are analyzed, which can be used to verify the defect detection capability of the CT inspection process for spherical defects 22 of specific sizes of powder bed fusion products under different wall thicknesses; by comparing the CT images of spherical defects 22 of different sizes (including the first spherical defect 22-1, the second spherical defect 22-2, the third spherical defect 22-3 and the fourth spherical defect 22-4) on the first test block matrix unit 11 of the same diameter, the details of the identifiable spherical defects 22 are analyzed, which can be used to verify the defect detection capability of the CT inspection process for spherical defects 22 of different sizes of powder bed fusion products under the same wall thickness.

[0061] By comparing the CT images of columnar defects 23 of the same density or melting state on the first test block matrix unit 11 and the second test block matrix unit 12 of different diameters, the details of the identifiable columnar defects 23 are analyzed, which can be used to verify the defect detection capability of the CT inspection process for columnar defects 23 of a specific density or melting state of powder bed fusion products under different wall thicknesses; by comparing the CT images of columnar defects 23 (including the first columnar defect 23-1, the second columnar defect 23-2, the third columnar defect 23-3 and the fourth columnar defect 23-4) of different densities or melting states on the first test block matrix unit 11 of the same diameter, the details of the identifiable columnar defects 23 are analyzed, which can be used to verify the defect detection capability of the CT inspection process for columnar defects 23 of different densities or melting states of powder bed fusion products under the same wall thickness.

[0062] By comparing the CT images of the flat-bottom holes 21 and the spherical defects 22 of the same size on the first test block base unit 11 of the same diameter, the details of the identifiable flat-bottom holes 21 and the spherical defects 22 are analyzed. This can be used to analyze the impact of the CT detection process on the CT detection sensitivity and defect recognition of the unmelted metal powder inside the spherical defects 22 of a specific size of the powder bed fusion product. It can be used to verify the defect detection capability of CT detection for powder bed fusion products, improve the reliability of CT detection results of powder bed fusion products and assist in defect assessment.

[0063] A powder bed fusion product CT inspection comparison test block and a preparation method thereof are disclosed. The comparison test block provided by the present invention can effectively simulate the porosity and unfused defects of the powder bed fusion product. The CT images of the comparison test block matrix units with different diameters can be used for comparative tests on the thickness sensitivity of CT inspection to the powder bed fusion product, verifying the defect detection capability of the CT inspection process for specific dimensions of internal details of the powder bed fusion product under different wall thicknesses, and at the same time verifying the defect detection capability of the CT inspection process for different dimensions of internal details of the powder bed fusion product under the same wall thickness.

[0064] By using the comparison test block of the present invention, by comparing the CT images of different types of defect units and analyzing the details of identifiable flat-bottom holes, spherical defects and columnar defects, it can be used to determine the influence of completely unmelted or partially unmelted metal powder inside the porosity and unfusion defects of powder bed fusion parts on CT detection sensitivity and defect identification, which helps to improve the reliability of CT detection results of powder bed fusion parts and assists in defect assessment.

[0065] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A powder bed fusion product CT inspection comparison test block, characterized in that: The comparison test block includes a test block matrix and a defect unit; The test block base is a stepped shaft structure composed of two cylinders of different diameters, and is used for comparative testing of the thickness sensitivity of CT detection to powder bed fusion products; The defect unit is composed of a number of flat-bottom holes, spherical defects and columnar defects of different diameters arranged on the test block substrate, and is used to verify the defect detection capability of CT detection for powder bed fusion products, improve the reliability of detection results and assist in defect assessment.

2. A powder bed fusion product CT inspection comparison test block according to claim 1, characterized in that: The test block matrix comprises two test block matrix units, namely a first test block matrix unit and a second test block matrix unit; the two test block matrix units are cylinders with the same height and different diameters, and the cylinders of the two test block matrix units are coaxial and form a stepped shaft structure; The cylindrical diameter of the first test block base unit is the same as the minimum thickness of the powder bed fusion product detected by CT, and the cylindrical diameter of the second test block base unit is the same as the maximum thickness of the powder bed fusion product detected by CT.

3. A powder bed fusion product CT inspection comparison test block according to claim 2, characterized in that: The two test block base units are provided with the same number of defect units; the defect units are provided with flat-bottom holes, spherical defects and columnar defects with the same diameter, and the centers of the spherical defects with the same diameter are on the axes of the flat-bottom holes, and the axes of the flat-bottom holes and columnar defects are parallel to the axes of the test block base units.

4. A powder bed fusion product CT inspection comparison test block according to claim 3, characterized in that: The flat bottom hole is a cylindrical hollow structure and is arranged in a vertical manner. One end of the flat bottom hole is located on the upper surface of the test block base unit and the end is open to the outside, and the other end is a sealed end and is located inside the test block base unit; The spherical defect is a spherical hole structure containing unmelted metal powder, and is arranged inside the test block matrix unit; The columnar defect is a cylindrical hole structure containing unmelted metal powder inside, and is vertically arranged inside the test block base unit; The flat-bottom holes, spherical defects and columnar defects are arranged on the test block base unit at equal axial intervals and are located at the upper part, the middle part and the lower part thereof respectively.

5. The powder bed fusion product CT inspection comparison test block according to claim 1, characterized in that: There are multiple flat-bottom holes, and the diameters of any two flat-bottom holes on the same test block base unit are different. The multiple flat-bottom holes are arranged at equal intervals in the circumferential direction on the upper part of the test block base unit, and the distance between each flat-bottom hole and the axis of the test block base unit is equal; There are multiple spherical defects and the number is equal to that of the flat-bottom holes. The diameters of any two spherical defects on the same test block base unit are different and correspond one-to-one to the diameters of the flat-bottom holes. The distribution position of the spherical defects in the middle of the test block base unit is the same as that of the flat-bottom holes. There are multiple columnar defects, and the diameter of each columnar defect on the same test block base unit is the same, the density inside each columnar defect is different, and the melting state of the metal powder inside the columnar defect decreases from completely melted to completely unmelted in sequence, and the distribution position of the columnar defects in the lower part of the test block base unit is the same as that of the flat-bottomed holes.

6. A method for manufacturing a powder bed fusion product CT test comparison block, used to manufacture the comparison test block in claims 1-5, characterized in that: The method comprises: S1, test block design, according to the requirements of CT inspection of powder bed fusion products, the size of the test block matrix, the position and size of the defect unit on the test block matrix are designed, and a digital model is established to complete the test block design; S2, test block forming, according to the digital model established in the test block design in S1, powder bed fusion forming of spherical defects and columnar defects in the test block matrix and defect units is performed, wherein the raw materials and process parameters for forming the test block matrix are the same as those of the powder bed fusion product to be tested, the spherical defects are hollow spherical holes preset in the digital model, and the energy density at the spherical holes is set to zero during forming to obtain a spherical hole structure containing unmelted metal powder inside, and the energy density at each cylindrical hole in the columnar defect forming is set to 75%, 50%, 25% to 0% of the part forming energy density to obtain a cylindrical hole structure containing metal powder of different densities or in a molten state inside, and then the test block matrix blank is obtained through post-processing; S3, test block screening, using X-ray or CT method to detect the test block base blank, determine the location and size of spherical defects and columnar defects in the defect unit, and screen out the test block base blank that meets the design requirements based on the X-ray or CT test results; S4, test block processing, machining the test block base blank selected from the test block in S3 into a stepped shaft structure of a first test block base unit and a second test block base unit, and then machining a flat bottom hole in the defective unit, and then performing surface treatment to obtain a comparative test block; S5, test block evaluation, uses X-ray, ultrasound or CT methods to test, evaluate and compare the comparison test blocks obtained from the test blocks in S4, and evaluate whether the shape, size and surface quality of the test block matrix, as well as the position and size of the defective unit meet the test block design requirements. If they meet the requirements, they will be accepted and marked, otherwise they will be remade.

Images