A method for brazing inspection of a diamond compact

Abstract

The application discloses a kind of methods for diamond compact brazing detection, it is related to brazing detection related field.The present application can quickly evaluate the release condition of residual stress in WC matrix after PDC brazing, through optimizing heating temperature, holding time and cooling system, and combining with DPI penetration detection, potential cracks under plane layer can be effectively identified, to avoid failure caused by thermal stress concentration, at the same time, the introduction of magnetic-acoustic coupling auxiliary detection mechanism, through low-frequency alternating magnetic field excitation internal stress response before penetration detection, and combining with acoustic emission signal, potential defects are pre-judged, realize the positioning and screening of micro-crack in advance, so as to reduce the probability of blind detection and improve detection efficiency, the method significantly improves crack detection rate and determination reliability, enhances detection consistency, can provide more reliable basis for brazing quality control, and improve product consistency and use stability.

Description

Technical Field

[0001] This invention relates to the field of brazing inspection, and in particular to a method for brazing inspection of diamond composite sheets. Background Technology

[0002] Polycrystalline diamond composite (PDC) sheets are widely used in oil drilling, geological exploration, and cutting tools due to their excellent hardness and wear resistance. Typically, PDC is bonded to a tungsten carbide (WC) matrix using a brazing process to ensure overall structural strength and service life. However, during the brazing process, uneven heating and cooling can easily lead to the formation of significant residual thermal stress within the WC matrix. If this stress is not released in time, it can cause a decrease in matrix strength and even result in thermal stress cracks found below the planar layer in DPI (penetrating penetration testing). Once cracks form, they are often located in deeper, multi-layered structural regions, involving complex thermal stress accumulation. This not only affects the reliability of the product but also increases the scrap rate.

[0003] In existing technologies, the control of PDC brazing quality largely relies on empirical process parameter adjustments, lacking a systematic stress release and verification process, making it difficult for quality control personnel to diagnose problems in a timely manner and take effective countermeasures. Summary of the Invention

[0004] Therefore, in order to overcome the above-mentioned shortcomings, the present invention provides a method for inspecting the brazing of diamond composite sheets.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for inspecting the brazing of diamond composite sheets, comprising the following steps: S1. A brazing material is placed on the surface of the WC matrix of the PDC sample, such that the brazing material covers 20% to 80% of the surface area of ​​the WC matrix, and the melting temperature of the brazing material is higher than 600°C. S2. Apply flux to the connection area between the brazing material and the PDC sample. The flux coating thickness ranges from 1 to 100 μm. S3. Place the marked PDC sample under an inert gas protective atmosphere for heating and brazing. The protective gas is nitrogen or argon. The brazing temperature is 650℃~780℃ and the holding time is 4~15 minutes. S4. Perform a composite cooling treatment on the brazed sample, including first cooling it naturally at room temperature for no more than 3 minutes, and then quenching the sample in a low-temperature medium to release the residual stress of the brazing. S5. Apply a low-frequency alternating magnetic field to the brazed PDC sample and simultaneously acquire acoustic emission signals (AE signals) to identify areas of internal residual stress concentration in advance. S6. Perform a penetrant test on the cooled sample. If a crack is detected in the WC matrix area below the PDC planar layer, the sample is deemed unqualified; otherwise, it is deemed qualified.

[0006] Preferably, the amount of brazing material used is 0.02 to 0.10 g / cm².

[0007] Preferably, the natural cooling time in the cooling step is 80 to 100 seconds.

[0008] Preferably, the DPI detection uses a water-washable fluorescent penetrant with an immersion time of 5 to 15 minutes. After removing excess penetrant from the surface, the crack imaging is observed under ultraviolet light.

[0009] Preferably, the stress prediction detection step in S5 is as follows: placing the cooled PDC sample inside the detection coil; applying a low-frequency alternating magnetic field (10-500 Hz); simultaneously deploying piezoelectric sensors to collect acoustic emission signals; when an abnormal acoustic emission mutation or abnormal peak in the spectrum is detected, it is determined to be a potential stress concentration area; and performing focused DPI penetration detection on this area.

[0010] The beneficial effects of this invention are: This invention enables rapid assessment of residual stress release in the WC matrix after PDC brazing. By optimizing heating temperature, holding time, and cooling regime, and combining with DPI penetrant testing, it can effectively identify potential cracks beneath the planar layer, avoiding failures caused by thermal stress concentration. Simultaneously, a magneto-acoustic coupling-assisted detection mechanism is introduced. Before penetrant testing, a low-frequency alternating magnetic field is used to excite the internal stress response, and combined with acoustic emission signals, potential defects are predicted, enabling early location and screening of microcracks. This reduces the probability of blind inspection and improves detection efficiency. This method significantly improves crack detection rate and judgment reliability, enhances detection consistency, provides a more reliable basis for brazing quality control, and improves product consistency and usage stability. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a non-conforming PDC sample of the present invention; Figure 2 This is a schematic diagram of the qualified PDC sample 1 of the present invention; Figure 3 This is a schematic diagram of the qualified PDC sample 2 of the present invention. Detailed Implementation

[0012] To further explain the technical solution of the present invention, a detailed description is provided below through specific embodiments.

[0013] This invention provides a method for inspecting the brazing of diamond composite sheets, comprising the following steps: S1. Brazing Material Preparation: Cover the WC substrate surface of the PDC sample with brazing material 5081, with a melting point range of 660℃~707℃. The amount of brazing material 5081 is 0.05g / cm², and its coverage area is 50% of the WC substrate surface area. S2. Flux Coating: Coat the brazing sheet and PDC sample surface with a flux compound of 25μm thickness to promote bonding and reduce oxidation. S3. Sample Loading: Place the PDC sample with the batch number marking in a ceramic boat. After the furnace temperature reaches the set value, send it to the fixed position inside the furnace. S4. Heating Process: Performed under an inert nitrogen protective atmosphere. Brazing, with a nitrogen flow rate of 1.2 L / min, a set temperature of 720℃, and a holding time of 8 minutes; S5, Cooling process: After the heated sample is removed, it is naturally cooled in a dry environment for 90 seconds, and then the sample is quickly quenched in cold water at 15℃; S6, DPI penetration test: DPI test is performed on the cooled sample. DPI test uses a water-washable fluorescent penetrant, and the penetration time is 5-15 minutes. After removing excess penetrant from the surface, the crack image is observed under ultraviolet light. When a crack is detected in the WC matrix area below the planar layer, the sample is judged to be unqualified; when no crack is detected, the sample is judged to be qualified. Before penetrant testing, a magnetic-acoustic coupling-assisted testing step is introduced. By applying a low-frequency alternating magnetic field to the cooled PDC sample, a micro-eddy current response is generated inside the WC matrix. At the same time, an acoustic emission sensor is used to collect the elastic wave signal generated during stress release. When an abnormal acoustic emission signal is detected, it is determined that there is potential residual stress concentration or microcrack defects in the corresponding area, and the area is subjected to focused penetrant testing, thereby improving the accuracy and efficiency of crack identification. WC matrix is ​​a conductive material, which will generate micro-eddy current effect under the action of alternating magnetic field; lattice distortion in residual stress concentration area → leads to abnormal local electromagnetic response; at the same time, under magnetic excitation, microcracks will generate microscale elastic release (acoustic emission).

[0014] To verify the reliability of the brazing detection method of the present invention in detecting cracks and the accuracy of brazing quality assessment, three groups of PDC samples with different annealing conditions were selected for comparative testing. Each group contained 10 samples, and the test comparisons are as follows: Group 1: Before brazing, the WC substrate was annealed at 600℃ for 1 hour (nitrogen protection), followed by brazing: brazing temperature: 720℃; holding time: 8 minutes and 30 seconds; nitrogen flow rate: 1.0 L / min; cooling: after natural cooling for 90 seconds, quenched in 20℃ cold water. Test results: DPI testing revealed cracks in the WC region below the planar layer, classifying the product as defective. This indicates that the low-temperature short-time annealing failed to effectively release residual stress. Figure 1 As shown.

[0015] For the second group, the annealing process is adjusted to 700℃×2h annealing (nitrogen protection), and the remaining brazing process is as above; Test results: No cracks were found in the DPI test, and the results of repeated tests were consistent, indicating that the product is qualified. This demonstrates that extending the annealing time at 700℃ can effectively eliminate residual stress. Figure 2 As shown.

[0016] The third group: the annealing process is adjusted to 680℃×3h annealing (nitrogen protection), and the remaining brazing processes are as above; Test results: No cracks were found in the DPI test, and all samples were deemed qualified. Furthermore, the microstructure stability was better than that under high-temperature annealing conditions, indicating that medium-temperature long-time annealing can also effectively release residual stress. Figure 3 As shown.

[0017] Testing and evaluation indicators: Crack detection rate (CR): The proportion of samples with cracks detected in DPI testing; Consistency (CE): The proportion of identical results in repeated tests; Reliability judgment rate (RR): The proportion of test results that are consistent with the actual annealing quality; Crack severity grading: Grade I: No cracks found (Pass) Level II: Minor cracks (warning) Grade III: Obvious cracks (unacceptable) By coordinating the control of brazing filler metal coverage, flux thickness, heating temperature, and cooling regime, potential cracks generated at the brazing interface are realistically visualized and reliably identified in DPI testing, increasing the testing accuracy from approximately 80% to a 100% reliable identification rate, significantly improving the quality control capability of diamond composite sheet products.

[0018] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for inspecting the brazing of diamond composite sheets, characterized in that: Includes the following steps: S1. A brazing material is placed on the surface of the WC matrix of the PDC sample, such that the brazing material covers 20% to 80% of the surface area of ​​the WC matrix, and the melting temperature of the brazing material is higher than 600°C. S2. Apply flux to the connection area between the brazing material and the PDC sample. The flux coating thickness ranges from 1 to 100 μm. S3. Place the marked PDC sample under an inert gas protective atmosphere for heating and brazing. The protective gas is nitrogen or argon. The brazing temperature is 650℃~780℃ and the holding time is 4~15 minutes. S4. Perform a composite cooling treatment on the brazed sample, including first cooling it naturally at room temperature for no more than 3 minutes, and then quenching the sample in a low-temperature medium to release the residual stress of the brazing. S5. Apply a low-frequency alternating magnetic field to the brazed PDC sample and simultaneously acquire acoustic emission signals (AE signals) to identify areas of internal residual stress concentration in advance. S6. Perform a penetrant test on the cooled sample. If a crack is detected in the WC matrix area below the PDC planar layer, the sample is deemed unqualified; otherwise, it is deemed qualified.

2. The method for inspecting the brazing of diamond composite sheets according to claim 1, characterized in that: The amount of brazing material used is 0.02 to 0.10 g / cm².

3. The method for inspecting the brazing of diamond composite sheets according to claim 1, characterized in that: The natural cooling time in the cooling step is 80 to 100 seconds.

4. The method for inspecting the brazing of diamond composite sheets according to claim 1, characterized in that: The DPI detection uses a water-washable fluorescent penetrant with an impregnation time of 5–15 minutes. After removing excess penetrant from the surface, the crack imaging is observed under ultraviolet light.

5. The method for inspecting the brazing of diamond composite sheets according to claim 1, characterized in that: The stress prediction detection step in S5 is as follows: place the cooled PDC sample inside the detection coil; apply a low-frequency alternating magnetic field (10-500Hz); simultaneously deploy piezoelectric sensors to collect acoustic emission signals; when abnormal acoustic emission abrupt changes or abnormal peak values ​​in the spectrum are detected, it is determined to be a potential stress concentration area; and perform key DPI penetration detection on this area.

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