A device and method for testing the compressive strength of a polycrystalline diamond compact

Abstract

The application discloses a kind of polycrystalline diamond compact compression strength testing device and method, by setting moving mechanism, indenter mechanism, force measuring system and PDC fixed mechanism, and indenter mechanism includes the lengthening rod being fixed with crossbeam and the indenter being fixed in the lower end of lengthening rod, and the working layer of indenter adopts PDC material;And PDC fixed mechanism is set to open V-shaped groove magnetic clamp, one side wall of V-shaped groove is opened by the circular arc groove being arranged from top to bottom, and the radius of circular arc groove is not less than the radius of the cylindrical PDC sample to be measured, and the sample to be measured is placed in the circular arc groove being arranged obliquely, and the mode that PDC indenter is used to the cylindrical edge of sample to be measured to apply pressure, can simulate the failure mode of PDC cylindrical edge under actual working condition, it is helpful to in-depth analysis of cylindrical edge failure mechanism under different angles;Also solve the problem that the traditional frontal compression method is followed at present, and the influence of hard alloy matrix strength is avoided simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of new material performance testing technology, and specifically relates to a device and method for testing the compressive strength of polycrystalline diamond composite sheets. Background Technology

[0002] Polycrystalline diamond compact (PDC) is an ultra-hard composite material prepared from diamond micropowder and a cemented carbide matrix at a sintering temperature of 1400–1500℃ and a sintering pressure of 5.0–7.0 GPa. Therefore, PDC possesses both the extremely high hardness and wear resistance of diamond and the good toughness and weldability of cemented carbide, making it widely used in many fields such as mining, oil and gas drilling, tunneling, and the processing of ceramics and non-ferrous alloys. It is a widely used cutting tool.

[0003] In practical applications, PDC (particulate concentrator) on drill bits needs to be tilted at a certain angle (0° < a < 90°) so that the cylindrical edges perform cutting action. This exposes the PDC directly to continuous friction, impact, and compression from the rock strata, easily leading to PDC failure. Currently, there are many methods for characterizing PDC performance using mechanical properties, such as microhardness, wear ratio, and impact toughness. Microhardness is an important indicator of the microscopic hardness of the PDC surface, calculated by indenting the sample surface with a regular square pyramidal diamond indenter under a certain load. This method can only characterize the hardness of the diamond particles in the PDC working layer, but it cannot detect the hardness of the bonding phases (CC, CW) that determine the strength of the PDC working layer. Furthermore, the detection area is at the microscale and cannot reflect the overall performance. In addition, this method deviates significantly from actual working conditions and is not very meaningful for exploring PDC performance. Wear ratio is a physical quantity characterizing the wear resistance of PDC surface. It is determined according to the industry standard JB / T3235-2013, using a standard hardness SiC grinding wheel to grind the cylindrical edges of PDC, tracking the wheel consumption and sample wear before and after grinding, and calculating the PDC wear ratio. This method has a high degree of standardization and is beneficial for quantifying the differences in PCD surface wear resistance. However, the grinding sample uses a standard SiC grinding wheel, which differs significantly from actual rock materials. Furthermore, the grinding parameters differ greatly from actual cutting parameters, making it difficult to accurately reflect the performance of PDC. Impact toughness is a physical quantity measuring the strength of PDC material under dynamic conditions. The test method uses an electromagnet to lift a hammer and then allow it to fall freely from a certain height, converting potential energy into impact kinetic energy. This hammer is repeatedly and perpendicularly impacted onto the PDC working layer surface until surface damage occurs. The accumulated impact energy characterizes the PDC's impact toughness. This method can simulate the impact of rock strata on PDC in actual applications to a certain extent, but it impacts the front of the PDC working layer, not the cylindrical edge of the PCD, and the impact energy is transmitted along the PDC generatrix, which is completely inconsistent with the actual stress on the circumferential edge. Therefore, it cannot effectively reflect the performance of PDC.

[0004] Compressive strength refers to the ability of a material to resist fracture under external force. It is a fundamental mechanical parameter characterizing PDC failure and directly reflects the mechanical properties of the PDC. Generally speaking, the higher the compressive strength, the stronger the resistance to failure and the longer the service life. Therefore, this parameter has always been of great concern to engineers. However, there is currently no scientific method to test the compressive strength of PDCs. The traditional frontal compression fracture method is generally used, but this method has several problems: ① Because the working layer of the PDC is supported by a cemented carbide matrix, the working layer and the cemented carbide matrix often fracture together during the traditional compression fracture test. This makes it difficult to distinguish between the compressive strength of the working layer and the compressive strength of the cemented carbide matrix. ② In the traditional compression fracture test, the indenter directly compresses the front of the PDC. The indenter material is often cemented carbide, ceramic, or hardened high-strength steel. However, the PDC working layer is sintered from high-density diamond particles, and its surface hardness is much higher than that of the indenter. This means that the indenter may fail before the PDC fractures, thus affecting the accuracy of the compressive strength value. ③ During use, PDC is tilted at a certain angle as a cutting edge during drilling. However, in the traditional compression fracture test, the indenter directly compresses the upper surface of PDC, which is seriously inconsistent with the actual working conditions and makes it difficult to accurately characterize the strength of PDC.

[0005] Therefore, the industry urgently needs to develop a PDC compressive strength testing method to accurately characterize the compressive strength of PDC, and to understand the strength of the cylindrical edge (cutting edge) of PDC and the stability of its circumferential cylindrical edge in a timely manner. This will have certain guiding significance for improving the performance of PDC products and extending their service life. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the prior art by providing a device and method for testing the compressive strength of polycrystalline diamond composite sheets, which solves the problems of inability to measure, inaccuracy, and inconsistency with actual working conditions in the current traditional frontal compressive strength test. It can also be used to explore the compressive strength stability of PCD.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A polycrystalline diamond composite sheet compressive strength testing device includes a moving mechanism, an indenter mechanism, a force measuring system and a PDC fixing mechanism, wherein the moving mechanism includes a body, linear modules that slide vertically on both sides of the body and a crossbeam fixed horizontally on the linear modules on both sides.

[0009] The pressure head mechanism includes an extension rod fixed to the crossbeam and a pressure head fixed at the lower end of the extension rod, and the working layer of the pressure head is a polycrystalline diamond layer.

[0010] The force measurement system includes a pressure sensor and a data acquisition system. The pressure sensor is fixed to the extension rod and the pressure value is acquired through the data acquisition system.

[0011] The PDC fixing mechanism is a magnetic clamp with a V-shaped groove, and a circular arc groove is arranged from top to bottom on one side wall of the V-shaped groove, and the radius of the circular arc groove is not less than the radius of the cylindrical PDC sample to be tested.

[0012] The top of the cylindrical PDC sample to be tested has a circumferentially arranged cutting edge.

[0013] The cylindrical PDC sample to be tested has circumferentially arranged cylindrical ridges at the cutting edge.

[0014] The V-groove of the magnetic clamp has an inclination angle of 45°.

[0015] The chamfer of the cylindrical edge is C = 0.5 × 45°.

[0016] The pressure head and the extension rod are fixed by welding.

[0017] The upper end of the cylindrical PDC sample to be tested is a polycrystalline diamond layer, and the lower end is a cemented carbide substrate.

[0018] A test method for a polycrystalline diamond composite sheet compressive strength testing device includes the following steps:

[0019] (1) Select PDC as the pressure head for the compressive strength test, fix the pressure head on the extension rod with its polycrystalline diamond layer facing down, and then fix it together with the extension rod to the pressure sensor;

[0020] (2) Place the cylindrical surface of the PDC sample to be tested into the V-groove of the magnetic clamp to tilt the PDC sample.

[0021] (3) Set the sampling frequency of the pressure sensor and the moving speed of the linear module so that the pressure head moves slowly to compress the cutting edge of the tilted cylindrical PDC sample to be tested until the cutting edge breaks. At this time, the pressure sensor will experience a sudden change in force, and the point of sudden change is the maximum resistance that the PDC can withstand, which is recorded as the maximum pressure value F1.

[0022] (4) Rotate the cylindrical PDC sample to be tested by an angle a, and then repeat step (3) to obtain the maximum pressure F2;

[0023] Subsequently, the cylindrical PDC sample to be tested is rotated by an angle a to obtain the corresponding maximum pressure value until one rotation is completed and m data points are obtained, where m = 360° / a;

[0024] (5) Calculate the compressive strength characterization parameters of the cylindrical PDC sample to be tested according to formulas (1) and (2). And circumferential strength stability S:

[0025]

[0026]

[0027] The compressive strength and circumferential strength stability of the cylindrical PDC sample to be tested can then be obtained.

[0028] The sampling frequency of the pressure sensor is fn = 50Hz to 100Hz.

[0029] The moving speed of the linear module is set to V = 0.1 mm / min ~ 1.0 mm / min.

[0030] The angle 'a' is set to 60° or 45°.

[0031] The beneficial effects of this invention are:

[0032] This invention discloses a polycrystalline diamond composite sheet compressive strength testing device and method. It comprises a moving mechanism, a pressure head mechanism, a force measuring system, and a PDC fixing mechanism. The pressure head mechanism includes an extension rod fixed to a crossbeam and a pressure head fixed to the lower end of the extension rod. The working layer of the pressure head is made of PDC material. The PDC fixing mechanism is a magnetic clamp with a V-groove. One side wall of the V-groove has circular arc grooves arranged from top to bottom, and the radius of the circular arc grooves is not less than the radius of the cylindrical PDC sample to be tested. The sample is placed in the inclined circular arc grooves. By applying pressure to the cylindrical edge of the sample using the PDC pressure head, the failure mode of the PDC cylindrical edge under actual working conditions can be simulated. This helps to deeply analyze the failure mechanism of the cylindrical edge at different angles, such as at what angle mechanical breakage, shear peeling, or brittle fracture occurs, which is more consistent with actual working conditions and can effectively reflect the performance of PDC. Furthermore, this invention can also be used to guide the angle design of PDC in drill bits, reducing the failure frequency and increasing service life. In addition, the present invention solves the problem of excessive pressure in the current traditional front compression method, while avoiding the influence of hard alloy matrix strength. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of the cylindrical PDC sample to be tested;

[0035] Figure 3 This is a schematic diagram of the magnetic clamp.

[0036] Figure 4 This is a schematic diagram of the rotational processing of the cylindrical PDC sample to be tested;

[0037] Table 1 shows the compressive strength test results of Example 1;

[0038] Table 2 shows the compressive strength test results of Example 2. Detailed Implementation

[0039] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0040] This invention provides a device and method for testing the compressive strength of polycrystalline diamond composite sheets, such as... Figures 1 to 4 As shown.

[0041] The polycrystalline diamond composite sheet compressive strength testing device includes a moving mechanism, an indenter mechanism, a force measuring system, and a PDC fixing mechanism. The moving mechanism includes a body 9, linear modules 6 that slide vertically on both sides of the body, and a crossbeam 7 that is fixed horizontally on the linear modules on both sides.

[0042] The pressure head mechanism includes an extension rod 5 fixedly connected to the crossbeam 7 and a pressure head 4 fixedly installed at the lower end of the extension rod 5. The working layer of the pressure head 4 is made of PDC material with a wear ratio of over 1 million. The surface parallelism of the working layer is 0.005 to 0.01 mm, and the roughness is Ra 0.1 to 0.4 μm. The connection between the pressure head 4 and the extension rod 5 is high-frequency welding, and the solder is copper-tin solder or brazing solder.

[0043] The force measurement system includes a pressure sensor 8 and a data acquisition system 10. The pressure sensor 8 is fixed to the extension rod 5 and the pressure value is acquired by the data acquisition system 10 and transmitted to the computer 11. The pressure sensor 8 can be a strain pressure sensor or a piezoelectric pressure sensor. The pressure sensor 8 has a testing range of 100N to 50kN and an accuracy level of 0.5.

[0044] The PDC fixing mechanism is a magnetic clamp 2 with a V-shaped groove. In this embodiment, the V-shaped groove of the magnetic clamp 2 has an inclination angle of 45°, and an arc groove 21 arranged from top to bottom is opened on one side wall of the V-shaped groove. The radius of the arc groove is not less than the radius of the cylindrical PDC sample 3 to be tested. A tool relief groove 22 is also opened at the bottom of the V-shaped groove.

[0045] In this embodiment, the cylindrical PDC sample 3 to be tested consists of a polycrystalline diamond layer 31 (PCD layer) at the upper end and a cemented carbide substrate 32 at the lower end, which are fixed together.

[0046] The top of the cylindrical PDC sample 3 to be tested is provided with a circumferentially arranged cutting edge. In this embodiment, the top of the cylindrical PDC sample 3 to be tested is provided with a circumferentially arranged cylindrical edge 33, and the chamfer of the cylindrical edge 33 is C=0.5×45°. When the sample to be tested is placed in the arc groove 21 of the V-shaped groove, the 45° chamfered cylindrical edge 33 is exactly on the horizontal plane. When the pressure head 4 presses down, the working layer of the pressure head 4 and the upper cylindrical edge 33 of the cylindrical PDC sample to be tested are in line / surface contact to apply pressure.

[0047] If the top of the cylindrical PDC sample 3 to be tested only has a circumferential cutting edge and no chamfer, that is, no cylindrical edge is provided, then when the pressure head 4 presses down, the working layer of the pressure head 4 and the upper cutting edge of the cylindrical PDC sample 3 to be tested will be in point / line contact to apply pressure.

[0048] A test method for a polycrystalline diamond composite sheet compressive strength testing device includes the following steps:

[0049] (1) Fix the pressure head 4 to the extension rod 5 with its polycrystalline diamond layer facing down, and then fix it together with the extension rod 5 to the pressure sensor 8.

[0050] (2) Place the cylindrical PDC sample to be tested on the V-groove of the magnetic clamp 2 so that the PDC sample is tilted.

[0051] (3) Set the sampling frequency of the pressure sensor 8 and the moving speed of the linear module 9, so that the pressure head 5 slowly moves to compress the cutting edge of the tilted cylindrical PDC sample to be tested until the cutting edge breaks. At this time, the pressure sensor will experience a sudden change in force, and the point of change is the maximum resistance that the PDC can withstand, which is recorded as the maximum pressure value F1; the sampling frequency of the pressure sensor f n =50Hz~100Hz; the moving speed of the linear module is set to V =0.1mm / min~1.0mm / min.

[0052] (4) Rotate the cylindrical PDC sample to be tested by an angle a, and then repeat step (3) to obtain the maximum pressure F2;

[0053] Subsequently, the cylindrical PDC sample to be tested is rotated by an angle 'a' to obtain the corresponding maximum pressure value until one full rotation is completed and m data points are obtained, where m = 360° / a. Angle 'a' can be set to any angle, but preferably 'a' can be set to 60° or 45°.

[0054] (5) Calculate the compressive strength characterization parameters of the cylindrical PDC sample to be tested according to formulas (1) and (2). And circumferential strength stability S:

[0055]

[0056]

[0057] The compressive strength and circumferential strength stability of the cylindrical PDC sample to be tested can then be obtained.

[0058] The present invention will be further described clearly and completely below with reference to the embodiments.

[0059] Example 1

[0060] Step 1: Select a cylindrical PDC sample A to be tested. The diameter of the cylindrical PDC sample is 16.0 mm, the total thickness is 20 mm, the working layer 31 is 3.5 mm thick, and the chamfer C of the cylindrical edge 33 is 0.5 × 45°.

[0061] Step 2: Place the cylindrical surface of the cylindrical PDC sample 3 to be tested against the arc groove 21 of the magnetic clamp 2, so that the PDC sample 3 is tilted at 45°.

[0062] Step 3: Set the pressure sensor acquisition frequency to f n =50Hz, the linear module moving speed is V=1.0mm / min, so that the pressure head 4 slowly moves to compress the cylindrical edge 33 of the PDC sample 3 to be tested until the cylindrical edge 33 breaks. At this time, the sudden force value F1 of the pressure sensor 8 is 13.48kN.

[0063] Step 4: Rotate the cylindrical PDC sample 3 to be tested by 60 degrees and repeat step 2 to obtain the corresponding maximum pressure F2 = 13.06 kN. Then continue to rotate the cylindrical PDC sample to be tested to obtain the corresponding maximum pressure F3 = 14.24 kN until it has rotated one full circle. At this time, 6 data points are obtained.

[0064] Step 5: Calculate the compressive strength parameters of the cylindrical PDC sample to be tested according to formulas (1) and (2). The circumferential strength stability S and the results are shown in Table 1.

[0065] Table 1. Compressive strength test results of Example 1

[0066]

[0067] Example 2

[0068] Step 1: Select a cylindrical PDC sample B to be tested. The diameter of the cylindrical PDC sample to be tested is 16.0 mm, the total thickness is 20 mm, the working layer 31 thickness is 3.5 mm, and the chamfer C of the cylindrical edge 33 is 0.5 × 45°.

[0069] Step 2: Place the cylindrical surface of the cylindrical PDC sample 3 to be tested against the arc groove 21 of the magnetic clamp 2, so that the cylindrical PDC sample 3 to be tested is tilted at 45°.

[0070] Step 3: Set the pressure sensor acquisition frequency to fn = 50Hz and the linear module moving speed to V = 1.0mm / min, so that the pressure head 4 moves slowly to compress the cylindrical edge 33 of the PDC sample 3 until the cylindrical edge 33 breaks. At this time, the sudden force value F1 of the pressure sensor 8 is 23.55kN.

[0071] Step 4: Rotate the cylindrical PDC sample 3 to be tested by 60 degrees, repeat step 2, and obtain the corresponding maximum pressure F2 = 26.36kN. Continue to rotate the cylindrical PDC sample to be tested and obtain the corresponding maximum pressure F3 = 23.36kN until it rotates one full circle. At this time, 6 data points are obtained.

[0072] Step 5: Calculate the compressive strength parameters of the PDC sample according to formulas (1) and (2). The circumferential strength stability S and the results are shown in Table 2.

[0073] Table 2. Compressive strength test results of Example 2

[0074]

[0075] By conducting compressive strength tests on cylindrical PDC samples of the same specifications from two brands under the same conditions, it was found that the compressive strength of PDC sample from brand B was significantly higher than that from brand A, but the circumferential strength stability of its PDC sample was slightly worse than that of brand A. Using the PDC compressive strength testing device and method of the present invention, the differences in PDC compressive strength and the differences in circumferential strength stability of cylindrical edges can be accurately quantified, which can provide mechanical property data support for controlling PDC product quality and improving product performance.

[0076] If this patent uses terms such as "first" and "second" to define components, those skilled in the art should know that the use of "first" and "second" is merely for the convenience of describing the invention and simplifying the description, and the above terms have no special meaning.

[0077] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this invention is defined by the appended claims and their equivalents.

[0078] In the description of this invention, it should be understood that the terms "front", "rear", "left", "right", "center", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to facilitate the description of this invention and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

Claims

1. A test method for a polycrystalline diamond composite sheet compressive strength testing device, characterized in that: The testing device includes a moving mechanism, a pressure head mechanism, a force measuring system, and a PDC fixing mechanism. The moving mechanism includes a body, linear modules that slide vertically on both sides of the body, and a crossbeam that is fixed horizontally on the linear modules on both sides. The pressure head mechanism includes an extension rod fixed to the crossbeam and a pressure head fixed at the lower end of the extension rod, and the working layer of the pressure head is a polycrystalline diamond layer. The force measurement system includes a pressure sensor and a data acquisition system. The pressure sensor is fixed to the extension rod and the pressure value is acquired through the data acquisition system. The PDC fixing mechanism is a magnetic clamp with a V-shaped groove, and a circular arc groove is arranged from top to bottom on one side wall of the V-shaped groove, and the radius of the circular arc groove is not less than the radius of the cylindrical PDC sample to be tested. The top of the cylindrical PDC sample to be tested has a circumferentially arranged cutting edge; The testing method includes the following steps: (1) Select PDC as the pressure head for the compressive strength test, fix the pressure head on the extension rod with its polycrystalline diamond layer facing down, and then fix it together with the extension rod to the pressure sensor; (2) Place the cylindrical PDC sample to be tested on the V-groove of the magnetic clamp with the cylindrical surface attached to it, so that the PDC sample is tilted; (3) Set the sampling frequency of the pressure sensor and the moving speed of the linear module so that the pressure head moves slowly to compress the cutting edge of the tilted cylindrical PDC sample to be tested until the cutting edge breaks. At this time, the pressure sensor will experience a sudden change in force, and the point of sudden change is the maximum resistance that the PDC can withstand, which is recorded as the maximum pressure value F1. (4) Rotate the cylindrical PDC sample to be tested by an angle a, and then repeat step (3) to obtain the maximum pressure F2; Subsequently, the cylindrical PDC sample to be tested is rotated by an angle a to obtain the corresponding maximum pressure value until one rotation is completed and m data points are obtained, where m = 360° / a. (5) Calculate the compressive strength characterization parameters of the cylindrical PDC sample to be tested according to formulas (1) and (2). And circumferential strength stability S: （1）； （2）； The compressive strength and circumferential strength stability of the cylindrical PDC sample to be tested can then be obtained.

2. The testing method for the compressive strength testing device of polycrystalline diamond composite sheet according to claim 1, characterized in that: The cylindrical PDC sample to be tested has circumferentially arranged cylindrical ridges at the cutting edge.

3. The testing method for the compressive strength testing device of polycrystalline diamond composite sheet according to claim 1, characterized in that: The V-groove of the magnetic clamp has an inclination angle of 45°.

4. The testing method for the compressive strength testing device of polycrystalline diamond composite sheet according to claim 2, characterized in that: The chamfer of the cylindrical edge is C = 0.5 × 45°.

5. The testing method for the compressive strength testing device of polycrystalline diamond composite sheet according to claim 1, characterized in that: The pressure head and the extension rod are fixed by welding.

6. The testing method for the compressive strength testing device of polycrystalline diamond composite sheet according to claim 1, characterized in that: The upper end of the cylindrical PDC sample to be tested is a polycrystalline diamond layer, and the lower end is a cemented carbide substrate.

7. The testing method for the compressive strength testing device of polycrystalline diamond composite sheet according to claim 1, characterized in that: The pressure sensor's sampling frequency f n =50Hz~100Hz.

8. The testing method for the compressive strength testing device of polycrystalline diamond composite sheet according to claim 1, characterized in that: The moving speed of the linear module is set to V = 0.1 mm / min ~ 1.0 mm / min.

9. The testing method for the compressive strength testing device of polycrystalline diamond composite sheet according to claim 1, characterized in that: The angle 'a' is set to 60° or 45°.

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