Semi-wrapped corrosion-resistant polycrystalline diamond compact substrate and manufacturing method thereof

Abstract

The invention relates to the technical field of manufacturing of superhard materials and polycrystalline diamond compacts, and discloses a semi-wrapped corrosion-resistant polycrystalline diamond compact substrate and a manufacturing method thereof.The substrate is of a cylinder structure and is divided into an upper layer area and a lower layer area from top to bottom; the upper layer area comprises an upper inner layer and an upper outer layer, the upper inner layer is a common alloy substrate layer, the upper outer layer is a corrosion-resistant alloy layer, and the corrosion-resistant alloy layer annularly wraps the upper inner layer; the material of the corrosion-resistant alloy layer comprises a tungsten-cobalt alloy and a corrosion-resistant element, and the corrosion-resistant element is selected from one or two of nickel, chromium, molybdenum and aluminum; the whole lower layer area is a common alloy substrate layer with high strength and toughness, and the common alloy substrate layer is made of tungsten-cobalt alloy. The corrosion resistance of the substrate is remarkably improved while the high toughness of the substrate is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of superhard material and polycrystalline diamond compact manufacturing, in particular to a semi-wrapped corrosion-resistant polycrystalline diamond compact substrate and a manufacturing method thereof. BACKGROUND

[0002] The polycrystalline diamond compact is a superhard composite material composed of a polycrystalline diamond layer and a hard alloy substrate, which combines the superhigh hardness and high wear resistance of the polycrystalline diamond with the good impact toughness and weldability of the hard alloy substrate, and is the core component of high-performance cutting tools, playing an irreplaceable role in the field of superhard materials.

[0003] The polycrystalline diamond compact is mainly used in the fields of oil exploration, coal exploration, and mine excavation. In these fields, the PDC needs to be combined with the alloy substrate and the tooth seat to form a PDC drill bit. Specifically, the alloy substrate is used as a connecting carrier to form a composite cutting unit with the PDC cutting tooth, and then is fixed to the tooth seat through welding process, and finally is assembled into a PDC drill bit that can realize rock cutting. The drill bit cuts the stratum rock through high-speed rotation, and is the key equipment in deep-sea oil and gas exploration and deep-land mineral exploration projects.

[0004] Currently, the main material of the polycrystalline diamond compact substrate for the PDC drill bit is tungsten-cobalt (YG type) alloy. This type of alloy can meet the strength and toughness requirements in the conventional environment, but has significant limitations in harsh service environments such as deep sea and deep land. The sea salt in the deep sea environment can easily cause electrochemical corrosion, and the electrochemical corrosion can also occur in the deep land environment. The cobalt element in the tungsten-cobalt alloy is easily dissolved in the above corrosion environment, resulting in a sharp decrease in the strength and toughness of the alloy substrate, and further causing the PDC cutting tooth to fall off and the drill bit to fail, which seriously shortens the service life of the PDC drill bit.

[0005] To improve the corrosion resistance of the substrate, the existing technology mainly adopts the method of replacing the cobalt binder phase with corrosion-resistant elements, such as adding nickel and chromium elements in the entire substrate. However, this method can significantly reduce the strength and toughness of the hard alloy, and cannot meet the high requirements of the substrate strength and toughness in deep-sea and deep-land drilling. Some technologies attempt to build a multi-layer structure substrate, but do not optimize the welding area. Although the welding area does not require high corrosion resistance, the corrosion-resistant material is still used, which not only increases the cost, but also may need to adjust the welding process due to the change of the material, thereby reducing the production efficiency. Therefore, the existing polycrystalline diamond compact substrate still needs further research in the aspects of "structure design adaptation to corrosion scene" and "material formula balance between corrosion resistance and strength and toughness" to meet the use requirements of the PDC drill bit in harsh environments such as deep sea and deep land. SUMMARY

[0006] ​The application aims to provide a semi-wrapped corrosion-resistant polycrystalline diamond compact substrate, which can ensure the intrinsic high impact toughness and brazing performance of the polycrystalline diamond compact substrate, and simultaneously solve the problems of the decrease of the high toughness and the short service life of the PDC drill bit caused by the corrosion of cobalt in deep sea (sea salt electrochemical corrosion) and deep earth (electrochemical corrosion) environments.

[0007] To solve the above problems, the application adopts the following technical scheme: Scheme one: a semi-wrapped corrosion-resistant polycrystalline diamond compact substrate, the substrate is a cylindrical structure, and is divided into an upper layer region and a lower layer region from top to bottom; the upper layer region includes an upper inner layer and an upper outer layer, the upper inner layer is a common alloy substrate layer, the upper outer layer is a corrosion-resistant alloy layer, and the corrosion-resistant alloy layer wraps the upper inner layer in a ring shape; the material of the corrosion-resistant alloy layer includes tungsten-cobalt alloy and a corrosion-resistant element selected from one or two of nickel, chromium, molybdenum and aluminum; the lower layer region is a common alloy substrate layer with high toughness as a whole, and the material of the common alloy substrate layer is tungsten-cobalt alloy.

[0008] Beneficial effects: through the semi-wrapped structure of "lower layer full common alloy + upper inner layer common alloy + upper outer layer ring-shaped corrosion-resistant alloy", while ensuring that the substrate main body (lower layer + upper inner layer) is a high-toughness tungsten-cobalt alloy, the ring-shaped corrosion-resistant alloy of the upper outer layer is used to resist electrochemical corrosion in deep sea and deep earth environments, the balance between "high toughness" and "corrosion resistance" is achieved, and the performance imbalance problem caused by a single material or full-layer doping of corrosion-resistant elements is avoided.

[0009] The common alloy substrate layer with high toughness refers to a substrate layer made of tungsten-cobalt alloy with a mass percentage of cobalt in the range of 8-15%.

[0010] The application significantly improves the corrosion resistance of the substrate while ensuring the high toughness performance of the substrate by designing a semi-wrapped substrate and using an extrusion type additive manufacturing technology, thereby ensuring the service life of the PDC drill bit in harsh environments.

[0011] Preferably, the top surface of the upper inner layer of the substrate is provided with a non-planar structure, the non-planar structure includes a plurality of cutting tooth mounting seat protrusions, the cutting tooth mounting seat protrusions are prismatic, and grooves are arranged between adjacent cutting tooth mounting seat protrusions; all the cutting tooth mounting seat protrusions are uniformly distributed along the center of the top surface of the upper inner layer; the material of the cutting tooth mounting seat protrusions is the common alloy substrate layer, and the corrosion-resistant alloy layer of the upper outer layer does not cover the cutting tooth mounting seat protrusions.

[0012] ​Beneficial effects: The groove-shaped and prism-shaped design is used to relieve stress. The prism-shaped cutting tooth mounting seat protrusion is adapted to the mounting requirements of the PDC cutting tooth, and the protrusion is made of ordinary alloy material, which not only ensures the mounting strength, but also ensures that the process does not need to be specially adjusted during compounding; at the same time, the corrosion-resistant alloy layer does not cover the protrusion, further simplifying the structure and reducing the manufacturing difficulty; the corrosion-resistant elements in the corrosion-resistant alloy layer may affect the combination of the PDC cutting tooth and the composite sheet from the four dimensions of "wettability, interface reaction, bonding strength, and stability", so using ordinary alloy material at the PDC combination position can avoid such adverse effects.

[0013] Preferably, in the ordinary alloy base layer, the mass percentage of cobalt is 8-15%; in the corrosion-resistant alloy layer, the mass percentage of cobalt is 7-13%, and the mass ratio of corrosion-resistant elements to cobalt elements is 1:5~1:3.

[0014] Preferably, in the ordinary alloy base layer, the mass percentage of cobalt is 8-15%; in the corrosion-resistant alloy layer, the mass percentage of cobalt is 7-13%, and the mass ratio of corrosion-resistant elements to cobalt elements is 1:5~1:3.

[0015] Beneficial effects: Limiting the proportion of corrosion-resistant elements in the corrosion-resistant alloy layer not only ensures the improvement of corrosion resistance, but also avoids the decline in the toughness of the corrosion-resistant alloy layer due to excessive doping of elements (YG13 bending strength 3550MPa; mass percentage of corrosion-resistant alloy cobalt 10%, mass ratio of corrosion-resistant elements 3%, bending strength 3320-3360MPa; limiting the mass percentage of cobalt in the ordinary alloy base layer to 8-15%, preferably 10-13%, to ensure that the toughness of the base body can meet the impact load bearing requirements of deep sea and deep earth drilling.

[0016] Preferably, the thickness of the corrosion-resistant alloy layer is 0.5-3.5mm; the height ratio of the upper layer region to the lower layer region is 2:1-1:3.

[0017] Preferably, the thickness of the corrosion-resistant alloy layer is 1-2mm.

[0018] Beneficial effects: Limiting the thickness of the corrosion-resistant alloy layer to 0.5-3.5mm, preferably 1-2mm, reduces the amount of corrosion-resistant material while ensuring corrosion resistance; limiting the height ratio of the upper layer to the lower layer to 2:1-1:3, the PDC drill bit is connected to the shank by brazing, the corrosion-resistant elements in the corrosion-resistant layer may affect the bonding strength from the four dimensions of "wettability, interface reaction, bonding strength, and stability", the reasonable height of the lower layer ensures the overall strength and toughness of the drill bit, and the upper layer of the corrosion-resistant layer improves the corrosion resistance of the exposed area.

[0019] The disadvantages of the corrosion-resistant elements of the commonly used corrosion-resistant alloy are: 1. The "wettability" is not as good as the tungsten-cobalt alloy substrate, which can cause holes, density reduction, strength and toughness reduction, etc. 2. When diamond is compounded, due to the element doping, the "interface reaction" at the diamond combination is not as good as the tungsten-cobalt alloy substrate (capillary effect is blocked), cracks and uneven stress are prone to occur, which can cause low "bonding strength". Therefore, if the commonly used corrosion-resistant alloy substrate is used for diamond compounding, the "stability" is not as good as the tungsten-cobalt alloy substrate. The present application ingeniously avoids the influence of the disadvantages of the corrosion-resistant elements in the corrosion-resistant alloy by not covering the upper inner layer of the base structure with corrosion-resistant materials and controlling the thickness of the corrosion-resistant alloy layer, so that the "wettability, interface reaction, bonding strength and stability" can reach a balanced state, and the best effect can be achieved.

[0020] In addition, compared with the full-substrate corrosion-resistant alloy polycrystalline diamond compact, the impact toughness of the semi-wrapped corrosion-resistant polycrystalline diamond compact of the present application is greatly increased. The full-substrate corrosion-resistant alloy polycrystalline diamond compact and the semi-wrapped corrosion-resistant polycrystalline diamond compact with the same corrosion resistance are subjected to impact resistance comparison test by drop hammer method, and the detection method is: starting from the initial impact energy of 10J, testing ten times; if the sample does not appear damage (cracking, delamination, etc.), the impact energy is increased to 15J, and ten times of testing are continued; if the sample still does not appear damage, the impact energy is increased to 20J for ten times of testing, and the test is stopped after the sample is damaged, and the impact energy x impact times is the impact work, and the impact toughness is directly judged by the impact work value because the drop hammer method is simple to operate, but the stress area of the workpiece is difficult to determine. The impact work of the full-substrate corrosion-resistant alloy polycrystalline diamond compact is 730J; the impact work of the semi-wrapped corrosion-resistant polycrystalline diamond compact is 940J.

[0021] The corrosion-resistant alloy material selected in the semi-wrapped corrosion-resistant polycrystalline diamond compact of the present application has better corrosion resistance. The corrosion resistance test is conducted on the corrosion-resistant alloy and the ordinary alloy. The corrosion-resistant alloy obtained is soaked in 3.5% NaCl solution (simulating deep sea environment) for 100h, and the weight loss rate is 0.95mg / h; the corrosion-resistant alloy is soaked in a solution containing 100ppm for 100h (simulating deep sea environment), and the weight loss rate is 1.12mg / h; the ordinary alloy is soaked in 3.5% NaCl solution for 100h, and the weight loss rate is 1.8mg / h; the ordinary alloy is soaked in a solution containing 100ppm for 100h, and the weight loss rate is 2.1mg / h, and the corrosion resistance of the corrosion-resistant alloy is obviously better than that of the ordinary alloy.

[0022] Scheme two: a method for manufacturing a semi-wrapped corrosion-resistant polycrystalline diamond compact substrate, used to manufacture the semi-wrapped corrosion-resistant polycrystalline diamond compact substrate as described above, comprising the following steps: Step one: preparing a high polymer binder: take paraffin, TPE, PP, and stearic acid according to the mass ratio of 65±10:25±10:6±3:4±3, mix and melt to prepare a high polymer binder; Step two: preparing mixed granules: respectively place the ordinary alloy powder and the corrosion-resistant alloy powder in the mixing machine with the high polymer binder prepared in step one, wherein the volume ratio of the powder to the high polymer binder is 50-70:50-30, mix and granulate to prepare ordinary alloy mixed granules and corrosion-resistant alloy mixed granules; Step three: extruding and printing a green body: use an extrusion additive manufacturing device to place the ordinary alloy and corrosion-resistant alloy mixture in two nozzles of the extrusion printer, heat and melt at an extrusion temperature of 160-190℃, and print according to a preset path: first, single-nozzle fast print the lower ordinary alloy base layer, then alternate printing of the two nozzles to prepare the inner ordinary alloy base layer and the semi-wrapped upper structure of the outer annular corrosion-resistant alloy layer by layer, to obtain a substrate green body; Step four: green body degreasing: first, solvent degreasing of the substrate green body, using one or more of kerosene and n-heptane as the degreasing solvent, and the degreasing time is 8-12h; then, solvent thermal degreasing, the degreasing temperature is 200-400℃, the heating rate is 1-3℃ / h, and the degreasing time is 15-20h; Step five: densification sintering: place the degreased green body in a sintering furnace, sinter at 1350-1480℃ for 2-4h in a vacuum environment with a vacuum degree of ≤0.1Pa, to prepare a semi-wrapped corrosion-resistant polycrystalline diamond compact substrate.

[0023] Beneficial effects: by quantifying the high polymer binder formula, the ratio of powder to binder, the extrusion temperature, and the degreasing parameters, etc. key processes, to ensure smooth extrusion of the mixture, high precision of the green body, no cracking during degreasing, and sintering densification; at the same time, the design of double nozzles realizes the synchronous printing of ordinary alloy and corrosion-resistant alloy, directly forming a semi-wrapped structure, without subsequent assembly, improving production efficiency.

[0024] Preferably, in step two, the ordinary alloy powder is tungsten-cobalt alloy powder, wherein the particle size of the tungsten carbide powder is 1-5μm, and the particle size of the cobalt powder is 0.5-2μm; the corrosion-resistant alloy powder is a mixed powder of tungsten carbide powder and corrosion-resistant element powder, wherein the particle size of the tungsten carbide powder is 1-5μm, and the particle size of the corrosion-resistant element powder is 0.5-2μm, and the corrosion-resistant element is one or two of nickel, chromium, molybdenum, and aluminum.

[0025] Beneficial effects: limit the powder particle size to 0.5-5 μm, ensure the uniform mixing of the powder and the high-molecular binder, and reduce the agglomeration in the mixed particles; at the same time, the powder with the same particle size range can ensure the consistent shrinkage rate during sintering, avoid the substrate cracking caused by the particle size difference, and improve the substrate forming quality.

[0026] Preferably, in step three, the extrusion speed of the extrusion type additive manufacturing equipment is 5-10 mm / s, the nozzle size is 0.8-1.2 mm, and the layer thickness during printing is 0.2-0.5 mm.

[0027] Beneficial effects: the extrusion speed of 5-10 mm / s matches the nozzle size of 0.8-1.2 mm, which ensures the green body printing accuracy (avoids the filament breakage caused by too fast speed or the accumulation caused by too slow speed) and controls the sample preparation time; the layer thickness of 0.2-0.5 mm ensures the close interlayer bonding, avoids the layering, and improves the overall strength of the substrate.

[0028] In addition, in step four, during the solvent debinding, the substrate green body is completely immersed in the debinding solvent, and the debinding environment temperature is 25-30℃; during the solvent thermal debinding, inert protective gas is introduced into the sintering furnace, and the carrier gas flow is 100-200 mL / min. The temperature and immersion method of the solvent debinding ensure the sufficient dissolution of the binder and avoid local residues; the control of the inert protective gas and the carrier gas flow can prevent the green body from being oxidized during the thermal debinding process, and further reduce the debinding residues, thereby improving the purity of the substrate after sintering.

[0029] In addition, in step five, the heating rate of the densification sintering is 5-10℃ / h, and the temperature is lowered to room temperature at a rate of 3-5℃ / h after the holding is completed. The slow heating and cooling rates can reduce the thermal stress in the substrate during the sintering process, and avoid cracking and deformation caused by thermal stress; at the same time, the sufficient holding time ensures the sufficient densification of the substrate, improves the hardness and toughness of the substrate, and meets the use requirements in harsh environments.

[0030] Scheme three: a PDC drill bit, comprising a tooth seat, a PDC cutting tooth, and a semi-wrapped corrosion-resistant polycrystalline diamond compact substrate as described above; the PDC cutting tooth is combined with the cutting tooth mounting seat protrusion of the substrate, and the lower region of the substrate is welded and fixed with the tooth seat.

[0031] Beneficial effects: the high corrosion resistance and toughness of the substrate of the application can improve the corrosion resistance and impact resistance of the PDC drill bit in deep-sea and deep-land environments, and prolong the service life of the drill bit; at the same time, the substrate welding area is a common alloy, which does not need to adjust the existing welding process, thereby reducing the assembly difficulty and production cost of the PDC drill bit.

[0032] The advantages of the application are: I. Performance dimension: Precise balance of "corrosion resistance" and "toughness", breaking through the contradiction of existing technology 1. Local corrosion resistance design, considering core performance: Only in the upper outer layer (corrosion exposed area) adopt "tungsten cobalt alloy + nickel, chromium, molybdenum, aluminum corrosion resistant elements" corrosion resistant layer, the substrate main body (lower layer + upper inner layer, including welding, installation area) is still high toughness tungsten cobalt (YG type) alloy, which not only resists deep sea salt, deep electrochemical corrosion (weight loss rate increases from 1.8-2.1 mg / h to 0.95-1.12 mg / h), but also avoids the decrease of toughness caused by doping corrosion resistant elements in all layers (upper layer half wrapped corrosion resistant material, little effect on bending strength; impact energy 910-940J, close to pure tungsten cobalt alloy level), solving the core contradiction of existing technology "sacrifice toughness to improve corrosion resistance". At the same time, considering the four dimensions of "wettability, interface reaction, bonding strength and stability", the best product effect is achieved.

[0033] 2. Structure adaptation to corrosion scene, avoiding performance redundancy: According to the scene characteristics of the composite sheet substrate "upper exposed easy corrosion, lower welding no corrosion", only the upper outer layer is treated with corrosion resistance, and the welding area (lower layer) remains pure tungsten cobalt alloy, which not only saves corrosion resistant materials, but also ensures the toughness of the welding area to meet the assembly requirements, avoiding the performance redundancy caused by "excessive corrosion protection".

[0034] II. Process dimension: Create new additive manufacturing technology, break through the limitations of traditional process 1. Double nozzle extrusion molding, realizing precise manufacturing of complex structure: Using extrusion type additive manufacturing double nozzle technology, ordinary alloy and corrosion resistant alloy materials are loaded synchronously, and the "local ring corrosion resistant layer + main body ordinary alloy" half wrapped structure is directly printed——without layering, molding and subsequent assembly, solving the technical bottleneck of traditional powder metallurgy (molding, sintering) that cannot realize "local heterogeneous materials + ring complex structure", and the green body forming precision can reach 0.2-0.5mm layer thickness, without layering and cracking problems.

[0035] 2. High flexibility of customization, reducing the cost of modification: Traditional molding process needs to develop molds separately for different structures, with high modification cost and long cycle; this invention can quickly adapt to the needs of different diameters, heights and mounting seat protrusion quantities of the substrate by adjusting the 3D printing preset path, without the need to redevelop molds, realizing "quick customization production", especially suitable for the differentiated needs of different drilling scenes in deep sea and deep earth.

[0036] 3. Optimize process parameters to ensure molding quality: Design the formula of high polymer binder (precise proportion of paraffin / TPE / PP / stearic acid), degreasing process (solvent + heat degreasing combined, slow heating to prevent cracking), sintering process (vacuum environment + slow temperature rise and fall) to ensure smooth extrusion of the mixture, sufficient degreasing of the green body, consistent shrinkage and sintering density (98.5%), and avoid cracks, pores and deformation problems that may occur in traditional processes.

[0037] III. Cost dimension: double optimization of materials and processes, significantly reducing industrialization cost 1. Compatible with existing welding process, reducing assembly cost: The base welding area (lower layer) maintains pure tungsten-cobalt alloy, which is fully compatible with the existing PDC bit holder welding process, without the need to adjust the welding temperature and welding material type, avoiding the cost of welding process modification due to material changes, and reducing the assembly difficulty and production line modification cost of PDC bit.

[0038] 2. Save mold development, reduce fixed cost: Extrusion type additive manufacturing does not need special mold for traditional mold pressing, only needs to adjust the printing parameters for different specifications of the base, saving the time and cost of mold design and manufacturing (single set of mold can save tens of thousands of yuan), especially suitable for small batch, multi-specification customized orders.

[0039] IV. Application dimension: deep adaptation to deep sea and deep earth scenarios, prolonging the service life of PDC bit 1. Strong anti-failure ability in harsh environment: In deep sea and deep earth environment, the corrosion-resistant layer can effectively prevent the corrosion and dissolution of cobalt elements, avoiding the PDC cutting tooth falling off and drill failure caused by the sharp decline of the base toughness, compared with the traditional pure tungsten-cobalt alloy base, the service life of PDC bit can be prolonged by 2-3 times.

[0040] 2. Structural stability adapts to drilling conditions: The base is a cylindrical structure, the height ratio of the inner and outer layers of the upper layer (2:1-1:3) and the thickness of the corrosion-resistant layer (0.5-3.5mm) are optimized mechanically, which can withstand high-speed rotation impact (rotation speed ≥1000r / min) during drilling, avoiding vibration or fracture caused by center of gravity deviation and weak structure, and improving the stability of the drilling process.

[0041] In summary, the present application not only solves the technical pain point of "corrosion resistance and toughness" of the existing polycrystalline diamond compact base, but also realizes "low-cost manufacturing of complex structure" through process innovation, and deeply adapts to the actual application scenario of deep sea and deep earth, with significant technical advancement and industrialization value. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 BSE diagram of the interface between the corrosion-resistant material and the ordinary material (YG13) of the present application.

[0043] Figure 2 is a perspective view of the substrate structure of the present application.

[0044] Figure 3 is a top view of the substrate structure of the present application.

[0045] The reference signs in the drawings of the specification include: corrosion-resistant alloy layer 1, cutting tooth mounting seat protrusion 2, upper inner layer 3, lower layer area 4. DETAILED DESCRIPTION

[0046] Further details are described below through specific embodiments: As shown in Figure 2 and Figure 3 The semi-wrapping type corrosion-resistant polycrystalline diamond compact substrate of the present application is a cylindrical structure, which is divided into an upper layer area and a lower layer area 4 from top to bottom; the upper layer area includes an upper inner layer 3 and an upper outer layer, the upper inner layer 3 is a WC-Co general alloy substrate layer, and the upper outer layer is a corrosion-resistant alloy layer 1, and the corrosion-resistant alloy layer 1 is annularly wrapped around the upper inner layer 3; the material of the corrosion-resistant alloy layer 1 includes tungsten-cobalt alloy and corrosion-resistant elements selected from one or two of nickel, chromium, molybdenum, and aluminum; the lower layer area 4 is a general alloy substrate layer as a whole, and the material of the general alloy substrate layer is tungsten-cobalt alloy. The lower layer area 4 and the upper inner layer 3 are integrally formed as a WC-Co general alloy substrate. Through the semi-wrapping type structure of "lower layer full general alloy + upper layer inner layer general alloy + upper layer outer layer annular corrosion-resistant alloy", while ensuring that the substrate main body (lower layer + upper inner layer 3) is a high-strength and tough tungsten-cobalt alloy, the upper outer layer annular corrosion-resistant alloy is used to resist electrochemical corrosion in deep sea and deep earth environment, to achieve the balance of "strength and toughness" and "corrosion resistance", and to avoid the performance imbalance problem caused by single material or full layer doping of corrosion-resistant elements.

[0047] Among them, the top surface of the upper inner layer 3 is provided with a cutting tooth mounting seat protrusion 2, the cutting tooth mounting seat protrusion 2 is in the shape of a prism platform, and is uniformly distributed along the center of the top surface of the upper inner layer 3; the material of the cutting tooth mounting seat protrusion 2 is a general alloy substrate layer, and the corrosion-resistant alloy layer 1 of the upper outer layer does not cover the cutting tooth mounting seat protrusion 2. The prism platform-shaped cutting tooth mounting seat protrusion 2 is adapted to the installation requirements of PDC cutting teeth, and the protrusion is made of a general alloy material, which not only ensures the installation strength, but also avoids the cost waste caused by using corrosion-resistant materials in non-corrosion areas (the composite of the mounting seat and the cutting tooth). At the same time, the corrosion-resistant alloy layer 1 does not cover the protrusion, which further simplifies the structure and reduces the manufacturing difficulty.

[0048] The mass percentage of cobalt in the corrosion-resistant alloy layer 1 is 7-13%, preferably 9-11%, and the mass ratio of corrosion-resistant elements to cobalt elements is 1:5~1:3. The mass percentage of cobalt in the ordinary alloy base layer is 8-15%, preferably 10-13%. Limiting the mass ratio of corrosion-resistant elements to cobalt in the corrosion-resistant alloy layer 1 ensures the improvement of corrosion resistance and avoids the decline of the toughness of the corrosion-resistant alloy layer 1 due to excessive doping of elements. Limiting the mass percentage of cobalt in the ordinary alloy base layer to 8-15% ensures that the strength and toughness of the base body can meet the impact load bearing requirements of deep sea and deep earth drilling.

[0049] The thickness of the corrosion-resistant alloy layer 1 is 0.5-3.5mm; the height ratio of the upper layer region to the lower layer region 4 is 2:1-1:3. Limiting the thickness of the corrosion-resistant alloy layer 1 to 0.5-3.5mm reduces the amount of corrosion-resistant material used and reduces costs while ensuring corrosion resistance. Limiting the height ratio of the upper layer to the lower layer to 2:1-1:3 ensures the stability of the overall center of gravity of the base body, avoids cutting vibration caused by the center of gravity deviation when the PDC drill bit rotates, and improves drilling stability.

[0050] The manufacturing method of the semi-wrapped corrosion-resistant polycrystalline diamond compact base of the present application is used to manufacture the semi-wrapped corrosion-resistant polycrystalline diamond compact base as described above, and comprises the following steps: Step one, preparing a high molecular binder: weigh 65±10:25±10:6±3:4±3 of paraffin, TPE, PP and stearic acid by mass ratio, mix and melt to prepare a high molecular binder; Step two, preparing mixed granules: respectively place the ordinary alloy powder and the corrosion-resistant alloy powder in the mixing machine with the high molecular binder prepared in step one, wherein the volume ratio of the powder to the high molecular binder is 50-70:50-30, mix and granulate to prepare ordinary alloy mixed granules and corrosion-resistant alloy mixed granules; Step three, extruding and printing green body: use an extrusion type additive manufacturing equipment, place the ordinary alloy and corrosion-resistant alloy mixed material in two nozzles of the extrusion printer, heat and melt at an extrusion temperature of 160-190℃, and print according to the preset path: first, single nozzle fast printing of the lower ordinary alloy base layer, then two nozzle alternate printing, layer by layer preparation of the inner ordinary alloy base layer and the outer ring-shaped corrosion-resistant alloy semi-wrapped upper layer structure, to obtain a base green body; Step four, green body degreasing: first, solvent degreasing of the base green body, using one or more of kerosene and n-heptane as the degreasing solvent, degreasing time is 8-12h; then, solvent thermal degreasing, degreasing temperature is 200-400℃, heating rate is 1-3℃ / h, degreasing time is 15-20h; Step five, densification sintering: the debinding green body is placed in a sintering furnace, and sintered at 1350-1480℃ for 2-4h under a vacuum degree of ≤0.1Pa to obtain a semi-encapsulated corrosion-resistant polycrystalline diamond compact substrate.

[0051] In step two, the ordinary alloy powder is tungsten-cobalt alloy powder, wherein the particle size of the tungsten carbide powder is 1-5μm, and the particle size of the cobalt powder is 0.5-2μm; the corrosion-resistant alloy powder is a mixed powder of tungsten carbide powder and corrosion-resistant element powder, wherein the particle size of the tungsten carbide powder is 1-5μm, and the particle size of the corrosion-resistant element powder is 0.5-2μm, and the corrosion-resistant element is one or two of nickel, chromium, molybdenum and aluminum. The powder particle size is limited to 0.5-5μm to ensure uniform mixing of the powder and the high molecular binder and reduce the agglomeration phenomenon in the mixed material particles; at the same time, the powder with the same particle size range can ensure consistent shrinkage rate during sintering, avoid substrate cracking caused by particle size difference, and improve the substrate forming quality.

[0052] In step three, the extrusion speed of the extrusion type additive manufacturing equipment is 5-10mm / s, and the nozzle size is 0.8-1.2mm; the layer thickness during printing is 0.2-0.5mm. The extrusion speed of 5-10mm / s matches the nozzle size of 0.8-1.2mm, which not only ensures the printing accuracy of the green body (avoids broken filament caused by too fast speed or accumulation caused by too slow speed), but also controls the sample preparation time; the layer thickness of 0.2-0.5mm ensures tight interlayer bonding, avoids layering, and improves the overall strength of the substrate.

[0053] In step four, during solvent debinding, the substrate green body is completely immersed in the debinding solvent, and the debinding environment temperature is 25-30℃, and the debinding time is 8-12h; during solvent thermal debinding, inert protective gas is introduced into the sintering furnace, and the carrier gas flow is 100-200mL / min. The temperature and immersion method of solvent debinding ensure that the binder is fully dissolved, avoiding local residues; the control of inert protective gas and carrier gas flow can prevent the green body from being oxidized during thermal debinding, while carrying away the volatile binder components, further reducing the debinding residues, and improving the purity of the substrate after sintering.

[0054] In step five, the heating rate of densification sintering is 5-10℃ / h, and after the holding period ends, the temperature is lowered to room temperature at a rate of 3-5℃ / h. Slow heating and cooling rates can reduce the thermal stress inside the substrate during sintering, avoiding cracking and deformation caused by thermal stress; at the same time, sufficient holding time ensures that the substrate is fully densified, improving the hardness and toughness of the substrate, and meeting the use requirements in harsh environments.

[0055] The PDC drill bit formed by using the semi-wrapping type corrosion-resistant polycrystalline diamond compact substrate structure comprises a tooth holder, a PDC cutting tooth and a semi-wrapping type corrosion-resistant polycrystalline diamond compact substrate as described above; the PDC cutting tooth is combined with the cutting tooth mounting seat protrusion 2 of the substrate, and the lower area 4 of the substrate is welded and fixed with the tooth holder. By using the high corrosion resistance and toughness of the substrate, the corrosion resistance and impact resistance of the PDC drill bit in the deep sea and deep land environment are improved, and the service life of the drill bit is prolonged. At the same time, the substrate welding area is a common alloy, and there is no need to adjust the existing welding process, thereby reducing the assembly difficulty and production cost of the PDC drill bit.

[0056] Embodiment 1 1.1 Substrate structure The substrate is a cylinder (diameter 15 mm, total height 10 mm), which is divided into an upper area (height 4 mm) and a lower area (height 6 mm) from top to bottom: The upper area: the upper inner layer (diameter 12 mm, height 4 mm) is YG13 tungsten-cobalt alloy, and the upper outer layer (thickness 1.5 mm, height 4 mm) is corrosion-resistant alloy (mass percentage of cobalt is 10%, mass percentage of corrosion-resistant elements (only containing nickel and chromium) is 3%); The top surface of the upper inner layer: 4 prism-shaped cutting tooth mounting seat protrusions (upper bottom diameter 3 mm, lower bottom diameter 4 mm, height 1 mm) are uniformly distributed along the center, and the protrusion material is YG13 tungsten-cobalt alloy; The lower area: the whole common alloy substrate layer is made of YG13 tungsten-cobalt alloy (mass percentage of cobalt is 13%).

[0057] 1.2 Preparation method 1) Preparation of high molecular binder: weigh paraffin, TPE, PP and stearic acid according to the mass ratio of 65:25:6:4, mix and melt at 180℃ for 30 min to prepare the high molecular binder; 2) Preparation of mixed material particles: Common alloy powder: YG13 tungsten-cobalt alloy powder (tungsten carbide particle size 3 μm, cobalt powder particle size 1 μm); Corrosion-resistant alloy powder: mass percentage of cobalt is 10%, mass percentage of corrosion-resistant elements is 3% (particle size of corrosion-resistant elements is 1 μm); Mix the two kinds of powders with the high molecular binder according to the volume ratio of 60:40, mix in a banbury mixer (temperature 170℃) for 30 min, and then granulate (particle diameter 2 mm) to prepare common alloy mixed material particles and corrosion-resistant alloy mixed material particles; 3) Extrusion printing of green body: Equipment: double-nozzle extrusion type 3D printer; Process parameters: extrusion temperature 180℃, extrusion speed 8 mm / s, nozzle size 1.0 mm, layer thickness 0.3 mm; Printing path: first, single nozzle rapid printing of the lower layer of general alloy base layer, then two nozzles alternate printing, layer by layer preparation of the inner layer of general alloy base layer and the outer layer of semi-enclosed upper structure of ring-shaped corrosion-resistant alloy, to obtain the base green body; 4) Green body degreasing: Solvent degreasing: immerse the green body in n-heptane at 25℃ for 10h; Solvent thermal degreasing: place in a sintering furnace, introduce argon gas (flow rate 150mL / min), heat to 300℃ at 2℃ / h, and keep for 18h to complete degreasing; 5) Densification sintering: In a vacuum environment (vacuum degree 0.05Pa), heat to 1400℃ at 8℃ / h, keep for 3h, and then cool to room temperature at 4℃ / h to obtain the target substrate.

[0058] 6) High temperature and high pressure sintering: Mix the diamond micro powder and cobalt powder according to a mass ratio of 20:1, put them into a molybdenum crucible together with the previously prepared hard alloy substrate, assemble a high temperature and high pressure synthesis block with NaCl, carbon tube, and pyrophyllite as auxiliary materials, sinter at 1550℃ and 8.5GPa, and keep for 12min to obtain a polycrystalline diamond compact (PDC) product 1.3 Performance test The performance of the prepared substrate was tested, and the results are as follows: Corrosion resistance: immerse in 3.5% NaCl solution (simulate deep sea environment) for 100h, the weight loss rate is 0.95mg / h; immerse in a solution containing 100ppm (simulate deep environment) for 100h, the weight loss rate is 1.12mg / h; Impact toughness: impact resistance comparison test of the compact was carried out by drop hammer method, the detection method was as follows: start from the initial impact energy of 10J and test ten times; if the sample has no damage (cracking, delamination, etc.), increase the impact energy to 15J and continue to test ten times; if there is still no damage, increase the impact energy to 20J and test ten times, gradually accumulate until the sample is damaged, and stop testing, the impact energy x impact times is the impact work, test five times for each layer and take the average value as 940J; Densification: the density is 99.5%, without cracking and porosity.

[0059] Comparative example 1: traditional full tungsten cobalt alloy substrate (existing structure) (the difference from example 1 is that the whole is a general alloy material) 1.1 Substrate structure The substrate is a cylinder (diameter 15 mm, total height 10 mm), the whole is YG13 tungsten-cobalt alloy (cobalt mass ratio 13%), and the top surface is provided with four prismatic tooth mounting seat protrusions which are the same as those in Example 1.

[0060] 1.2 Preparation method The traditional molding-sintering process is adopted: 1) YG13 tungsten-cobalt alloy powder is molded (pressure 700 MPa) to obtain a green body; 2) After the green body is degreased, it is sintered at 1400 ℃ for 3 h in a vacuum environment at a temperature rising rate of 8 ℃ / h, and then cooled to room temperature at a temperature falling rate of 4 ℃ / h to obtain the substrate.

[0061] 1.3 Performance test Corrosion resistance: immersed in 3.5% NaCl solution for 100 h, the weight loss rate is 1.8 mg / h; immersed in a solution containing 100 ppm of Cl- for 100 h, the weight loss rate is 2.1 mg / h; impact energy 970 J; density: 99.7%.

[0062] Comparative Example 2: substrate doped with corrosion-resistant elements in the whole layer (existing improved scheme) (the difference from Example 1 is that the whole is a corrosion-resistant alloy material) 2.1 Substrate structure The same as Comparative Example 1 (the whole cylinder, the top surface is provided with protrusions), the material is a cobalt mass ratio of 10% and a corrosion-resistant element mass ratio of 3% (doped in the whole layer).

[0063] 2.2 Preparation method The molding-sintering process of Comparative Example 1.

[0064] 2.3 Performance test Corrosion resistance: immersed in 3.5% NaCl solution for 100 h, the weight loss rate is 0.21 mg / h; immersed in a solution containing 100 ppm of Cl- for 100 h, the weight loss rate is 0.25 mg / h; Bending strength: 3360 MPa Impact energy: 850 J; Density: 99.3%.

[0065] Comparative Example 3: traditional multi-layer structure substrate (existing multi-layer scheme) (the difference from Example 1 is that the upper and lower layers are ordinary alloy materials, and the middle layer is a traditional corrosion-resistant alloy material) 3.1 Substrate structure ​​Cylinder (diameter 15mm, total height 10mm), from top to bottom: "upper layer YG13 tungsten-cobalt alloy (height 2mm, with protrusions) + middle layer corrosion-resistant alloy (height 3mm) + lower layer YG13 tungsten-cobalt alloy (height 5mm)", all layers covered with corrosion-resistant alloy, no annular design.

[0066] 3.2 Preparation method 3D printing-sintering process: same as example 1, only the printing path is different, which is first single-nozzle rapid printing of the lower layer of ordinary alloy base layer, then replacing the nozzle to print the middle layer of corrosion-resistant alloy, and finally switching back to the lower layer nozzle to print the upper layer of ordinary alloy base layer to obtain the green body of the base; 3.3 Performance test Corrosion resistance: immersed in 3.5% NaCl solution for 100h, the weight loss rate is 1.13mg / h; immersed in a solution containing 100ppm for 100h, the weight loss rate is 1.21mg / h; Impact energy: 675J; Density: 98.7%.

[0067] Table 1

[0068] The examples of the present application and the prior art comparative examples are significantly different, and the present application has the following characteristics compared with the prior art: 1) Performance balance breakthrough: as shown in Table 1, the prior art cannot simultaneously achieve "high corrosion resistance" and "high toughness" - comparative example 1 (all tungsten-cobalt) has poor corrosion resistance, and comparative example 2 (all layers doped) has a significant decrease in toughness; and the present application realizes the optimal balance between corrosion resistance (1 times higher than comparative example 1) and toughness (comparable to comparative example 1, significantly better than comparative examples 2 and 3) through the semi-enclosed structure of "local annular corrosion-resistant layer + main body of ordinary alloy", solving the core contradiction of the prior art.

[0069] 2) Process innovation and cost reduction and efficiency improvement: the traditional die pressing process (comparative examples 1 and 2) cannot realize the precise forming of the "annular local corrosion-resistant layer", and needs to be layered and pressed (cannot be automatically fully pressed) or doped with all layers, resulting in low production efficiency, high cost, and poor structural flexibility (such as product structure adjustment, which requires the traditional die pressing process to re-make the mold); and the present application uses extrusion type additive manufacturing double-nozzle technology to directly print the complex semi-enclosed structure of "local annular + main body of ordinary alloy", without subsequent processing, and the process parameters (such as binder formulation and debinding rate) are optimized to ensure that the shrinkage rates of the two types of material powders are consistent, avoiding green body cracking, and achieving the structure and performance goals that the traditional process cannot achieve, significantly improving production efficiency.

[0070] 3) Particle size control and performance differentiation: The WC particle size design of "coarse outside and fine inside" (particle size difference ≤0.3 μm) is adopted to actively control the liquid phase migration behavior in the sintering process. The outer binder phase migrates inward, thereby causing the liquid phase content of the outer layer to decrease, and the wear resistance and corrosion resistance of the outer layer are improved; at the same time, the inner layer is significantly enhanced in toughness due to the increase in the liquid phase content.

[0071] 4) From Figure 1 It can be seen that the two layers are tightly combined, and there are no defects such as pores and cracks at the interface, indicating that the two materials in this embodiment are well fused.

[0072] Example 2 The difference between this embodiment and Example 1 is that in Step 1 of this embodiment, the high molecular binder is prepared: paraffin, TPE, PP and stearic acid are weighed according to the mass ratio of 55:35:3:7, and the high molecular binder is prepared after being mixed and melted; the powder flowability and shape retention obtained in this embodiment are not as good as in Example 1, and higher temperature and pressure may be required for printing, which requires high printing requirements and increases the cost.

[0073] Example 3 The difference between this embodiment and Example 1 is that in Step 1 of this embodiment, the high molecular binder is prepared: paraffin, TPE, PP and stearic acid are weighed according to the mass ratio of 75:15:3:7, and the high molecular binder is prepared after being mixed and melted; the green strength obtained in this embodiment is poor and is easy to change; the substrate is easy to crack, bubble, deform and have poor density after sintering, resulting in poor substrate size accuracy, low yield and performance effect not as good as in Example 1.

[0074] Example 4 The difference between this embodiment and Example 1 is that in Step 2, the mixed granules are prepared: the ordinary alloy powder and the corrosion-resistant alloy powder are respectively mixed with the high molecular binder prepared in Step 1, and the volume ratio of the powder to the high molecular binder is 50:50, and the ordinary alloy mixed granules and the corrosion-resistant alloy mixed granules are prepared after mixing and granulating. Since 50:50 belongs to low loading ratio, although the flowability is good, the skeleton is loose and fragile after debinding, and uneven shrinkage, warping and deformation may occur due to surface tension, gravity and internal stress during sintering, resulting in poor substrate size accuracy and low yield; the substrate performance effect obtained in this embodiment is not as good as in Example 1.

[0075] Example 5 The difference between this embodiment and embodiment 1 is that in step 2, the mixed granules are prepared: the general alloy powder and the corrosion-resistant alloy powder are respectively mixed with the polymer binder prepared in step 1, and the volume ratio of the powder to the polymer binder is 70:30. After mixing, the general alloy mixed granules and the corrosion-resistant alloy mixed granules are prepared by granulation. Since 70:30 belongs to an ultrahigh loading ratio, it is theoretically possible to obtain the smallest shrinkage and the best dimensional accuracy, but the process window is very narrow, the technical difficulty is the highest, and the practicality is extremely low. The substrate performance effect obtained in this embodiment is not as good as that in embodiment 1.

[0076] Embodiment 6 Compared with embodiment 1, this embodiment is a double-layer substrate containing an aluminum corrosion-resistant layer and a preparation method thereof.

[0077] 1.1 Substrate structure The substrate is a cylinder (diameter 15 mm, total height 10 mm), which is divided into an upper layer region (height 4 mm) and a lower layer region (height 6 mm) from top to bottom: The upper layer region: the upper inner layer (diameter 12 mm, height 4 mm) is YG13 tungsten-cobalt alloy, and the upper outer layer (thickness 1.5 mm, height 4 mm) is a corrosion-resistant alloy (mass percentage of cobalt is 10%, mass ratio of corrosion-resistant elements (only containing molybdenum and aluminum) is 2.1%). In this embodiment, only “aluminum” and “molybdenum” are added as corrosion-resistant elements (aluminum mass percentage is 0.6%, molybdenum is 1.5%); The simultaneous addition of trace amounts of aluminum and molybdenum in tungsten-cobalt alloy produces a synergistic complementary effect. They act on different “short boards” of the material system respectively, and optimize the comprehensive performance of the alloy together. Molybdenum can be regarded as an excellent “microstructure optimizer”, which lays a solid foundation for the role of aluminum as a “performance enhancer” by improving interface quality and bonding uniformity. A dense and well-bonded matrix can better withstand the internal stress introduced by aluminum particles, thereby to some extent alleviating the problem of rapid decrease in toughness caused by the addition of aluminum alone.

[0078] The upper inner layer top surface: 4 prism-shaped cutting tooth mounting seat protrusions (upper bottom diameter 3 mm, lower bottom diameter 4 mm, height 1 mm) are uniformly distributed along the center, and the protrusion material is YG13 tungsten-cobalt alloy; The lower layer region: the whole general alloy substrate layer is made of YG13 tungsten-cobalt alloy (mass percentage of cobalt is 13%).

[0079] 1.2 Preparation method 1) Preparation of polymer binder: weigh paraffin, TPE, PP, and stearic acid according to a mass ratio of 65:25:6:4, mix and melt at 180°C for 30 min to prepare the polymer binder; 2) Preparation of mixed granules: Common alloy powder: YG13 tungsten-cobalt alloy powder (tungsten carbide particle size 3 μm, cobalt powder particle size 1 μm); Corrosion-resistant alloy powder: tungsten-cobalt alloy powder + aluminum powder (aluminum powder particle size 20-30 nm, mass ratio 0.6%, high-purity aluminum powder is selected to avoid the influence of impurities on corrosion resistance); Mix the two kinds of powder with the polymer binder at a volume ratio of 60:40, mix in a closed mixer (temperature 170°C) for 30 min, and then granulate (granule diameter 2 mm) to obtain common alloy mixture granules and corrosion-resistant alloy mixture granules; 3) Extrusion printing of green body: Equipment: double-nozzle extrusion 3D printer; Process parameters: extrusion temperature 180°C, extrusion speed 8 mm / s, nozzle size 1.0 mm, layer thickness 0.3 mm; Printing path: first, single-nozzle rapid printing of the lower common alloy base layer, then two-nozzle alternate printing to layer-by-layer prepare the inner common alloy base layer and the outer semi-encapsulated upper structure of annular corrosion-resistant alloy, to obtain the base green body; 4) Green body debinding: Solvent debinding: immerse the green body in n-heptane at 25°C for 10 h; Solvent debinding: immerse the green body in n-heptane at 25°C for 10 h; 5) Densification sintering: Vacuum environment (vacuum degree 0.05 Pa), temperature rise to 1400°C at a rate of 8°C / h, keep for 3 h, and then temperature drop to room temperature at a rate of 4°C / h to obtain the target base.

[0080] 6) High-temperature and high-pressure sintering: Mix diamond micro-powder with cobalt powder at a mass ratio of 20:1, and put it into a molybdenum crucible together with the previously prepared hard alloy base, and then assemble a high-temperature and high-pressure synthesis block with NaCl, carbon tube, and pyrophyllite as auxiliary materials. After sintering at 1550°C and 8.5 GPa for 12 min, a polycrystalline diamond compact (PDC) product is obtained.

[0081] 1.3 Performance test The performance of the obtained base is tested, and the results are as follows: Corrosion resistance: weight loss rate 1.09 mg / h in 3.5% NaCl solution (simulating deep sea environment) for 100 h; weight loss rate 1.25 mg / h in a solution containing 100 ppm (simulating deep environment) for 100 h; Bending strength: 3320 MPa Impact toughness: impact resistance comparative experiments were carried out on the composite sheet by using drop hammer method, and the detection method was as follows: starting from the initial impact energy of 10 J, ten times of tests were carried out; if the sample did not appear damage (collapse, delamination, etc.), the impact energy was increased to 15 J, and ten times of tests were continued; if the damage still did not appear, the impact energy was increased to 20 J for ten times of tests, and the tests were stopped after the sample was damaged, and the impact energy x impact times was the impact work, and the average value of five tests of each layer was 910 J; Compactness: compactness 99.3%, no cracking, air hole.

[0082] Three groups of targeted comparative examples were set, and comparative analysis was carried out with example 6: Comparative example 4: the difference between this example and example 6 was that the particle size of aluminum powder was 1 μm 4.1 Structure and preparation Structure: completely consistent with example 6, but the particle size of corrosion-resistant element aluminum in the corrosion-resistant layer powder was 1 μm Preparation: the same as the extrusion type additive manufacturing process of example 6.

[0083] 4.2 Performance test Corrosion resistance: immersed in 3.5% NaCl solution (simulating deep sea environment) for 100 h, the weight loss rate was 1.01 mg / h; immersed in 100 ppm containing solution (simulating deep environment) for 100 h, the weight loss rate was 1.17 mg / h; (basically consistent with example 6); Toughness: bending strength 2330 MPa, impact work 700 J (decreased by 29.8%, 23.1% respectively compared with example 6); Problem: the particle size of aluminum powder is too coarse (not nano level), which will become a crack source, and the crack will be generated and expanded from the interface between the coarse particle and the matrix when bearing load; at the same time, it will seriously cut the binder phase, so that the strength and toughness of the material will decrease sharply.

[0084] Comparative example 5: tungsten-cobalt alloy substrate doped with aluminum in all layers (existing single material improvement idea) 5.1 Structure and preparation Structure: overall cylinder (diameter 15 mm, total height 10 mm), all layers are "tungsten-cobalt alloy + 1% aluminum" (cobalt mass ratio 12%), and the top surface is provided with the same protrusion as example 6; Preparation: the same as the extrusion type additive manufacturing process of example 6.

[0085] 5.2 Performance test Corrosion resistance: immersed in 3.5% NaCl solution (simulating deep sea environment) for 100 h, the weight loss rate was 1.22 mg / h; immersed in 100 ppm in 3.5% NaCl solution (simulate deep sea environment) for 100h, the weight loss rate was 0.53mg / h; in 100ppm H2S solution (simulate deep sea environment) for 100h, the weight loss rate was 0.61mg / h; (significantly improved compared with Example 6); Toughness: bending strength 2480MPa, impact energy 525J (decreased by 25.3%, 42.3% respectively compared with Example 6); Problem: the cobalt content of the ordinary alloy is insufficient, although the role of the corrosion-resistant layer is retained, the main toughness does not meet the "high toughness" standard, and the drill is easy to break due to impact.

[0086] Comparative Example 6: containing aluminum corrosion-resistant layer but ordinary alloy cobalt content exceeds the standard (deviating from the definition of the application) 6.1 Structure and preparation Structure: completely consistent with Example 6, but the mass percentage of cobalt in the ordinary alloy base layer is 6% (lower than the high toughness definition of "8-15%"); Preparation: same as the extrusion type additive manufacturing process of Example 6.

[0087] 6.2 Performance test Corrosion resistance: in 3.5% NaCl solution (simulate deep sea environment) for 100h, the weight loss rate was 0.53mg / h; in 100ppm H2S solution (simulate deep sea environment) for 100h, the weight loss rate was 0.61mg / h; (significantly improved compared with Example 6); Corrosion resistance: in 3.5% NaCl solution (simulate deep sea environment) for 100h, the weight loss rate was 0.53mg / h; in 100ppm H2S solution (simulate deep sea environment) for 100h, the weight loss rate was 0.61mg / h; (significantly improved compared with Example 6); Toughness: bending strength 2480MPa, impact energy 525J (decreased by 25.3%, 42.3% respectively compared with Example 6); Problem: the cobalt content of the ordinary alloy is insufficient, although the role of the corrosion-resistant layer is retained, the main toughness does not meet the "high toughness" standard, and the drill is easy to break due to impact.

[0088] This embodiment breaks through the inherent contradiction between "single corrosion-resistant element and toughness" in the prior art. If aluminum is used as a corrosion-resistant element, it is usually "full layer doping" (such as Comparative Example 5), which can improve corrosion resistance, but will inevitably lead to a significant decrease in toughness. While using aluminum and molybdenum as corrosion-resistant elements, the toughness is maintained at a high level of "bending strength 3320MPa, impact energy 910J", solving the cognitive limitation of the prior art that "aluminum doping must sacrifice toughness", and not simply adding elements.

[0089] The embodiment defines the cobalt content range of the "high toughness ordinary alloy", and the technical targetedness of Comparative Example 6 proves that if the cobalt content of the ordinary alloy is lower than 8%, even if the corrosion-resistant layer containing aluminum and molybdenum is matched, the main toughness cannot meet the demand of deep sea drilling; the ordinary alloy substrate layer of the present application is defined as "tungsten-cobalt alloy with 8-15% cobalt", which is a precise range verified by performance, rather than an arbitrarily selected parameter - the range not only ensures the toughness effect of cobalt as a binder phase, but also avoids the increase of corrosion sensitivity caused by too high cobalt content, which reflects the deep control of the relationship between material composition and performance, and has non-obviousness.

[0090] The substrate of Embodiment 6 has a deep adaptability to the application scene, and the corrosion resistance of the substrate is slightly better than that of the scheme of full-layer doping aluminum (the weight loss rate is 0.03-0.12 mg / h), and the toughness is much higher than that of the latter (the bending strength is 30.2% higher), and is compatible with the existing welding process (the lower layer is an ordinary tungsten-cobalt alloy), perfectly adapting to the "corrosion resistance-toughness-assembly" triple demand of the PDC drill bit in harsh environment - such multi-dimensional scene adaptation capability cannot be achieved by the single performance improvement in the prior art, further proving its non-obviousness.

[0091] The above is only an embodiment of the present application, and the well-known specific technical solutions and / or common sense in the scheme are not described in detail. It should be noted that for those skilled in the art, without departing from the technical solutions of the present application, some modifications and improvements can be made, which should also be considered as the protection scope of the present application, and these will not affect the effect and practicality of the present application. The protection scope of the present application should be subject to the content of its claims, and the specific embodiments and the like in the specification can be used to explain the content of the claims.

Claims

1. A semi-encapsulated corrosion-resistant polycrystalline diamond compact substrate, characterized by, The substrate is a cylindrical structure, which is divided into an upper layer region and a lower layer region from top to bottom; the upper layer region comprises an upper inner layer and an upper outer layer, the upper inner layer is a common alloy substrate layer, the upper outer layer is a corrosion-resistant alloy layer, and the corrosion-resistant alloy layer is annularly wrapped around the upper inner layer; the material of the corrosion-resistant alloy layer comprises tungsten-cobalt alloy and corrosion-resistant elements selected from one or two of nickel, chromium, molybdenum and aluminum; the lower layer region is a high-toughness common alloy substrate layer as a whole, and the material of the common alloy substrate layer is tungsten-cobalt alloy.

2. The semi-wrapped corrosion-resistant PDC bit substrate of claim 1, wherein, The top surface of the upper inner layer of the substrate is provided with a non-planar structure, which comprises a plurality of cutting tooth mounting seat protrusions, the cutting tooth mounting seat protrusions are prisms, and grooves are arranged between adjacent cutting tooth mounting seat protrusions; all the cutting tooth mounting seat protrusions are uniformly distributed along the center of the top surface of the upper inner layer; the material of the cutting tooth mounting seat protrusions is the common alloy substrate layer, and the corrosion-resistant alloy layer of the upper outer layer does not cover the cutting tooth mounting seat protrusions.

3. The semi-wrapped corrosion resistant PDC bit substrate of claim 1, wherein, In the common alloy substrate layer, the mass percentage of cobalt is 8-15%; in the corrosion-resistant alloy layer, the mass percentage of cobalt is 7-13%, and the mass ratio of the corrosion-resistant element to cobalt element is 1:5~1:

3.

4. The semi-wrapped corrosion resistant PDC bit substrate of claim 3, wherein, In the common alloy substrate layer, the mass percentage of cobalt is 10-13%; in the corrosion-resistant alloy layer, the mass percentage of cobalt is 9-11%, and the mass ratio of the corrosion-resistant element to cobalt element is 1:3.

5.

5. The semi-flush corrosion resistant PCD table base of claim 1, wherein, The thickness of the corrosion-resistant alloy layer is 0.5-3.5mm; the height ratio of the upper layer region to the lower layer region is 2:1-1:

3.

6. The semi-wrapped corrosion resistant PDC bit substrate of claim 5, wherein, The thickness of the corrosion-resistant alloy layer is 1-2mm.

7. A method of manufacturing a semi-encapsulated corrosion-resistant polycrystalline diamond compact substrate, characterized by, A method for manufacturing the semi-wrapped corrosion-resistant PDC substrate according to any one of claims 1-6, comprising the following steps: Step one, preparing a polymer binder: weighing paraffin, TPE, PP and stearic acid according to the mass ratio of 65±10:25±10:6±3:4±3, mixing and melting to prepare a polymer binder; Step two, preparing mixed material particles: respectively placing the common alloy powder and the corrosion-resistant alloy powder in a mixing mill with the polymer binder prepared in step one, wherein the volume ratio of the powder to the polymer binder is 50-70:50-30, and after mixing and granulation, common alloy mixed material particles and corrosion-resistant alloy mixed material particles are prepared; Step three, extruding and printing a green body: using an extrusion additive manufacturing device, placing the common alloy and corrosion-resistant alloy mixed materials in two nozzles of the extrusion printer, heating and melting at an extrusion temperature of 160-190℃, and printing according to a preset path: first, single-nozzle rapid printing of the lower common alloy substrate layer, then two-nozzle alternate printing, layer-by-layer preparation of the inner common alloy substrate layer and the outer annular corrosion-resistant alloy to obtain a substrate green body. Step four, green body degreasing: first, the green body of the substrate is degreased by solvent, the degreasing solvent is one or more of kerosene and n-heptane, the degreasing time is 8-12h; then, the green body is degreased by solvent thermal, the degreasing temperature is 200-400℃, the heating rate is 1-3℃ / h, and the degreasing time is 15-20h; Step five, densification sintering: the degreased green body is placed in a sintering furnace, sintered at 1350-1480℃ for 2-4h under a vacuum degree of ≤0.1Pa, and a semi-enclosed corrosion-resistant polycrystalline diamond compact substrate is prepared.

8. The manufacturing method according to claim 7, wherein In step two, the ordinary alloy powder is tungsten-cobalt alloy powder, the particle size of the tungsten carbide powder is 1-5μm, and the particle size of the cobalt powder is 0.5-2μm; the corrosion-resistant alloy powder is a mixed powder of tungsten carbide powder and corrosion-resistant element powder, the particle size of the tungsten carbide powder is 1-5μm, the particle size of the corrosion-resistant element powder is 0.5-2μm, and the corrosion-resistant element is one or two of nickel, chromium, molybdenum and aluminum.

9. The production method according to claim 7, wherein In step three, the extrusion speed of the extrusion additive manufacturing equipment is 5-10mm / s, the nozzle size is 0.8-1.2mm, and the layer thickness during printing is 0.2-0.5mm.

10. A PDC drill bit characterized by, The semi-enclosed corrosion-resistant polycrystalline diamond compact substrate as claimed in any one of claims 1-7 is used in a PDC bit, which comprises a bit body, a PDC cutting tooth and the semi-enclosed corrosion-resistant polycrystalline diamond compact substrate, the PDC cutting tooth is combined with the cutting tooth mounting seat protrusion of the substrate, and the lower area of the substrate is welded and fixed with the bit body.

Images