High-strength coating alloy drill bit

Abstract

The invention relates to the technical field of drill bits, in particular to a high-strength coating alloy drill bit. The drill bit adopts a multi-layer composite coating structure and comprises a chromium-cobalt co-sputtering deposition transition layer and a plasma enhanced chemical vapor deposition diamond-like carbon coating. The key process is as follows: a transition layer is formed on the surface of a matrix through co-sputtering of a chromium target and a cobalt target, then heat treatment is performed at 750-850 DEG C in a propane atmosphere, and finally the diamond-like carbon coating is deposited. The technical process is simple and convenient, industrial application is easy, the abrasion resistance and the service life of the alloy drill bit are effectively improved, and the requirements of the modern manufacturing industry for high-performance cutting tools are met.

Description

Technical Field

[0001] The present invention relates to the technical field of drill bits, and particularly to a high-strength coated alloy drill bit. Background Art

[0002] Due to its excellent balance of hardness and toughness, cemented carbide drill bits are widely used in the drilling of difficult-to-machine materials such as metals, composites, and rocks. However, with the continuous improvement of the requirements for processing efficiency and tool life in modern manufacturing, traditional cemented carbide drill bits can no longer meet the increasingly stringent process requirements under high-speed, dry, or minimum quantity lubrication cutting conditions. During the drilling process, the high temperature, high pressure, and intense friction between the drill bit and the workpiece will cause the drill bit to wear rapidly, seriously affecting the machining accuracy and production efficiency.

[0003] To improve the wear resistance of cemented carbide tools, coating hard coatings on their surfaces has become the mainstream technical route. Among them, diamond-like carbon (DLC) coatings are considered ideal wear-resistant coating materials because of their hardness close to that of diamond, extremely low friction coefficient, and excellent chemical stability. However, there are significant differences in physical and chemical properties between DLC coatings and cemented carbide substrates, such as lattice constant mismatch, large differences in thermal expansion coefficients, and poor affinity between carbon atoms and cobalt elements, resulting in low bonding strength between the coating and the substrate and easy peeling failure in actual processing.

[0004] Traditional solutions usually use a single metal transition layer (such as Ti, Cr, W, etc.) to improve the bonding force between the DLC coating and the cemented carbide substrate. Although these metal elements can form stable carbides with carbon, a single metal transition layer often cannot meet the requirements of good bonding with both the substrate and the DLC coating at the same time. Especially in the harsh drilling environment of high temperature and high pressure, the structural stability and interfacial bonding strength of a single metal transition layer are still insufficient, and the phenomenon of coating peeling is still common.

[0005] Therefore, there is an urgent need to develop a high-strength coated alloy drill bit to solve the technical problem of low bonding strength between the diamond-like coating and the cemented carbide drill bit substrate and meet the urgent needs of modern manufacturing for high-performance cutting tools. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a high-strength coated alloy drill bit to solve the problem of low bonding strength between the diamond-like coating and the cemented carbide drill bit substrate.

[0007] Based on the above purpose, the present invention provides a high-strength coated alloy drill bit, including a transition layer and a diamond-like coating; the transition layer is obtained by dual-target co-sputtering deposition on the surface of the alloy drill bit substrate; the diamond-like coating is obtained by plasma-enhanced chemical vapor deposition on the surface of the transition layer.

[0008] The sputtering targets for the dual-target co-sputtering deposition are a chromium target and a cobalt target. The working gas is argon, and the reaction gas is propane. The sputtering power of the chromium target is 300 - 400 W, the sputtering power of the cobalt target is 120 - 180 W, the substrate bias voltage is -80 ± 5 V, and the deposition time is 25 - 35 min.

[0009] The working gas for the plasma-enhanced chemical vapor deposition is argon, the reaction gas is propane, the ion beam voltage is 1500 - 1700 V, the substrate bias voltage is -700 ± 50 V, and the deposition time is 110 - 130 min.

[0010] The transition layer is pretreated before the plasma-enhanced chemical vapor deposition. The steps are as follows: Heat-treat the alloy drill bit with the transition layer in a propane gas atmosphere at 750 - 850 °C, with a heating rate of 5 - 20 °C / min, a gas pressure of 0.08 - 0.12 MPa, an insulation treatment time of 10 - 20 min, and then take it out and cool it in the furnace to obtain the pretreated alloy drill bit with the transition layer.

[0011] Preferably, the alloy drill bit substrate is pretreated before the dual-target co-sputtering deposition. The steps are as follows: Immerse the alloy drill bit substrate in a sodium hydroxide solution, perform ultrasonic treatment at 55 - 65 °C for 15 - 25 min, take it out and perform sandblasting treatment to obtain a pretreated alloy drill bit substrate with a surface roughness of 0.6 - 1 μm.

[0012] Preferably, the concentration of the sodium hydroxide solution is 12 wt% - 18 wt%.

[0013] Preferably, the raw material for the sandblasting treatment is white corundum sand with a mesh size of 150 - 250, and the pressure is 0.5 - 0.7 MPa.

[0014] Preferably, the purity of the chromium target is ≥99.9%, and the purity of the cobalt target is ≥99.9%.

[0015] Preferably, the argon flow rate for the dual-target co-sputtering deposition is 200 - 300 sccm, and the propane flow rate is 30 - 80 sccm.

[0016] Preferably, the target-substrate distance for the dual-target co-sputtering deposition is 6 - 8 cm, the background vacuum of the vacuum chamber is pumped to 2×10 -3 -4×10 -3 Pa, the sputtering gas pressure is 0.4 - 0.5 Pa, and the substrate temperature is 280 - 320 °C.

[0017] Preferably, the argon flow rate for the plasma-enhanced chemical vapor deposition is 40 - 60 sccm, and the propane flow rate is 180 - 220 sccm.

[0018] Preferably, the target-substrate distance in the plasma enhanced chemical vapor deposition is 4-6 cm, the background vacuum of the vacuum chamber is pumped to 2-4×10 -3 Pa, the deposition pressure is 1.5-2.5 Pa, and the substrate temperature is 280-320 °C.

[0019] Advantages of the present invention: The present invention provides a high-strength coated alloy drill bit. By designing a multi-layer composite coating structure, a perfect combination of high bonding strength and excellent wear resistance is achieved. The core of the present invention lies in introducing a composite transition layer prepared by chromium-cobalt co-sputtering and performing heat treatment pretreatment under specific conditions, which solves the technical problems of poor interfacial bonding and easy peeling when directly depositing a diamond-like carbon coating on the surface of cemented carbide.

[0020] The present invention uses the chromium-cobalt co-sputtering process to prepare the transition layer. Chromium provides good hardness and corrosion resistance, while cobalt, as an excellent binding phase, promotes the uniform distribution and diffusion of carbon atoms at the interface, forming a more stable structure. The synergistic effect of the two elements optimizes the physical and chemical properties of the transition layer and improves the interfacial bonding strength of the coating system.

[0021] The present invention uses a lower substrate bias voltage for depositing the transition layer, forming a transition layer with a specific surface morphology, enhancing the mechanical interlocking effect and effective contact area between the coating and the substrate. The transition layer deposited under such conditions has better elasticity and toughness, can effectively buffer stress concentration, and improves the mechanical stability of the entire coating system.

[0022] The present invention performs high-temperature pretreatment on the transition layer in a propane atmosphere, which is a key step in the entire process. This process not only promotes the diffusion and rearrangement of elements inside the transition layer, optimizes the organizational structure, but also allows carbon atoms to penetrate into the surface of the transition layer, forming a gradient transition region. This carbon-containing transition layer significantly improves the chemical affinity and structural matching with the upper diamond-like carbon coating, and at the same time, the formed metal carbide phase provides ideal nucleation and growth sites for the diamond-like carbon coating.

[0023] The multi-layer composite coating design of the present invention realizes a stress gradient distribution, effectively reduces interfacial stress concentration, improves the fatigue resistance and service life of the coating. The entire process flow is reasonably designed, easy to operate, and easy to be applied in industrial production, providing an effective technical solution for improving the wear resistance and service life of cemented carbide drill bits. Specific embodiments

[0024] To make the purpose, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention with specific embodiments. Embodiment

[0025] Step 1: Substrate pretreatment Immerse the YG8 cemented carbide drill bit substrate (Φ10mm×100mm) in a 15wt% sodium hydroxide solution, and ultrasonically treat it at 60°C for 20 minutes to remove the surface grease. After taking it out, sandblast it with 200-mesh white corundum sand under a pressure of 0.6 MPa to obtain a pre-treated alloy drill bit substrate with a surface roughness of Ra = 0.8μm; Step Two: Transition Layer Deposition Deposit a transition layer on the surface of the pre-treated alloy drill bit substrate by dual-target co-sputtering. The sputtering targets are a chromium target (purity 99.95%) and a cobalt target (purity 99.9%). The working gas is argon (flow rate 200 sccm), the reaction gas is propane (flow rate 30 sccm), the target-substrate distance is 6 cm, and the background vacuum of the vacuum chamber is pumped to 2×10 -3 Pa, the sputtering gas pressure is 0.4 Pa, the substrate temperature is 280°C, the sputtering power of the chromium target is 300 W, the sputtering power of the cobalt target is 120 W, the substrate bias voltage is -85V, and the deposition time is 25 minutes to obtain an alloy drill bit with a transition layer; Step Three: Transition Layer Pretreatment Heat-treat the alloy drill bit with a transition layer in a propane gas atmosphere at 750°C, with a heating rate of 5°C / min, a gas pressure of 0.08 MPa, and a holding time of 10 minutes. Take it out after cooling in the furnace to obtain a pre-treated alloy drill bit with a transition layer; Step Four: Diamond-like Carbon Coating Deposition Deposit a diamond-like carbon coating on the surface of the pre-treated alloy drill bit with a transition layer by plasma-enhanced chemical vapor deposition. The working gas is argon (flow rate 40 sccm), the reaction gas is propane (flow rate 180 sccm), the target-substrate distance is 4 cm, and the background vacuum of the vacuum chamber is pumped to 2×10 -3 Pa, the deposition gas pressure is 1.5 Pa, the substrate temperature is 280°C, the ion beam voltage is 1500V, the substrate bias voltage is -750V, and the deposition time is 110 minutes to obtain a high-strength coating alloy drill bit. Example

[0026] Step One: Substrate Pretreatment Immerse the YG8 cemented carbide drill bit substrate (Φ10mm×100mm) in a 15wt% sodium hydroxide solution, and ultrasonically treat it at 60°C for 20 minutes to remove the surface grease. After taking it out, sandblast it with 200-mesh white corundum sand under a pressure of 0.6 MPa to obtain a pre-treated alloy drill bit substrate with a surface roughness of Ra = 0.8μm; Step Two: Transition Layer Deposition A transition layer was deposited on the surface of the pre-treated alloy drill bit substrate by dual-target co-sputtering. The sputtering targets were a chromium target (purity 99.95%) and a cobalt target (purity 99.9%). The working gas was argon (flow rate 250 sccm), the reaction gas was propane (flow rate 50 sccm), the target-substrate distance was 7 cm, and the background vacuum of the vacuum chamber was pumped to 3×10 -3 Pa. The sputtering gas pressure was 0.45 Pa, the substrate temperature was 300 °C, the sputtering power of the chromium target was 350 W, the sputtering power of the cobalt target was 150 W, the substrate bias voltage was -80 V, and the deposition time was 30 min to obtain an alloy drill bit with a transition layer; Step three: Pretreatment of the transition layer The alloy drill bit with a transition layer was heat-treated at 800 °C in a propane gas atmosphere with a heating rate of 10 °C / min, a gas pressure of 0.1 MPa, and a heat preservation treatment time of 15 min, and then taken out after cooling in the furnace to obtain a pre-treated alloy drill bit with a transition layer; Step four: Deposition of diamond-like carbon coating A diamond-like carbon coating was deposited on the surface of the pre-treated alloy drill bit with a transition layer by plasma-enhanced chemical vapor deposition. The working gas was argon (flow rate 50 sccm), the reaction gas was propane (flow rate 200 sccm), the target-substrate distance was 5 cm, and the background vacuum of the vacuum chamber was pumped to 3×10 -3 Pa. The deposition gas pressure was 2 Pa, the substrate temperature was 300 °C, the ion beam voltage was 1600 V, the substrate bias voltage was -700 V, and the deposition time was 120 min to obtain a high-strength coated alloy drill bit. Example

[0027] Step one: Substrate pretreatment The matrix of the YG8 cemented carbide drill bit (Φ10 mm×100 mm) was immersed in a 15 wt% sodium hydroxide solution and ultrasonically treated at 60 °C for 20 min to remove surface grease. After taking it out, it was sandblasted with 200-mesh white corundum sand under a pressure of 0.6 MPa to obtain a pre-treated alloy drill bit substrate with a surface roughness of Ra = 0.8 μm; Step two: Deposition of the transition layer A transition layer was deposited on the surface of the pre-treated alloy drill bit substrate by dual-target co-sputtering. The sputtering targets were a chromium target (purity 99.95%) and a cobalt target (purity 99.9%). The working gas was argon (flow rate 300 sccm), the reaction gas was propane (flow rate 80 sccm), the target-substrate distance was 8 cm, and the background vacuum of the vacuum chamber was pumped to 4×10 -3 Pa. The sputtering gas pressure was 0.5 Pa, the substrate temperature was 320 °C, the sputtering power of the chromium target was 400 W, the sputtering power of the cobalt target was 180 W, the substrate bias voltage was -75 V, and the deposition time was 35 min to obtain an alloy drill bit with a transition layer; Step three: Pretreatment of the transition layer The alloy drill bit with a transition layer is heat-treated at 850 °C in a propane gas atmosphere, with a heating rate of 20 °C / min, a gas pressure of 0.12 MPa, a heat preservation treatment time of 20 min, and is taken out after furnace cooling to obtain a pre-treated alloy drill bit with a transition layer; Step Four: Deposition of diamond-like carbon coating A diamond-like carbon coating is deposited on the surface of the pre-treated alloy drill bit with a transition layer by plasma-enhanced chemical vapor deposition. The working gas is argon (flow rate 60 sccm), the reaction gas is propane (flow rate 220 sccm), the target-substrate distance is 6 cm, and the background vacuum of the vacuum chamber is pumped to 4×10 -3 Pa, the deposition pressure is 2.5 Pa, the substrate temperature is 320 °C, the ion beam voltage is 1700 V, the substrate bias voltage is -650 V, and the deposition time is 130 min to obtain a high-strength coated alloy drill bit.

[0028] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the transition layer is deposited by sputtering a single chromium target; The specific steps are as follows: Step One: Substrate pretreatment The matrix of the YG8 cemented carbide drill bit (Φ10 mm×100 mm) is immersed in a 15 wt% sodium hydroxide solution and ultrasonically treated at 60 °C for 20 min to remove surface grease. After taking it out, it is sandblasted with 200-mesh white corundum sand under a pressure of 0.6 MPa to obtain a pre-treated alloy drill bit matrix with a surface roughness of Ra = 0.8 μm; Step Two: Deposition of transition layer A transition layer is deposited on the surface of the pre-treated alloy drill bit matrix by single-target sputtering. The sputtering target is a chromium target (purity 99.95%), the working gas is argon (flow rate 250 sccm), the reaction gas is propane (flow rate 50 sccm), the target-substrate distance is 7 cm, and the background vacuum of the vacuum chamber is pumped to 3×10 -3 Pa, the sputtering pressure is 0.45 Pa, the substrate temperature is 300 °C, the sputtering power of the chromium target is 350 W, the substrate bias voltage is -80 V, and the deposition time is 30 min to obtain an alloy drill bit with a transition layer; Step Three: Pretreatment of transition layer The alloy drill bit with a transition layer is heat-treated at 800 °C in a propane gas atmosphere, with a heating rate of 10 °C / min, a gas pressure of 0.1 MPa, a heat preservation treatment time of 15 min, and is taken out after furnace cooling to obtain a pre-treated alloy drill bit with a transition layer; Step Four: Deposition of diamond-like carbon coating A diamond-like carbon coating was deposited on the surface of an alloy drill bit with a pre-treated transition layer by plasma-enhanced chemical vapor deposition. The working gas was argon (flow rate 50 sccm), the reaction gas was propane (flow rate 200 sccm), the target-substrate distance was 5 cm, and the background vacuum of the vacuum chamber was pumped to 3×10 -3 Pa, the deposition pressure was 2 Pa, the substrate temperature was 300 °C, the ion beam voltage was 1600 V, the substrate bias voltage was -700 V, and the deposition time was 120 min to obtain a coated alloy drill bit.

[0029] Comparative Example 2: The difference between Comparative Example 2 and Example 2 was that the substrate bias voltage for the deposition of the transition layer was -160 V; The specific steps were as follows: Step 1: Substrate pretreatment The matrix of the YG8 cemented carbide drill bit (Φ10 mm × 100 mm) was immersed in a 15 wt% sodium hydroxide solution and ultrasonically treated at 60 °C for 20 min to remove surface grease. After taking it out, it was sandblasted with 200-mesh white corundum sand under a pressure of 0.6 MPa to obtain a pre-treated alloy drill bit matrix with a surface roughness of Ra = 0.8 μm; Step 2: Transition layer deposition A transition layer was deposited on the surface of the pre-treated alloy drill bit matrix by dual-target co-sputtering. The sputtering targets were a chromium target (purity 99.95%) and a cobalt target (purity 99.9%). The working gas was argon (flow rate 250 sccm), the reaction gas was propane (flow rate 50 sccm), the target-substrate distance was 7 cm, and the background vacuum of the vacuum chamber was pumped to 3×10 -3 Pa, the sputtering pressure was 0.45 Pa, the substrate temperature was 300 °C, the sputtering power of the chromium target was 350 W, the sputtering power of the cobalt target was 150 W, the substrate bias voltage was -160 V, and the deposition time was 30 min to obtain an alloy drill bit with a transition layer; Step 3: Transition layer pretreatment The alloy drill bit with a transition layer was heat-treated at 800 °C in a propane gas atmosphere, with a heating rate of 10 °C / min, a gas pressure of 0.1 MPa, and a holding time of 15 min. It was taken out after cooling in the furnace to obtain a pre-treated alloy drill bit with a transition layer; Step 4: Diamond-like carbon coating deposition A diamond-like carbon coating was deposited on the surface of the pre-treated alloy drill bit with a transition layer by plasma-enhanced chemical vapor deposition. The working gas was argon (flow rate 50 sccm), the reaction gas was propane (flow rate 200 sccm), the target-substrate distance was 5 cm, and the background vacuum of the vacuum chamber was pumped to 3×10 -3Pa, the deposition pressure was 2 Pa, the substrate temperature was 300 °C, the ion beam voltage was 1600 V, the substrate bias voltage was -700 V, and the deposition time was 120 min, obtaining a coated alloy drill bit.

[0030] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the transition layer was not pretreated; The specific steps are as follows: Step 1: Substrate pretreatment Immerse the YG8 cemented carbide drill bit substrate (Φ10 mm × 100 mm) in a 15 wt% sodium hydroxide solution, ultrasonically treat it at 60 °C for 20 min to remove surface grease, and after taking it out, perform sandblasting treatment with 200-mesh white corundum sand under a pressure of 0.6 MPa to obtain a pretreated alloy drill bit substrate with a surface roughness of Ra = 0.8 μm; Step 2: Transition layer deposition Deposit a transition layer on the surface of the pretreated alloy drill bit substrate by dual-target co-sputtering. The sputtering targets are a chromium target (purity 99.95%) and a cobalt target (purity 99.9%). The working gas is argon (flow rate 250 sccm), the reaction gas is propane (flow rate 50 sccm), the target-substrate distance is 7 cm, and the background vacuum of the vacuum chamber is pumped to 3×10 -3 Pa, the sputtering pressure is 0.45 Pa, the substrate temperature is 300 °C, the sputtering power of the chromium target is 350 W, the sputtering power of the cobalt target is 150 W, the substrate bias voltage is -80 V, and the deposition time is 30 min, obtaining an alloy drill bit with a transition layer; Step 3: Diamond-like carbon coating deposition Deposit a diamond-like carbon coating on the surface of the alloy drill bit with a transition layer by plasma-enhanced chemical vapor deposition. The working gas is argon (flow rate 50 sccm), the reaction gas is propane (flow rate 200 sccm), the target-substrate distance is 5 cm, and the background vacuum of the vacuum chamber is pumped to 3×10 -3 Pa, the deposition pressure is 2 Pa, the substrate temperature is 300 °C, the ion beam voltage is 1600 V, the substrate bias voltage is -700 V, and the deposition time is 120 min, obtaining a coated alloy drill bit.

[0031] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the pretreatment temperature of the transition layer is 400 °C; The specific steps are as follows: Step 1: Substrate pretreatment Immerse the YG8 cemented carbide drill bit substrate (Φ10mm×100mm) in a 15wt% sodium hydroxide solution, and ultrasonically treat it at 60°C for 20 min to remove surface grease. After taking it out, perform sandblasting treatment with 200-mesh white corundum sand under a pressure of 0.6 MPa to obtain a pre-treated alloy drill bit substrate with a surface roughness of Ra = 0.8 μm; Step 2: Transition layer deposition Deposit a transition layer on the surface of the pre-treated alloy drill bit substrate by dual-target co-sputtering. The sputtering targets are a chromium target (purity 99.95%) and a cobalt target (purity 99.9%). The working gas is argon (flow rate 250 sccm), the reaction gas is propane (flow rate 50 sccm), the target-substrate distance is 7 cm, and the background vacuum of the vacuum chamber is pumped to 3×10 -3 Pa, the sputtering pressure is 0.45 Pa, the substrate temperature is 300°C, the sputtering power of the chromium target is 350 W, the sputtering power of the cobalt target is 150 W, the substrate bias voltage is -80 V, and the deposition time is 30 min to obtain an alloy drill bit with a transition layer; Step 3: Pretreatment of the transition layer Heat-treat the alloy drill bit with a transition layer in a propane gas atmosphere at 400°C, with a heating rate of 10°C / min, a gas pressure of 0.1 MPa, and a heat preservation treatment time of 15 min. Take it out after cooling in the furnace to obtain a pre-treated alloy drill bit with a transition layer; Step 4: Deposition of diamond-like carbon coating Deposit a diamond-like carbon coating on the surface of the pre-treated alloy drill bit with a transition layer by plasma-enhanced chemical vapor deposition. The working gas is argon (flow rate 50 sccm), the reaction gas is propane (flow rate 200 sccm), the target-substrate distance is 5 cm, and the background vacuum of the vacuum chamber is pumped to 3×10 -3 Pa, the deposition pressure is 2 Pa, the substrate temperature is 300°C, the ion beam voltage is 1600 V, the substrate bias voltage is -700 V, and the deposition time is 120 min to obtain a coated alloy drill bit.

[0032] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the gas atmosphere for the pretreatment of the transition layer is argon; The specific steps are as follows: Step 1: Substrate pretreatment Immerse the YG8 cemented carbide drill bit substrate (Φ10mm×100mm) in a 15wt% sodium hydroxide solution, and ultrasonically treat it at 60°C for 20 min to remove surface grease. After taking it out, perform sandblasting treatment with 200-mesh white corundum sand under a pressure of 0.6 MPa to obtain a pre-treated alloy drill bit substrate with a surface roughness of Ra = 0.8 μm; Step 2: Transition layer deposition A transition layer was deposited on the surface of the pretreated alloy drill bit matrix by dual-target co-sputtering. The sputtering targets were a chromium target (purity 99.95%) and a cobalt target (purity 99.9%). The working gas was argon (flow rate 250 sccm), the reaction gas was propane (flow rate 50 sccm), the target-substrate distance was 7 cm, and the background vacuum of the vacuum chamber was pumped to 3×10 -3 Pa. The sputtering gas pressure was 0.45 Pa, the substrate temperature was 300 °C, the sputtering power of the chromium target was 350 W, the sputtering power of the cobalt target was 150 W, the substrate bias voltage was -80 V, and the deposition time was 30 min to obtain an alloy drill bit with a transition layer; Step three: Pretreatment of the transition layer The alloy drill bit with a transition layer was heat-treated at 800 °C in an argon gas atmosphere with a heating rate of 10 °C / min, a gas pressure of 0.1 MPa, and a holding time of 15 min, and then taken out after furnace cooling to obtain a pretreated alloy drill bit with a transition layer; Step four: Deposition of diamond-like carbon coating A diamond-like carbon coating was deposited on the surface of the pretreated alloy drill bit with a transition layer by plasma-enhanced chemical vapor deposition. The working gas was argon (flow rate 50 sccm), the reaction gas was propane (flow rate 200 sccm), the target-substrate distance was 5 cm, and the background vacuum of the vacuum chamber was pumped to 3×10 -3 Pa. The deposition gas pressure was 2 Pa, the substrate temperature was 300 °C, the ion beam voltage was 1600 V, the substrate bias voltage was -700 V, and the deposition time was 120 min to obtain a coated alloy drill bit.

[0033] Performance test: Coating adhesion test: A WS-2005 type scratch tester was used, with a loading rate of 50 N / min, a maximum load of 100 N, and a diamond indenter curvature radius of 0.2 mm. The critical load value Lc was recorded. When the acoustic emission signal suddenly increased and the friction coefficient fluctuated by more than 15%, the coating was determined to fail. The results are shown in Table 1.

[0034] Coefficient of friction measurement: An MMU-10G friction and wear tester was used, with a ball-disk contact mode. The counterbody was a Φ6 mm GCr15 steel ball (hardness 62 HRC), the normal load was 10 N, the sliding speed was 0.2 m / s, and the total travel was 500 m. During the test, the coefficient of friction was recorded in real time through a torque sensor, and the average value of the last 300 m travel was taken as the final result. The results are shown in Table 1.

[0035] Wear resistance test: Install standard quartz sand abrasive (mesh size 80, flow rate 10 g / min) on the ML-100 abrasive wear testing machine, set the contact pressure at 15 N, and the sample rotation speed at 200 r / min. Stop the machine every 10 minutes for weighing (accuracy 0.1 mg), plot the mass loss-time curve, and stop the test and record the wear time when the cumulative mass loss reaches 10 mg.

[0036] Table 1 Performance test results Critical load value / N Coefficient of friction Wear time / min Example 1 67 0.13 280 Example 2 72 0.15 310 Example 3 69 0.18 290 Comparative example 1 58 0.14 210 Comparative example 2 63 0.16 240 Comparative example 3 51 0.15 180 Comparative example 4 65 0.16 230 Comparative example 5 60 0.14 200 Data analysis: From the data of Examples 1-3 in Table 1, it can be seen that the high-strength coated alloy drill bit prepared by the present invention has excellent comprehensive performance. The critical load value reaches 72 N, the friction coefficient is 0.15, and the wear time is as long as 310 minutes, indicating that the coated drill bit has good bonding strength and wear resistance. The lower friction coefficient indicates that a graphite-like carbon structure may be formed on the coating surface, having good solid lubrication performance. The excellent bonding strength and wear resistance of the coating system may be due to the stress gradient distribution realized by the multi-layer structure design, reducing the interfacial stress concentration, and improving the fatigue resistance and service life of the coating.

[0037] From the data of Example 2 and Comparative Example 1 in Table 1, it can be seen that compared with the scheme of using only chromium target for single sputtering, the scheme of using co-sputtering of chromium target and cobalt target to prepare the transition layer has significantly improved coating adhesion and wear resistance. This may be because the introduction of cobalt element forms a more favorable microstructure in the transition layer, enhancing the bonding strength between the transition layer and the substrate and the upper diamond-like carbon coating. As an excellent bonding phase, cobalt element may promote the uniform distribution and diffusion of carbon atoms on the surface of the transition layer, forming a more stable interfacial structure. At the same time, the composite transition layer formed by co-sputtering of chromium and cobalt may have more suitable lattice constants and thermal expansion coefficients, reducing the interfacial stress and improving the overall stability of the coating system.

[0038] From the data of Example 2 and Comparative Example 2 in Table 1, it can be seen that compared with using a higher substrate bias (-160 V), using a lower substrate bias (-80 V) for depositing the transition layer can obtain a higher critical load value and a longer wear resistance time. This may be because a lower substrate bias may form a rougher porous surface structure, increasing the contact area and mechanical interlocking effect between the coating and the substrate, thereby enhancing the interfacial bonding force. In addition, the transition layer deposited under lower bias conditions may maintain better elasticity and toughness, being able to buffer stress concentration more effectively, improving the fatigue resistance of the coating system under friction conditions, and finally showing more excellent wear resistance.

[0039] From the data of Example 2 and Comparative Example 3 in Table 1, it can be seen that heat treatment pretreatment of the transition layer can significantly improve the adhesion and wear resistance of the coating compared to no pretreatment. This may be because the heat treatment process promotes the diffusion and rearrangement of elements within the transition layer, optimizes the microstructure and chemical composition distribution of the transition layer, and eliminates the internal stress generated during the deposition process. At the same time, heat treatment in a propane atmosphere may cause carbon atoms to penetrate the surface of the transition layer, forming a transition region, which improves the chemical affinity and structural matching between the transition layer and the upper diamond-like carbon coating. Heat treatment may also promote the formation of carbide phases in the transition layer, such as chromium carbide and cobalt carbide, and these carbide phases can serve as favorable sites for the nucleation and growth of the diamond-like carbon coating, enhancing the interfacial adhesion. In addition, heat treatment may endow the surface of the transition layer with specific surface topography and structural features, increasing the surface roughness and effective contact area, thereby further enhancing the mechanical interlocking effect.

[0040] From the data of Example 2 and Comparative Example 4 in Table 1, it can be seen that when the pretreatment temperature of the transition layer is 800 °C compared to 400 °C, a higher coating adhesion and longer wear resistance time can be obtained. This may be because a higher pretreatment temperature can provide more sufficient thermal activation energy to promote the diffusion and recombination of elements within the transition layer, forming a more stable microstructure. At a higher temperature, the reaction between metal elements and carbon atoms in the transition layer is more sufficient, and more metal carbides, such as chromium carbide and cobalt carbide, may be formed. These compounds have high hardness and stability, which is beneficial to improving the overall mechanical properties of the coating. At the same time, heat treatment at a high temperature may more effectively release the residual stress accumulated during the deposition process, reduce interface defects, and improve the bonding strength of the coating. In addition, heat treatment at a higher temperature may cause a certain degree of reconstruction on the surface of the transition layer, forming a surface topography and chemical state more suitable for the growth of the diamond-like carbon coating. At a temperature of 800 °C, carbon atoms in the propane atmosphere may be more likely to penetrate the surface of the transition layer, forming a more ideal gradient transition structure, thereby enhancing the overall stability and wear resistance of the coating system.

[0041] From the data of Example 2 and Comparative Example 5 in Table 1, it can be seen that pre-treating the transition layer in a propane atmosphere can significantly improve the adhesion and wear resistance of the coating compared to pre-treating in an argon atmosphere. This may be because the propane atmosphere provides a rich carbon source, enabling carbon atoms to diffuse and penetrate the surface of the transition layer during the heat treatment process, forming carbide precursors that are beneficial for the growth of the subsequent diamond-like carbon coating. This transition layer containing carbon elements may have a better compositional gradient and chemical affinity with the upper diamond-like carbon coating, thereby enhancing the interfacial adhesion. In contrast, the inert argon atmosphere lacks an active carbon source and cannot achieve the formation of such carbides and the gradient distribution of carbon elements. In addition, propane may undergo a decomposition reaction at high temperatures, and the generated carbon atoms may participate in the formation of specific surface microstructures, such as carbon nanotubes or graphite-like structures, which may play a positive role in improving the interfacial adhesion and wear resistance.

[0042] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high-strength coated alloy drill bit, characterized in that: It comprises a transition layer and a diamond-like coating; the transition layer is deposited on the surface of the alloy drill bit substrate by double-target co-sputtering; the diamond-like coating is deposited on the surface of the transition layer by plasma enhanced chemical vapor deposition; The sputtering targets of the dual-target co-sputtering deposition are a chromium target and a cobalt target, the working gas is argon, the reaction gas is propane, the sputtering power of the chromium target is 300-400W, the sputtering power of the cobalt target is 120-180W, the substrate bias voltage is -80±5V, and the deposition time is 25-35min; The working gas of the plasma enhanced chemical vapor deposition is argon, the reaction gas is propane, the ion beam voltage is 1500-1700V, the substrate bias voltage is -700±50V, and the deposition time is 110-130min; The transition layer is pretreated before plasma enhanced chemical vapor deposition, and the steps are: heat treating the alloy drill bit containing the transition layer at 750-850°C in a propane gas atmosphere, with a heating rate of 5-20°C / min, a gas pressure of 0.08-0.12MPa, and a heat preservation time of 10-20min, and taking it out with the furnace cooling to obtain a pretreated alloy drill bit containing the transition layer.

2. The high-strength coated alloy drill bit according to claim 1, characterized in that: The alloy drill bit substrate is pretreated before dual-target co-sputtering deposition, and the steps are: immersing the alloy drill bit substrate in a sodium hydroxide solution, ultrasonically treating it at 55-65° C. for 15-25 minutes, and then taking it out and sandblasting it to obtain a pretreated alloy drill bit substrate with a surface roughness of 0.6-1 μm.

3. The high-strength coated alloy drill bit according to claim 1, characterized in that: The concentration of the sodium hydroxide solution is 12wt%-18wt%.

4. The high-strength coated alloy drill bit according to claim 1, characterized in that: The raw material for sandblasting is 150-250 mesh white corundum sand, and the pressure is 0.5-0.7MPa.

5. The high-strength coated alloy drill bit according to claim 1, characterized in that: The purity of the chromium target is ≥99.9%, and the purity of the cobalt target is ≥99.9%.

6. The high-strength coated alloy drill bit according to claim 1, characterized in that: The argon flow rate of the dual-target co-sputtering deposition is 200-300 sccm, and the propane flow rate is 30-80 sccm.

7. The high-strength coated alloy drill bit according to claim 1, characterized in that: The target-substrate distance of the dual-target co-sputtering deposition is 6-8 cm, and the background vacuum of the vacuum chamber is evacuated to 2×10 -3 -4×10 -3 Pa, the sputtering gas pressure is 0.4-0.5 Pa, and the substrate temperature is 280-320℃.

8. The high-strength coated alloy drill bit according to claim 1, characterized in that: The argon flow rate of the plasma enhanced chemical vapor deposition is 40-60 sccm, and the propane flow rate is 180-220 sccm.

9. The high-strength coated alloy drill bit according to claim 1, characterized in that: The target-substrate distance of the plasma enhanced chemical vapor deposition is 4-6 cm, and the background vacuum of the vacuum chamber is evacuated to 2-4×10 -3 Pa, the deposition gas pressure is 1.5-2.5 Pa, and the substrate temperature is 280-320℃.