A high-strength coated alloy drill bit

Abstract

The present invention relates to the technical field of drill bits, and particularly to a high-strength coated alloy drill bit. The drill bit adopts a multi-layer composite coating structure, including a transition layer deposited by co-sputtering of chromium and cobalt and a diamond-like carbon coating deposited by plasma-enhanced chemical vapor deposition. The key process is as follows: first, a transition layer is formed on the substrate surface by co-sputtering of a chromium target and a cobalt target, then heat treatment is carried out at 750-850 °C in a propane atmosphere, and finally a diamond-like carbon coating is deposited. The technical process is simple and easy to be applied industrially, effectively improving the wear resistance and service life of the alloy drill bit and meeting the requirements of modern manufacturing industry for high-performance cutting tools.

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 DLC coatings and cemented carbide substrates. Although these metal elements can form stable carbides with carbon, a single metal transition layer often cannot meet the good bonding requirements 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 widespread.

[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 diamond-like coatings and cemented carbide drill bit substrates 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 diamond-like coatings and cemented carbide drill bit substrates.

[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, 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 is -80±5V, and the deposition time is 25-35min.

[0009] The working gas for 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.

[0010] 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. The drill bit is taken out after cooling in the furnace to obtain a pretreated alloy drill bit containing the transition layer.

[0011] Preferably, the alloy drill bit substrate is pretreated before dual-target co-sputtering deposition, the steps of which are: immersing the alloy drill bit substrate in a sodium hydroxide solution, ultrasonically treating it at 55-65° C. for 15-25 minutes, taking it out and sandblasting it 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 12wt%-18wt%.

[0013] Preferably, the raw material for sandblasting is 150-250 mesh white corundum sand, 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 of 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 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℃.

[0017] Preferably, the argon flow rate of 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 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:

[0020] The present invention provides a high-strength coated alloy drill bit. By designing a multi-layer composite coating structure, the 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.

[0021] 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 bonding phase, promotes the uniform distribution and diffusion of carbon atoms at the interface, forming a more stable structure. The two elements work together synergistically to optimize the physical and chemical properties of the transition layer and improve the interfacial bonding strength of the coating system.

[0022] 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, which can effectively buffer stress concentration and improve the mechanical stability of the entire coating system.

[0023] 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 an ideal nucleation and growth site for the diamond-like carbon coating.

[0024] The multi-layer composite coating design of the present invention realizes a stress gradient distribution, effectively reduces the 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. Detailed embodiments

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention with specific embodiments. Embodiment

[0026] Step 1: Substrate pretreatment

[0027] Immerse the YG8 cemented carbide drill bit substrate (Φ10mm×100mm) in a 15wt% sodium hydroxide solution, and perform ultrasonic treatment at 60°C for 20 minutes 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 pretreated alloy drill bit substrate with a surface roughness of Ra = 0.8μm;

[0028] Step 2: Transition layer deposition

[0029] 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 200 sccm), the reaction gas is propane (flow rate 30 sccm), the target-substrate distance is 6 cm, 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 -85 V, and the deposition time is 25 minutes to obtain an alloy drill bit with a transition layer;

[0030] Step 3: Transition layer pretreatment

[0031] 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 heat preservation treatment time of 10 minutes. Take it out after cooling in the furnace to obtain a pretreated alloy drill bit with a transition layer;

[0032] Step 4: Diamond-like carbon coating deposition

[0033] Deposit a diamond-like carbon coating on the surface of the pretreated 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, 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 1500 V, the substrate bias voltage is -750 V, and the deposition time is 110 minutes to obtain a high-strength coating alloy drill bit. Example

[0034] Step 1: Substrate pretreatment

[0035] Immerse the YG8 cemented carbide drill bit substrate (Φ10mm×100mm) in a 15wt% sodium hydroxide solution, and perform ultrasonic treatment 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;

[0036] Step 2: Transition layer deposition

[0037] 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 gas 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;

[0038] Step 3: Pretreatment of the transition layer

[0039] Heat-treat the alloy drill bit with a transition layer in a propane gas atmosphere at 800°C, with a heating rate of 10°C / min, a gas pressure of 0.1 MPa, and a holding time of 15 min. Take it out after cooling in the furnace to obtain a pre-treated alloy drill bit with a transition layer;

[0040] Step 4: Deposition of diamond-like carbon coating

[0041] 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 gas 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 high-strength coating alloy drill bit. Example

[0042] Step 1: Substrate pretreatment

[0043] Immerse the YG8 cemented carbide drill bit substrate (Φ10mm×100mm) in a 15wt% sodium hydroxide solution, and perform ultrasonic treatment 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;

[0044] Step 2: Transition layer deposition

[0045] A transition layer is deposited on the surface of the pretreated alloy drill bit matrix 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 300 sccm), the reaction gas is propane (flow rate 80 sccm), the target-substrate distance is 8 cm, the background vacuum of the vacuum chamber is pumped to 4×10 -3 Pa, the sputtering gas pressure is 0.5 Pa, the substrate temperature is 320 °C, the sputtering power of the chromium target is 400 W, the sputtering power of the cobalt target is 180 W, the substrate bias voltage is -75 V, and the deposition time is 35 min to obtain an alloy drill bit with a transition layer;

[0046] Step 3: Pretreatment of the transition layer

[0047] The alloy drill bit with a transition layer is heat-treated at 850 °C in a propane gas atmosphere. The heating rate is 20 °C / min, the gas pressure is 0.12 MPa, and the holding time is 20 min. It is taken out after cooling in the furnace to obtain a pretreated alloy drill bit with a transition layer;

[0048] Step 4: Deposition of diamond-like carbon coating

[0049] A diamond-like carbon coating is deposited on the surface of the pretreated 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, the background vacuum of the vacuum chamber is pumped to 4×10 -3 Pa, the deposition gas 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 coating alloy drill bit.

[0050] Comparative Example 1:

[0051] The difference between Comparative Example 1 and Example 2 is that the transition layer is sputtered with a single chromium target;

[0052] The specific steps are as follows:

[0053] Step 1: Substrate pretreatment

[0054] 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 pretreated alloy drill bit matrix with a surface roughness of Ra = 0.8 μm;

[0055] Step 2: Transition layer deposition

[0056] A transition layer is deposited on the surface of the pretreated alloy drill bit substrate 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 gas 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;

[0057] Step three: Pretreatment of the transition layer

[0058] The alloy drill bit with a transition layer is heat-treated at 800 °C in a propane gas atmosphere, the heating rate is 10 °C / min, the gas pressure is 0.1 MPa, the holding time is 15 min, and it is taken out after furnace cooling to obtain a pretreated alloy drill bit with a transition layer;

[0059] Step four: Deposition of diamond-like carbon coating

[0060] A diamond-like carbon coating is deposited on the surface of the pretreated 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 gas 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.

[0061] Comparative example 2:

[0062] The difference between comparative example 2 and example 2 is that the substrate bias voltage for transition layer deposition is -160 V;

[0063] The specific steps are as follows:

[0064] Step one: Substrate pretreatment

[0065] The substrate 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 pretreated alloy drill bit substrate with a surface roughness of Ra = 0.8 μm;

[0066] Step two: Transition layer deposition

[0067] A transition layer is deposited 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 gas 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 -160 V, and the deposition time is 30 min to obtain an alloy drill bit with a transition layer;

[0068] Step three: Pretreatment of the transition layer

[0069] The alloy drill bit with a transition layer is heat-treated at 800 °C in a propane gas atmosphere. The heating rate is 10 °C / min, the gas pressure is 0.1 MPa, the heat preservation treatment time is 15 min, and it is taken out after cooling in the furnace to obtain a pre-treated alloy drill bit with a transition layer;

[0070] Step four: Deposition of diamond-like carbon coating

[0071] 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 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 gas 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.

[0072] Comparative example 3:

[0073] The difference between comparative example 3 and example 2 is that the transition layer is not pre-treated;

[0074] The specific steps are as follows:

[0075] Step one: Substrate pretreatment

[0076] The YG8 cemented carbide drill bit substrate (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 substrate with a surface roughness of Ra = 0.8 μm;

[0077] Step two: Deposition of the transition layer

[0078] A transition layer was deposited on the surface of the pretreated 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 down 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;

[0079] Step three: Deposition of diamond-like carbon coating

[0080] A diamond-like carbon coating was deposited on the surface of the 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 down 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.

[0081] Comparative example 4:

[0082] The difference between comparative example 4 and example 2 was that the temperature of the transition layer pretreatment was 400 °C;

[0083] The specific steps were as follows:

[0084] Step one: Substrate pretreatment

[0085] 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 pretreated alloy drill bit substrate with a surface roughness of Ra = 0.8 μm;

[0086] Step two: Deposition of transition layer

[0087] A transition layer was deposited on the surface of the pretreated 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 down to 3×10 -3Pa, 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 -80 V, and the deposition time was 30 min to obtain an alloy drill bit with a transition layer;

[0088] Step 3: Pretreatment of the transition layer

[0089] The alloy drill bit with a transition layer was heat-treated at 400 °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 furnace cooling to obtain a pretreated alloy drill bit with a transition layer;

[0090] Step 4: Deposition of diamond-like carbon coating

[0091] Plasma-enhanced chemical vapor deposition was used to deposit a diamond-like carbon coating on the surface of the pretreated alloy drill bit with a transition layer. 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.

[0092] Comparative example 5:

[0093] The difference between comparative example 5 and example 2 is that the gas atmosphere for the pretreatment of the transition layer is argon;

[0094] The specific steps are as follows:

[0095] Step 1: Pretreatment of the substrate

[0096] 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 pretreated alloy drill bit matrix with a surface roughness of Ra = 0.8 μm;

[0097] Step 2: Deposition of the transition layer

[0098] Dual-target co-sputtering was used to deposit a transition layer on the surface of the pretreated alloy drill bit matrix. 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 -3Pa, 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 -80 V, and the deposition time was 30 min, obtaining an alloy drill bit with a transition layer;

[0099] Step 3: Pretreatment of the transition layer

[0100] 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 an insulation treatment time of 15 min. It was taken out after furnace cooling, obtaining a pretreated alloy drill bit with a transition layer;

[0101] Step 4: Deposition of diamond-like carbon coating

[0102] 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 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.

[0103] Performance testing:

[0104] Coating adhesion test: Using a WS-2005 type scratch tester, set the loading rate at 50 N / min, the maximum load at 100 N, the curvature radius of the diamond indenter at 0.2 mm, record the critical load value Lc, and determine that the coating fails when the acoustic emission signal suddenly increases and the friction coefficient fluctuates by more than 15%. The results are shown in Table 1.

[0105] Coefficient of friction measurement: Using an MMU-10G friction and wear tester, adopting a ball-on-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, 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.

[0106] Abrasion resistance test: Install standard quartz sand abrasive (particle size 80 mesh, flow rate 10 g / min) on an ML-100 abrasive wear tester, 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.

[0107] Table 1 Performance test results

[0108] 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

[0109] Data analysis:

[0110] As can be seen from the data of Examples 1 - 3 in Table 1, 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, with good solid lubrication performance. The excellent bonding strength and wear resistance of the coating system may be due to the stress gradient distribution achieved by the multi-layer structure design, reducing the interfacial stress concentration, and improving the fatigue resistance and service life of the coating.

[0111] As can be seen from the data of Example 2 and Comparative Example 1 in Table 1, compared with the scheme of using only a chromium target for single sputtering, the scheme of using co-sputtering of a chromium target and a cobalt target to prepare the transition layer has significantly improved coating adhesion and wear resistance. This may be because the introduction of cobalt elements 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 elements may promote the uniform distribution and diffusion of carbon atoms on the surface of the transition layer, forming a more stable interface structure. At the same time, the composite transition layer formed by chromium-cobalt co-sputtering may have a more suitable lattice constant and thermal expansion coefficient, reducing the interfacial stress and improving the overall stability of the coating system.

[0112] As can be seen from the data of Example 2 and Comparative Example 2 in Table 1, compared with using a higher substrate bias (-160 V), using a lower substrate bias (-80 V) for the deposition of 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 more rough and 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, which can more effectively buffer stress concentration and improve the fatigue resistance of the coating system under friction conditions, ultimately resulting in more excellent wear resistance.

[0113] 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.

[0114] 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 complete, 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.

[0115] 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 composition 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.

[0116] Those of ordinary skill in the art should understand that the discussion of any 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, and they are not provided in detail for the sake of brevity.

Claims

1. A high-strength coated alloy drill bit, characterized in that, It includes a transition layer and a diamond-like carbon coating; the transition layer is obtained by dual-target co-sputtering deposition on the surface of an alloy drill bit substrate; the diamond-like carbon coating is obtained by plasma-enhanced chemical vapor deposition on the surface of the transition layer; For the dual-target co-sputtering deposition, the sputtering targets 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 - 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; For the plasma-enhanced chemical vapor deposition, the working gas 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; The transition layer is pretreated before the plasma-enhanced chemical vapor deposition. The steps are as follows: The alloy drill bit with the transition layer is heat-treated at 750 - 850 °C in a propane gas atmosphere, the heating rate is 5 - 20 °C / min, the gas pressure is 0.08 - 0.12 MPa, the heat preservation treatment time is 10 - 20 min, and it is taken out after furnace cooling to obtain a pretreated alloy drill bit with the transition layer.

2. The high-strength coated alloy drill bit according to claim 1, wherein The alloy drill bit substrate is pretreated before the dual-target co-sputtering deposition. The steps are as follows: The alloy drill bit substrate is immersed in a sodium hydroxide solution and ultrasonically treated at 55 - 65 °C for 15 - 25 min, and then taken out for sandblasting treatment 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 2, wherein The concentration of the sodium hydroxide solution is 12 wt% - 18 wt%.

4. The high-strength coated alloy drill bit according to claim 2, wherein 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.

5. The high-strength coated alloy drill bit according to claim 1, wherein 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, wherein For the dual-target co-sputtering deposition, the argon flow rate 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 for the dual-target co-sputtering deposition is 6-8 cm, and 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.

8. The high-strength coated alloy drill bit according to claim 1, wherein For the plasma-enhanced chemical vapor deposition, the argon flow rate 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, 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.