Oxygen-carbon co-permeation method for presetting oxygen on titanium surface

Abstract

The invention discloses an oxygen-carburizing method for presetting oxygen on a titanium surface, which comprises the following steps of: 1, sequentially polishing, deoiling and removing an oxide layer on a titanium material to obtain a titanium material with an activated surface; 2, performing micro-arc oxidation on the surface-activated titanium material to obtain a titanium material with an oxidation film; and thirdly, the titanium material with the oxidation film is placed in double-layer glow plasma metal cementation equipment, oxygen-carbon co-cementation is carried out, a carbon layer is deposited, and the titanium material with the oxygen-carbon co-cementation composite modified layer containing carbon, titanium oxide and titanium carbide formed on the surface is obtained. According to the method, the surface-activated titanium material is subjected to micro-arc oxidation treatment, a compact and smooth oxidation film is obtained, oxygen is preset on the titanium surface, then oxygen-carbon co-permeation is carried out, a carbon layer is deposited, an anti-attrition carbon layer and a permeation-diffusion wear-resisting layer containing a titanium oxide and titanium carbide mixture are obtained on the titanium surface, and the method is easy to implement and low in cost. The method can be achieved only through existing micro-arc oxidation equipment and glow plasma cementation metallization equipment, and is high in reliability, safe, environmentally friendly, capable of being used for batch production and suitable for popularization.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface hardening of titanium and titanium alloys, and particularly relates to a method for oxygen-carbon co-permeation with pre-deposited oxygen on the titanium surface. Background Art

[0002] Due to their high specific strength, titanium and titanium alloys have been widely used in the aerospace field. However, they have problems such as relatively low hardness (not exceeding 400 HV) and poor wear resistance, making it difficult to meet frictional requirements or be used as wear-resistant parts. Therefore, surface hardening treatment is required, and preparing a hardened layer is the most effective, economical, and widely used method. There are methods such as carburizing and oxygen permeation on the titanium surface. The invention patent "Equipment and Method for Oxygen-Carbon Co-Permeation on the Surface of Titanium and Titanium Alloys" with the publication number CN101177774A generates a mixed infiltration layer of titanium carbide and titanium oxide on the surface of titanium and titanium alloys by means of oxygen-carbon co-permeation. Oxygen-carbon co-permeation can break the dense bright white layer of a single carburized layer and provide a channel for further element diffusion. However, this method requires special equipment and special technology. Nevertheless, this patent provides the idea that oxygen-carbon co-permeation is superior to single carburizing and oxygen permeation.

[0003] In addition, scientific and technological workers have also conducted research on surface oxygen permeation strengthening of titanium and titanium alloys. Patents CN102400086A, CN1632158A, and CN1363713A disclose some methods for surface oxygen permeation strengthening treatment of titanium and titanium alloys. Their main implementation schemes are all to coat titanium and titanium alloy materials with ZrO 2 , MgO, Al 2 O 3 , SiO 2 , C powder and other powder media, heat and keep warm in an ordinary air heating furnace in an atmospheric atmosphere, and form an oxygen solid solution hardened layer on the surface of the titanium alloy specimen. Its essence belongs to high-temperature gas oxygen permeation, and the coated powder medium delays the formation of brittle oxide scales on the surface of the titanium alloy. From the perspective of the film structure, since the surface of the atmospheric oxygen permeation layer of titanium and titanium alloys is loose, hard and brittle, the thickened oxide layer needs to be subjected to subsequent surface finishing treatment.

[0004] Since titanium can easily form a layer of oxide film on its surface to play a protective role, but this oxygen is uncontrollable. Oxygen permeation on the titanium surface can improve hardness, mainly including powder-pack cementation method, vacuum gas oxygen permeation method, and anodic oxidation to prepare an oxide layer and then diffusion method. Powder-pack cementation method patents include CN102400086A (a method for surface strengthening treatment of titanium alloy by oxygen permeation), CN1363713A (a method for oxygen permeation of titanium alloy), etc. It is to embed titanium materials in a powder medium containing oxides, place them in a heating furnace in the atmospheric environment for heating and insulation, and form an oxygen permeation layer on the titanium surface. However, due to the uncontrollable oxygen permeation atmosphere, the surface is porous. The vacuum gas oxygen permeation method has the patent CN109972074A (a method for preparing high-corrosion-resistant marine titanium plates), which realizes controllable oxygen permeation by introducing oxygen in a vacuum and high-temperature environment. However, this treatment method causes serious oxidation of the vacuum equipment, at the cost of damaging the service life and normal use of the equipment. CN105112979A (a method for local oxygen permeation on the surface of titanium and titanium alloy components), CN116180189A (a method for oxygen permeation of titanium alloy), CN105019000A (a method for preparing an oxygen permeation hardening coating on the surface of titanium and titanium alloy), etc. are methods to obtain an oxide film on the titanium surface by anodic oxidation, and then perform heat treatment in a vacuum furnace to obtain an oxygen permeation layer. Due to the technological characteristics of anodic oxidation, the obtained oxide film is relatively thin and difficult to provide sufficient oxygen source for diffusion. By using micro-arc oxidation to obtain a thicker oxide film, it can provide an effective and sufficient oxygen source for diffusion.

[0005] Therefore, there is a need for an oxygen-carbon co-permeation method for pre-oxygen deposition on the titanium surface by using micro-arc oxidation. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an oxygen-carbon co-permeation method for pre-oxygen deposition on the titanium surface in view of the above-mentioned deficiencies of the prior art. This method performs micro-arc oxidation treatment on the surface-activated titanium material to obtain a dense and smooth oxide film to achieve pre-oxygen deposition on the titanium surface, and then performs oxygen-carbon co-permeation and carbon layer deposition to obtain a wear-reducing carbon layer and a diffusion wear-resistant layer containing a mixture of titanium oxide and titanium carbide on the titanium surface. By combining micro-arc oxidation and oxygen-carbon co-permeation, carbon deposition and oxygen-carbon co-permeation on the titanium surface are realized, and a composite modification layer with both a diffusion wear-resistant layer of a mixture of titanium oxide and titanium carbide and a carbon layer is obtained.

[0007] To solve the above technical problem, the technical solution adopted by the present invention is: an oxygen-carbon co-permeation method for pre-oxygen deposition on the titanium surface, characterized in that the method comprises the following steps:

[0008] Step 1: Grind, degrease, and remove the oxide layer from the titanium material in sequence to obtain a surface-activated titanium material;

[0009] Step 2: Clamp the surface-activated titanium material obtained in Step 1 using a fixture, then immerse it in the sodium silicate-based electrolyte in the electrolytic cell of the micro-arc oxidation equipment. After that, using the surface-activated titanium material as the anode and stainless steel as the cathode, adjust the parameters of the pulsed micro-arc oxidation equipment and carry out micro-arc oxidation in a stepwise voltage-increasing manner. During the micro-arc oxidation process, add titanium dioxide sol dropwise to the sodium silicate-based electrolyte. Finally, clean the titanium material after micro-arc oxidation to obtain a titanium material with an oxide film.

[0010] Step 3: Place the titanium material with an oxide film obtained in Step 2 on the workpiece stage of the workpiece electrode in the vacuum chamber of the double glow plasma metal penetration equipment as the workpiece electrode, use high-purity graphite as the source electrode, carry out oxygen-carbon co-permeation and deposit a carbon layer to obtain a titanium material with an oxygen-carbon co-permeation composite modified layer containing carbon, titanium oxide, and titanium carbide formed on the surface.

[0011] In the present invention, the titanium material is first pretreated by grinding, degreasing, and removing the oxide layer to prevent impurities on the surface of the titanium material from affecting the subsequent micro-arc oxidation. Then, micro-arc oxidation is used to obtain a dense and smooth oxide layer on the surface of the titanium material. By first removing the oxide layer and then obtaining a titanium material with an oxide film, the controllability of the oxide film is ensured, the thickness of the oxide film is uniform, and the dense and smooth oxide layer also improves the wear resistance of the product. Then, it is placed in a double glow plasma metal penetration equipment for oxygen-carbon co-permeation and deposition of a carbon layer to obtain a wear-reducing carbon layer and a diffusion wear-resistant layer containing a mixture of titanium oxide and titanium carbide on the surface of the titanium material, that is, an oxygen-carbon co-permeation composite modified layer containing carbon, titanium oxide, and titanium carbide. The composite modified layer obtained in this way can achieve oxygen-carbon co-permeation and also has a wear-reducing layer that oxygen-carbon co-permeation does not have. Among them, the carbon layer has a self-lubricating effect during the friction process, which helps to reduce wear. Among them, titanium oxide and titanium carbide have high hardness and play a wear-resistant role, and the deposited carbon is soft and plays a lubricating role, that is, a wear-reducing role.

[0012] The micro-arc oxidation process is a process of continuously breaking down the oxide film layer by high voltage. Therefore, generally, the film layer prepared by micro-arc oxidation is relatively rough and has a certain loose layer. The present invention adopts measures such as a stepwise voltage-increasing control method and dropping titanium dioxide sol during the oxidation process to ensure the denseness and smoothness of the oxide film.

[0013] The above-mentioned oxygen-carbon co-permeation method for pre-oxygenating the titanium surface is characterized in that the titanium material described in Step 1 is titanium or a titanium alloy. The oxygen-carbon co-permeation with pre-oxygenation on the surface of the present invention has a wide range of applications, and is applicable not only to titanium but also to titanium alloys.

[0014] The above-mentioned method for oxygen-carbon co-permeation with pre-deposited oxygen on the titanium surface is characterized in that, in step one, the grinding is carried out by successively grinding with 180# and 1500# water-resistant abrasive papers until the surface is smooth and bright, and then placing it on a polishing machine for polishing; the degreasing is carried out by ultrasonic cleaning in a metal cleaning agent solution with a temperature of 30°C to 40°C and a mass concentration of 0.5% to 1% for 10 min to 15 min after washing with water, and then rinsing under running water after taking out; the removal of the oxide layer is carried out by soaking in a mixed acid solution of nitric acid and hydrofluoric acid for 5 s to 10 s, and then rinsing with distilled water to remove the residual acid solution on the surface, and drying with a hair dryer. The present invention removes impurities on the surface of the titanium material by controlling the process and parameters of grinding, removes oil stains on the surface of the titanium material by controlling the process and parameters of degreasing, and removes the oxide layer on the surface of the titanium material by controlling the process and parameters of removing the oxide layer.

[0015] The above-mentioned method for oxygen-carbon co-permeation with pre-deposited oxygen on the titanium surface is characterized in that, in step two, the micro-arc oxidation uses a sodium silicate system electrolyte composed of sodium silicate, potassium hydroxide, sodium tetraborate, sodium tungstate, triethanolamine, nano-titanium dioxide, glycerol, potassium fluozirconate and deionized water. The concentration of sodium silicate in the sodium silicate system electrolyte is 10 g / L to 15 g / L, the concentration of potassium hydroxide is 1 g / L to 2 g / L, the concentration of nano-titanium dioxide is 4 g / L to 6 g / L, the concentration of sodium tetraborate is 4 g / L to 6 g / L, the concentration of sodium tungstate is 1 g / L to 5 g / L, the concentration of triethanolamine is 3 ml / L to 5 ml / L, the concentration of glycerol is 3 ml / L to 5 ml / L, and the concentration of potassium fluozirconate is 5 g / L to 10 g / L; the particle size of the nano-titanium dioxide is 10 nm to 30 nm; the power supply for the micro-arc oxidation is a constant current power supply; the process of stepwise voltage increase is as follows: increasing the voltage to 200 V to 350 V at a speed of 100 V / min, with a pulse frequency of 500 Hz, a duty cycle of 20%, and a current density of 12 A / dm 2 ~16 A / dm 2 , the oxidation time is 10 min, then decreasing to 100 V, and then increasing to 200 V to 350 V at a speed of 50 V / min, and then decreasing to 0 V; in the micro-arc oxidation, magnetic stirring and circulating cooling are carried out on the sodium silicate system electrolyte; the cleaning is carried out by ultrasonic cleaning in tap water, taking out and drying with a hair dryer, and then placing it in deionized water for ultrasonic cleaning, taking out and drying with a hair dryer. The present invention obtains a dense and smooth micro-arc oxidation film layer on the surface of the titanium material by controlling the composition of the electrolyte; the present invention gradually increases from a lower voltage to a higher voltage and conducts oxidation reactions at the corresponding increased voltages respectively, effectively regulating the growth of the oxide layer, avoiding the porous layer caused by long-term high-voltage treatment, and ensuring the density and thickness of the oxide layer; the present invention ensures the uniformity of the electrolyte by magnetic stirring and circulating cooling of the electrolyte, ensuring the stable progress of the micro-arc oxidation; the present invention removes the residual electrolyte without damaging the oxide film by controlling the cleaning method.

[0016] The above-mentioned method for oxygen-carbon co-permeation with pre-deposited oxygen on the titanium surface is characterized in that the carbon content of the high-purity graphite in step three is greater than 99.99%. By controlling the carbon content of the high-purity graphite, the present invention ensures the effect of oxygen-carbon co-permeation and prevents the introduction of impurities.

[0017] The above-mentioned method for oxygen-carbon co-permeation with pre-deposited oxygen on the titanium surface is characterized in that the process of oxygen-carbon co-permeation and carbon layer deposition in step three is as follows: adjust the distance between the high-purity graphite and the workpiece electrode to 100 mm - 200 mm, then pre-pump the vacuum to 1×10 -2 Pa, then introduce argon gas, adjust the air pressure to 10 Pa - 50 Pa, the applied voltage of the workpiece electrode is 300 V - 500 V, heat the workpiece electrode to 600 °C - 900 °C, keep it warm for 2 h, then adjust the air pressure to 10 Pa - 200 Pa, the applied voltage of the source electrode is 800 V - 1200 V, the applied voltage of the workpiece electrode is 350 V - 600 V, heat the workpiece electrode to 700 °C - 1000 °C, perform oxygen-carbon co-permeation on the workpiece electrode, stop heating the workpiece electrode after the oxygen-carbon co-permeation ends, adjust the voltage of the source electrode to 500 V - 800 V, deposit a carbon layer on the surface of the workpiece electrode, and finally turn off the heating; the layer thickness of the carbon layer in the deposited carbon layer is 1 μm - 5 μm. The process of oxygen-carbon co-permeation and carbon layer deposition in the present invention is divided into three steps. In the first step, first control a suitable working distance between the high-purity graphite and the workpiece electrode, adjust the air pressure by pre-pumping the vacuum and introducing argon gas to prevent the influence of other gases, and facilitate glow arcing. And by controlling the applied voltage of the workpiece electrode to be 300 V - 500 V, heating the workpiece electrode to 600 °C - 900 °C, and keeping it warm for 2 h, utilize the bombardment effect of glow plasma to realize the diffusion of oxygen and obtain an oxygen diffusion layer on the surface of the titanium material. In the second step, control and adjust the air pressure to 10 Pa - 200 Pa, the applied voltage of the source electrode is 800 V - 1200 V, the applied voltage of the workpiece electrode is 350 V - 600 V, heat the workpiece electrode to 700 °C - 1000 °C, perform oxygen-carbon co-permeation on the workpiece electrode, mainly perform glow plasma carburization and supplemented by oxygen permeation to obtain a diffusion wear-resistant layer of a mixture of titanium oxide and titanium carbide. In the third step, control to stop heating the workpiece electrode, adjust the voltage of the source electrode to 500 V - 800 V, do not perform oxygen-carbon co-permeation, and deposit a carbon layer on its surface to realize oxygen-carbon co-permeation and carbon layer deposition; by controlling the layer thickness of the carbon layer, the present invention can ensure that when the titanium oxide and titanium carbide layers are worn, this thin carbon layer plays a lubricating role.

[0018] The present invention has the following advantages compared with the prior art:

[0019] 1. The present invention subjects surface-activated titanium materials to micro-arc oxidation treatment to obtain a dense and smooth oxide film for pre-oxygenating the titanium surface, and then performs oxygen-carbon co-permeation and deposits a carbon layer, obtaining a wear-reducing carbon layer and a diffusion wear-resistant layer containing a mixture of titanium oxide and titanium carbide on the titanium surface. By combining micro-arc oxidation and oxygen-carbon co-permeation, carbon deposition and oxygen-carbon co-permeation on the titanium surface are achieved, obtaining a composite modified layer with both a diffusion wear-resistant layer of a mixture of titanium oxide and titanium carbide and a carbon layer.

[0020] 2. The present invention can be realized only by using existing micro-arc oxidation equipment and glow plasma metal penetration equipment, without additional equipment, with lower requirements for equipment, high processing efficiency, low preparation cost and short preparation time, suitable for batch industrial production, easy to realize, high in reliability, safe, environmentally friendly, short in preparation time, can be used for batch production, and suitable for popularization.

[0021] 3. The present invention effectively regulates the growth of the oxide layer by controlling the process of stepwise boosting the voltage, gradually increasing from a lower voltage to a higher voltage and performing oxidation reactions at the corresponding increased voltages respectively, avoiding the loose and porous layer caused by long-term high-voltage treatment, and ensuring the denseness and thickness of the oxide layer.

[0022] 4. The present invention can ensure that when the titanium oxide and titanium carbide layers are worn, this thin carbon layer plays a lubricating role by depositing a carbon layer and controlling the layer thickness of the carbon layer.

[0023] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0024] Figure 1 XRD pattern of TA2 pure titanium with an oxide film obtained in Step 2 of Example 1 of the present invention.

[0025] Figure 2 XRD pattern of TA2 pure titanium with an oxygen-carbon co-permeation composite modified layer containing carbon, titanium oxide and titanium carbide formed on the surface obtained in Step 3 of Example 1 of the present invention. Detailed Embodiments

[0026] Example 1

[0027] This example includes the following steps:

[0028] Step 1: Grind TA2 pure titanium with 180# and 1500# water-resistant sandpaper step by step until the surface is smooth and shiny. Then place it on a polishing machine for polishing. After washing with water, immerse it in a metal cleaning agent solution with a temperature of 35°C and a mass concentration of 0.5%, and place it in an ultrasonic generator for ultrasonic cleaning for 10 minutes. Take it out and rinse it under running water. Then soak it in a mixed acid solution of nitric acid and hydrofluoric acid for 5 seconds, and then rinse it with distilled water to remove the residual acid solution on the surface. Dry it with a hair dryer to obtain surface-activated TA2 pure titanium;

[0029] Step 2: Clamp the surface-activated TA2 pure titanium obtained in Step 1 with a jig, and then immerse it in the sodium silicate system electrolyte in the electrolytic cell of the micro-arc oxidation equipment. The concentration of sodium silicate in the electrolyte is 13 g / L, the concentration of potassium hydroxide is 1.5 g / L, the concentration of nano-titanium dioxide is 5 g / L, the concentration of sodium tetraborate is 5 g / L, the concentration of sodium tungstate is 2.5 g / L, the concentration of triethanolamine is 4 ml / L, the concentration of glycerol is 4 ml / L, and the concentration of potassium fluozirconate is 7 g / L. The particle size of nano-titanium dioxide is 10 nm - 30 nm. Then, using the surface-activated TA2 pure titanium as the anode and the stainless steel plate as the cathode, adjust the parameters of the pulsed micro-arc oxidation equipment and carry out micro-arc oxidation in a step-by-step voltage boost manner. Specifically, use a constant current power supply, boost the voltage to 200 V at a speed of 100 V / min, the pulse frequency is 500 Hz, the duty cycle is 20%, and the current density is 12 A / dm 2 , the oxidation time is 10 minutes. Then, after reducing the voltage to 100 V, boost the voltage to 200 V at a speed of 50 V / min, and then reduce it to 0 V. During the micro-arc oxidation process, add titanium dioxide sol to the sodium silicate system electrolyte, carry out magnetic stirring and circulating cooling of the electrolyte. Finally, place the TA2 pure titanium after micro-arc oxidation in tap water for ultrasonic cleaning for 20 minutes, take it out, dry it with a hair dryer, and then place it in deionized water for ultrasonic cleaning for 10 minutes, take it out and dry it with a hair dryer to obtain TA2 pure titanium with an oxide film;

[0030] Step 3: Place the TA2 pure titanium with an oxide film obtained in Step 2 on the workpiece electrode carrier table in the vacuum chamber of the double glow plasma metal penetration equipment as the workpiece electrode. Use high-purity graphite with a carbon content greater than 99.99% as the source electrode to carry out oxygen-carbon co-permeation and deposit a carbon layer. Specifically, adjust the distance between the high-purity graphite and the workpiece electrode to 200 mm, and then pre-pump the vacuum to 1×10 -2Pa, then introduce argon, adjust the air pressure to 10 Pa, the loading voltage of the workpiece electrode is 300 V, heat the temperature of the workpiece electrode to 600 °C, keep it warm for 2 h, then adjust the air pressure in the furnace to 200 Pa, the loading voltage of the source electrode is 800 V, the loading voltage of the workpiece electrode is 350 V, heat the temperature of the workpiece electrode to 700 °C, carry out oxygen-carbon co-permeation on the workpiece electrode. After the oxygen-carbon co-permeation ends, stop heating the workpiece electrode, adjust the voltage of the source electrode to 500 V, deposit a 1-μm-thick carbon layer on the surface of the workpiece electrode. Finally, turn off the heating, evacuate to cool the workpiece electrode to room temperature, and form an oxygen-carbon co-permeation composite modification layer containing carbon, titanium oxide, and titanium carbide on the surface of TA2 pure titanium.

[0031] Perform XRD analysis on the TA2 pure titanium with an oxide film obtained in step two of this example and the TA2 pure titanium with an oxygen-carbon co-permeation composite modification layer containing carbon, titanium oxide, and titanium carbide on the surface obtained in step three. The results are shown in Figure 1 and Figure 2 , from Figure 1 and Figure 2 it can be seen that for the TA2 pure titanium with an oxide film, the main components are TiO 2 , and a small amount of Ti. The components of the TA2 pure titanium with an oxygen-carbon co-permeation composite modification layer containing carbon, titanium oxide, and titanium carbide on the surface are TiO 2 , TiO, Ti 3 O, TiC, Ti, C, etc. Compared with the TA2 pure titanium with an oxide film that only undergoes micro-arc oxidation, in the TA2 pure titanium that undergoes oxygen-carbon co-permeation and carbon layer deposition in step three, the oxide changes from TiO 2 , mainly to TiO and Ti 3 O, indicating that the O content decreases, and the TiC phase and the C phase appear, indicating the successful preparation of the oxygen-carbon co-permeation composite modification layer containing carbon, titanium oxide, and titanium carbide.

[0032] Example 2

[0033] This example includes the following steps:

[0034] Step one: Grind the TC4 titanium alloy with 180# and 1500# water-resistant abrasive papers step by step until the surface is smooth and shiny, then place it on a polishing machine for polishing. After washing with water, immerse it in a metal cleaning agent solution with a temperature of 30 °C and a mass concentration of 1%, and place it in an ultrasonic generator for ultrasonic cleaning for 15 min. Take it out, rinse it under running water, then soak it in a mixed acid solution of nitric acid and hydrofluoric acid for 10 s, and then rinse it with distilled water to remove the residual acid solution on the surface. Dry it with a hair dryer to obtain a surface-activated TC4 titanium alloy;

[0035] Step 2: Clamp the surface-activated TC4 titanium alloy obtained in Step 1 using a fixture, and then immerse it in the sodium silicate-based electrolyte in the electrolytic cell of the micro-arc oxidation equipment. The concentration of sodium silicate in the electrolyte is 10 g / L, the concentration of potassium hydroxide is 2 g / L, the concentration of nano-titanium dioxide is 4 g / L, the concentration of sodium tetraborate is 6 g / L, the concentration of sodium tungstate is 1 g / L, the concentration of triethanolamine is 5 ml / L, the concentration of glycerol is 3 ml / L, and the concentration of potassium fluozirconate is 10 g / L. The particle size of the nano-titanium dioxide is 10 nm to 30 nm. Then, using the surface-activated TC4 as the anode and a stainless steel plate as the cathode, adjust the parameters of the pulsed micro-arc oxidation equipment and carry out micro-arc oxidation in a stepwise voltage-increasing manner. Specifically, use a constant current power supply to increase the voltage to 350 V at a speed of 100 V / min, with a pulse frequency of 500 Hz, a duty cycle of 20%, and a current density of 16 A / dm 2 , the oxidation time is 10 min. After reducing the voltage to 100 V, increase the voltage to 350 V at a speed of 50 V / min, then reduce it to 0 V. During the micro-arc oxidation process, add titanium dioxide sol to the sodium silicate-based electrolyte, perform magnetic stirring and circulating cooling on the electrolyte. Finally, place the TC4 titanium alloy after micro-arc oxidation in tap water for ultrasonic cleaning for 20 min, take it out, dry it with a hair dryer, then place it in deionized water for ultrasonic cleaning for 10 min, take it out and dry it with a hair dryer to obtain the TC4 titanium alloy with an oxide film;

[0036] Step 3: Place the TC4 titanium alloy with an oxide film obtained in Step 2 on the workpiece electrode carrier table in the vacuum chamber of the double glow plasma metal penetration equipment as the workpiece electrode. Use high-purity graphite with a carbon content greater than 99.99% as the source electrode, and carry out oxygen-carbon co-permeation and deposit a carbon layer. Specifically, adjust the distance between the high-purity graphite and the workpiece electrode to 100 mm, then pre-pump the vacuum to 1×10 -2 Pa, then introduce argon, adjust the air pressure to 50 Pa, the loading voltage of the working electrode is 500 V, heat the temperature of the working electrode to 900 °C, and keep it warm for 2 h. Then adjust the air pressure in the furnace to 10 Pa, the loading voltage of the source electrode is 1200 V, the loading voltage of the workpiece electrode is 600 V, heat the temperature of the workpiece electrode to 1000 °C, and carry out oxygen-carbon co-permeation on the workpiece electrode. After the oxygen-carbon co-permeation is completed, stop heating the workpiece electrode, adjust the voltage of the source electrode to 800 V, deposit a 5-μm-thick carbon layer on the surface of the workpiece electrode. Finally, turn off the heating, pump the vacuum until the workpiece electrode cools to room temperature, and form an oxygen-carbon co-permeation composite modification layer containing carbon, titanium oxide, and titanium carbide on the surface of the TC4 titanium alloy.

[0037] The TC4 titanium alloy and TC4 alloy with an oxygen-carbon co-permeation composite modified layer containing carbon, titanium oxide, and titanium carbide formed on the surface obtained in this example were tested using an HV and HK dual indenter automatic turret microhardness tester (HXD-1000TMSC / LCD, Shanghai Taiming) in accordance with the specifications of the national standard GB / T 4340.1-1999 "Vickers Hardness Test for Metallic Materials". The surface Vickers hardness of the TC4 titanium alloy with an oxygen-carbon co-permeation composite modified layer containing carbon, titanium oxide, and titanium carbide was 986HV, 968HV, and 985HV, and the surface Vickers hardness of the TC4 alloy was 321HV, 307HV, and 319HV. It can be seen that the surface hardness has been greatly improved. The thickness of the infiltration layer of the TC4 titanium alloy with an oxygen-carbon co-permeation composite modified layer containing carbon, titanium oxide, and titanium carbide is greater than 150μm, and the hardness at different positions from the surface is shown in Table 1.

[0038] Table 1

[0039]

[0040] Example 3

[0041] This example includes the following steps:

[0042] Step 1: The TC4 titanium alloy was polished step by step with 180# and 1500# waterproof abrasive papers until the surface was smooth and shiny, and then placed on a polishing machine for polishing. After washing with water, it was immersed in a metal cleaning agent solution with a temperature of 40°C and a mass concentration of 0.8%, and placed in an ultrasonic generator for ultrasonic cleaning for 12 minutes. After taking it out, it was rinsed under running water, then immersed in a mixed acid solution of nitric acid and hydrofluoric acid for 8 seconds, and then rinsed with distilled water to remove the residual acid solution on the surface, and dried with a hair dryer to obtain a surface-activated TC4 titanium alloy;

[0043] Step 2: The surface-activated TC4 titanium alloy obtained in Step 1 was clamped with a fixture and then immersed in a sodium silicate-based electrolyte in the electrolytic cell of a micro-arc oxidation device. The concentration of sodium silicate in the electrolyte was 15g / L, the concentration of potassium hydroxide was 1g / L, the concentration of nano-titanium dioxide was 6g / L, sodium tetraborate was 4g / L, sodium tungstate was 5g / L, triethanolamine was 3ml / L, glycerol was 5ml / L, potassium fluozirconate was 5g / L, and the particle size of the nano-titanium dioxide was 10nm - 30nm. Then, with the surface-activated TC4 as the anode and a stainless steel plate as the cathode, the parameters of the pulsed micro-arc oxidation device were adjusted to perform micro-arc oxidation in a step-by-step voltage-increasing manner. Specifically, a constant current power supply was used to increase the voltage to 300V at a speed of 100V / min, the pulse frequency was 500Hz, the duty cycle was 20%, and the current density was 14A / dm 2, the oxidation time was 10 min. After that, the voltage was reduced to 100 V, then increased to 300 V at a rate of 50 V / min, and then reduced to 0 V. During micro-arc oxidation, titanium dioxide sol was dropped into the electrolyte of the sodium silicate system. The electrolyte was magnetically stirred and circulated for cooling. Finally, the TC4 titanium alloy after micro-arc oxidation was placed in tap water for ultrasonic cleaning for 20 min, taken out, dried with a hair dryer, then placed in deionized water for ultrasonic cleaning for 10 min, taken out and dried with a hair dryer to obtain a TC4 titanium alloy with an oxide film;

[0044] Step 3: Place the TC4 titanium alloy with an oxide film obtained in Step 2 on the workpiece electrode carrier table in the vacuum chamber of the double glow plasma metal penetration equipment as the workpiece electrode. Use high-purity graphite with a carbon content greater than 99.99% as the source electrode for oxygen-carbon co-permeation and carbon layer deposition. Specifically, adjust the distance between the high-purity graphite and the workpiece electrode to 150 mm, then pre-pump the vacuum to 1×10 -2 Pa, then introduce argon gas, adjust the air pressure to 30 Pa, the loading voltage of the working electrode is 400 V, heat the temperature of the working electrode to 750 °C, keep it warm for 2 h, then adjust the air pressure in the furnace to 100 Pa, the loading voltage of the source electrode is 1000 V, the loading voltage of the workpiece electrode is 500 V, heat the temperature of the workpiece electrode to 850 °C for oxygen-carbon co-permeation of the workpiece electrode. After the oxygen-carbon co-permeation ends, stop heating the workpiece electrode, adjust the voltage of the source electrode to 650 V, deposit a 3-μm-thick carbon layer on the surface of the workpiece electrode. Finally, turn off the heating, pump the vacuum until the workpiece electrode cools to room temperature, and form an oxygen-carbon co-permeation composite modification layer containing carbon, titanium oxide, and titanium carbide on the surface of the TC4 titanium alloy.

[0045] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for oxygen-carbon co-diffusion of titanium surface with oxygen pre-placed, characterized in that: The method comprises the following steps: Step 1: grinding, degreasing and removing the oxide layer of the titanium material in sequence to obtain a surface activated titanium material; Step 2: clamp the surface activated titanium material obtained in step 1 with a hanger, and then immerse it in a sodium silicate system electrolyte in the electrolytic cell of the micro-arc oxidation equipment. Then, the surface activated titanium material is used as the anode and the stainless steel is used as the cathode. The parameters of the pulse micro-arc oxidation equipment are adjusted to perform micro-arc oxidation in a step-by-step voltage-boosting manner. During the micro-arc oxidation, titanium dioxide sol is dripped into the sodium silicate system electrolyte. Finally, the titanium material after micro-arc oxidation is cleaned to obtain a titanium material with an oxide film. Step 3: Place the titanium material with an oxide film obtained in step 2 on the workpiece stage of the vacuum chamber of a double-layer glow plasma metallization equipment as the workpiece pole, use high-purity graphite as the source pole, perform oxygen-carbon co-diffusion and deposit a carbon layer to obtain a titanium material with an oxygen-carbon co-diffusion composite modified layer containing carbon, titanium oxide and titanium carbide formed on the surface.

2. The method for oxycarburizing titanium surface with oxygen pre-placed on the surface according to claim 1, characterized in that: The titanium material in step 1 is titanium or titanium alloy.

3. The method for oxycarburizing titanium surface with oxygen pre-placed on the surface according to claim 1, characterized in that: The polishing in step 1 is to use 180# and 1500# water-resistant abrasive paper to polish step by step until the surface is flat and smooth, and then place it on a polishing machine for polishing; the degreasing is to immerse it in a metal cleaning agent solution with a temperature of 30°C to 40°C and a mass concentration of 0.5% to 1% for ultrasonic cleaning for 10min to 15min after washing with water, and then rinse it under running water after taking it out; the deoxidation layer is placed in a mixed acid solution of nitric acid and hydrofluoric acid and immersed for 5s to 10s, then rinse with distilled water to remove the residual acid on the surface, and blow dry it with a hair dryer.

4. The method for oxycarburizing titanium surface with oxygen pre-placed on the surface according to claim 1, characterized in that: The micro-arc oxidation in step 2 uses a sodium silicate system electrolyte composed of sodium silicate, potassium hydroxide, sodium tetraborate, sodium tungstate, triethanolamine, nano titanium dioxide, glycerol, potassium fluorozirconate and deionized water, wherein the concentration of sodium silicate in the sodium silicate system electrolyte is 10 g / L to 15 g / L, the concentration of potassium hydroxide is 1 g / L to 2 g / L, the concentration of nano titanium dioxide is 4 g / L to 6 g / L, the concentration of sodium tetraborate is 4 g / L to 6 g / L, and the concentration of sodium tungstate is 1 g / L ~5g / L, triethanolamine 3ml / L~5ml / L, propylene glycol 3ml / L~5ml / L, potassium fluorozirconate 5g / L~10g / L; the particle size of the nano titanium dioxide is 10nm~30nm; the power supply of the micro-arc oxidation is a constant current power supply; the step-by-step voltage boosting process is: boosting to 200V~350V at a speed of 100V / min, the pulse frequency is 500Hz, the duty cycle is 20%, and the current density is 12A / dm 2 ~16A / dm 2 The oxidation time is 10 minutes, then it is reduced to 100V, then increased to 200V~350V at a speed of 50V / min, and then reduced to 0V; the sodium silicate system electrolyte is magnetically stirred and circulated cooled during the micro-arc oxidation; the cleaning is placed in tap water for ultrasonic cleaning, taken out and dried with a hair dryer, then placed in deionized water for ultrasonic cleaning, and taken out and dried with a hair dryer.

5. The method for oxycarburizing titanium surface with pre-oxygenation according to claim 1, characterized in that: The carbon content of the high-purity graphite in step 3 is greater than 99.99%.

6. The method for oxycarburizing titanium surface with oxygen pre-placed on the surface according to claim 1, characterized in that: The process of oxygen-carbon co-penetration and carbon layer deposition in step 3 is as follows: adjusting the distance between the high-purity graphite and the workpiece to 100 mm to 200 mm, and then pre-evacuating to 1×10 -2 Pa, then introduce argon, adjust the gas pressure to 10Pa~50Pa, the loading voltage of the workpiece pole is 300V~500V, heat the workpiece pole to 600℃~900℃, keep warm for 2h, then adjust the gas pressure to 10Pa~200Pa, the loading voltage of the source pole is 800V~1200V, the loading voltage of the workpiece pole is 350V~600V, heat the workpiece pole to 700℃~1000℃, perform oxygen-carbon co-diffusion on the workpiece pole, stop heating the workpiece pole after oxygen-carbon co-diffusion, adjust the voltage of the source pole to 500V~800V, deposit a carbon layer on the surface of the workpiece pole, and finally turn off the heating; the thickness of the carbon layer in the deposited carbon layer is 1μm~5μm.

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