CN106011971A - Method for preparing ceramic film/glaze film composite coating on titanium alloy surface - Google Patents

Abstract

The invention relates to a method for preparing a ceramic film/glaze film composite coating on a titanium alloy surface. First, a ceramic coating is prepared on the surface of a matrix by a micro-arc oxidation technology on a titanium alloy; and then, the ceramic surface is subjected to glazing and hole sealing, and is sintered to prepare the composite coating. The method combines the micro-arc oxidation (MAO) technology with the surface glazing technology to prepare the ceramic film/glaze film composite coating to improve the surface hardness, wear resistance and high-temperature heat stability of the matrix, and the coating has good film base binding force; and as the ceramic and the glaze layer are high in hardness and density, the wear resistance and the corrosion resistance of the titanium alloy are improved. The method is green and environment-friendly, low in equipment requirements, simple in operation and low in cost.

Description

A method for preparing ceramic film/glaze film composite coating on the surface of titanium alloy

(1) Technical field

The invention relates to a method for preparing a ceramic film/glaze film composite coating on the surface of a titanium alloy.

(2) Background technology

Titanium and its alloys have the characteristics of low relative density, the highest specific strength among metals, and the elastic modulus is about half that of steel. Moreover, titanium can be used for a long time at a temperature of 600°C or even higher. At the same time, it has low temperature resistance. It can maintain good ductility and toughness in a low temperature environment of minus 196-253°C, thereby avoiding the cold brittleness of the metal. In addition, titanium also has the advantages of non-magnetic, non-toxic, and no pollution to the environment. Therefore, titanium and its alloys are widely used in the fields of aerospace, shipbuilding, chemical industry, medical equipment and implant materials, and are known as "space metals" and "ocean metals".

Principle of titanium alloy: As an allotrope, the structure of titanium will change at different temperatures. When titanium is in an environment lower than 882 ° C, it presents a close-packed hexagonal lattice structure. Titanium with this structure is called α -Titanium; when titanium is in an environment above 882°C, it presents a body-centered cubic lattice structure, and titanium of this structure is called β-titanium. Due to its good heat resistance, strength, plasticity, toughness, formability, weldability, corrosion resistance and biocompatibility, Ti6Al4V has become the first practical titanium alloy, known as the trump card in the titanium alloy industry alloy. The amount of this alloy has accounted for 75% to 85% of all titanium alloys. Many other titanium alloys can be regarded as modifications of Ti6Al4V alloys. my country has started large-scale production of titanium and titanium alloy related industries for more than 50 years, and has now become the fifth largest producer of titanium industry. In view of the excellent comprehensive performance of titanium alloy, it may become the rising "third metal" after iron and aluminum.

Titanium and titanium alloys have the above-mentioned series of advantages, but they also have problems such as low surface hardness and poor wear resistance. In many cases, it is difficult to meet the requirements of practical application in production. Therefore, it is urgent to study the preparation of wear-resistant and corrosion-resistant coatings on the surface of titanium alloys. The most important of these is the application of surface strengthening technology to optimize the surface of titanium and titanium alloys. At present, most of the various methods of metal surface treatment have been applied to the surface treatment of titanium alloys, including carburizing (nitrogen, boron), metal plating, anodic oxidation, micro-arc oxidation, ion nitriding, vacuum Electron beam surface treatment, laser surface treatment, plasma spraying, etc.

While the above-mentioned surface treatment technologies of titanium and titanium alloys have their own advantages, they also have obvious defects. Such as: carburizing technology, boronizing technology and nitriding technology have problems such as long processing period and easy deformation of the workpiece; the structure of the coating prepared by thermal spraying technology is loose and the bonding force between the coating and the substrate is weak; the laser surface alloy Chemical and other high-energy beam heat treatment adopts the method of local heating treatment. Although it overcomes the shortcomings of overall heating of chemical heat treatment, in actual production and application, there are occasional defects such as uneven surface of the alloy layer and cracks and voids at the junction with the substrate. Most importantly, the above-mentioned methods are relatively expensive, and most of them remain in the laboratory stage, which is not conducive to large-scale market promotion and application in the true sense. Therefore, it is necessary to study effective and economical methods to effectively protect titanium and titanium alloys and improve their wear and corrosion resistance to meet the requirements of practical applications.

(3) Contents of the invention

The purpose of the invention is to overcome the defects of the existing titanium alloy surface coating technology, and provide a coating preparation method for improving the performance of the titanium alloy surface coating. The surface of the coating has high hardness, good wear resistance and high temperature thermal stability, and the film-base bonding force of the coating is strong. The method is green and environment-friendly, has low equipment requirements, simple operation and low cost.

The technical scheme adopted in the present invention is:

A method for preparing a ceramic film/glaze film composite coating on the surface of a titanium alloy, the method comprising:

(1) Perform micro-arc oxidation on the surface of titanium alloy to prepare a micro-arc oxidation coating; the electrolyte composition of the micro-arc oxidation is as follows: 8-10g/L Na ₂ SiO ₃ , 2-3g/L Na ₃ PO ₄ , 1-2g/L NaOH, 3-4g/L sodium citrate, the solvent is deionized water; the micro-arc oxidation parameters are as follows: voltage 350-380V, frequency 500Hz, processing time 20-35min;

(2) Evenly spray the prepared glaze slurry on the surface of the micro-arc oxidation ceramic coating of titanium alloy, and stop spraying when the glaze covers the color of the micro-arc oxidation ceramic coating; the mass composition of the glaze used for preparing the glaze slurry is as follows: SiO ₂ 52-59%, PbO 16-19%, Al ₂ O ₃ 3-8%, B ₂ O ₃ 5-9%, Na ₂ O 3-7%, TiO ₂ 3-5%, ZnO 7-9% The preparation method is as follows: the glaze is kept and melted at 1380°C, when the mixture is completely melted and has good fluidity, it is poured into a ball mill tank containing deionized water and quenched (adjust the mass ratio of water content to glaze to 1:1) , then add kaolin with a glaze mass of 3wt%, and stir and grind for 100 hours to form a glaze slurry, dissolve the glaze slurry in water at a mass ratio of 1:30 to prepare a solution, stir well and evenly for use;

(3) Put the alloy workpiece sprayed with glaze slurry in a drying oven, and dry at 50-60°C for 20-30 minutes until the water in the solution on the surface of the sample is completely volatilized, and the glaze slurry is deposited on the ceramic surface and no longer flows, then take it out;

(4) Place the workpiece in an isobaric furnace, heat it from room temperature to 800-850° C., keep it warm for 2-3 hours and leave the furnace to prepare a ceramic film/glaze film composite coating.

The present invention uses micro-arc oxidation (MAO) technology and surface glazing technology to prepare ceramic film/glaze film composite coating to improve substrate hardness, wear resistance and thermal stability at high temperature, and the film-base bonding force of the coating is good . Firstly, a ceramic coating is prepared on the surface of the substrate by using micro-arc oxidation technology on the titanium alloy, and then the composite coating is prepared by glaze sealing the holes on the ceramic surface and sintering. At present, there are few reports on the preparation of composite coatings combining micro-arc oxidation ceramic films and low-temperature enamel layers on titanium alloys.

The titanium alloy is preferably Ti6Al4V.

Preferably, micro-arc oxidation is carried out after the titanium alloy is pre-treated, and the pre-treatment method is as follows: the magnesium alloy is sequentially treated with 180#, 400#, 600#, 800#, 1200#, 1500#, 2000# sandpaper Grinding, and then polishing the titanium alloy sample to Ra≈0.3 μm with a polishing machine, polishing cloth and 1 μm alumina polishing paste.

Specifically, the method is as follows:

(1) Ti6Al4V titanium alloy 180#, 400#, 600#, 800#, 1200#, 1500#, 2000# sandpaper is polished, and then the titanium alloy sample is polished to Ra≈0.3μm;

(2) Perform micro-arc oxidation on the surface of the titanium alloy to prepare a micro-arc oxidation coating; the electrolyte composition of the micro-arc oxidation is as follows: 8g/L Na ₂ SiO ₃ , 2.5g/L Na ₃ PO ₄ , 1.4g /L NaOH, 3g/L sodium citrate, the solvent is deionized water; the micro-arc oxidation parameters are as follows: voltage 360V, frequency 500Hz, treatment time 25min;

(3) Evenly spray the prepared glaze slurry on the surface of the micro-arc oxidation ceramic coating of titanium alloy; the mass composition of the glaze material used for preparing the glaze slurry is as follows: SiO ₂ 55%, PbO 18%, Al ₂ O ₃ 5%, B ₂ O ₃ 6%, Na ₂ O 4%, TiO ₂ 4%, ZnO 8%;

(4) Place the alloy workpiece coated with glaze slurry in a drying oven, dry at 50°C for 20min, and then take it out;

(5) Place the workpiece in an isobaric furnace, heat it from room temperature to 830° C., keep it warm for 2 hours, and leave the furnace to obtain a ceramic film/glaze film composite coating.

The beneficial effects of the present invention are mainly reflected in: the present invention utilizes micro-arc oxidation (MAO) technology and surface glazing technology to combine to prepare ceramic film/glaze film composite coating to improve substrate surface hardness, wear resistance and thermal stability at high temperature , and the film-base bonding force of the coating is good; due to the high hardness and high density of the ceramic and glaze layer, the wear resistance and corrosion resistance of the titanium alloy are improved. The method is green and environment-friendly, has low equipment requirements, simple operation and low cost.

(4) Description of drawings

Figure 1 shows the size and appearance of titanium alloy parts;

Fig. 2 is the schematic diagram of micro-arc oxidation device; 1 three-phase power supply; 2 micro-arc oxidation DC power supply; 3 controller; 4 cooling water; 5 electrolyte; 6 sample; 7 cooling tower; 8 agitator;

Figure 3 is a schematic diagram of the glaze spraying device; ① sample; ② glaze storage bottle; ③ air pump; ④ bracket;

(5) Specific implementation methods

The present invention is further described below in conjunction with specific embodiment, but protection scope of the present invention is not limited thereto:

Example 1:

1. Pretreatment of titanium alloy samples

The titanium alloy TC4 sample is processed as shown in Figure 1, with a thickness of 20 mm. Grind the processed samples with 180#, 400#, 600#, 800#, 1200#, 1500#, 2000# sandpaper until the surface is smooth. Then use a polishing machine, a polishing cloth and a 1 μm alumina polishing paste to polish the titanium alloy sample to a mirror surface appearance of Ra≈0.3 μm.

2. Preparation of micro-arc oxidation coating

Rinse the polished titanium alloy samples with clean water respectively, and then place the samples in an acetone solution for ultrasonic cleaning for 10 minutes to remove oil. The cleaning frequency is 100,000HZ. Rinse with deionized water after ultrasonic cleaning, take out and blow dry. Then the sample was installed on the micro-arc oxidation equipment (as shown in Figure 2), and its electrolyte composition and micro-arc oxidation parameters are shown in Table 1.

Table 1: Electrolyte composition and micro-arc oxidation parameters

3. Preparation of composite coating

The low-temperature glaze was prepared, and its chemical composition is shown in Table 2. Melt the glaze at 1380°C. When the mixture is completely melted and has good fluidity, pour it into a ball mill jar containing deionized water and quench it (adjust the mass ratio of water content to glaze to 1:1), and then add 3wt 100% of kaolin is stirred and ground together for 100 hours to form a glaze slurry, and the glaze slurry is dissolved in water at a mass ratio of 1:30 to prepare a solution, fully stirred evenly and set aside.

Table 2: Chemical composition of low temperature glazes

Put the micro-arc oxidation sample prepared in the previous step flat on a clean glass plate, use a self-made glaze spraying device (as shown in Figure 3), insert it into the glaze solution, turn on the air pump, and generate air flow under the effect of pressure difference Next, spray the glaze solution evenly on the upper surface of the micro-arc oxidation ceramic coating, and stop spraying when the glaze covers the color of the micro-arc oxidation ceramic coating. Put the sample together with the glass plate in the drying oven, open the drying oven, set the temperature at 50°C, take it out after drying for 20 minutes; then, sinter the above glaze in an isobaric furnace at 830°C for about 2 hours, and finally Qualified products have been obtained, and the surface performance meets the requirements after the company's acceptance.

The surface finish, roughness, hardness, Wear resistance and corrosion resistance were tested: the results are as follows:

Surface hardness above HV710; surface roughness 0.15-0.19um;

The Tafel polarization curve test of the sample in 3.5wt.% NaCl solution shows that the corrosion potential of the ceramic coating is: -0.3V (the substrate is -0.6V), and the corrosion current density/Acm of the ceramic coating is: 2.0*10- ¹⁰

The substrate is 1.58*10 ^-7 ; after three hours of corrosion at room temperature, the corrosion amount of the ceramic layer is only 1/3 of the substrate. The scratch test shows that the film-base binding force of the coating is greater than 60N.

The present invention is not limited to the above-mentioned embodiments, wherein the micro-arc oxidation parameters used can be adjusted appropriately, the electrolyte formula and the glaze formula can also be appropriately changed according to the performance requirements, and the final firing temperature can be adjusted according to the glaze formula. Change.

Claims (4)

1., in a method for preparing ceramic film on titanium alloy surface/glaze film composite coating, described method includes:

(1) carry out differential arc oxidation at titanium alloy surface, prepare differential arc oxidation coating；The described differential of the arc The electrolyte composition of oxidation is as follows: 8～10g/L Na₂SiO₃, 2～3g/L Na₃PO₄, 1～2g/L NaOH, 3～4g/L sodium citrate, solvent is deionized water；Described differential arc oxidation parameter As follows: voltage 350～380V, frequency 500Hz, process the time 20～35min；

(2) by the glaze slip even application for preparing at the arc differential oxide ceramic coating surface of titanium alloy；Join Enamel frit makeing slurry glaze quality used composition is as follows: SiO₂52～59%, PbO 16～19%, Al₂O₃ 3～8%, B₂O₃5～9%, Na₂O 3～7%, TiO₂3～5%, ZnO 7～9%；

(3) alloy workpiece having sprayed glaze slip is placed in drying baker, at 50～60 DEG C, is dried 20～30 Min, then takes out；

(4) workpiece is placed in isobaric stove, is heated to 800～850 DEG C from room temperature, is incubated 2～3 hours Come out of the stove, obtain ceramic membrane/glaze film composite coating.

2. the method for claim 1, it is characterised in that described titanium alloy is Ti6Al4V.

3. method as claimed in claim 1 or 2, it is characterised in that described titanium alloy is first after pre-treatment Carrying out differential arc oxidation again, described pre-treating method is as follows: magnesium alloy successively with 180#, 400#, 600#, 800#, 1200#, 1500#, 2000# sand papering, then combine 1 μm with buffing machine, polishing cloth Titanium alloy sample is polished to Ra ≈ 0.3 μm by aluminium oxide antiscuffing paste.

4. the method for claim 1, it is characterised in that described method is as follows:

(1) Ti6Al4V titanium alloy 180#, 400#, 600#, 800#, 1200#, 1500#, 2000# Sand papering, then combine the aluminium oxide antiscuffing paste of 1 μm by titanium conjunction with buffing machine, polishing cloth Gold sample is polished to Ra ≈ 0.3 μm；

(2) carry out differential arc oxidation at titanium alloy surface, prepare differential arc oxidation coating；The described differential of the arc The electrolyte composition of oxidation is as follows: 8g/L Na₂SiO₃、2.5g/L Na₃PO₄、1.4g/L NaOH, 3g/L sodium citrate, solvent is deionized water；Described differential arc oxidation parameter is such as Under: voltage 360V, frequency 500Hz, process time 25min；

(3) by the glaze slip even application for preparing at the arc differential oxide ceramic coating surface of titanium alloy；Join Enamel frit makeing slurry glaze quality used composition is as follows: SiO₂55%, PbO 18%, Al₂O₃5%, B₂O₃6%, Na₂O 4%, TiO₂4%, ZnO 8%；

(4) alloy sample having sprayed glaze slip is placed in drying baker, is dried 20min at 50 DEG C, so Rear taking-up；

(5) workpiece is placed in isobaric stove, is heated to 830 DEG C from room temperature, is incubated and comes out of the stove for 2 hours, Obtain ceramic membrane/glaze film composite coating.