CN112391625B - Method for preparing titanium alloy high-temperature oxidation-resistant coating through laser alloying composite micro-arc oxidation - Google Patents

Abstract

The invention discloses a method for preparing a titanium alloy anti-high temperature oxidation coating by laser alloying combined micro-arc oxidation, which mainly uses laser alloying and micro-arc oxidation to treat the surface of the titanium alloy, so as to solve the problem of titanium alloy under high temperature service. The surface is prone to oxidation, which leads to the decline of the overall performance of the workpiece; the main creativity of the present invention is reflected in: breaking through the limitation of the traditional immersion micro-arc oxidation on the size of the workpiece, it can be used for the overall/partial treatment of large-scale titanium alloy workpieces; through the micro-arc oxidation technology Introduced to reduce the thickness of the coating required for laser alloying, reduce the damage to the substrate caused by laser treatment, and improve the service performance and life of the treated material; at the same time, the quality of the micro-arc oxidation film and the Density solves the problem of limited performance improvement of the micro-arc oxidation coating due to the porous nature.

Description

A laser alloying composite micro-arc oxidation method for preparing titanium alloy anti-high temperature oxidation coating method

technical field

The invention discloses a method for preparing a titanium alloy high-temperature oxidation-resistant coating by laser alloying combined micro-arc oxidation, which relates to laser alloying and micro-arc oxidation technology, and is used for improving the high-temperature oxidation resistance of the titanium alloy surface.

Background technique

Titanium and titanium alloys are light metal structural materials with low density and high strength, which are widely used in aerospace, chemical industry, shipbuilding and other fields. For example, aircraft engine pressure plates, blades and casings made of titanium alloys can improve the thrust-to-weight ratio of aero-engines and the maneuverability of aircraft. As the proportion of titanium alloys used in high-performance aircraft increases, higher requirements will naturally be placed on its service temperature. However, under high-temperature service, the surface of titanium alloys is prone to oxidation and oxygen embrittlement, especially above 600 °C, the high-temperature oxidation resistance of alloys shows a sharp decline, which severely limits the development of titanium alloys to higher temperatures. In this regard, we can start from the surface of the material, and use appropriate surface treatment technology to enhance the high-temperature oxidation resistance of the outer layer of titanium alloy, so that the surface can withstand harsher environments without affecting its internal performance, and further expand the properties of titanium alloy. application field.

Laser surface alloying is a method of locally modifying the surface of metal materials. The added alloy elements and the surface of the base material are melted and mixed under the action of a high-energy density laser beam, and a thickness of about 0.01-2mm is formed in a short time. A method of surface alloying coatings to improve the properties of metallic materials. The method can effectively improve the high-temperature oxidation resistance performance of the titanium alloy by adding certain anti-oxidation alloy elements, and the depth and width of the modified layer are controllable.

Micro-arc oxidation technology is a surface treatment method developed from anodic oxidation process. It raises the inter-electrode voltage from the Faraday zone of ordinary anodic oxidation to the high-voltage discharge zone, generates micro-arc plasma spark discharge, and uses the instantaneous sintering effect of the arc to grow a ceramic film in situ on the surface of the valve metal, so as to treat the substrate. New technologies for protection. Due to its in-situ growth characteristics, using this method to prepare ceramic coatings on the surface of titanium alloys will not affect the original performance characteristics of titanium alloys, and can improve the high-temperature oxidation resistance of titanium alloys.

Although the above two technologies have improved the high temperature oxidation resistance of titanium alloys to a certain extent, a single treatment obviously cannot meet the higher requirements. For this reason, the present invention proposes a method for preparing a titanium alloy anti-high temperature oxidation coating by laser alloying combined selective area micro-arc oxidation based on these two technologies.

Contents of the invention

The purpose of the invention is to provide a method for preparing a titanium alloy anti-high temperature oxidation coating by laser alloying combined micro-arc oxidation. First, an alloyed layer with good high-temperature oxidation resistance is prepared on the surface of the titanium alloy by laser alloying technology, and then a ceramic film layer containing a high-temperature oxidation-resistant phase is prepared on the surface of the alloyed layer by micro-arc oxidation technology to further improve the alloy. The high temperature oxidation resistance of the layer (as shown in Figure 1).

Technical scheme of the present invention is as follows:

A method for preparing a titanium alloy anti-high temperature oxidation coating by laser alloying composite micro-arc oxidation, the method comprising:

(1) grinding, cleaning, and air-drying the surface of the titanium alloy to be treated, for subsequent use;

The titanium alloy is for example: TC4 alloy;

It is preferable to grind the surface of the titanium alloy to Ra 1.6 μm;

(2) preset alloy coating on the titanium alloy surface prepared in step (1), and carry out laser alloying treatment after it is completely air-dried and the laser processing technology is set;

The alloy coating is composed of an alloy component, a solvent, and a binder; wherein, the composition of the alloy component is Al: 50-80wt.%, Si: 15-25wt.%, Nb: 5-25wt.%. The solvent is absolute ethanol; the adhesive is shellac; and the mass ratio of the alloy component, solvent, and adhesive is 5:12:1;

The thickness of the preset alloy coating layer is 0.2-0.8mm;

The conditions of the laser processing technology are: the diameter of the laser spot is 0.24mm, the control mode of the laser movement is galvanometer scanning, the laser power is 500-1000W, the scanning speed is 200-1000mm/s, and the scanning distance is 0.04-0.08mm;

(3) grinding, degreasing, cleaning the titanium alloy surface after the laser alloying treatment in step (2), for subsequent use;

Further, it is preferred that the surface roughness after grinding is Ra 0.8-1.6 μm;

(4) Electrolyte is configured, and the titanium alloy prepared in step (3) is subjected to micro-arc oxidation to obtain a surface anti-high temperature oxidation coating;

The composition of the electrolyte is: NaAlO ₂ 4-15g/L, Na ₂ SiO ₃ 4-8g/L, ZrO ₂ 2-5g/L, and the solvent is deionized water;

In the micro-arc oxidation process, the stainless steel tube is used as the cathode, the titanium alloy is used as the anode, the electrolyte is directly sprayed to the surface of the anode through the stainless steel tube, and the distance between the stainless steel tube and the titanium alloy is the electrode spacing;

The electrical process parameters of the micro-arc oxidation are: constant current mode, pulse power supply current density 3-9A/dm ² , pulse frequency 500-1000Hz, duty cycle 10-30%; electrode spacing 10-15mm; electrolyte flow rate 0.5-1.5mm/s; the moving speed of the cathode is 3-5mm/min; the overlapping rate of the film layer is 20-40%.

Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

(1) The present invention combines two surface modification technologies of laser alloying and micro-arc oxidation, which can overcome the shortcomings of these two technologies in single treatment, greatly improve the high-temperature oxidation resistance of the titanium alloy surface, and achieve 1+ The effect of 1>2. At the same time, the invention breaks through the limitation of the size of the workpiece by traditional immersion micro-arc oxidation, and can be used for the overall/partial treatment of large-sized titanium alloy workpieces.

(2) Compared with a single laser alloying treatment, the introduction of the micro-arc oxidation technology in the present invention can reduce the thickness of the coating required for laser alloying, which is conducive to improving the quality of the alloyed layer and reducing the impact of laser treatment on the substrate. Damage, improve the performance and life of the treated material.

(3) Compared with the single micro-arc oxidation treatment, the present invention can improve the quality and density of the micro-arc oxidation film by adjusting the composition of the alloying layer, and solve the problem of performance improvement caused by the porous nature of the micro-arc oxidation coating. limit problem.

Description of drawings

Figure 1 Schematic diagram of the method for preparing titanium alloy anti-high temperature oxidation coatings by laser alloying composite selective area micro-arc oxidation;

1-laser, 2-alloy powder, 3-titanium alloy, 4-stainless steel cathode tube, 5-electrolyte, 6-laser alloying coating.

Fig. 2 Comparison of surface oxidation weight gain of substrate, micro-arc oxidation, laser alloying and laser alloying/macro-arc oxidation after high temperature oxidation at 900 °C for 100 h.

Detailed ways

The present invention will be further described below through specific examples, but the protection scope of the present invention is not limited thereto.

In the following examples, the titanium alloy material used is TC4 alloy, and the sample size is 50×20×5mm;

The diameter of the laser spot is 0.24mm, and the control method of the laser movement is the scanning of the galvanometer;

The diameter of the stainless steel tube used in the micro-arc oxidation is 8 mm, and the diameter of the tube is 5 mm.

Example 1

1) Pre-treatment of titanium alloy, including grinding, cleaning and drying.

2) Pre-place the alloy coating on the surface of the material, and control the layer thickness to 0.5mm. The alloy components in the alloy coating are: Al: 80wt.%, Si: 15wt.%, Nb: 5wt.%, and it can be carried out after it is completely air-dried Next step.

3) Set the laser alloying process: laser power 1000W, scanning speed 1000mm/s, scanning distance 0.04mm, laser alloying treatment on the sample;

4) Grinding the surface of the sample after laser alloying treatment to Ra 0.8 μm;

5) Configure electrolyte: NaAlO ₂ 15g/L, Na ₂ SiO ₃ 4g/L, ZrO ₂ 2g/L;

6) Set the pulse power supply current density of the micro-arc oxidation process to 9A/dm ² , the pulse frequency to 500Hz, the duty ratio to 30%, the electrode spacing to 10mm, the flow rate of the electrolyte to 0.5mm/s, and the moving speed of the cathode to 3mm/min. The overlapping rate of the film layer is 40%, and the micro-arc oxidation treatment is carried out;

The surface of the prepared coating was inspected, and the surface quality of the coating was good without defects.

After high-temperature oxidation at 900°C for 100 hours, the oxidation weight gain of the substrate was 27.92 mg/cm ² , the oxidation weight gain of the single laser alloying treatment sample was 10.31 mg/cm ² , and the oxidation weight gain of the single micro-arc oxidation treatment sample was 23.25 mg/cm 2 cm ² , the oxidation weight gain of the laser alloyed composite micro-arc oxidation treatment sample is 5.32mg/cm ² , which is 0.19 of the matrix oxidation weight gain, and the high temperature oxidation resistance performance is obviously improved.

Example 2

The alloy composition in the alloy paint is: Al: 50wt.%, Si: 25wt.%, Nb: 25wt.%, and the thickness of the control layer is 0.5mm.

Set the laser alloying process: laser power 1000W, scanning speed 1000mm/s, scanning distance 0.04mm.

Grind the surface of the sample after laser alloying treatment to Ra 0.8μm

Prepare electrolyte: NaAlO ₂ 4g/L, Na ₂ SiO ₃ 8g/L, ZrO ₂ 5g/L.

Set the pulse power supply current density of the micro-arc oxidation process to 9A/dm ² , the pulse frequency to 500Hz, the duty cycle to 30%, the electrode spacing to 10mm, the electrolyte flow rate to 0.5mm/s, the cathode moving speed to 3mm/min, and the film layer The overlap rate is 40%.

Other processing steps are as embodiment 1.

The surface of the prepared coating was inspected, and the surface quality of the coating was good without defects.

After high-temperature oxidation at 900°C for 100 hours, the oxidation weight gain of the substrate was 27.92 mg/cm ² , the oxidation weight gain of the single laser alloying treatment sample was 12.45 mg/cm ² , and the oxidation weight gain of the single micro-arc oxidation treatment sample was 25.67 mg/cm 2 cm ² , the oxidation weight gain of the laser alloyed composite micro-arc oxidation treatment sample is 3.68mg/cm ² , which is 0.13 of the matrix oxidation weight gain, and the high temperature oxidation resistance performance is obviously improved.

Example 3

The alloy components in the alloy paint are: Al: 80wt.%, Si: 15wt.%, Nb: 5wt.%, and the control layer thickness is 0.2.

Set the laser alloying process: laser power 500W, scanning speed 200mm/s, scanning distance 0.08mm.

Grinding the surface of the sample after laser alloying treatment to Ra 1.6μm

Prepare electrolyte: NaAlO ₂ 15g/L, Na ₂ SiO ₃ 4g/L, ZrO ₂ 2g/L.

Set the pulse power supply current density of the micro-arc oxidation process to 3A/dm ² , the pulse frequency to 1000Hz, the duty cycle to 10%, the electrode spacing to 15mm, the electrolyte flow rate to 1.5mm/s, the cathode moving speed to 5mm/min, and the film layer The overlap rate is 20%.

Other processing steps are as embodiment 1.

The surface of the prepared coating was inspected, and the surface quality of the coating was good without defects.

After high-temperature oxidation at 900°C for 100 hours, the oxidation weight gain of the substrate was 27.92 mg/cm ² , the oxidation weight gain of the single laser alloying treatment sample was 14.32 mg/cm ² , and the oxidation weight gain of the single micro-arc oxidation treatment sample was 21.79 mg/cm 2 cm ² , the oxidation weight gain of the laser alloyed composite micro-arc oxidation treatment sample is 7.89mg/cm ² , which is 0.28 of the matrix oxidation weight gain, and the high temperature oxidation resistance performance is obviously improved.

Example 4

The alloy composition in the alloy paint is: Al: 65wt.%, Si: 20wt.%, Nb: 15wt.%, and the thickness of the control layer is 0.3mm.

Set the laser alloying process: laser power 750W, scanning speed 600mm/s, scanning distance 0.06mm.

Grind the surface of the sample after laser alloying treatment to Ra 0.8μm

Prepare electrolyte: NaAlO ₂ 10g/L, Na ₂ SiO ₃ 6g/L, ZrO ₂ 3g/L.

Set the current density of the pulse power supply for the micro-arc oxidation process to 6A/dm ² , the pulse frequency to 750Hz, the duty ratio to 25%, the electrode spacing to 10mm, the flow rate of the electrolyte to 1mm/s, the cathode moving speed to 4mm/min, and the film overlap The acceptance rate is 30%.

Other processing steps are as embodiment 1.

The surface of the prepared coating was inspected, and the surface quality of the coating was good without defects.

After high-temperature oxidation at 900°C for 100 hours, the oxidation weight gain of the substrate was 27.92 mg/cm ² , the oxidation weight gain of the single laser alloying treatment sample was 11.78 mg/cm ² , and the oxidation weight gain of the single micro-arc oxidation treatment sample was 24.31 mg/cm 2 cm ² , the oxidation weight gain of the laser alloyed composite micro-arc oxidation treatment sample was 1.85mg/cm ² .

The composite coating prepared by the present invention has good high-temperature oxidation resistance, and shows better performance improvement than single laser alloying or micro-arc oxidation treatment, and the oxidation weight gain of the material surface after treatment is 0.06 of the matrix oxidation weight gain. ,as shown in picture 2.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (3)

1. A method for preparing a titanium alloy high-temperature oxidation-resistant coating by laser alloying composite micro-arc oxidation is characterized by comprising the following steps:

(1) Polishing, cleaning and air-drying the surface of the titanium alloy to be treated for later use;

(2) Presetting an alloy coating on the surface of the titanium alloy prepared in the step (1), and performing laser alloying treatment after the titanium alloy is completely air-dried and a laser processing process is set;

the alloy coating consists of alloy components, a solvent and a binder; wherein the alloy comprises the following components: 50-80wt.%, si:15-25wt.%, nb:5-25wt.%; the solvent is absolute ethyl alcohol; the adhesive is lac; and the mass ratio of the alloy components, the solvent and the binder is 5:12:1; the thickness of the preset alloy coating layer is 0.2-0.8mm;

the conditions of the laser processing technology are as follows: the diameter of a laser spot is 0.24mm, the control mode of laser motion is galvanometer scanning, the laser power is 500-1000W, the scanning speed is 200-1000mm/s, and the scanning interval is 0.04-0.08mm;

(3) Polishing, degreasing and cleaning the titanium alloy surface subjected to the laser alloying treatment in the step (2) for later use; the roughness of the surface after polishing treatment is Ra 0.8-1.6 μm;

(4) Preparing electrolyte, and performing micro-arc oxidation on the titanium alloy prepared in the step (3) to prepare a surface high-temperature oxidation-resistant coating;

the electrolyte comprises the following components: naAlO ₂ 4-15 g/L、Na ₂ SiO ₃ 4-8 g/L、ZrO ₂ 2-5g/L, and the solvent is deionized water;

in the micro-arc oxidation process, the stainless steel pipe is used as a cathode, the titanium alloy is used as an anode, the electrolyte is directly sprayed to the surface of the anode through the stainless steel pipe, and the distance between the stainless steel pipe and the titanium alloy is the electrode spacing;

the electrical technological parameters of the micro-arc oxidation are as follows: constant current mode, pulse power supply current density 3-9A/dm ² The pulse frequency is 500-1000Hz, and the duty ratio is 10-30%; the electrode spacing is 10-15mm; the flow rate of the electrolyte is 0.5-1.5mm/s; the moving speed of the cathode is 3-5mm/min; the overlapping rate of the film layer is 20-40%.

2. The method for preparing the titanium alloy high-temperature oxidation resistant coating through laser alloying composite micro-arc oxidation as claimed in claim 1, wherein in the step (1), the titanium alloy is TC4 alloy.

3. The method for preparing the titanium alloy high-temperature oxidation-resistant coating by laser alloying composite micro-arc oxidation as claimed in claim 1, wherein in the step (1), the surface of the titanium alloy is polished to Ra 1.6 μm.

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