WO2012126138A1 - Composite modified layer of titanium and titanium alloy and preparing method thereof - Google Patents

Abstract

A composite modified layer of titanium and titanium alloy, comprises a laser transformation hardening layer and a nitriding layer prepared on a substrate of titanium and titanium alloy. Also provided is a preparing method of composite modified layer of titanium and titanium alloy, comprising: steps of surface pretreating and blackening, and steps of laser transformation hardening and low-temperature nitriding.

Description

 Titanium and titanium alloy composite modified layer and preparation method thereof

 The invention relates to the technical field of surface modification and strengthening of metal materials, in particular to a laser phase transformation hardening-low temperature nitriding composite modified layer of titanium and titanium alloy surface and a preparation method thereof.

Background technique

 Titanium and titanium alloys are available in aerospace, chemical and biomedical fields due to their low density, high specific strength, non-magnetic properties, good corrosion resistance, excellent biocompatibility, excellent low temperature toughness and high temperature mechanical properties. A wide range of applications, as well as applications in the automotive industry, military, food and other civilian industries are also increasing.

 However, titanium and titanium alloys have low surface hardness and high chemical activity. Under sliding friction conditions, frictional properties are poor, especially friction and wear resistance are relatively low, which severely limits their application. Therefore, further improvement of the surface properties such as wear resistance, high temperature oxidation resistance and corrosion resistance of titanium and titanium alloys has become an urgent problem to be solved. In addition to improving the composition and preparation process of the alloy, surface modification of titanium alloy is currently the most effective method. Therefore, the surface modification technology of titanium alloy has become a hot research topic at home and abroad. The surface modification methods and characteristics of titanium alloys that are common in the prior art are as follows:

 The surface mechanical strengthening method is simple in process and convenient in operation; however, it has disadvantages such as large surface roughness and complicated stress distribution.

The temperature required for physical vapor deposition is low, the deformation of the workpiece is small, and the interior of the substrate is not softened. It is most suitable for surface strengthening treatment of titanium alloy workpieces with high precision requirements. However, compared with the chemical vapor deposition method, the physical vapor deposition method forms a thin coating, generally 1 to 3 μm, has a slightly lower adhesion to the substrate, and has poorer winding properties. Compared with physical vapor deposition, chemical vapor deposition has the characteristics of fast film formation, good diffraction of coating, high purity of coating, complete crystallization, smooth deposition surface and low radiation damage. However, since the device requires high temperature, high vacuum and other environmental conditions, its popularization and application has been greatly limited. The traditional gas nitriding has simple equipment, low investment, wide application range, can be used for various shapes and complicated parts, and has stable process and low production cost, and has been widely used; however, it has a long cycle, high temperature and permeability. The thin layer, the difficulty in controlling the structure, and the need to heat the entire workpiece for a long time. Summary of the invention

 The object of the present invention is to overcome the technical defects existing in the prior art, and to provide a phase change hardening-low temperature of titanium and titanium alloy which is particularly suitable for use in thin-walled parts, has good wear resistance and candle resistance, and has low surface roughness. Nitrided composite modified layer. The technical solution adopted by the present invention is: A composite modified layer of titanium and titanium alloy, characterized in that: the composite modified layer comprises a laser phase transformation hardened layer and a nitrided layer prepared on a titanium and titanium alloy substrate. Further, in the technical solution of the present invention, the laser phase transformation hardening layer includes a completely hardened layer and a partially hardened layer. According to still another aspect of the present invention, the nitriding layer includes a nitride layer and a nitrogen diffusion layer.

 O. 03~0 The thickness of the nitrogen diffusion layer is 0. 03~0. The thickness of the nitride layer is 0. . 2 Sa. The technical solution of the present invention is as follows: The specific steps of the preparation method are as follows -

(1) subjecting the titanium and titanium alloy substrate to surface pretreatment;

 (2) performing surface blackening treatment on the titanium and titanium alloy base after pretreatment;

 (3) performing a laser phase transformation hardening treatment on the surface of the titanium and titanium alloy substrate after the surface blackening treatment;

(4) Low temperature nitriding treatment of the surface of the titanium and titanium alloy substrate treated by laser transformation hardening. The technical solution of the present invention is further: the specific process of the surface pretreatment is: combining the titanium and titanium The gold substrate was ground to a surface roughness Ra < G. 8 μm and ultrasonically cleaned in acetone.

The squirting coating of the surface of the titanium and titanium alloy is sprayed with a layer of 0. 03~0. lmm S i0 ₂ light absorbing coating.

 According to the technical solution of the present invention, the nitriding treatment is carried out at a temperature lower than the conventional nitriding temperature by 100 to 30 (TC).

 According to the technical solution of the present invention, the low temperature nitriding treatment is gas nitriding.

 According to the technical solution of the present invention, the low temperature nitriding treatment is ion nitriding.

 The invention has the beneficial effects that: the titanium and titanium alloy substrate are processed by the preparation method, and the workpiece is not easily deformed, and the nitriding can be significantly reduced after the laser phase transformation hardening, thereby reducing the cost and saving. Energy consumption. In the invention, the nitride hardening wear layer formed by the laser transformation hardening-low temperature nitriding composite modification has high bonding strength with the titanium and titanium alloy matrix, the surface roughness is low, no subsequent treatment, no crack, and the thickness of the modified layer Large and uniform. The surface and section hardness measurements showed that the surface hardness of titanium and titanium alloys was significantly improved, and the hardness was changed along the depth direction. According to the friction and wear test, the composite modified layer of the invention has small friction coefficient and wear scar depth, and has a compact structure, and has good anti-friction and anti-friction lubrication effects. The corrosion resistance test and comparative analysis of the composite modified layer and the matrix show that the self-corrosion potential of the laser transformation hardening-low temperature nitriding composite modified layer is higher than that of the matrix, that is, the laser transformation hardening-low temperature nitriding composite modification The ability of the layer to resist localized corrosion and general corrosion is significantly improved. It is therefore particularly suitable for use in the machining of thin-walled parts of titanium and titanium alloys.

DRAWINGS

 1 is a schematic view of a laser phase transformation hardening experimental device for titanium and titanium alloy substrates;

 2 is a schematic view showing the structure of a laser transformation hardening-low temperature nitriding modified layer;

Figure 3 is a hard nitriding layer of gas nitriding at 430 °C after TA2 substrate laser phase transformation hardening treatment Comparison of the hardness of the nitride layer with the degree of direct nitriding;

 Figure 4 is a plot of the potentiodynamic polarization of the TA2 matrix and the original TA2 matrix after laser phase transformation hardening-low temperature gas nitriding treatment.

 Among them, 1 is a laser beam, 2 is a surface of a titanium and titanium alloy substrate subjected to laser beam treatment, 3 is a titanium and titanium alloy substrate, 4 is a nitride white bright layer, 5 is a nitrogen diffusion region, and 6 is a phase transformation hardened region.

detailed description

 The invention will now be described in detail with reference to the accompanying drawings. The steps of the implementation process of the present invention are as follows:

1. First, the surface of the titanium and titanium alloy substrate 3 is ground to a surface roughness Ra < G. 8 μ m, and ultrasonically cleaned in acetone;

2〜2的吸光涂料; 2mm S i0 ₂ absorbing coating;

3. The black phase treated titanium and titanium alloy substrate 3 is subjected to laser phase transformation hardening treatment by laser beam 1. The specific process parameters are: laser power 5 G0~3000 W, scanning speed 500~5000 mm/min, spot size is l OmmX 1 hidden or Φ 3mn! ~ 5mm, the shielding gas is Ar or N ₂ , and the gas flow rate is l~40L/h;

 4. The titanium and titanium alloy matrix 3 after laser transformation hardening treatment is subjected to gas nitriding or ion nitriding treatment, and the nitriding parameters are selectable.

 Example 1

The laser phase transformation hardening gas temperature nitriding composite treatment is applied to the TA2 thin plate. The process parameters of the laser phase transformation hardening process are: laser power 500~3000 W, scanning speed 500~5000 mm/min, spot size 10 legs X lmm or Φ 3ΙΜ! ~ 5 hidden, protective gas Ar, gas flow rate is 10~ ³⁰ L / h; nitriding process parameters are: nitriding gas NH ₃ , decomposition rate 20% ~ 60%, flow rate l ~ 40L / h, temperature 400 ~ 700 °C, time l~10h, pressure is one atmosphere.

After laser phase transformation hardening-low temperature gas nitriding composite treatment, the surface of TA2 substrate has a certain thickness and properties. Good laser phase transformation hardening-low temperature gas nitriding composite modified layer. The cross-sectional view of the composite modified layer is shown in Fig. 2. The total thickness of the laser phase transformation hardening-low temperature gas nitriding composite modified layer is 300~600 μ ιη, ΕΡΜΑ analysis of the sample treated under a certain parameter to find Ν element The infiltration thickness is about 30 μm, and the nitrogen content decreases with the increase of the surface depth. After the microhardness tester, the hardness of the titanium and titanium alloy matrix 3 is HV23G, and the highest hardness of the laser phase transformation hardening-low temperature nitriding composite layer is HV1002. 9. The hardness change curve is shown in Fig. 3. It can be seen from Fig. 3 Laser phase transformation hardening - the microhardness of the composite modified layer after low temperature gas nitriding is significantly higher than that of the non-laser phase transition treatment. According to the friction and wear test, the surface friction coefficient and the wear scar depth of the composite modified layer are very small, and have good anti-friction effect. The corrosion resistance test and comparative analysis of titanium alloy composite modified layer and titanium and titanium alloy matrix 3 were carried out by M283 potentiostat and M352 test analysis software. It was found that the laser phase transformation hardening-TA2 sample after low temperature gas nitriding treatment The self-corrosion potential is 28mV higher than that of the substrate. Compared with the TA2 matrix, the laser phase transformation hardening-the low-temperature gas nitriding layer has an increasing self-corrosion potential, indicating that the laser phase transformation hardening-low temperature gas nitriding treatment can reduce the self-corrosion of TA2. The tendency is mainly due to the high self-corrosion potential of TiN, which plays a protective role. The dynamic potential polarization curve was found by fitting calculation. The self-corrosion potential of the laser phase transformation hardening-low temperature gas nitriding layer is about 1/2 of that of the TA2 matrix, which is equivalent to a two-fold increase in corrosion resistance. 4.

Example 2 _;

The laser phase transformation hardening-low temperature ion nitriding composite treatment of TA2 thin plate and round tube, the process parameters of laser phase transformation hardening treatment are: laser power 500~3000 W, scanning speed 500~5000 mm/min, spot size is 10 hidden XI hidden or Φ 3 let ~ 5 let, protective gas Ar, gas flow is 10~30L / h; nitriding process is: vacuum the furnace to 10Pa, turn on high voltage start, make the voltage to 600V, pass H ₂ and N ₂ , adjust the voltage, current duty and other parameters to make the furnace temperature reach the specified temperature, the total gas flow rate is about 150ml / min, the temperature is 400 ~ 600 ° C, time 1 ~: L 0h, the furnace pressure 10 ~ : L 00Pa. deal with A laser phase transformation hardening-low temperature ion nitriding composite modified layer with a certain thickness and a smooth surface and a uniform surface can be obtained on the surface of the rear substrate. After testing, the hardness, wear resistance and corrosion resistance of the composite modified layer were significantly improved compared with the TA2 matrix.

 The above description is not intended to limit the invention, and the invention is not limited to the above examples, and variations, modifications, additions or substitutions made by those skilled in the art within the scope of the invention also belong to the invention. protected range.

Claims

Rights request A composite modified layer of titanium and titanium alloy, characterized in that: the composite modified layer comprises a laser transformation hardening layer and a nitrided layer prepared on a titanium and titanium alloy substrate.  The titanium and titanium alloy composite modified layer according to claim 1, wherein the laser phase transformation hardened layer comprises a completely hardened layer and a partially hardened layer.  The titanium and titanium alloy composite modified layer according to claim 1, wherein the nitrided layer comprises a nitride layer and a nitrogen diffusion layer.  The thickness of the nitride phase change layer is 5~50. The thickness of the nitride phase change layer is 5~50. The thickness of the nitride phase change layer is 5~50. 2〜。 2mm。 The thickness of 0. 03~0. 2mm.  A method for preparing a titanium and titanium alloy composite modified layer according to claim 1, wherein the specific steps of the preparation method are as follows:  (1) subjecting the titanium and titanium alloy substrate to surface pretreatment;  (2) performing surface blackening treatment on the titanium and titanium alloy substrate after pretreatment;  (3) performing laser phase transformation hardening treatment on the surface of the titanium and titanium alloy substrate after surface blackening treatment; (4) subjecting the surface of the titanium and titanium alloy substrate subjected to laser transformation hardening treatment to low temperature nitriding treatment.  The method for preparing a titanium and titanium alloy composite modified layer according to claim 5, wherein: the surface pretreatment is performed by: grinding the titanium and tantalum alloy substrate to a surface roughness Ra < 0. 8 μ πι, ultrasonic cleaning in acetone. I. The surface of the titanium and titanium alloy substrate is sprayed with a thickness of 0. 03~ 0. lmm S i0 ₂ light absorbing coating. The method for preparing a composite layer of titanium and titanium alloy according to claim 5, wherein the nitriding treatment is carried out at a temperature lower than a conventional nitriding temperature by 1 G G to 3 G (TC).  The method for producing a composite modified layer of titanium and titanium alloy according to claim 5, wherein the low temperature nitriding treatment is gas nitriding.  10. The method for preparing a titanium and titanium alloy composite modified layer according to claim 5, wherein the low temperature nitriding treatment is ion nitriding.