CN114934251A - Laser gas alloying method and laser gas alloying device for metal surface - Google Patents

Abstract

The invention relates to a metal surface laser gas alloying method and a laser gas alloying device. The method adopts the laser beam emitted by the carbon dioxide laser and the laser beam emitted by the short-wavelength laser to simultaneously irradiate the area to be alloyed on the metal surface, and provides alloying gas as a reactive gas atmosphere, and the wavelength of the laser beam emitted by the short-wavelength laser is less than 10640nm. Combining a carbon dioxide laser and a short-wavelength laser can give full play to the advantages of both, that is, the laser beam emitted by the carbon dioxide laser can ionize the alloying gas and increase the content of alloying gas elements in the molten pool. The laser beam emitted by the laser is more easily absorbed by the metal efficiently, increasing the penetration depth of the molten pool and the depth of the alloying layer. The thickness of the alloying layer and the content of the alloying gas can be taken into account at the same time.

Description

A kind of metal surface laser gas alloying method and laser gas alloying device

technical field

The invention relates to the technical field of metal surface alloying, in particular to a metal surface laser gas alloying method and a laser gas alloying device.

Background technique

Laser surface alloying is a method in which a high-energy laser beam is used to heat and melt the surface layer of the substrate and add elements, so that it solidifies rapidly after mixing, thereby forming a new surface alloy layer based on raw materials. Laser gas alloying is one of them, in which a gas (such as nitrogen, oxygen, carburizing atmosphere, etc.) that can react with the base metal to form a strengthening phase is injected into the metal molten pool, and reacts with the base element to form a compound alloy layer.

Taking titanium alloys as an example, the application environment and service conditions of titanium alloys often have high requirements on wear resistance. The problem of poor wear resistance of titanium alloy substrates leads to short service life of structures or simply cannot meet actual production applications. requirements, so that the application of titanium alloys is greatly restricted. When titanium alloy is used as sliding parts such as valve, guide rod, piston pin and connecting rod shaft, it is easy to stick to the material and cause wear. Titanium alloys have been widely used in various high-performance blades such as aero-engines, some medium-temperature blade substrates of gas turbine compressors, and large-scale blades at the final stage of steam turbines, but titanium alloy substrates cannot meet the service environment of wear resistance and corrosion resistance. Therefore, how to prepare a well-bonded deep high-performance wear-resistant layer on the surface of titanium alloy and withstand harsher service environment is an important technical problem to expand the application scope of titanium alloy.

Laser gas nitriding is a commonly used method for strengthening titanium alloys. This method actually uses a high-energy laser beam to melt the surface of titanium alloys in a high-purity nitrogen atmosphere, and nitrogen is irradiated with high-energy laser beams. The high-temperature titanium alloy molten metal in the molten pool undergoes a strong chemical/metallurgical interaction, which significantly changes the chemical composition and composition of the molten metal in the molten pool, and finally obtains a nitride layer with hard titanium nitride as the reinforcing phase after rapid solidification.

However, the thickness of the nitrided layer is currently within 0.5mm. However, in order to adapt to more use environments, it is necessary to increase the depth of the nitrided layer on the metal surface, that is, the depth of the alloyed layer. The existing methods are to increase the power of the laser. However, this method leads to the increase of heat input, which leads to the deterioration of the performance of the matrix, and the nitrogen content in the obtained nitrided layer is low, which leads to the poor strength of the nitrided layer. limit.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of laser gas alloying method of metal surface, in order to solve the problem that the thickness of the alloyed layer and the content of alloying elements obtained from the metal surface existing in the prior art cannot be obtained simultaneously; meanwhile, the purpose of the present invention is It is also to provide a laser gas alloying apparatus for implementing the above method.

In order to achieve the above-mentioned purpose, a metal surface gas alloying method of the present invention adopts the following technical scheme: a metal surface laser gas alloying method adopts a laser beam emitted by a carbon dioxide laser and a laser beam emitted by a short-wavelength laser to irradiate the metal surface simultaneously. The area to be alloyed on the surface, and the alloying gas is provided as a reactive gas atmosphere, and the wavelength of the laser beam emitted by the short-wavelength laser is less than 10640 nm.

The short-wavelength laser is selected from Nd:YAG laser, semiconductor laser and free electron laser.

The short-wavelength laser is an Nd:YAG laser, and the wavelength of the laser beam emitted by the Nd:YAG laser is 1064 nm.

A laser gas alloying device for implementing the above-mentioned metal surface gas alloying method of the present invention adopts the following technical scheme: the laser gas alloying device includes a carbon dioxide laser and a short-wavelength laser, a laser processing head of the carbon dioxide laser and a short-wavelength laser The laser processing heads are all facing the area to be alloyed on the metal surface, so that the laser beams emitted by the two lasers can simultaneously irradiate the area to be alloyed on the metal surface; the wavelength of the laser beam emitted by the short-wavelength laser is less than 10640nm; each laser has Atmosphere cover, the gas outlet of each atmosphere cover is directed to the area to be alloyed on the metal surface to provide alloying gas as a reaction gas atmosphere.

The short-wavelength laser is selected from Nd:YAG laser, semiconductor laser and free electron laser.

The wavelength laser is an Nd:YAG laser, and the wavelength of the laser beam emitted by the Nd:YAG laser is 1064 nm.

Beneficial effects of the invention: the wavelength of the laser beam emitted by the carbon dioxide laser is 10640nm, the energy of the laser beam is easily absorbed by nitrogen, and through the reverse bremsstrahlung effect, the alloying gas is ionized to form plasma, and the plasma energy is higher, It is easier to react with the molten pool, increase the content of alloying gas elements in the molten pool, and increase the content of alloying gas elements in the alloying layer, but the laser beam is not easily absorbed by the metal, and the metal absorption rate is low, so the molten pool compares Shallow, the alloying layer is also relatively shallow. The laser beam emitted by the short-wavelength laser is more easily absorbed by the metal, which can increase the depth of the molten pool and the depth of the alloying layer. However, the short-wavelength laser is not easily absorbed by the alloying gas, and the alloying gas is not easily ionized to form a plasma. It is not easy to occur with the molten pool. In the reaction, the content of gas elements in the molten pool is low, and the content of gas elements in the alloyed layer is low. Combining a carbon dioxide laser and a short-wavelength laser can give full play to the advantages of both, that is, the laser beam emitted by the carbon dioxide laser can ionize the alloying gas and increase the content of gas elements in the alloying layer. The short-wavelength laser The emitted laser beam is more easily absorbed by the metal and increases the penetration depth of the molten pool and the depth of the alloying layer, which can take into account the thickness of the alloying layer and the content of alloying elements at the same time.

Description of drawings

Fig. 1 is the structural representation when adopting single laser to carry out laser gas alloying of metal surface in Comparative Example 1 and Comparative Example 2 of the present invention;

2 is a schematic structural diagram of a laser gas alloying device in an experimental example of the present invention;

3 is a schematic diagram of the variation of nitrogen content in the metal surface nitride layer obtained in Comparative Example 1;

Fig. 4 is the pattern of the metal surface nitride layer obtained in the comparative example 1;

5 is a schematic diagram of the variation of nitrogen content in the metal surface nitride layer obtained in Comparative Example 2;

Fig. 6 is the pattern of the metal surface nitride layer obtained in comparative example two;

Fig. 7 is the schematic diagram of nitrogen content variation in the metal surface nitride layer obtained in the experimental example;

FIG. 8 is a pattern of the metal surface nitride layer obtained in the experimental example.

Detailed ways

In an embodiment of the method for metal surface laser gas alloying of the present invention, a laser beam emitted by a carbon dioxide laser and a laser beam emitted by a short-wavelength laser are used to simultaneously irradiate the area to be alloyed on the metal surface, and an alloying gas is provided as a reaction gas Atmosphere, the wavelength of the laser beam emitted by the short wavelength laser is less than 10640nm. In this embodiment, the wavelength of the laser beam emitted by the carbon dioxide laser is 10640 nm, and the laser transmitters whose emitted laser beam wavelength is less than 10640 nm are collectively referred to as short-wavelength lasers. Specifically, a Nd:YAG laser (Neodymium-doped Yttrium Aluminium Garnet; Nd: Y3Al5O12) is selected as the short-wavelength laser, and the wavelength of the laser beam emitted by the Nd:YAG laser is 1064 nm.

The laser gas alloying device for implementing the above-mentioned metal surface laser gas alloying method of the present invention, as shown in FIG. 2, includes a carbon dioxide laser 5 and a short-wavelength laser 6, a laser processing head 9 of the carbon dioxide laser and a laser of the short-wavelength laser The processing heads are all directed towards the area to be alloyed 8 of the metal surface 7, so that the laser beams (10, 11) emitted by the two lasers can simultaneously irradiate the area to be alloyed on the metal surface. The wavelength of the laser beam emitted by the short-wavelength laser is required to be less than 10640 nm. Each laser has an atmosphere cover 12, each atmosphere cover has an air inlet 13, the air outlet of each atmosphere cover is directed to the area to be alloyed on the metal surface, and each atmosphere cover is supplied with alloying gas from the air inlet to provide nitrogen as a reaction. atmosphere.

Comparative Example 1

The workpiece is made of TC4 titanium alloy, and a single carbon dioxide laser is used. The wavelength of the emitted laser beam 1 is 10640nm. The device used is shown in Figure 1. The carbon dioxide laser is used to irradiate the area to be alloyed on the surface of the titanium alloy workpiece. At the same time, nitrogen gas is sprayed from the atmosphere cover as alloying gas, and the nitrogen gas exhausts the air near the molten pool and surrounds the molten pool. The nitrogen reacts with the high temperature molten pool and enters the molten pool, and the molten pool cools and solidifies to form a nitride layer. Nitrogen plays the role of second phase strengthening or solid solution strengthening in the nitrided layer, and improves the surface hardness and wear resistance of titanium alloys. The experimental parameters are shown in Table 1. The variation of nitrogen content in the obtained metal surface nitride layer is shown in Figure 3. The pattern of the obtained metal surface nitride layer is shown in Figure 4. The maximum nitrogen content of the nitride layer is 50%. However, the maximum depth of the nitride layer is only 0.5mm.

Table 1

Comparative Example 2

The workpiece is made of TC4 titanium alloy, and a single Nd:YAG laser is used. The wavelength of the emitted laser beam 1 is 1064nm. The surface of the alloy is melted to form a molten pool, and at the same time, nitrogen gas is sprayed from the atmosphere hood as an alloying gas, and the nitrogen gas discharges the air near the molten pool and surrounds the molten pool. The nitrogen reacts with the high temperature molten pool and enters the molten pool, and the molten pool cools and solidifies to form a nitride layer. Nitrogen plays the role of second phase strengthening or solid solution strengthening in the nitrided layer, and improves the surface hardness and wear resistance of titanium alloys. The experimental parameters are shown in Table 2. The variation of nitrogen content in the obtained metal surface nitride layer is shown in Figure 5. The pattern of the obtained metal surface nitride layer is shown in Figure 6. The maximum nitrogen content of the nitride layer is only 35%. However, the depth of the nitride layer can be up to 1mm.

Table 2

Experimental example

The workpiece is made of TC4 titanium alloy, and a carbon dioxide laser and a short-wavelength laser are used in combination. The wavelength of the laser beam emitted by the carbon dioxide laser is 10640nm, and the short-wavelength laser is an Nd:YAG laser. The wavelength of the laser beam emitted is 1064nm. The device used is such as shown in Figure 2. Carbon dioxide laser and Nd:YAG laser are used to irradiate the area to be alloyed on the surface of the titanium alloy workpiece at the same time, and the surface of the titanium alloy is melted to form a molten pool. At the same time, nitrogen gas is sprayed from each atmosphere hood as an alloying gas. surrounding the molten pool. The nitrogen reacts with the high temperature molten pool and enters the molten pool, and the molten pool cools and solidifies to form a nitride layer. Nitrogen plays the role of second phase strengthening or solid solution strengthening in the nitrided layer, and improves the surface hardness and wear resistance of titanium alloys. The experimental parameters are shown in Table 3, the variation of nitrogen content in the obtained metal surface nitride layer is shown in Figure 7, the pattern of the obtained metal surface nitride layer is shown in Figure 8, the maximum nitrogen content of the nitride layer is 45.5%, However, the maximum depth of the nitride layer is 0.91mm.

table 3

From the above experimental example and comparative example 1 and comparative example 2, it can be known that the sampling carbon dioxide laser and the short-wavelength laser are compounded, and the high content of gas elements and the depth of the two lasers can be obtained under the condition that both lasers are located at low power. Alloy layer.

In other embodiments of the present invention, the short-wavelength laser can also use a semiconductor laser, and the wavelength of the laser beam emitted by the semiconductor laser is 976 nm; the short-wavelength laser can also use a free electron laser, and the wavelength of the laser beam emitted by the free electron laser is 3000nm ; Short-wavelength lasers can also use other types of lasers, but the wavelength of the laser beam emitted by this type of laser is less than 10640nm; the alloying gas can also not use nitrogen, and other alloying gases can be selected according to needs.

Claims (6)

1. A metal surface laser gas alloying method is characterized in that: the laser beam emitted by a carbon dioxide laser and the laser beam emitted by a short-wavelength laser are simultaneously irradiated on the area to be alloyed on the surface of the metal, and alloying gas is provided as a reaction gas atmosphere, and the wavelength of the laser beam emitted by the short-wavelength laser is less than 10640 nm.

2. The metal surface laser gas alloying method of claim 1 wherein: the short-wavelength laser is selected from one of Nd, semiconductor laser and free electron laser.

3. The metal surface laser gas alloying method according to claim 2, wherein: the short-wavelength laser is an Nd-YAG laser, and the wavelength of a laser beam emitted by the Nd-YAG laser is 1064 nm.

4. A laser gas alloying apparatus for carrying out the method of laser gas alloying of metal surfaces according to claim 1, characterized in that: the alloying device comprises a carbon dioxide laser and a short-wavelength laser, wherein a laser processing head of the carbon dioxide laser and a laser processing head of the short-wavelength laser face to a to-be-alloyed area on the surface of the metal, so that laser beams emitted by the two lasers can simultaneously irradiate the to-be-alloyed area on the surface of the metal; the wavelength of the laser beam emitted by the short-wavelength laser is less than 10640 nm; each laser is provided with an atmosphere cover, and the gas outlet of each atmosphere cover faces to a region to be alloyed on the metal surface to provide alloying gas as reaction gas atmosphere.

5. The laser gas alloying apparatus of claim 4 wherein: the short wavelength laser is selected from one of Nd, YAG, semiconductor and free electron laser.

6. The laser gas alloying apparatus of claim 5 wherein: the wavelength laser is an Nd-YAG laser, and the wavelength of a laser beam emitted by the Nd-YAG laser is 1064 nm.

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