阅读说明：本技术 纳秒激光碳化提高锆基非晶合金表面硬度的方法 (Method for improving surface hardness of zirconium-based amorphous alloy through nanosecond laser carbonization ) 是由 黄虎 张洪洋 钱永峰 王超 张帝 刘翰林 于 2021-01-08 设计创作，主要内容包括：本发明涉及一种纳秒激光碳化提高锆基非晶合金表面硬度的方法,属于非晶合金表面改性技术领域。对锆基非晶合金表面进行研磨、抛光、冲洗和干燥,获得镜面表面；将石墨粉和水混合,配置石墨粉水溶液；将锆基非晶合金样品放置在圆形透明容器内,调节激光焦点至样品表面,滴入配置好的石墨粉水溶液,控制液面高于样品表面1mm；调控纳秒激光工艺参数,实现不同搭接率的逐线扫描,利用碳元素与锆元素在高温条件下易反应生成碳化锆相的特性,在锆基非晶合金表面引入硬度较高的碳化锆相,实现其表面硬度的大幅提升。本发明操作简单,通过控制激光工艺参数可方便地获取不同硬化程度的锆基非晶合金表面,对于扩展其作为表面功能材料的应用具有重要意义。(The invention relates to a method for improving surface hardness of a zirconium-based amorphous alloy through nanosecond laser carbonization, and belongs to the technical field of surface modification of amorphous alloys. Grinding, polishing, washing and drying the surface of the zirconium-based amorphous alloy to obtain a mirror surface; mixing graphite powder with water to prepare a graphite powder aqueous solution; placing a zirconium-based amorphous alloy sample in a round transparent container, adjusting a laser focus to the surface of the sample, and dripping a prepared graphite powder aqueous solution, wherein the liquid level is controlled to be 1mm higher than the surface of the sample; the nanosecond laser process parameters are regulated and controlled, line-by-line scanning of different lap joint rates is achieved, the characteristic that a zirconium carbide phase is easily generated by reacting a carbon element and a zirconium element at a high temperature is utilized, the zirconium carbide phase with high hardness is introduced to the surface of the zirconium-based amorphous alloy, and the surface hardness of the zirconium-based amorphous alloy is greatly improved. The method is simple to operate, can conveniently obtain the surfaces of the zirconium-based amorphous alloys with different hardening degrees by controlling the laser process parameters, and has important significance for expanding the application of the zirconium-based amorphous alloys as surface functional materials.)

1. A method for improving the surface hardness of a zirconium-based amorphous alloy through nanosecond laser carbonization is characterized by comprising the following steps: adopt nanosecond laser irradiation submergence in the zirconium base amorphous alloy of graphite powder aqueous solution, utilize carbon element and the easy reaction of zirconium element to generate zirconium carbide phase's characteristic under the high temperature condition, introduce zirconium carbide phase on zirconium base amorphous alloy surface, realize promoting by a wide margin of its surface hardness, specifically include following step:

step one, grinding, polishing, washing and drying the surface of a zirconium-based amorphous alloy substrate to obtain a mirror surface;

mixing graphite powder and water to prepare a graphite powder aqueous solution;

and thirdly, placing the zirconium-based amorphous alloy matrix in a circular transparent container, adjusting the focus of a laser beam emitted by a nanosecond laser to the surface of the zirconium-based amorphous alloy matrix, dripping the prepared graphite powder aqueous solution, controlling the liquid level of the graphite powder aqueous solution to be 1mm higher than the surface of the zirconium-based amorphous alloy matrix, regulating and controlling the process parameters of the nanosecond laser, and realizing line-by-line scanning with different lap joint rates.

2. The method for improving the surface hardness of the zirconium-based amorphous alloy through nanosecond laser carbonization, according to claim 1, is characterized in that: the obtaining of the mirror surface in the first step is specifically: and sequentially grinding the surface of the zirconium-based amorphous alloy matrix by using 400-mesh, 800-mesh, 1200-mesh and 2000-mesh silicon carbide sand paper, removing a surface oxide layer, polishing to a mirror surface state, washing for 2min by using absolute ethyl alcohol, and drying in air.

3. The method for improving the surface hardness of the zirconium-based amorphous alloy through nanosecond laser carbonization, according to claim 1, is characterized in that: the weight ratio of the graphite powder to the water in the second step is 1: and 7, mixing, fully stirring, and carrying out ultrasonic vibration on the solution for 5min to uniformly disperse the graphite powder in the aqueous solution.

4. The method for improving the surface hardness of the zirconium-based amorphous alloy through nanosecond laser carbonization, according to claim 1, is characterized in that: the nanosecond laser comprises the following process parameters: the average laser power is 3.24W, the laser wavelength is 1064nm, the scanning speed is 5mm/s, the scanning times are 1 time, the pulse frequency is 600kHz, the pulse width is 7ns, the spot diameter is 42 mu m, and the lap-joint rate is 30-90%.

5. The nanosecond laser carbonization method for improving the surface hardness of the zirconium-based amorphous alloy according to claim 1 or 4, wherein: and step three, the change of the lapping rate is realized by changing the distance between the adjacent scanning lines, and the distance between the adjacent scanning lines is 4-28.4 mu m.

Technical Field

The invention relates to the technical field of amorphous alloy surface modification, in particular to a method for improving the surface hardness of a zirconium-based amorphous alloy through nanosecond laser carbonization. The method can obviously improve the surface hardness of the zirconium-based amorphous alloy, and has important significance for expanding the application of the zirconium-based amorphous alloy as a surface functional material.

Background

The amorphous alloy has a long-range disordered and short-range ordered atomic arrangement structure, so that the defects of inherent dislocation, grain boundary and the like of crystalline metal are avoided, and excellent performances such as high hardness, high wear resistance, strong corrosion resistance and the like are endowed. However, most amorphous alloys have poor plastic deformability and exhibit typical brittle fracture characteristics due to rapid expansion of a single or a few shear bands. The low plastic deformability limits the use of amorphous alloys as structural materials, while on the other hand the high hardness and wear resistance properties of amorphous alloys provide new opportunities for their use as surface functional materials. Although the amorphous alloy has high hardness, if the surface hardness and the wear resistance of the amorphous alloy can be further improved, the functional application of the amorphous alloy can be greatly enriched and expanded, and therefore, the method for improving the surface hardness of the amorphous alloy needs to be developed. In the early stage, nanosecond laser is used for irradiating the zirconium-based amorphous alloy in nitrogen, and a zirconium nitride phase is introduced to the surface of the amorphous alloy, so that the surface hardness of the amorphous alloy can be improved (Journal of Alloys and Compounds 770 (2019) 864-874). However, the method uses the circulating nitrogen, the content of the zirconium nitride phase introduced on the surface of the amorphous alloy is limited, the effect of improving the surface hardness of the amorphous alloy is not obvious, and the surface nano indentation hardness is only improved from initial 6.399GPa to 7.403GPa, so that the method for greatly improving the surface hardness of the amorphous alloy needs to be developed.

Disclosure of Invention

The invention aims to provide a method for improving the surface hardness of a zirconium-based amorphous alloy through nanosecond laser carbonization, which solves the problems in the prior art. According to the invention, based on the characteristic that carbon element and zirconium element are easy to react to generate zirconium carbide phase at high temperature, nanosecond laser is used for irradiating the zirconium-based amorphous alloy immersed in the graphite powder aqueous solution, and the zirconium carbide phase is introduced into the surface of the zirconium-based amorphous alloy, so that the surface hardness of the zirconium-based amorphous alloy is greatly improved.

The above object of the present invention is achieved by the following technical solutions:

the method for improving the surface hardness of the zirconium-based amorphous alloy through nanosecond laser carbonization adopts nanosecond laser to irradiate the zirconium-based amorphous alloy immersed in a graphite powder water solution, utilizes the characteristic that carbon and zirconium are easy to react to generate a zirconium carbide phase under a high-temperature condition, introduces the zirconium carbide phase into the surface of the zirconium-based amorphous alloy, realizes the great improvement of the surface hardness of the zirconium-based amorphous alloy, and specifically comprises the following steps:

step one, grinding, polishing, washing and drying the surface of a zirconium-based amorphous alloy substrate to obtain a mirror surface;

mixing graphite powder and water to prepare a graphite powder aqueous solution;

and thirdly, placing the zirconium-based amorphous alloy matrix in a circular transparent container, adjusting the focus of a laser beam emitted by a nanosecond laser to the surface of the zirconium-based amorphous alloy matrix, dripping the prepared graphite powder aqueous solution, controlling the liquid level of the graphite powder aqueous solution to be 1mm higher than the surface of the zirconium-based amorphous alloy matrix, regulating and controlling the process parameters of the nanosecond laser, and realizing line-by-line scanning with different lap joint rates.

The obtaining of the mirror surface in the first step is specifically: and sequentially grinding the surface of the zirconium-based amorphous alloy matrix by using 400-mesh, 800-mesh, 1200-mesh and 2000-mesh silicon carbide sand paper, removing a surface oxide layer, polishing to a mirror surface state, washing for 2min by using absolute ethyl alcohol, and drying in air.

The weight ratio of the graphite powder to the water in the second step is 1: and 7, mixing, fully stirring, and carrying out ultrasonic vibration on the solution for 5min to uniformly disperse the graphite powder in the aqueous solution.

The nanosecond laser comprises the following process parameters: the average laser power is 3.24W, the laser wavelength is 1064nm, the scanning speed is 5mm/s, the scanning times are 1 time, the pulse frequency is 600kHz, the pulse width is 7ns, the spot diameter is 42 mu m, and the lap-joint rate is 30-90%.

And step three, the change of the lapping rate is realized by changing the distance between the adjacent scanning lines, and the distance between the adjacent scanning lines is 4-28.4 mu m.

The invention has the beneficial effects that: based on the characteristic that carbon and zirconium are easy to react to generate a zirconium carbide phase at a high temperature, nanosecond laser is used for irradiating the zirconium-based amorphous alloy immersed in the graphite powder water solution, and the zirconium carbide phase is introduced into the surface of the zirconium-based amorphous alloy, so that the surface hardness of the zirconium-based amorphous alloy is greatly improved, and the carbonization surface hardness is improved by 130-200% compared with the initial surface hardness. By controlling the laser irradiation process parameters, the zirconium-based amorphous alloy surfaces with different hardening degrees can be conveniently obtained, and the method has important significance for expanding the application of the zirconium-based amorphous alloy as a surface functional material. In addition, the method provided by the invention is simple to operate, low in cost, high in efficiency and strong in practicability.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention.

FIG. 1 is a schematic diagram of the configuration of a nanosecond laser system according to the invention;

FIG. 2 is a schematic view of a scanning trajectory of a nanosecond laser system according to the invention;

FIG. 3 is a hardness value comparison of an initial surface and a carburized surface of the present invention;

FIG. 4 is a nano indentation load-depth curve of an initial surface and a carbonized surface of the present invention, with an indentation load fixed at 150 mN;

FIG. 5 is an SEM topography of initial surface nanoindentation of the present invention;

FIG. 6 is a SEM topography of nano-indentations of a carbonized surface according to the invention;

FIG. 7 is a load-depth curve of the initial surface and the carbonized surface and a corresponding depth difference-load curve, wherein the indentation load is fixed at 150mN, and the loading rate is 1 mN/s.

In the figure: 1. a computer and a control system; 2. a nanosecond laser; 3. a laser beam; 4. a mirror; 5. a focusing mirror; 6. a circular transparent container; 7. graphite powder aqueous solution; 8. a zirconium-based amorphous alloy matrix.

Detailed Description

The details of the present invention and its embodiments are further described below with reference to the accompanying drawings.

Referring to fig. 1 to 7, in the method for improving the surface hardness of the zirconium-based amorphous alloy through nanosecond laser carbonization, nanosecond laser is adopted to irradiate the zirconium-based amorphous alloy immersed in a graphite powder aqueous solution, and a zirconium carbide phase with higher hardness is introduced into the surface of the zirconium-based amorphous alloy by utilizing the characteristic that a carbon element and a zirconium element are easy to react at a high temperature to generate the zirconium carbide phase, so that the surface hardness of the zirconium-based amorphous alloy is greatly improved, and the method specifically comprises the following steps:

step one, grinding, polishing, washing and drying the surface of a zirconium-based amorphous alloy matrix 8 to obtain a mirror surface;

step two, mixing graphite powder and water to prepare a graphite powder aqueous solution 7;

and thirdly, placing the zirconium-based amorphous alloy matrix 8 in a circular transparent container 6, adjusting a reflector 4 and a focusing mirror 5 to enable the focus of a laser beam 3 emitted by the nanosecond laser 2 to reach the surface of the zirconium-based amorphous alloy matrix 8, dripping a prepared graphite powder aqueous solution 7, controlling the liquid level of the graphite powder aqueous solution 7 to be 1mm higher than the surface of the zirconium-based amorphous alloy matrix 8, and adjusting and controlling the process parameters of the nanosecond laser 2 through a computer and a control system 1 to realize line-by-line scanning with different lap ratios.

The obtaining of the mirror surface in the first step is specifically: and sequentially grinding the surface of the zirconium-based amorphous alloy matrix 8 by using 400-mesh, 800-mesh, 1200-mesh and 2000-mesh silicon carbide sand paper, removing a surface oxide layer, polishing to a mirror surface state, washing for 2min by using absolute ethyl alcohol, and drying in air.

The weight ratio of the graphite powder to the water in the second step is 1: and 7, mixing, fully stirring, and carrying out ultrasonic vibration on the solution for 5min to uniformly disperse the graphite powder in the aqueous solution.

The nanosecond laser 2 in the third step has the following process parameters: the average laser power is 3.24W, the laser wavelength is 1064nm, the scanning speed is 5mm/s, the scanning times are 1 time, the pulse frequency is 600kHz, the pulse width is 7ns, the spot diameter is 42 mu m, and the lap-joint rate is 30-90%.

And step three, the change of the lapping rate is realized by changing the distance between the adjacent scanning lines, and the distance between the adjacent scanning lines is 4-28.4 mu m.

Example (b):

with Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5The following examples are provided to further illustrate the operation and benefits of the present invention by using nanosecond laser to scan the surface of the zirconium-based amorphous alloy immersed in the graphite powder aqueous solution at different overlapping rates.

Referring to fig. 3, the carbonized surface with the lapping rate of 30% is obtained by the method provided by the present invention under the conditions that the average laser power is 3.24W, the scanning speed is 5mm/s, the scanning times are 1, the pulse frequency is 600kHz, and the distance between adjacent scanning lines is 28.4 μm, the average value obtained by measuring 10 times of nano indentation hardness after polishing the carbonized surface is 19.2GPa, compared with 6.4GPa of the initial surface, the hardness value is improved by 12.8GPa, the hardness is improved by 200%, which shows that the laser carbonization in the graphite powder aqueous solution plays a role in surface hardening, and the surface hardness of the zirconium-based amorphous alloy can be greatly improved.

Referring to fig. 3, the carbonized surface with a 90% lap joint rate is obtained by the method provided by the present invention under the conditions that the average laser power is 3.24W, the scanning speed is 5mm/s, the scanning times are 1, the pulse frequency is 600kHz, and the distance between adjacent scanning lines is 4 μm, the average value obtained by measuring 10 nano indentation hardnesses after polishing the carbonized surface is 15.1GPa, and compared with 6.4GPa of the initial surface, the hardness value is increased by 8.7GPa, which shows that the laser carbonization in the graphite powder aqueous solution plays a role in surface hardening no matter under the conditions of low lap joint rate or high lap joint rate, and the mechanical property of the surface of the zirconium-based amorphous alloy can be improved.

Fig. 4 shows a nano indentation load-depth curve of the initial surface and the carbonized surface, and it can be seen from the curve that under the same load of 150mN, the maximum indentation depth of the initial surface is significantly greater than that of the carbonized surface, indicating that the hardness of the carbonized surface is greatly improved compared with that of the initial surface, which also confirms that the laser carbonization in the graphite powder aqueous solution plays a role in surface hardening.

The nanoindentation residual morphology of the surface before and after carbonization is shown in fig. 5 and 6, and it can be seen that the indentation size of the carbonized surface is significantly reduced from the initial surface indentation size, which further illustrates the surface hardening effect of laser carbonization in the graphite powder aqueous solution.

Referring to fig. 7, which shows a load-depth curve and a depth difference-load curve obtained under the conditions that the indentation load is fixed at 150mN and the loading rate is 1mN/s, it can be found that many surface shear bands and saw tooth rheologies are generated on the initial surface, and the carbonized surface has no shear bands and saw tooth rheologies, which shows that the introduction of the zirconium carbide phase prevents the generation of the surface shear bands and regulates the plastic deformation characteristics of the zirconium-based amorphous alloy surface, when being combined with fig. 5 and 6.

According to the method for improving the surface hardness of the zirconium-based amorphous alloy through nanosecond laser carbonization, nanosecond laser is adopted to irradiate the zirconium-based amorphous alloy immersed in the graphite powder water solution, and the zirconium carbide phase with higher hardness is introduced into the surface of the zirconium-based amorphous alloy by utilizing the characteristic that carbon and zirconium are easy to react at high temperature to generate the zirconium carbide phase, so that the surface hardness of the zirconium-based amorphous alloy can be greatly improved.

The above description is only a preferred example of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like of the present invention shall be included in the protection scope of the present invention.