阅读说明：本技术 一种合金钢表面复合强化工艺 (Alloy steel surface composite strengthening process ) 是由 任云鹏 万瀚宇 陆恒 辛志铎 李致宇 于 2020-11-24 设计创作，主要内容包括：本发明提供了一种合金钢表面复合强化工艺,包括如下步骤：将靶材表面预处理；将表面处理后的靶材敷设吸收层和约束层,通过激光对靶材表面进行高能量短脉冲的激光冲击；将激光冲击后的靶材进行除污处理,将处理后的靶材装入热处理炉内进行碳氮共渗和低温回火处理。本发明是激光冲击与碳氮共渗复合处理的工艺,其中激光冲击可以产生高密度位错、晶粒细化、晶界增多等缺陷,可以提高碳、氮原子的渗入浓度与深度,降低热处理工艺的保温温度,进而改善因温度过高而造成的变形和氧化现象。(The invention provides a composite strengthening process for an alloy steel surface, which comprises the following steps: pretreating the surface of the target material; laying an absorption layer and a constraint layer on the target material after surface treatment, and performing high-energy short-pulse laser impact on the surface of the target material through laser; and (3) carrying out decontamination treatment on the target after laser impact, and loading the treated target into a heat treatment furnace for carbonitriding and low-temperature tempering treatment. The invention relates to a laser shock and carbonitriding composite treatment process, wherein the laser shock can generate defects of high-density dislocation, grain refinement, increased grain boundary and the like, can improve the infiltration concentration and depth of carbon and nitrogen atoms, and reduces the heat preservation temperature of a heat treatment process, thereby improving the deformation and oxidation phenomena caused by overhigh temperature.)

1. The alloy steel surface composite strengthening process is characterized by comprising the following steps of:

pretreating the surface of the target material;

laying an absorption layer and a constraint layer on the target material after surface treatment, and performing high-energy short-pulse laser impact on the surface of the target material through laser;

and (3) carrying out decontamination treatment on the target after laser impact, and loading the treated target into a heat treatment furnace for carbonitriding and low-temperature tempering treatment.

2. The alloy steel surface composite strengthening process according to claim 1, wherein the surface pretreatment is step-by-step grinding and polishing by using sand paper and a metallographic polishing agent to make the surface roughness lower than Ra0.3, and the target material is placed into an acetone or absolute ethyl alcohol solution for ultrasonic cleaning and then dried.

3. The alloy steel surface composite strengthening process according to claim 1, wherein the thickness of the absorption layer is 0.1-1 mm, and the thickness of the constraint layer is 0.1-2 mm.

4. The alloy steel surface composite strengthening process of claim 1, wherein when the target material is low-carbon bearing steel, in the laser impact process of the high-energy short pulse, the pulse width of the laser is 1-100 ns, the repetition frequency of the laser is 1-20 Hz, and the power density of the laser is 1-100 GW/cm²。

5. The alloy steel surface composite strengthening process according to claim 4, wherein the spot diameter of the laser is 1-10 mm, and the lap joint rate of the laser is 30-70%.

6. The alloy steel surface composite strengthening process according to claim 4, wherein the decontamination treatment is to remove impurities and remaining absorption layers and confinement layers on the target surface.

Technical Field

The invention relates to the field of heat treatment or laser shock technology, in particular to a composite strengthening process for an alloy steel surface.

Background

The shaft, the bearing and the gear bear extremely high friction force in the working process, the defects of fatigue pitting corrosion, peeling and the like are easily generated, and the surface hardness, the wear resistance and the contact fatigue strength of the material need to be improved through a certain process.

At present, the strength and the wear resistance of parts such as shafts, gears, bearings and the like are improved mainly through heat treatment processes such as carburizing, nitriding or carbonitriding at home. After carburization, the carburized layer is easy to peel off under stress due to poor binding property of the carburized layer. The hardened layer after nitriding treatment is thin and is not suitable for use in a high-speed impact environment. Carbonitriding is mainly carburizing and nitriding. The carbide formed after carbon infiltration can promote the formation of nitride, and the completion of the carburization process can be effectively promoted after the nitride is formed. In addition, the carbon element in the nitride can also improve the hardness of the material and improve the wear resistance of the material. Therefore, the carbonitriding can make up for the deficiency of single carburizing or nitriding process to a certain extent, and is especially important for improving the comprehensive surface performance of the material. However, the heat preservation temperature is high, the surface structure grains of the part are coarse, the phenomena of thermal deformation and oxidation are easy to generate, and the carbon and nitrogen compounds are not uniform.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an alloy steel surface composite strengthening process, through a laser shock and carbonitriding composite treatment process, the laser shock can generate the defects of high-density dislocation, grain refinement, increased grain boundary and the like, the penetration concentration and depth of carbon and nitrogen atoms can be improved, the heat preservation temperature of a heat treatment process is reduced, and the deformation and oxidation phenomena caused by overhigh temperature are further improved. And the crystal grains after heat treatment are refined and uniformly distributed, the local stress concentration is reduced, and the surface hardness, the wear resistance and the like of the material are improved.

The present invention achieves the above-described object by the following technical means.

A composite strengthening process for the surface of alloy steel comprises the following steps:

pretreating the surface of the target material;

laying an absorption layer and a constraint layer on the target material after surface treatment, and performing high-energy short-pulse laser impact on the surface of the target material through laser;

and (3) carrying out decontamination treatment on the target after laser impact, and loading the treated target into a heat treatment furnace for carbonitriding and low-temperature tempering treatment.

Further, the surface pretreatment is to perform gradual grinding and polishing through sand paper and a metallographic polishing agent to enable the surface roughness to be lower than Ra0.3, then put the target material into acetone or absolute ethyl alcohol solution to perform ultrasonic cleaning, and then blow-dry.

Furthermore, the thickness of the absorption layer is 0.1-1 mm, and the thickness of the restraint layer is 0.1-2 mm.

Further, when the target material is low-carbon bearing steel, in the laser impact process of the high-energy short pulse, the pulse width of the laser is 1-100 ns, the repetition frequency of the laser is 1-20 Hz, and the power density of the laser is 1-100 GW/cm²。

Further, the diameter of a light spot of the laser is 1-10 mm, and the lap joint rate of the laser is 30-70%.

Further, the decontamination treatment is to remove impurities on the surface of the target material and the remaining absorption layer and the remaining constraint layer.

The invention has the beneficial effects that:

according to the alloy steel surface composite strengthening process, laser impacts the surface of the target material, so that surface structure grains are refined, grain boundaries are increased, channels are provided for diffusion of carbon and nitrogen atoms, the diffusion depth and concentration of carbonitrides are improved, the heat preservation temperature of carbonitriding is reduced, and the material deformation and oxidation phenomena caused by overhigh temperature are improved. The crystal grains of the surface structure of the carbonitriding part subjected to laser impact are refined and uniformly distributed, no obvious boundary is formed between the crystal grains and a transition layer, the local stress concentration is reduced, the hardness of the material is improved, the maximum value of a sample treated by a composite process can reach 422.99HV, the carbonitriding process is 408.84HV, the thickness of an influence layer of the composite process can reach 319.091 mu m, the carbonitriding process is 231.356 mu m, the thickness of the influence layer of the composite process can be improved by 37.92%, and the service performance of the part is remarkably improved.

Drawings

FIG. 1 is a flow chart of the alloy steel surface composite strengthening process of the present invention.

FIG. 2 is a schematic processing diagram of the alloy steel surface composite strengthening process of the present invention.

FIG. 3 is a comparison of the carburized layer of the present invention and the carburized layer of the existing carbonitriding process.

FIG. 4 is a graph comparing the hardness of the composite process of the present invention with the hardness of the existing carbonitriding process.

Detailed Description

The invention will be further described with reference to the following figures and specific examples, but the scope of the invention is not limited thereto.

As shown in fig. 1 and fig. 2, the alloy steel surface composite strengthening process of the invention is characterized in that:

the method comprises the following steps: firstly, gradually grinding and polishing an annealed target material by using abrasive paper and a metallographic polishing agent to ensure that the surface roughness is lower than Ra0.3, then carrying out ultrasonic cleaning in an acetone or absolute ethyl alcohol solution, and then immediately drying;

step two: laying an absorption layer and a constraint layer on the target material after surface treatment, and performing high-energy short-pulse laser impact on the surface of the target material through laser; the absorption protective layer is aluminum foil, black paint or black adhesive tape, and the thickness range of the absorption protective layer is 0.1-1 mm. The restraint layer is made of ionized water or K9 glass and the like, and the thickness range is 0.1-2 mm. The pulse width of the high-energy short pulse laser is 1-100 ns, the laser power density is 1-100 GW/cm2, the diameter of a laser spot is 1-10 mm, the overlapping rate of the laser spot is 30-70%, and a single-point, single-point repetition, multipoint distribution, multipoint repetition and overlapping large-area impact mode is adopted.

Step three: removing the absorption layer, and cleaning the surface residues with acetone solution or absolute ethyl alcohol solution;

step four: and (3) putting the target material into a vacuum furnace for carbonitriding, and performing low-temperature tempering after oil quenching.

The main processes of the invention are laser shock peening and carbonitriding, as shown in figure 1. Wherein the laser is a nanosecond laser, and the heat treatment furnace is a vacuum atmosphere furnace. With the attached figure 2, the laser impact process provided by the invention is characterized in that the plasma generated by the high-energy short-pulse laser impact absorption protective layer bombards the surface of the target material, so that the surface structure generates microstructure changes such as high-density dislocation, lattice distortion, grain refinement and the like, and simultaneously, the energy of grains is improved, the heat preservation temperature of austenitizing is further reduced, and the goal of reducing the carbonitriding temperature is realized.

Example (b):

the method for reducing the carbonitriding temperature of 20Cr2Ni4A alloy steel by laser shock comprises the following steps:

the method comprises the following steps: firstly, putting a target material into a heat treatment furnace at 850 ℃ for heat preservation for 1 hour, then cooling along with the furnace, and discharging the target material from the furnace for air cooling after 300 ℃;

step two: cutting the annealed target material into a cuboid with the size of 15 multiplied by 10mm, grinding the cuboid by 400#, 800#, 1200# and 1500# abrasive paper step by step, then polishing the cuboid by using a metallographic polishing agent with the specification of 0.5-3.5 mu m step by step, then performing ultrasonic cleaning in an acetone or absolute ethanol solution, and then immediately drying the cuboid;

step three: laying an absorption layer and a restraint layer on the target after surface treatment, wherein the absorption layer is aluminum foil adhesive tape paper with the thickness of 0.12mm, and the restraint layer is deionized water with the thickness of 2 mm. The target material is impacted by high-energy short pulse laser with single pulse energy of 10J, the pulse width of the high-energy short pulse laser is 10ns, and the laser power density is 8.5GW/cm²The wavelength is 1064nm, the repetition frequency is 5Hz, the laser spot diameter is 3mm, the spot lap ratio is 50%, and the impact area is 12 multiplied by 12mm²。

Step four: removing the absorption layer, cleaning the surface residues with acetone or absolute ethyl alcohol solution, and then immediately drying the surface;

step five: and (3) putting the target material into a vacuum furnace for carbonitriding, and then performing oil quenching and low-temperature tempering on the target material.

As shown in the combined graph of FIG. 3 and FIG. 4, the hardness of the existing carbonitriding process can reach 408.84HV to the maximum, the carbonitriding layer is 118.068 μm, and the influence layer is 231.356 μm; the hardness of the laser shock and carbonitriding composite process can reach 422.99HV to the maximum, the carbonitriding layer is 165.958 microns, the influence layer is 319.091 microns, and compared with the existing carbonitriding process, the hardness of the laser shock and carbonitriding composite process is improved by 40.56 percent, the hardness of the influence layer is improved by 40.56 percent, and the hardness of the influence layer is improved by 3.4 percent. And the hardness of the composite process tends to be stable when the hardness of the composite process is deep to 300 mu m, and the hardness of the composite process tends to be stable when the existing carbonitriding process is deep to 250 mu m. And the enlarged view of the carburized layer shows that the grains and the carbon-nitrogen compounds are uniformly distributed in the composite process, and no obvious boundary exists between the carbon-nitrogen co-carburized layer and the transition layer, so that the local stress concentration is reduced, and the generation of fatigue cracks is effectively inhibited.

The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.