阅读说明：本技术 一种超高速激光熔覆铁基非晶涂层的制备方法 (Preparation method of ultra-high-speed laser cladding iron-based amorphous coating ) 是由 王豫跃 牛强 张景纯 杨冠军 李长久 于 2021-08-03 设计创作，主要内容包括：本发明公开了一种超高速激光熔覆铁基非晶涂层的制备方法,属于表面工程技术领域,采用激光功率为1.0kW～2.5kW,扫描速度为100mm/s～250mm/s的超高速激光熔覆工艺在基板表面制备一层铁基非晶涂层,通过优化激光功率和扫描速度之间的配合,将铁基非晶涂层的成型性能提高至最佳,并将基板对铁基非晶涂层的稀释率降低至最低,成功的将最新的超高速激光熔覆技术应用于铁基非晶合金涂层的制备中,将铁基非晶合金制备成厚度薄(百微米)的无缺陷表面防护涂层,不仅能够避免非晶脆性和尺寸效应的限制,还能充分发挥其优异的耐蚀抗磨性能,从而实现对采矿液压支架活塞杆表面的防护,减小液压支架活塞杆失效导致的经济损失。(The invention discloses a preparation method of an ultra-high speed laser cladding iron-based amorphous coating, belonging to the technical field of surface engineering, wherein an ultra-high speed laser cladding process with the laser power of 1.0kW-2.5kW and the scanning speed of 100 mm/s-250 mm/s is adopted to prepare an iron-based amorphous coating on the surface of a substrate, the forming performance of the iron-based amorphous coating is improved to the best by optimizing the matching between the laser power and the scanning speed, the dilution rate of the substrate to the iron-based amorphous coating is reduced to the lowest, the latest ultra-high speed laser cladding technology is successfully applied to the preparation of the iron-based amorphous alloy coating, the iron-based amorphous alloy is prepared into a defect-free surface protective coating with thin thickness (hundred microns), the limitation of amorphous brittleness and size effect can be avoided, the excellent corrosion resistance and wear resistance can be fully exerted, and the protection on the surface of a mining hydraulic support piston rod is realized, and economic loss caused by failure of the piston rod of the hydraulic support is reduced.)

1. A preparation method of an ultra-high-speed laser cladding iron-based amorphous coating is characterized by comprising the following steps:

flatly placing a clean substrate on a workbench, adding dried Fe-based amorphous powder into a powder feeder, adjusting the powder feeding flow and carrier gas flow to preset values, and adjusting the distance between a gun head and a test plate through a robot control box to ensure that the defocusing amount range in the ultra-high speed laser cladding process is always between 15mm and 20 mm;

preparing an iron-based amorphous coating on the surface of the substrate by adopting an ultra-high speed laser cladding process, wherein the laser power in the adopted ultra-high speed laser cladding process is 1.0kW-2.5kW, and the scanning speed is 100 mm/s-250 mm/s.

2. The method for preparing the ultra-high speed laser cladding iron-based amorphous coating according to claim 1, wherein the laser power in the adopted ultra-high speed laser cladding process is 1.5kW, and the scanning speed is 200 mm/s.

3. The method for preparing the ultra-high speed laser cladding iron-based amorphous coating according to claim 1, wherein the powder feeding rate in the ultra-high speed laser cladding process is 25g/min, and the carrier gas flow rate is 6L/min.

4. The method for preparing the ultra-high speed laser cladding iron-based amorphous coating according to claim 1, wherein the defocusing distance of the iron-based amorphous powder is 18 mm.

5. The method for preparing the ultra-high speed laser cladding iron-based amorphous coating according to claim 1, wherein the thickness of the iron-based amorphous coating is 200-300 μm.

6. The method for preparing the ultra-high-speed laser cladding iron-based amorphous coating according to claim 1, wherein the structure at the joint surface of the iron-based amorphous coating and the substrate is a planar crystal and a columnar crystal, the structure at the middle part of the iron-based amorphous coating is an equiaxed crystal, and the structure at the top part of the iron-based amorphous coating is an amorphous region.

7. The method for preparing an ultra-high speed laser cladding iron-based amorphous coating according to claim 6, wherein the width of the columnar crystal region is 10 μm to 15 μm.

Technical Field

The invention relates to the technical field of surface engineering, in particular to a preparation method of an ultra-high-speed laser cladding iron-based amorphous coating.

Background

At present, the method for improving the wear resistance and the corrosion resistance in industry is mainly to prepare a coating on the surface of the iron-based amorphous alloy, and the iron-based amorphous alloy has the characteristics of long-range disorder-free short-range order, no grain boundary dislocation and the like, has excellent corrosion resistance and wear resistance, and is the optimal choice for preparing the surface corrosion-resistant and wear-resistant coating. But the conventional preparation of the iron-based amorphous coating mainly adopts the methods of thermal spraying and traditional laser cladding. The bonding strength of the coating prepared by thermal spraying and the substrate is low, and the porosity of the coating is high, so that the required performance is difficult to achieve; the traditional laser cladding has the problems of large dilution, low cooling rate and the like, so that the amorphous forming quantity is small, the crystallization is serious, and the excellent performance of the iron-based amorphous alloy is difficult to fully exert.

Disclosure of Invention

The invention provides a preparation method of an ultra-high-speed laser cladding iron-based amorphous coating, which applies the latest ultra-high-speed laser cladding technology to the preparation of the iron-based amorphous alloy coating, prepares the iron-based amorphous alloy into a defect-free surface protective coating with a thin thickness (hundred microns), can avoid the limitations of amorphous brittleness and size effect, and can fully exert the excellent corrosion resistance and wear resistance of the iron-based amorphous alloy, thereby realizing the protection of the surface of a piston rod of a mining hydraulic support and reducing the economic loss caused by the failure of the piston rod of the hydraulic support.

The specific technical scheme provided by the invention is as follows:

the preparation method of the ultra-high-speed laser cladding iron-based amorphous coating provided by the invention comprises the following steps:

flatly placing a clean substrate on a workbench, adding dried Fe-based amorphous powder into a powder feeder, adjusting the powder feeding flow and carrier gas flow to preset values, and adjusting the distance between a gun head and a test plate through a robot control box to ensure that the defocusing amount range in the ultra-high speed laser cladding process is always between 15mm and 20 mm;

preparing an iron-based amorphous coating on the surface of the substrate by adopting an ultra-high speed laser cladding process, wherein the laser power in the adopted ultra-high speed laser cladding process is 1.0kW-2.5kW, and the scanning speed is

100mm/s～250mm/s。

Optionally, the laser power in the adopted ultra-high-speed laser cladding process is 1.5kW, and the scanning speed is 200 mm/s.

Optionally, the powder feeding rate in the ultra-high speed laser cladding process is 25g/min, and the carrier gas flow rate is 6L/min.

Optionally, the defocus distance of the iron-based amorphous powder is 18 mm.

Optionally, the thickness of the iron-based amorphous coating is 200-300 μm.

Optionally, the structure at the joint surface of the iron-based amorphous coating and the substrate is a planar crystal and a columnar crystal, the middle structure of the iron-based amorphous coating is an equiaxed crystal, and the top structure of the iron-based amorphous coating is an amorphous region.

Optionally, the width of the columnar crystal region is 10 μm to 15 μm.

The invention has the following beneficial effects:

the invention provides a preparation method of an ultra-high speed laser cladding iron-based amorphous coating, which adopts an ultra-high speed laser cladding process with the laser power of 1.0kW-2.5kW and the scanning speed of 100 mm/s-250 mm/s to prepare an iron-based amorphous coating on the surface of a substrate, improves the forming performance of the iron-based amorphous coating to the best through optimizing the matching between the laser power and the scanning speed, reduces the dilution rate of the substrate to the iron-based amorphous coating to the lowest, successfully applies the latest ultra-high speed laser cladding technology to the preparation of the iron-based amorphous alloy coating, prepares the iron-based amorphous alloy into a defect-free surface protective coating with thin thickness (hundreds of microns), can not only avoid the limitation of amorphous brittleness and size effect, but also can fully play the excellent corrosion resistance and wear resistance, thereby realizing the protection of the surface of a piston rod of a mining hydraulic support, and economic loss caused by failure of the piston rod of the hydraulic support is reduced.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic cross-sectional view of an iron-based amorphous coating with varying laser power according to an embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating the effect of laser power on dilution ratio according to an embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of the Fe-based amorphous coating at different scanning speeds according to the embodiment of the present invention;

FIG. 4 is a graph illustrating the effect of scan speed on dilution ratio according to an embodiment of the present invention;

FIG. 5 is a schematic view of the microstructure of the cross section of a multi-pass lap coating at different positions according to an embodiment of the present invention;

FIG. 6 is a graph showing the polarization curve of the Fe-based amorphous coating in 3.5 wt.% NaCl solution according to the example of the present invention;

FIG. 7 is a schematic diagram of the abrasion loss and the change of the abrasion rate of the iron-based amorphous coating according to the embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terms "comprises," "comprising," and "having," and any variations thereof, in the description and claims of this invention, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The method for preparing the ultra-high-speed laser cladding iron-based amorphous coating according to the embodiment of the invention will be described in detail with reference to fig. 1 to 7.

The preparation method of the ultra-high-speed laser cladding iron-based amorphous coating provided by the embodiment of the invention comprises the steps of flatly placing a clean substrate on a workbench, adding dried Fe-based amorphous powder into a powder feeder, adjusting the powder feeding flow and carrier gas flow to preset values, and adjusting the distance between a gun head and a test plate through a robot control box to ensure that the defocusing amount range in the ultra-high-speed laser cladding process is always between 15mm and 20 mm; preparing an iron-based amorphous coating on the surface of the substrate by adopting an ultra-high speed laser cladding process, wherein the laser power in the adopted ultra-high speed laser cladding process is 1.0kW-2.5kW, and the scanning speed is 100 mm/s-250 mm/s.

Specifically, a clean substrate is flatly placed on a workbench, dried Fe-based amorphous powder is added into a powder feeder, and then the powder feeding flow and the carrier gas flow are adjusted to preset values, wherein the powder feeding speed is 25g/min, and the carrier gas flow is adjusted to 6L/min. Through the distance between robot control box adjustment rifle head and the test panel, the defocusing amount scope can guarantee the best powder and assemble the ability at 15 ~ 20mm, and creative experiment discovers that the defocusing distance of iron-based amorphous powder is the best when 18mm, opens supporting laser instrument water cooling system, rifle head protection gas system. And adjusting the technological parameters of laser cladding in the control box to a preset value, then performing personal protection work, starting an automatic operation mode, and preparing a cladding layer. In the coating preparation process, the powder supply condition of the powder feeder to powder is observed at any time, whether the powder discharge, water cooling and protective gas operation of the laser cladding gun head is abnormal or not is judged, and if the powder discharge, water cooling and protective gas operation are abnormal, whether the machine is stopped or not is judged according to the condition in time. And after the coating is prepared, cleaning the surface of the coating by using a brush to remove the powder, observing the forming quality of the cladding layer, preliminarily judging whether the parameter selection is reasonable or not, and completing the preparation of the cladding layer according to the steps and the principle to form the iron-based amorphous coating.

According to the preparation method of the ultra-high-speed laser cladding iron-based amorphous coating provided by the embodiment of the invention, preferably, the laser power in the adopted ultra-high-speed laser cladding process is 1.5kW, and the scanning speed is 200 mm/s.

In the embodiment of the invention, a metallographic specimen with the specification of 10 multiplied by 7 multiplied by 5mm, which is processed by wire cutting, is prepared into the metallographic specimen through the steps of ultrasonic cleaning, sample embedding, sample grinding, polishing and the like. And then, etching the Fe-based amorphous coating by using aqua regia (HCl: HNO 3: 3:1), wherein the etching strategy adopts an etching method, a prepared reagent is dripped on the surface of the sample to be etched for 10s, then the surface of the sample is quickly washed by deionized water, dried after being washed by alcohol, and finally the tissue morphology of the Fe-based amorphous coating is observed by using a scanning electron microscope after the sample is subjected to ultrasonic cleaning.

Firstly, the embodiment of the invention researches the influence of single-pass cladding process parameters on the forming of the iron-based amorphous coating to prepare a series of single-pass cladding iron-based amorphous coatings, wherein the research finds that the influence of laser power and scanning speed on the section structure appearance of the coating is most obvious, the appearance of the section of the iron-based amorphous coating is observed, and the influence of the laser power P and the scanning speed V on the dilution rate, the section structure appearance and the interface element diffusion condition of the coating is mainly analyzed.

TABLE 1 list of coating preparation Process parameters

In the embodiment of the invention, the spark wire is used for cutting along the direction vertical to cladding, the section of the iron-based amorphous coating is cut to prepare the metallographic sample, and the structure appearance of the section is observed by adopting a scanning electron microscope, as shown in figure 1, the appearance of the section of the low-power coating is changed under the condition of laser power. From fig. 1, it can be found that the iron-based amorphous coating has good overall forming, a semi-elliptical shape, a compact internal structure, no obvious defect, an obvious interface at the bonding position of the base material, and an increased melting ratio of the base material along with the increase of the laser power.

According to the sectional morphology of the iron-based amorphous coating shown in the attached drawing 1, in combination with the characteristic of a very thin ultra-high-speed laser cladding coating, the dilution rate of the iron-based amorphous coating is calculated by an area method, and as a result, as shown in fig. 2, the iron-based amorphous coating can be diluted to be close to zero at 1.0kW, the dilution rate of the iron-based amorphous coating is gradually increased along with the increase of laser power, when the laser power is increased from 1.0kW to 2.5kW, the power is increased by 150%, the dilution rate is increased from 0.13 to 29%, and the dilution rate is increased by nearly 30 times, which indicates that the influence of the change of the laser power on the dilution rate is obvious. Therefore, when the iron-based amorphous coating is prepared, the proportion of the iron-based amorphous coating diluted by the base material can be smaller and better under the condition of ensuring metallurgical bonding of the iron-based amorphous coating and the base material, and the method is favorable for avoiding the condition that the components of the coating deviate from the nominal design components due to dilution to weaken the forming capability of the amorphous components in the iron-based amorphous coating.

Referring to the change of the cross-sectional morphology of the iron-based amorphous coating when the scanning speed is increased from 100mm/s to 250mm/s shown in fig. 3, it can be seen from fig. 3 that the thickness of the coating deposit is gradually decreased with the increase of the scanning speed, the melting ratio of the parent metal is reduced, and in the case of low scanning speed, the cracking condition in the iron-based amorphous coating is found, which is related to that the linear energy is large when the scanning speed is low, and the thermal stress between the matrix and the coating is too large due to the increase of the dilution ratio. According to the cross-sectional morphology shown in fig. 3, the dilution ratio of the iron-based amorphous coating at different scanning speeds is calculated, and as a result, as shown in fig. 4, the dilution ratio is slightly reduced with the increase of the scanning speed. Comparing the effect of the laser power change on the dilution ratio of the iron-based amorphous coating shown in fig. 2, it is found that the dilution ratio is in positive correlation with the laser power and in negative correlation with the scanning speed. However, when the scanning speed is increased from 100mm/s to 250mm/s, the forming amplification is also 150%, the coating dilution rate is only reduced from 9.4% to 4.8%, and the reduction amplitude is only 49%, so that the influence of the scanning speed on the dilution rate is not significant.

Through the research and the cross-sectional shape analysis of the iron-based amorphous coating, the inventor conducts creative work to find that the iron-based amorphous coating formed by the ultra-high-speed laser cladding technology has the best forming performance and smaller dilution rate under the coordination of the laser power of 1.5kw and the scanning speed of 200 mm/s.

The research on the influence rule of the process parameters of single-channel cladding on the coating forming and the microstructure lays a foundation for preparing a single-layer multi-channel lap coating, the preparation of a large-area continuous iron-based amorphous coating can promote the iron-based amorphous coating to play a role in the field of surface corrosive wear, and the research on the multi-channel lap coating is an inevitable step for the industrial application of the iron-based amorphous coating. Comprehensive research shows that the adopted ultrahigh-speed laser cladding process has the laser power of 1.5kW and the scanning speed of 200mm/s, which are excellent parameters, and the parameters are used for preparing a multi-channel lap joint coating, the near surface and the cross section grinding section tissue morphology of the coating are observed and analyzed, and the cross section morphology of the multi-channel lap joint iron-based amorphous coating is shown in figure 5.

As shown in fig. 5, the structure of the multiple overlapping iron-based amorphous coatings at different positions of the section plane is shown. Fig. 5(a) shows the macroscopic texture morphology, and it can be seen from fig. 5 that the thickness of the fe-based amorphous coating is about 250 μm, the fe-based amorphous coating bonds well with the substrate, the internal texture is dense, the defects are few, the surface of the coating has small fluctuation, which indicates that the flatness is high, and the top position is observed with attached powder particles. As shown in fig. 5(b-d), the microstructure of the bottom portion of the high power lower coating layer near the bonding interface, the middle portion of the coating layer, and the upper portion of the coating layer near the surface, respectively.

Referring to the bottom position of the iron-based amorphous coating shown in fig. 5(b), at the position close to the interface between the iron-based amorphous coating and the substrate, due to the characteristic of high cooling speed of laser cladding, and the heat conduction effect of the substrate on the coating, the cooling rate close to the interface is high, so that a layer of planar crystal is formed first, and then a single-oriented columnar crystal grows on the planar crystal in an epitaxial growth manner, the width of a columnar crystal region is about 10-15 μm, and the columnar crystal region becomes a mixed structure of a black plum blossom-shaped crystalline phase and a gray amorphous phase after finishing, wherein the size of the crystalline phase is 2-4 μm. The temperature of the directional growth of the columnar crystal area at the bottom is gradually increased along the direction from the substrate to the top of the coating, the temperature gradient is gradually reduced, the temperature gradient is smaller upwards, the temperature gradient is reduced along with the approach of the middle part of the coating, the growth of the columnar crystal is gradually stopped, and the columnar crystal area is converted into a fine isometric structure.

As shown in fig. 5(c), the texture of the middle portion of the fe-based amorphous coating is shown, and it can be seen from fig. 5 that the middle portion is a texture in which a black crystalline phase is completely embedded in a gray amorphous phase, because when the middle region is overlapped for a plurality of times, the heat dissipation condition is poor due to repeated heat accumulation, the cooling rate is low, and thus a part of fine crystalline phases are formed. As shown in fig. 5(d) showing the microstructure of the top portion, it can be seen from fig. 5 that the number of black crystal phases is gradually decreased in the mixed region of amorphous and crystal phases, the proportion of gray amorphous phases is increased, the top portion is far from the interface, and under the influence of dilution, the high amorphous forming ability can be maintained, while the influence of overlapping is small, and the solidification rate at the final position of the top portion is fast, so that the crystal phase is decreased.

Through the research, the plurality of overlapping coatings are also shown as a gradient structure tissue distribution from bottom to top when viewed from the whole. The tissue morphology from bottom to top is fine plane crystal, columnar crystal area, mixed area of amorphous and crystalline phase and high amorphous phase ratio area in turn.

In order to better evaluate the corrosion resistance and the wear resistance of the iron-based amorphous coating prepared by the embodiment of the invention, the dynamic information of a metal electrode of a test sample in the corrosion process is analyzed, a dynamic potential polarization method is generally used for measuring a polarization curve, a dynamic potential polarization curve test is carried out on a matrix and the iron-based amorphous coating prepared by an experiment, and the test result is shown in fig. 6.

According to the embodiment of the invention, Tafel linear extrapolation method is adopted to fit the obtained polarization curve, corrosion potential and corrosion current density of the iron-based amorphous coating are calculated, and the calculation result is shown in Table 2. The experimental results show that: the self-corrosion potential of the base material is as follows: and the self-corrosion potential is increased to-0.437V after the iron-based amorphous coating is prepared on the surface of the substrate, and is increased by 41 percent compared with that of the substrate.

The corrosion current density reflects the speed of the surface corrosion behavior, and the matrix corrosion current density is shown as follows from the fitting result: 5.53x10^-5A cm2, preparing the iron-based amorphous coating, and after protection, the method comprises the following steps: 4.31x10^-6A cm2, the corrosion current density is reduced by more than 1 order of magnitude, and the corrosion rate is reduced to 2.8x10^-2 mm/a。

TABLE 2 Tafel fitting self-etch potential and etch current density

A pin-disc type friction wear testing machine is adopted to perform wear resistance testing characterization on the iron-based amorphous coating and the matrix prepared by the embodiment of the invention, and the wear behavior under the real working condition is simulated. GCr15, load 100N, rotating speed 100r/min and friction time 40min are selected as grinding auxiliary materials, and the change of the friction coefficient in the abrasion process and the change of weight loss before and after abrasion are monitored in an experiment. The results are shown in fig. 7, and it can be seen from fig. 7 that under the same abrasion conditions, the abrasion weight loss of the fe-based amorphous coating is only 7.33mg, while the weight loss of the 27SiMn substrate is 26.93mg, and the matrix weight loss is about 4 times that of the fe-based amorphous coating. The wear rates of the two materials under the same wear condition are calculated, and the surface wear rate of the matrix after being protected by the amorphous coating is only 2.99 multiplied by 10 from the view of the wear rate^-5mm3N^-1m^-1Compared with a matrix, the wear resistance of the iron-based amorphous coating prepared by the ultra-high speed laser cladding technology is reduced by 73 percent, and the wear resistance of the iron-based amorphous coating is superior to that of the matrix material.

The invention provides a preparation method of an ultra-high speed laser cladding iron-based amorphous coating, which adopts an ultra-high speed laser cladding process with the laser power of 1.0kW-2.5kW and the scanning speed of 100 mm/s-250 mm/s to prepare an iron-based amorphous coating on the surface of a substrate, improves the forming performance of the iron-based amorphous coating to the best through optimizing the matching between the laser power and the scanning speed, reduces the dilution rate of the substrate to the iron-based amorphous coating to the lowest, successfully applies the latest ultra-high speed laser cladding technology to the preparation of the iron-based amorphous alloy coating, prepares the iron-based amorphous alloy into a defect-free surface protective coating with thin thickness (hundreds of microns), can not only avoid the limitation of amorphous brittleness and size effect, but also can fully play the excellent corrosion resistance and wear resistance, thereby realizing the protection of the surface of a piston rod of a mining hydraulic support, and economic loss caused by failure of the piston rod of the hydraulic support is reduced.

It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to encompass such modifications and variations.