CN113737175B - A laser composite repair method for the plunger rod of an ultra-high pressure plunger pump - Google Patents

Abstract

The invention provides a laser composite repair method for a plunger rod of an ultra-high pressure plunger pump, and relates to the technical field of laser processing, including grinding the surface layer of the plunger rod, configuring the laser cladding repair powder according to the chemical composition of the plunger rod matrix, and regulating the laser cladding. Repair process parameters, surface laser shock strengthening, elimination of interface effects through EBSD observation, adjustment of laser shock parameters, etc., to complete the repair of the surface wear of the plunger rod. The present invention selects repair powder with similar impedance to the plunger rod base, and adjusts the laser cladding process parameters and the laser shock process parameters, and utilizes the shock wave generated by the laser shock to generate large-scale transmission at the interface of the adjacent impedance material, resulting in cladding. The change of grain characteristics in the bonding area between the cladding layer and the plunger rod matrix eliminates the interface between the cladding layer and the plunger rod matrix, and increases the bonding strength between the cladding layer and the plunger rod matrix, thereby improving the plunger rod. service life after repair.

Description

Laser composite repair method for plunger rod of ultra-high pressure plunger pump

technical field

The invention relates to the technical field of laser processing, in particular to a laser composite repair method for a plunger rod of an ultra-high pressure plunger pump.

Background technique

Laser shock strengthening is the use of high-energy laser beams to act on the surface of materials to produce high-strain strengthening effects, introduce residual compressive stress on the surface of materials, and refine grains, so as to achieve the purpose of surface modification of materials. It can effectively improve the fatigue life, wear resistance and corrosion resistance of parts.

Laser cladding is a new type of surface additive manufacturing technology. It melts alloy powder through high-energy and high-density laser beams to achieve the effect of metal smelting and improves the mechanical properties of materials such as tensile resistance and wear resistance. It is suitable for processing Localized damage to metal parts.

At present, pure water jet is widely used in material surface cleaning and material cutting. Its ultra-high pressure greatly improves the erosion effect of water jet, and has been widely used in material cutting, rust removal and industrial cleaning. However, due to the damage of ultra-high pressure water, eccentric wear and sealing form, etc., the plunger rod in the plunger pump is caused by wear and fatigue damage, and the plunger rod with serious damage due to high pressure and wear greatly reduces the operating efficiency and efficiency of the entire system. life. Due to the complex manufacturing process and high production cost of the plunger rod of the plunger pump, the optimization of the repair and remanufacturing technology of the plunger rod has high economic benefits and social value.

The Chinese patent with the authorized announcement number CN102166702B discloses a laser cladding repair method for the piston rod, and the Chinese patent with the authorized announcement number CN106148943B discloses a repair method for the piston rod of the AGC hydraulic cylinder of the rolling mill. In the above two patents, through The laser cladding process conveniently and effectively repairs the damaged part of the piston rod, repairs the mechanical properties of the plunger rod, and restores the normal use of the plunger rod, but the complex problem of the cladding layer interface has not been solved.

The Chinese patent with the authorized notification number CN104480476B discloses a laser thermal combined remanufacturing method for damaged metal parts. Laser shock treatment is performed after each layer of cladding repair to refine the overall cladding layer grains and improve the cladding layer. Defects such as micropores. However, the subsequent cladding process will destroy the previous laser shock process. The next laser cladding will form a melting zone in the previous laser shock strengthening area, and the refined grains will recrystallize at high temperature to form large grains, and the laser shock strengthening The role of the repair cannot be guaranteed, which affects the service life of the plunger rod after repair. In addition, due to the existence of the interface in the laser cladding process, it is easy to generate local stress concentration, which leads to the hidden danger of the next damage to the plunger rod.

Contents of the invention

The purpose of the present invention is to provide a laser composite repair method for the plunger rod of an ultra-high pressure plunger pump. By adjusting the composition of the cladding powder, the cladding layer and the plunger rod matrix have close impedance, and the shock wave generated by the laser shock is used in the near Large-scale transmission occurs at the interface of the impedance material, which changes the grain characteristics near the interface and eliminates the interface between the cladding layer and the plunger rod.

Above-mentioned technical purpose of the present invention is achieved through the following technical solutions:

A laser composite repair method for a plunger rod of an ultra-high pressure plunger pump, specifically comprising the following steps,

S1. Polish the surface of the plunger rod by machining until the largest wear pits are ground away;

S2. Configure the repair powder according to the chemical composition of the plunger rod; wherein, the composition and weight percentage of the plunger rod are: carbon 25.5%-27%, sulfur 0.2%-0.3%, potassium 0.1%-0.3%, calcium 0.3%- 0.4%, chromium 0.6%-0.8%, iron 3.5%-4%, cobalt 9.5%-11%, tungsten 57.3%-58.2%; the composition and weight percentage of the restoration powder are: carbon 23%-25.5%, sulfur 0.2% %-0.3%, potassium 0.2%-0.5%, calcium 0.4%-0.6%, chromium 1.6%-1.9%, iron 3.7%-5%, cobalt 8.4%-8.6%, tungsten 57.6%-62.5%;

S3. Carry out rapid laser cladding treatment, cladding the repair powder onto the surface of the polished plunger rod to form a cladding layer, and grinding the surface of the cladding layer to make it smooth; wherein, the laser cladding process parameters are specifically: laser pulse Width 15ns, laser power 1000-1300W, spot diameter 2-4mm, overlap rate 50%, powder feeding rate 0.3-0.5r/min, scanning speed 1000-1200mm/min;

S4. Perform laser shock strengthening treatment on the smooth surface of the cladding layer formed by the laser cladding repair powder on the plunger rod substrate to eliminate the interface between the plunger rod substrate and the cladding layer, and at the same time use the laser to shock the cladding layer The elimination effect of the interface between the base body and the plunger rod is used to test the ratio of the repair powder for cladding and the parameters of the laser cladding process;

S5. Use EBSD detection technology to inspect the change of grain characteristics at the interface between the cladding layer and the plunger rod substrate, and verify the interface elimination effect between the cladding layer and the plunger rod substrate. If the interface elimination effect meets the requirements, then Determine the repair powder composition ratio in step S2 and the laser cladding process parameters in step S3; if the interface elimination effect does not meet the repair requirements, repeat steps S2-S5, adjust the repair powder composition ratio in step S2 and step S3 Laser cladding process parameters in ;

S6. After verifying that the cladding repair powder and laser cladding process parameters can eliminate the interface to meet the repair requirements, adjust the laser shock process parameters to perform laser shock on the cladding layer, and optimize the effect of laser shock on the interface in combination with step S5. Complete the repair of the plunger rod, and grind the surface of the plunger rod to make the repaired surface flush with the surface of the intact plunger rod, and meet the requirements of the plunger rod for surface roughness.

Further, the powder particle size of the restoration powder prepared in the step S2 is 45-105 μm, and the purity is 99.9%.

Further, in the step S3, during the laser cladding process, nitrogen protection and nitrogen powder feeding are adopted, and the protective gas flow rate is 6 L/min, and the powder feeding pressure is 0.6 MPa.

Further, in the step S3, the thickness of the cladding layer formed by laser cladding and repairing powder is 45-55 μm higher than that of the original plunger rod after grinding and smoothing.

Further, in the step S4, during the laser shock peening treatment, the power density of the laser shock is selected as a medium power density of 7.96GW/cm ² .

Further, in the step S5, during the EBSD detection, use the FEI Quanta 650 scanning electron microscope and the matching HKL NordlysNano EBSD probe to collect the cross-sectional data of the cladding layer after the laser shock in step S4, and observe the interface area of the cladding layer cross-section To verify the effect of laser shock on the interface between the cladding layer and the plunger rod matrix, the change of the grain characteristics is verified.

Further, in the step S6, when adjusting the laser shock process parameters, choose a laser power density of 5.31-11.15GW/cm ² , and shock 3 times under the same laser power density, with a spot diameter of 2-5mm and an overlap rate of 25%- 90%; during the laser shock process, aluminum foil with a thickness of 0.1mm was used as the absorbing layer, and deionized water with a thickness of 2mm was used as the constraining layer.

In summary, the present invention has the following beneficial effects:

1. Determine the formula and content of the repair powder through continuous regulation, so that the impedance between the cladding layer formed by the laser cladding repair powder and the plunger rod matrix is similar;

2. By screening specific laser cladding process parameters and laser shock parameters, the bonding strength between the cladding layer and the plunger rod substrate is guaranteed, the cladding efficiency is improved, and the ratio of laser shock wave transmission and reflection at the interface is controlled;

3. The chemical composition of the repair powder and the plunger rod matrix is similar, so that the impedance between the cladding layer and the plunger rod matrix is similar, and then the laser shock wave is generated at the interface between the cladding layer and the plunger rod matrix due to the similar impedance. Proportional transmission, so that the laser shock can change the grain characteristics at the interface between the cladding layer and the plunger rod, thereby eliminating the interface between the cladding layer and the plunger rod substrate, thereby improving the cladding layer and the column. The bonding strength of the plug rod matrix improves the service life of the plunger rod after repair.

Description of drawings

Fig. 1 is a flow chart of a laser composite repair method for a plunger rod of an ultra-high pressure plunger pump;

Fig. 2 is a wear diagram of the surface of the plunger rod;

Fig. 3 is a statistical diagram of the grain size of the upper, middle and bottom grains of the cladding layer in Examples 1, 2, and 3 without laser shock; wherein, (1) is without laser shock, (2) is Embodiment 1, and (3) ) is embodiment two, and (4) is embodiment three;

Fig. 4 is a comparison diagram of the interface area between the cladding layer and the plunger rod substrate in the first, second, and third embodiments without laser shock; where (a) is without laser shock, (b) is embodiment one, (c) is embodiment two, and (d) is embodiment three.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Embodiment one:

A laser composite repair method for a plunger rod of an ultra-high pressure plunger pump, as shown in Figure 1, specifically includes the following steps,

S1. Polish the surface of the plunger rod by machining until the largest wear pit is ground away, that is, all the outer surface of the plunger rod needs to be polished. The surface wear of the plunger rod is shown in Figure 2.

S2. Configure the repair powder according to the chemical composition of the plunger rod. The composition and content of the repair powder and the plunger rod should be similar to ensure that the impedance between the two is similar. Among them, the composition and weight percentage of the plunger rod are specifically: carbon 25.5%-27%, sulfur 0.2%-0.3%, potassium 0.1%-0.3%, calcium 0.3%-0.4%, chromium 0.6%-0.8%, iron 3.5% %-4%, cobalt 9.5%-11%, tungsten 57.3%-58.2%; the composition and weight percentage of the restoration powder are: carbon 23%-25.5%, sulfur 0.2%-0.3%, potassium 0.2%-0.5%, Calcium 0.4%-0.6%, chromium 1.6%-1.9%, iron 3.7%-5%, cobalt 8.4%-8.6%, tungsten 57.6%-62.5%. In addition, the powder particle size of the restoration powder is 45-105 μm, and the purity is 99.9%.

In this embodiment, the composition and weight percentage of the plunger rod matrix are: 26.45% carbon, 0.26% sulfur, 0.21% potassium, 0.36% calcium, 0.79% chromium, 3.75% iron, 10.52% cobalt, and 57.66% tungsten. Correspondingly, the composition and weight percentage of the restoration powder are: carbon 24.45%, sulfur 0.26%, potassium 0.31%, calcium 0.52%, chromium 1.79%, iron 4.37%, cobalt 8.48%, tungsten 59.82%, and the powder particles of the restoration powder The degree is 85 μm.

S3. Carry out rapid laser cladding treatment, cladding the repair powder to the surface layer of the polished plunger rod to form a cladding layer, and polish the cladding layer to make the surface smooth, and the thickness of the cladding layer after polishing is as high as the original The plunger rod is 45-55 μm. Among them, the laser cladding process parameters are as follows: laser pulse width 15ns, laser power 1000-1300W, spot diameter 2-4mm, lap rate 50%, powder feeding rate 0.3-0.5r/min, scanning speed 1000-1200mm/min . During the laser cladding process, nitrogen protection and nitrogen powder feeding are used, and the protective gas flow rate is 6L/min, and the powder feeding pressure is 0.6MPa. In this embodiment, the selected laser cladding process parameters are: laser pulse width 15ns, laser power 1000W, spot diameter 4mm, overlapping rate 50%, powder feeding rate 0.3r/min, scanning speed 1200mm/min. The thickness of the cladding layer formed by laser cladding repair powder is 50 μm higher than that of the original plunger rod after grinding and smoothing.

S4. Perform laser shock strengthening treatment on the smooth surface of the cladding layer formed by the laser cladding repair powder on the plunger rod substrate. The power density of the laser shock is selected as a medium power density of 7.96GW/ ^cm2 to eliminate the plunger rod substrate and The interface between the cladding layers, and the elimination effect of the interface between the cladding layer and the plunger rod substrate after laser shock are used to test the ratio of the repair powder for cladding and the parameters of the laser cladding process. The principle of laser shock to eliminate the interface is that the chemical composition of the repair powder and the plunger rod matrix is similar to ensure that the impedance of the cladding layer and the plunger rod matrix is similar, so that the laser shock wave is caused by the impedance at the interface between the cladding layer and the plunger rod matrix. A large proportion of transmission occurs so that the laser shock can change the grain characteristics at the interface between the cladding layer and the plunger rod, thereby eliminating the interface between the cladding layer and the plunger rod substrate. Among them, the change of grain characteristics refers to the continuous refinement of the grains in the interface area, forming a region where fine grains are mixed and have no clear boundaries, and the fine grains have the respective grain characteristics of the cladding layer and the plunger rod substrate.

S5. Use EBSD detection technology to inspect the change of grain characteristics at the interface between the cladding layer and the plunger rod substrate, and verify whether the elimination effect of the interface between the cladding layer and the plunger rod substrate meets the repair requirements. Use the FEI Quanta650 scanning electron microscope and the matching HKL NordlysNano EBSD probe to collect the cross-section data of the cladding layer after the laser shock in step S4, and observe the changes in the grain characteristics of the interface area of the cladding layer cross-section to verify the impact of the laser shock on the cladding layer. The interface with the plunger rod base eliminates the effect. If the effect of eliminating the interface meets the requirements, then determine the composition ratio of the repair powder in step S2 and the laser cladding process parameters in step S3. If the interface elimination effect between the cladding layer and the plunger rod substrate does not meet the repair requirements, repeat steps S2-S5, fine-tune the repair powder composition ratio in step S2 and the laser cladding process parameters in step S3.

S6. After verifying that the cladding repair powder and the elimination effect of the laser cladding process parameters on the interface meet the repair requirements, optimize the laser shock process parameters to perform laser shock on the cladding layer, and optimize the elimination effect of the laser shock on the interface in combination with step S5. Among them, the optimization of laser shock process parameters is as follows: choose laser power density 5.31-11.15GW/cm ² , shock 3 times under the same laser power density, spot diameter 2-5mm, overlap rate 25%-90%; During the process, aluminum foil with a thickness of 0.1mm was used as the absorbing layer, and deionized water with a thickness of 2mm was used as the constraining layer to complete the repair of the worn part on the surface of the plunger rod, and to polish the surface of the plunger rod to make the repaired surface and the intact column The surface of the plunger rod is flush and meets the requirements for the surface roughness of the plunger rod. In this embodiment, step S6 uses a laser power density of 11.15 GW/cm ² for 3 impacts, a spot diameter of 4 mm, and an overlap rate of 50%. For the plunger rod repaired in this embodiment, the grain size of the upper, middle and bottom parts of the cladding layer is shown in (2) in Figure 3, and the interface elimination and grain refinement effect between the cladding layer and the plunger rod matrix are as follows Shown in (b) in Figure 4.

Embodiment two:

The difference between this embodiment and Embodiment 1 is that in this embodiment, in step S2, the composition and weight percentage of the restoration powder are: 23% carbon, 0.2% sulfur, 0.2% potassium, 0.4% calcium, and 1.6% chromium , Iron 3.7%, Cobalt 8.4%, Tungsten 62.5%.

In step S3, the selected laser cladding process parameters are: laser pulse width 15ns, laser power 1200W, spot diameter 2mm, overlap rate 50%, powder feeding rate 0.4r/min, scanning speed 1100mm/min.

In step S6, a laser with a power density of 7.96 GW/cm ² is selected for 3 impacts, the spot diameter is 5 mm, and the overlapping rate is 90%.

For the plunger rod repaired in this embodiment, the grain size of the upper, middle and bottom of the cladding layer is shown in (3) in Figure 3, and the interface elimination and grain refinement effect between the cladding layer and the plunger rod matrix are as follows Shown in (c) in Figure 4.

Embodiment three:

The difference between this embodiment and Embodiment 1 and Embodiment 2 is that in this embodiment, in step S2, the composition and weight percentage of the restoration powder are: 25.5% carbon, 0.3% sulfur, 0.5% potassium, and 0.6% calcium , chromium 1.9%, iron 5%, cobalt 8.6%, tungsten 57.6%.

In step S3, the selected laser cladding process parameters are: laser pulse width 15ns, laser power 1300W, spot diameter 3mm, overlap rate 50%, powder feeding rate 0.5r/min, scanning speed 1000mm/min.

In step S6, a laser with a power density of 5.31 GW/cm ² is selected for 3 impacts, the spot diameter is 2 mm, and the overlap rate is 25%.

For the plunger rod repaired in this embodiment, the grain size of the upper, middle and bottom parts of the cladding layer is shown in (4) in Figure 3, and the interface elimination and grain refinement effect between the cladding layer and the plunger rod matrix are as follows Shown in (d) in Figure 4.

As shown in Figure 3 and Figure 4, according to the statistics of the grain size of the upper, middle and bottom parts of the cladding layer in the first, second and third embodiments, as well as the cladding layer and plunger From the comparison of the interface area between the rod matrix, when the repair powder, laser cladding process parameters, and laser shock process parameters are the specific configurations in Example 1, the effect of eliminating the interface between the cladding layer and the plunger rod matrix is the best. Well, the change in grain character is most pronounced in the interfacial region. Next is embodiment two, the effect of interface elimination is more obvious, but the change of grain characteristics in the interface area is not obvious, and finally embodiment three, the interface elimination effect is not as good as embodiment one and embodiment two, and the crystal grain characteristics in the interface area are basically no change.

In the present invention, by selecting the repair powder with the impedance similar to that of the plunger rod matrix, and adjusting the parameters of the laser cladding process and the laser shock process, the shock wave generated by the laser shock is used to produce large-scale transmission at the interface of the impedance material close to the interface area, and the crystal grains in the interface area Refinement forms a region where fine grains are mixed and there is no clear boundary area, and the fine grains have the grain characteristics of the cladding layer and the matrix respectively, eliminating the interface between the cladding layer and the plunger rod matrix, increasing the The bonding strength between the cladding layer and the plunger rod matrix improves the service life of the plunger rod after repair.

Among them, for the control of impedance, it is first necessary to adjust the repair powder formula, control the transmission ratio of the shock wave between the cladding layer and the plunger rod substrate, and then detect the interface area through EBSD and other means to observe the change of grain characteristics and verify The validity of the repair powder formula, the rationality of the laser cladding process parameters and the laser shock strengthening process parameters.

The foregoing description shows and describes preferred embodiments of the present invention, and as previously stated, it is to be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments but may be applied to various other embodiments. Combinations, modifications and circumstances, and can be modified within the scope of the inventive concept described herein, by the above teachings or by skill or knowledge in the relevant field. However, changes and changes made by those skilled in the art do not depart from the spirit and scope of the present invention, and should all be within the protection scope of the appended claims of the present invention.

Claims (7)

1. A laser composite repairing method for a plunger rod of an ultrahigh pressure plunger pump is characterized by comprising the following steps: the method specifically comprises the following steps of,

s1, polishing the surface layer of the plunger rod through machining until the maximum abrasion pits are polished;

s2, preparing repair powder according to the chemical composition of the plunger rod; the plunger rod comprises the following components in percentage by weight: 25.5 to 27 percent of carbon, 0.2 to 0.3 percent of sulfur, 0.1 to 0.3 percent of potassium, 0.3 to 0.4 percent of calcium, 0.6 to 0.8 percent of chromium, 3.5 to 4 percent of ferrum, 9.5 to 11 percent of cobalt and 57.3 to 58.2 percent of tungsten; the repair powder comprises the following components in percentage by weight: 23 to 25.5 percent of carbon, 0.2 to 0.3 percent of sulfur, 0.2 to 0.5 percent of potassium, 0.4 to 0.6 percent of calcium, 1.6 to 1.9 percent of chromium, 3.7 to 5 percent of ferrum, 8.4 to 8.6 percent of cobalt and 57.6 to 62.5 percent of tungsten;

s3, carrying out rapid laser cladding treatment, cladding the repair powder on the surface layer of the polished plunger rod to form a cladding layer, and polishing the surface of the cladding layer to be smooth; the laser cladding process parameters are as follows: the laser pulse width is 15ns, the laser power is 1000-1300W, the spot diameter is 2-4mm, the lap joint rate is 50%, the powder feeding rate is 0.3-0.5r/min, and the scanning speed is 1000-1200mm/min;

s4, performing laser shock strengthening treatment on the smooth surface of the cladding layer formed on the plunger rod substrate by laser cladding repair powder to eliminate the interface between the plunger rod substrate and the cladding layer, and simultaneously checking the selected cladding repair powder ratio and laser cladding process parameters by using the elimination effect of the interface between the cladding layer and the plunger rod substrate after laser shock;

s5, detecting the grain characteristic change condition at the interface between the cladding layer and the plunger rod substrate through an EBSD detection technology, verifying the interface elimination effect between the cladding layer and the plunger rod substrate, and if the interface elimination effect meets the requirement, determining the component ratio of the repair powder in the step S2 and the laser cladding process parameters in the step S3; if the interface elimination effect does not meet the repair requirement, repeating the steps S2-S5, and adjusting the component proportion of the repair powder in the step S2 and the laser cladding process parameters in the step S3;

s6, after verifying that the elimination effect of the cladding repair powder and the laser cladding process parameters on the interface meets the repair requirement, regulating and controlling the laser impact process parameters to carry out laser impact on the cladding layer, optimizing the elimination effect of the laser impact on the interface in combination with the step S5, completing the repair of the plunger rod, and polishing the surface of the plunger rod to enable the repair surface to be flush with the surface of the intact plunger rod and meet the requirement of the plunger rod on the surface roughness.

2. The laser composite repair method for the plunger rod of the ultrahigh-pressure plunger pump according to claim 1, which is characterized by comprising the following steps of: the repair powder prepared in the step S2 has a powder granularity of 45-105 μm and a purity of 99.9%.

3. The laser composite repair method for the plunger rod of the ultrahigh-pressure plunger pump according to claim 1, which is characterized by comprising the following steps of: in the step S3, in the laser cladding process, nitrogen protection and nitrogen powder feeding are adopted, the flow rate of protective gas is 6L/min, and the powder feeding pressure is 0.6MPa.

4. The laser composite repair method for the plunger rod of the ultrahigh-pressure plunger pump according to claim 1, characterized by comprising the following steps of: in the step S3, the thickness of the polished and smoothed cladding layer formed by laser cladding repair powder is 45-55 μm higher than that of the original plunger rod.

5. The laser composite repair method for the plunger rod of the ultrahigh-pressure plunger pump according to claim 1, which is characterized by comprising the following steps of: in the step S4, the power density of laser shock is selected to be 7.96GW/cm during laser shock strengthening treatment ² Medium power density.

6. The laser composite repair method for the plunger rod of the ultrahigh-pressure plunger pump according to claim 1, which is characterized by comprising the following steps of: in the step S5, during EBSD detection, the FEIQuanta650 scanning electron microscope and the matched hklnordysnanoebsd probe are used to collect the data of the cross section of the cladding layer after laser impact in the step S4, and the variation of the grain characteristics of the interface region of the cross section of the cladding layer is observed to verify the effect of laser impact on eliminating the interface between the cladding layer and the plunger rod substrate.

7. The laser composite repair method for the plunger rod of the ultrahigh-pressure plunger pump according to claim 1, which is characterized by comprising the following steps of: in the step S6, when the laser impact process parameters are adjusted, the laser power density is selected to be 5.31-11.15GW/cm ² Impacting 3 times under the same laser power density, wherein the diameter of a light spot is 2-5mm, and the lap joint rate is 25% -90%; during laser shock, an aluminum foil with the thickness of 0.1mm is used as an absorption layer, and deionized water with the thickness of 2mm is used as a restraint layer.

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