Marine piston head ring groove side wall laser cladding process optimization method

Abstract

The invention relates to a marine piston head ring groove side wall laser cladding process optimization method. The marine piston head ring groove side wall laser cladding process optimization method comprises the following steps that alloy powder, E-51 epoxy resin and absolute ethyl alcohol are mixed and then coated on an experimental flat plate and a groove side wall to form a preset cladding layer; under the condition that the laser incident angle is 90 degrees, cladding tests are carried out on an experiment flat plate through different laser powers, and the optimal power, the optimal component dilution rate and the optimal linear energy density are determined; performing a cladding test by adopting different incident angles, and determining an optimal power value under each incident angle according to the optimal component dilution rate; the optimal power when the laser incident angle is 90 degrees is compared, an incident angle-power attenuation proportion formula is obtained, and then a power compensation formula is obtained; and according to a power compensation formula, the cladding power corresponding to each laser incident angle in groove side wall cladding is calculated. Aiming at the problem of incident angle energy attenuation, unpredictability of energy attenuation is eliminated through a power compensation formula, energy is utilized to the maximum extent, and cladding efficiency is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of laser cladding, and in particular to a laser cladding process optimization method for a ring groove sidewall of a marine piston head. BACKGROUND

[0002] The marine piston head is one of the core moving parts of a large marine low-speed diesel engine, is located inside a cylinder liner, is connected to a combustion chamber at the top and is connected to a piston rod or a connecting rod at the bottom, and together with a cylinder cover and the cylinder liner forms a sealed combustion chamber. The piston ring is installed through an annular groove (ring groove) to block the downward channeling of the combustion gas and control the upward channeling of the engine oil. The ring groove of the marine piston head becomes a concentrated attack point of abrasive particles, high temperature, carbon deposition and fatigue, and the ring groove sidewall is subjected to thermal impact of the combustion gas while maintaining long-term axial impact and radial friction with the piston ring. Under such a harsh service environment, the ring groove sidewall of the piston head needs excellent wear resistance. When the traditional hard chromium plating layer is used for the ring groove sidewall of the piston head, the effective thickness that can be achieved is limited due to the characteristics of the electrolytic process, the service life is short under high wear, high pressure and high temperature conditions, and high-toxic Cr 6+ waste water is generated in the whole chromium plating process. Therefore, a green remanufacturing process is urgently needed to improve the thickness while having high wear resistance and metallurgical bonding and meeting the long life requirement of the ring groove sidewall of the marine piston head.

[0003] Laser cladding uses a high-power density laser beam to melt an additional material and a substrate surface at the same time and realizes metallurgical bonding, and has outstanding advantages such as low heat input, small deformation and green environmental protection. However, the laser cladding of the groove sidewall is limited by the following reasons: (1) Limited space accessibility: the depth-width ratio of the groove cavity is large, and the opening is narrow, the conventional coaxial powder / solid wire feeding nozzle is limited by the working distance, it is difficult to normally clad the root of the groove sidewall, when the powder / solid wire is fed in a side-shaft mode, the powder gathering point and the laser focal point are difficult to be synchronously located on the sidewall surface. At the same time, the powder beam / solid wire is easy to mechanically interfere with the groove wall, the cladding process stability is poor, and the coating is easy to be unmelted and lack of meat.

[0004] (2) Energy attenuation of the incident angle: the sidewall geometry constraint forces the laser beam to be incident at a non-perpendicular angle, under the action of the Fresnel absorption effect, the effective power density per unit area is reduced, the temperature of the molten pool is insufficient, the metallurgical bonding strength is synchronously reduced, and the coating is easy to have the risk of local peeling or overall debonding.

[0005] (3) High wear resistance requirement of the coating: due to the lack of systematic research on the relationship between the laser incident angle and the energy attenuation ratio of different alloy materials, it is currently difficult to accurately determine the law of the energy attenuation characteristics changing with the incident angle.

[0006] In pursuit of better coating adhesion, increasing power and decreasing scanning speed leads to increased linear energy input to the substrate. However, this can cause excessive dilution of the coating components, resulting in reduced hardness and compromised wear resistance. Therefore, developing a suitable laser cladding process for the sidewalls of marine piston head ring grooves, eliminating the unpredictability of energy decay, and ensuring stable cladding while maintaining good adhesion between the coating and the substrate and preserving the dilution rate of the coating components, is a pressing issue that needs to be addressed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an optimized method for laser cladding process of sidewall of piston head ring groove in marine applications.

[0008] This invention is achieved through the following technical solution: An optimized method for laser cladding process of the sidewall of the ring groove of a marine piston head includes the following steps: S1. Mix alloy powder with 2-5% E-51 epoxy resin and 2-5% anhydrous ethanol by weight of the alloy powder to form a paste, coat it on the experimental plate and the side wall of the groove, and dry it to form a pre-formed cladding layer. S2. Single-factor experiments were conducted with fixed process parameters. Under the condition of a laser incident angle of 90°, cladding experiments were carried out on the pre-set cladding layer of the experimental plate with different laser powers to screen out the optimal power and its corresponding optimal component dilution rate and optimal linear energy density. S3. Cladding tests were conducted using different laser incident angles and different laser powers, and the optimal power values ​​at each laser incident angle were determined based on the optimal component dilution rate. S4. Compare the optimal power at a laser incident angle of 90°, calculate the attenuation ratio at each laser incident angle, obtain the incident angle-power attenuation ratio formula, and then obtain the power compensation formulas for scanning speed, laser incident angle, and power. S5. Perform laser cladding on the sidewall of the groove. After each cladding cycle, change the laser incident angle and calculate the cladding power corresponding to each laser incident angle in the cladding of the sidewall of the groove according to the power compensation formula.

[0009] According to the above technical solution, preferably, in step S1, the alloy powder includes chromium powder, titanium carbide powder, nickel powder, and silicon powder, wherein the mass ratio of chromium powder is 10-16%, the mass ratio of titanium carbide powder is 10-30%, the mass ratio of nickel powder is 52-79%, and the mass ratio of silicon powder is 1-2%.

[0010] According to the above technical solution, preferably, in step S1, the material is placed in a drying oven at 150°C and dried for 2 hours to form a pre-formed cladding layer with a thickness controlled between 0.5-2 mm.

[0011] According to the above technical solution, preferably, in step S2, the component dilution rate is used as the metallurgical bonding evaluation index to screen out the optimal power, and then substituted into the linear energy density formula to obtain the corresponding optimal linear energy density. The linear energy density formula is: , Where P is power, in W; v is scan speed, in mm / s; and E is linear energy density, in J / mm.

[0012] According to the above technical solution, preferably, step S3 includes: S31. Adjust the laser incident angle to 30°, conduct cladding tests with different laser powers, determine the component dilution rate, and determine the optimal power value when the laser incident angle is 30° based on the optimal component dilution rate. S32. Based on the optimal power at a laser incident angle of 90° and the preferred power value at a laser incident angle of 30°, linear fitting is performed on the power and laser incident angle to narrow the range of laser power for cladding tests at other laser incident angles; S33. Conduct cladding tests with laser incident angles of 30-90° within the optimized laser power range, and determine the preferred power values ​​for each laser incident angle based on the optimal component dilution rate.

[0013] According to the above technical solution, preferably, step S4 includes: S41. Compare the optimal power at a laser incident angle of 90°, and calculate the optimal power compensation value for each laser incident angle. , Where P3 is the preferred power value for each laser incident angle, in W; P1 is the optimal power when the laser incident angle is 90°, in W; and ΔP is the optimal power compensation value for each laser incident angle, in W. S42. Calculate the attenuation ratio λ for each laser incident angle. , Where ΔP is the optimal power compensation value for each laser incident angle, in W, and P1 is the optimal power when the laser incident angle is 90°, in W. S43. Based on the laser incident angle and the attenuation ratio λ of each laser incident angle, obtain the incident angle-power attenuation ratio formula, and then combine it with the linear energy density formula to obtain the power compensation formula for scanning speed, laser incident angle, and power.

[0014] The beneficial effects of this invention are: This invention addresses the problem of energy attenuation at the incident angle by combining the incident angle power attenuation ratio formula with the linear energy formula to obtain a power compensation formula. This allows for the pre-calculation of the actual required laser cladding power for any incident angle before processing, completely eliminating the unpredictability of energy attenuation. During application, by dynamically adjusting the cladding trajectory on the side of the groove and the movement trajectory of the cladding head, the incident angle is gradually increased, reducing energy attenuation. This maximizes energy utilization, improves cladding efficiency, and maintains coating quality. Based on the energy compensation strategy, both metallurgical-grade bonding between the sidewall cladding layer and the substrate is ensured, while precisely controlling the coating component dilution rate and coating performance. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the laser incident angle for laser cladding of the groove sidewall according to the present invention. Figure One .

[0016] Figure 2 This is a schematic diagram of the laser incident angle for laser cladding of the groove sidewall according to the present invention. Figure Two .

[0017] Figure 3 These are metallographic images of the coating after laser cladding, obtained by calculating and determining the process parameters based on the laser cladding process optimization method of this invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] As shown in the figure, the present invention includes the following steps: S1. Alloy powder and 2-5% E-51 epoxy resin and 2-5% anhydrous ethanol by weight of the alloy powder are mixed into a paste, coated on the experimental plate and the side wall of the groove, and dried to form a pre-formed cladding layer.

[0020] Specifically, this example employs a coating-type pre-coated layer preparation method. The alloy powder includes chromium powder, titanium carbide powder, nickel powder, and silicon powder, wherein the mass ratio of chromium powder is 10-16%, the mass ratio of titanium carbide powder is 10-30%, the mass ratio of nickel powder is 52-79%, and the mass ratio of silicon powder is 1-2%, with a particle size range of 50-106 μm. Separately, 2-5% of E-51 epoxy resin and 2-5% of anhydrous ethanol by weight of the alloy powder are mixed into a uniform paste. This paste is then manually and uniformly coated onto the experimental plate and the sidewalls of the groove, controlling the thickness to be 0.5-2 mm (preferably 1.5 mm). After coating, the workpiece is placed in a 150°C drying oven for 2 hours to complete the preparation of the pre-coated cladding layer.

[0021] S2. Single-factor experiments were conducted with fixed process parameters. Under the condition of a laser incident angle of 90°, cladding experiments were carried out on the pre-set cladding layer of the experimental plate with different laser powers to screen out the optimal power and its corresponding optimal component dilution rate and optimal linear energy density.

[0022] Specifically, single-factor experiments were conducted with fixed process parameters, including an 8000W laser, a laser incident angle α=90° (the angle between the laser and the substrate surface), a working distance of 25mm, a circular spot diameter of 4mm at the working distance, a scanning speed of 16.7mm / s, a protective gas flow rate of 20L / min, and a single-channel transverse displacement of 2mm. The laser power was adjusted (1200W, 1500W, 1800W, 2100W, 2400W, 2700W, 3000W, 3300W, 3600W) and cladding experiments were conducted on a pre-prepared experimental plate.

[0023] After cladding, the coating thickness is ground to 1 mm using a surface grinder. The coating composition is then tested using a handheld spectrometer, with the Fe elemental composition used as the component dilution rate (η) as the metallurgical bonding evaluation index. Simultaneously, the coating surface hardness is tested to screen for the optimal power. This optimal power is then substituted into the linear energy density formula to obtain the corresponding optimal linear energy density. The linear energy density formula is as follows: , Where P is power, measured in watts (W, or J / s); v is scan speed, measured in millimeters per second (mm / s); and E is linear energy density, measured in joules per millimeter (J / mm).

[0024] Table 1. Component dilution rate and linear energy density at different laser powers when the laser incident angle is 90°.

[0025] To ensure coating adhesion, the component dilution rate is selected to be within 5%-10%. As shown in Table 1, when the power is 1800W, the component dilution rate η is 5.42%, which exhibits high adhesion, minimal hardness loss, and a linear energy density E of 107.78 J / mm. The optimal power is 1800W, denoted as P1; the optimal component dilution rate is 5.42%, denoted as η1; and the optimal linear energy density is 107.78 J / mm, denoted as E1.

[0026] S3. Cladding tests were conducted using different laser incident angles and different laser powers, and the optimal power value at each laser incident angle was determined based on the optimal component dilution rate.

[0027] Specifically, the steps include the following: S31. First, adjust the cladding gun head, adjust the laser incident angle to 30°, keep the working distance at 25mm, the diameter of the circular spot at the working distance is 4mm, the scanning speed is 16.7mm / s, the protective gas is 20L / min, and the single-channel lateral movement is 2mm.

[0028] Cladding tests were conducted with different laser powers (1800W, 2100W, 2400W, 2700W, 3000W, 3300W, 3600W) to determine the component dilution rate. Based on the optimal component dilution rate, the preferred power value was determined when the laser incident angle was 30°, that is, the power value within the range of η1±0.5% when the incident angle α was 30°.

[0029] Table 2. Component dilution rate at different laser powers when laser incident angle is 30°

[0030] As shown in Table 2, the dilution rate of the components is not within the range of η1±0.5% at various power levels. Therefore, additional tests were conducted at 3100W and 3200W.

[0031] Table 3. Component dilution rates of lasers with incident angles of 30° and laser powers of 3100W and 3200W.

[0032] As shown in Table 3, when the laser incident angle α is 30°, the component dilution rate is appropriate at a power of 3100W.

[0033] S32. Based on the optimal power at a laser incident angle of 90° and the preferred power value at a laser incident angle of 30°, linear fitting is performed on the power and laser incident angle to narrow the range of laser power for cladding tests at other laser incident angles.

[0034] available, , Where P2 is the predicted power value corresponding to each incident angle, in watts (W); α is the laser incident angle, in degrees (°). Substituting the values ​​for other incident angles, we obtain Table 4.

[0035] Table 4. Predicted power values ​​for different laser incident angles after linear fitting.

[0036] S33. Cladding tests were conducted with laser incident angles of 30-90° within the optimized laser power range. The optimal power value at each laser incident angle was determined based on the best component dilution rate. Specifically, using the laser incident angles and predicted power values ​​in Table 4, laser power was selected within the range before and after the predicted power value for cladding tests. The absolute value of the difference between the component dilution rate η2 and the optimal component dilution rate η1 at each laser incident angle and laser power was calculated using the following formula.

[0037] , Where η1 is the optimal component dilution rate; η2 is the component dilution rate at various incident angles and laser powers; and Δη is the absolute value of the difference between the component dilution rate η2 and the optimal component dilution rate η1 at various laser incident angles and laser powers.

[0038] Table 5. Component dilution rates and absolute values ​​of differences under different laser incident angles and laser powers.

[0039] The power corresponding to the minimum value of Δη among each laser incident angle is selected and determined as the preferred power value for each laser incident angle, denoted as P3, as shown in Table 6.

[0040] Table 6 Optimal power values ​​for different laser incident angles

[0041] S4. Compare the optimal power at a laser incident angle of 90°, calculate the attenuation ratio for each laser incident angle, obtain the incident angle-power attenuation ratio formula, and then obtain the power compensation formulas for scanning speed, laser incident angle, and power. Specifically, this includes the following steps: S41. Compare the optimal power at a laser incident angle of 90°, and calculate the optimal power compensation value for each laser incident angle. , Where P3 is the preferred power value for each laser incident angle, in watts (W), P1 is the optimal power at a laser incident angle of 90°, in watts (W), and ΔP is the optimal power compensation value for each laser incident angle, in watts (W).

[0042] S42. Calculate the attenuation ratio λ for each laser incident angle: , Where ΔP is the optimal power compensation value for each laser incident angle, in watts (W), and P1 is the optimal power at a laser incident angle of 90°, in watts (W).

[0043] Table 7 Optimal power compensation values ​​and attenuation ratios for each laser incident angle.

[0044] S43. Based on the laser incident angle and the attenuation ratio λ of each laser incident angle, obtain the incident angle-power attenuation ratio formula, and then combine it with the linear energy density formula to obtain the power compensation formula for scanning speed, laser incident angle, and power.

[0045] Specifically, the incident angle-power attenuation ratio formula is obtained through numerical fitting based on the laser incident angle α and the attenuation ratio λ for each laser incident angle. , Using the above incident angle-power attenuation ratio formula, combined with the linear energy density formula, we can obtain the power compensation formula for scanning speed, laser incident angle, and power, namely: , Where α is the laser incident angle in degrees (°); v is the scanning speed in millimeters per second (mm / s); E1 is the optimal linear energy density in joules per millimeter (J / mm); and P is the power in watts (W, i.e., J / s).

[0046] S5. Perform laser cladding on the sidewall of the groove. After each cladding cycle, change the laser incident angle and calculate the cladding power corresponding to each laser incident angle in the cladding of the sidewall of the groove according to the power compensation formula.

[0047] by Figure 1 Taking a groove as an example, the cladding trajectory on the sidewall of the groove and the movement trajectory of the cladding head are designed. The sidewall height of the groove is 18mm and the width is 15mm. A horizontal rotary table is used for scanning and cladding. After each rotation, the laser cladding head adjusts its posture to the next point, and the center of the circular spot moves 2mm upwards along the sidewall of the groove, while the working distance of the laser cladding head remains at 25mm. As the laser cladding head is gradually adjusted, such as... Figure 2 As shown, the laser incident angle gradually increases from point 1 to point 10.

[0048] Based on the designed cladding trajectory, the laser incident angles are 36.87°, 39.81°, 43.15°, 46.97°, 51.34°, 56.31°, 61.93°, 68.20°, 75.07°, and 82.41°. In this example, the scanning speed is adjusted according to each incident angle (16.7 mm / s, 20.05 mm / s, 33.4 mm / s, and 50.1 mm / s) while keeping the optimal linear energy density E1 constant, and the cladding power is adjusted using the power compensation formula.

[0049] Table 8. Cladding power calculated based on the power compensation formula for each laser incident angle.

[0050] For a laser with a rated power of 8000W, based on the equipment conditions, to maximize the cladding efficiency, appropriate process parameters (cladding power and scanning speed) are selected and cladding is carried out according to the predetermined cladding trajectory, as shown in Table 9.

[0051] Table 9. Process parameters calculated based on the laser cladding process optimization method.

[0052] Using the process parameters in Table 9, cladding was performed according to the predetermined cladding trajectory, resulting in a coating composition dilution rate of 5.67% and a hardness of 55.03 HRC. Figure 3 Metallographic images of the coating show that it bonds well to the substrate, is free of porosity and linear non-fusion defects, and the substrate melting depth is controllable with a small heat-affected zone. Furthermore, the surface is smooth after cladding and after machining, with uniform TiC particle distribution.

[0053] In summary, this invention addresses the issue of energy attenuation at the incident angle by combining the incident angle power attenuation ratio formula with the linear energy formula to obtain a power compensation formula. This allows for the pre-calculation of the actual required laser cladding power for any incident angle before processing, completely eliminating the unpredictability of energy attenuation. During application, by dynamically adjusting the cladding trajectory on the side of the groove and the movement trajectory of the cladding head, the incident angle is gradually increased, reducing energy attenuation. This maximizes energy utilization, improves cladding efficiency, and maintains coating quality. Based on the energy compensation strategy, both metallurgical-grade bonding between the sidewall cladding layer and the substrate is ensured, while precisely controlling the coating component dilution rate and coating performance.

[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An optimized method for laser cladding process of the sidewall of the ring groove of a marine piston head, characterized in that, Includes the following steps: S1. Mix alloy powder with 2-5% E-51 epoxy resin and 2-5% anhydrous ethanol by weight of the alloy powder to form a paste, coat it on the experimental plate and the side wall of the groove, and dry it to form a pre-formed cladding layer. S2. Single-factor experiments were conducted with fixed process parameters. Under the condition of a laser incident angle of 90°, cladding experiments were carried out on the pre-set cladding layer of the experimental plate with different laser powers to screen out the optimal power and its corresponding optimal component dilution rate and optimal linear energy density. S3. Cladding tests were conducted using different laser incident angles and different laser powers, and the optimal power values ​​at each laser incident angle were determined based on the optimal component dilution rate. S4. Compare the optimal power at a laser incident angle of 90°, calculate the attenuation ratio at each laser incident angle, obtain the incident angle-power attenuation ratio formula, and then obtain the power compensation formulas for scanning speed, laser incident angle, and power. S5. Perform laser cladding on the sidewall of the groove. After each cladding cycle, change the laser incident angle and calculate the cladding power corresponding to each laser incident angle in the cladding of the sidewall of the groove according to the power compensation formula.

2. The method for optimizing the laser cladding process of the sidewall of the annular groove of a marine piston head according to claim 1, characterized in that, In step S1, the alloy powder includes chromium powder, titanium carbide powder, nickel powder, and silicon powder. The mass ratio of the chromium powder is 10-16%, the mass ratio of the titanium carbide powder is 10-30%, the mass ratio of the nickel powder is 52-79%, and the mass ratio of the silicon powder is 1-2%.

3. The method for optimizing the laser cladding process of the sidewall of the annular groove of a marine piston head according to claim 2, characterized in that, In step S1, the product is placed in a 150°C drying oven and dried for 2 hours to form a pre-formed cladding layer with a thickness controlled between 0.5 and 2 mm.

4. The method for optimizing the laser cladding process of the sidewall of the annular groove of a marine piston head according to claim 1, characterized in that, In step S2, the component dilution rate is used as the metallurgical bonding evaluation index to screen out the optimal power, and then substituted into the linear energy density formula to obtain the corresponding optimal linear energy density. The linear energy density formula is as follows: ， Where P is power, in W; v is scan speed, in mm / s; and E is linear energy density, in J / mm.

5. The method for optimizing the laser cladding process of the sidewall of the annular groove of a marine piston head according to claim 4, characterized in that, Step S3 includes: S31. Adjust the laser incident angle to 30°, conduct cladding tests with different laser powers, determine the component dilution rate, and determine the optimal power value when the laser incident angle is 30° based on the optimal component dilution rate. S32. Based on the optimal power at a laser incident angle of 90° and the preferred power value at a laser incident angle of 30°, linear fitting is performed on the power and laser incident angle to narrow the range of laser power for cladding tests at other laser incident angles; S33. Conduct cladding tests with laser incident angles of 30-90° within the optimized laser power range, and determine the preferred power values ​​for each laser incident angle based on the optimal component dilution rate.

6. The method for optimizing the laser cladding process of the sidewall of the annular groove of a marine piston head according to claim 5, characterized in that, Step S4 includes: S41. Compare the optimal power at a laser incident angle of 90°, and calculate the optimal power compensation value for each laser incident angle. ， Where P3 is the preferred power value for each laser incident angle, in W; P1 is the optimal power when the laser incident angle is 90°, in W; and ΔP is the optimal power compensation value for each laser incident angle, in W. S42. Calculate the attenuation ratio λ for each laser incident angle. ， Where ΔP is the optimal power compensation value for each laser incident angle, in W, and P1 is the optimal power when the laser incident angle is 90°, in W. S43. Based on the laser incident angle and the attenuation ratio λ of each laser incident angle, obtain the incident angle-power attenuation ratio formula, and then combine it with the linear energy density formula to obtain the power compensation formula for scanning speed, laser incident angle, and power.

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