A method for optimizing laser cladding process of a marine piston head ring groove side wall

Abstract

The present application relates to a kind of marine piston head ring groove side wall laser cladding process optimization method, comprising the following steps: alloy powder, E-51 epoxy resin, after mixing with anhydrous ethanol, it is coated on experimental flat plate and groove side wall to form pre-cladding layer;Under the condition that laser incidence angle 90°, by different laser power, cladding test is carried out on experimental flat plate, and the best power, the best component dilution rate, the best linear energy density are determined;Cladding test is carried out using different incidence angles, and the preferred power value under each incidence angle is determined according to the best component dilution rate;The best power when laser incidence angle 90° is compared, and incidence angle-power attenuation proportion formula is obtained, and then power compensation formula is obtained;According to power compensation formula, the cladding power corresponding to each laser incidence angle in groove side wall cladding is calculated.The present application is aimed at the energy attenuation problem of incidence angle, eliminates the unpredictability of energy attenuation by power compensation formula, maximizes the use of energy, and improves cladding efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser cladding, and particularly relates 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 head and a cylinder liner forms a sealed combustion chamber. A piston ring is installed through an annular groove (ring groove) to block the downward channeling of combustion gas and control the upward channeling of 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 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 a 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 process of chromium plating. Therefore, there is an urgent need for a green remanufacturing process that can 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, laser cladding of the groove sidewall is limited by the following reasons:

[0004] (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 by a side shaft, the powder gathering point and the laser focal point are difficult to fall on the sidewall surface at the same time. At the same time, the powder beam / solid wire is easy to mechanically interfere with the groove wall, the cladding process has poor stability, and the coating is easy to be unmelted and have a lack of meat.

[0005] (2) Energy attenuation of incident angle: the sidewall geometry forces the laser beam to be incident at a non-perpendicular angle, under the action of 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 simultaneously reduced, and the coating is easy to have a risk of local peeling or overall debonding.

[0006] (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.

[0007] In order to pursue the coating adhesion, by increasing the power and reducing the scanning speed, the input of the substrate line energy is increased, which is easy to cause the composition dilution to be too large, resulting in the hardness reduction and the loss of the wear resistance. Therefore, developing a proper laser cladding process for the ring groove side wall of the marine piston head, eliminating the unpredictability of the energy attenuation, and making the cladding process stable and the coating adhesion good while keeping the coating composition dilution rate are the problems to be solved at present. SUMMARY

[0008] The technical problem to be solved by the present application is to overcome the deficiencies in the prior art and provide a laser cladding process optimization method for the ring groove side wall of a marine piston head.

[0009] The present application is implemented by the following technical solutions:

[0010] A laser cladding process optimization method for the ring groove side wall of a marine piston head, comprising the following steps:

[0011] S1. Alloy powder and 2-5% E-51 epoxy resin and 2-5% anhydrous ethanol by weight are mixed into a paste, which is coated on the experimental plate and the groove side wall, and after drying, a pre-cladding layer is formed;

[0012] S2. Single factor test is carried out by fixing the process parameters, and under the condition of laser incidence angle 90°, cladding test is carried out on the pre-cladding layer of the experimental plate by different laser powers, and the best power and its corresponding best composition dilution rate and best line energy density are selected;

[0013] S3. Cladding test is carried out by using different laser incidence angles and different laser powers, and the optimal power value under each laser incidence angle is determined according to the best composition dilution rate;

[0014] S4. The best power at the laser incidence angle of 90° is compared, the attenuation ratio of each laser incidence angle is calculated, the incidence angle-power attenuation ratio formula is obtained, and then the scanning speed, laser incidence angle and power compensation formula are obtained;

[0015] S5. Laser cladding is carried out on the groove side wall, the laser incidence angle is changed after each cladding, and the cladding power corresponding to each laser incidence angle in the groove side wall cladding is calculated according to the power compensation formula.

[0016] According to the above technical solution, preferably, in step S1, the alloy powder comprises 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%.

[0017] According to the technical scheme, preferably, in step S1, the pre-cladding layer is formed by drying in a drying oven at 150 DEG C for 2 hours, and the thickness is controlled to be 0.5-2 mm.

[0018] According to the technical scheme, preferably, in step S2, the optimal power is screened out by taking the component dilution rate as the metallurgical bonding evaluation index, and then the optimal linear energy density corresponding to the optimal power is obtained by substituting the optimal power into the linear energy density formula.

[0019] ,

[0020] Wherein, P is the power, W; v is the scanning speed, mm / s; E is the linear energy density, J / mm.

[0021] According to the technical scheme, preferably, step S3 comprises:

[0022] S31. The cladding test is carried out by adjusting the laser incidence angle to 30 DEG, and the component dilution rate is measured, and the optimal power value when the laser incidence angle is 30 DEG is determined according to the optimal component dilution rate;

[0023] S32. The power and the laser incidence angle are linearly fitted according to the optimal power when the laser incidence angle is 90 DEG and the optimal power value when the laser incidence angle is 30 DEG, so as to narrow the laser power range of the cladding test at other laser incidence angles;

[0024] S33. The cladding test is carried out at the optimized laser power range when the laser incidence angle is 30-90 DEG, and the optimal power value under each laser incidence angle is determined according to the optimal component dilution rate.

[0025] According to the technical scheme, preferably, step S4 comprises:

[0026] S41. The optimal power compensation value of each laser incidence angle is calculated by comparing the optimal power when the laser incidence angle is 90 DEG,

[0027] ,

[0028] Wherein, P3 is the optimal power value of each laser incidence angle, W; P1 is the optimal power when the laser incidence angle is 90 DEG, W; and ΔP is the optimal power compensation value of each laser incidence angle, W;

[0029] S42. The attenuation ratio λ of each laser incidence angle is calculated,

[0030] ,

[0031] Wherein, ΔP is the optimal power compensation value of each laser incidence angle, unit: W, P1 is the optimal power when the laser incidence angle is 90°, unit: W;

[0032] S43. Obtain the incidence angle-power attenuation ratio formula according to the laser incidence angle and the attenuation ratio λ of each laser incidence angle, and obtain the power compensation formula of the scanning speed, the laser incidence angle and the power by combining the linear energy density formula.

[0033] The beneficial effects of the present application are:

[0034] The present application aims at the energy attenuation problem of incidence angle, and obtains the power compensation formula by combining the incidence angle power attenuation ratio formula with the linear energy formula. Thus, the actual laser cladding power required for any incidence angle can be calculated a priori before processing, and the unpredictability of energy attenuation is completely eliminated. In the application process, by dynamically regulating the cladding track of the groove side and the movement track of the cladding head, the incidence angle is gradually increased, the energy attenuation is reduced, the energy can be maximized, the cladding efficiency is improved, and the coating quality is maintained. According to the energy compensation strategy, the side wall cladding layer and the substrate can realize metallurgical bonding, and the coating composition dilution rate and coating performance can be accurately controlled. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is the laser incidence angle of the laser cladding of the groove side wall of the present application Figure One .

[0036] Figure 2 is the laser incidence angle of the laser cladding of the groove side wall of the present application Figure Two .

[0037] Figure 3 is the metallographic picture of the coating after laser cladding according to the process parameters calculated and determined by the laser cladding process optimization method of the present application. DETAILED DESCRIPTION

[0038] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in combination with the drawings and the best embodiment. All other embodiments obtained by those skilled in the art on the basis of the embodiments in the present application without creative labor belong to the scope of protection of the present application.

[0039] As shown in the figure, the present application comprises the following steps:

[0040] S1. Adopting alloy powder and mixing 2-5% E-51 epoxy resin and 2-5% anhydrous ethanol by weight to paste, coating on the experimental plate and the groove side wall, and drying to form a pre-cladding layer.

[0041] Specifically, in this example, the coating method is used to prepare the pre-coating layer, and the alloy powder includes chromium powder, titanium carbide powder, nickel powder, and silicon powder, wherein 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%, and the particle size range is 50-106 μm. Another alloy powder is mixed with 2-5% E-51 epoxy resin and 2-5% anhydrous ethanol to form a uniform paste, and the paste is uniformly coated on the experimental plate and the groove side wall by hand, and the thickness is controlled to be 0.5-2 mm (preferably 1.5 mm). After the coating is completed, the workpiece is placed in a 150°C drying oven for 2 hours to complete the preparation of the pre-coating cladding layer.

[0042] S2. Single factor test is performed by fixing the process parameters, and cladding test is performed on the pre-coating cladding layer of the experimental plate by different laser powers under the condition that the laser incidence angle is 90°, and the best power and the corresponding best composition dilution rate and the best line energy density are selected.

[0043] Specifically, single factor test is performed by fixing the process parameters, wherein an 8000W laser is selected, the laser incidence angle α is 90° (the angle between the laser and the substrate surface), the working distance is 25 mm, the circular spot diameter at the working distance is 4 mm, the scanning speed is 16.7 mm / s, the protective gas is 20 L / min, the single-channel horizontal displacement is 2 mm, the laser power (1200W, 1500W, 1800W, 2100W, 2400W, 2700W, 3000W, 3300W, 3600W) is adjusted, and the cladding test is performed on the pre-prepared experimental plate.

[0044] After the cladding is completed, the coating thickness is ground to 1 mm by using a flat grinder, the coating composition is tested by using a handheld spectrometer, the Fe element composition is used as the composition dilution rate (η), which is used as the metallurgical bonding evaluation index, the coating surface hardness is tested, the best power is selected, and the corresponding best line energy density is obtained by substituting the line energy density formula, and the line energy density formula is:

[0045] ,

[0046] wherein P is the power, the unit is watt (W, i.e. J / s); v is the scanning speed, the unit is millimeter / second (mm / s); and E is the line energy density, the unit is joule / millimeter (J / mm).

[0047] Table 1. Composition dilution rate and line energy density under different laser powers when the laser incidence angle is 90°

[0048]

[0049] To ensure the coating adhesion, the component dilution rate is selected within 5%-10%. As shown in Table 1, when the power is 1800W, the component dilution rate η is 5.42%, which has higher adhesion and minimum hardness loss, and the linear energy density E is 107.78J / mm. The optimal power 1800W is denoted as P1; the optimal component dilution rate 5.42% is denoted as η1; and the optimal linear energy density 107.78J / mm is denoted as E1.

[0050] S3. Cladding tests are performed at different laser incidence angles and by different laser powers, and the optimal power value at each laser incidence angle is determined according to the optimal component dilution rate.

[0051] Specifically, the method comprises the following steps:

[0052] S31. First, adjust the cladding gun head, adjust the laser incidence angle to 30°, and keep the working distance at 25mm. The circular spot diameter at the working distance is 4mm, the scanning speed is 16.7mm / s, the protective gas is 20L / min, and the single-channel horizontal displacement is 2mm.

[0053] Cladding tests are performed by different laser powers (1800W, 2100W, 2400W, 2700W, 3000W, 3300W, 3600W), the component dilution rate is determined, and the optimal power value when the laser incidence angle is 30° is determined according to the optimal component dilution rate, i.e. the power value within the range of η1±0.5% when the incidence angle α is 30° is obtained.

[0054] Table 2 Component dilution rate under different laser powers when the laser incidence angle is 30°

[0055]

[0056] As shown in Table 2, the component dilution rate under each power is not within the range of η1±0.5%, so 3100W and 3200W tests are supplemented.

[0057] Table 3 Component dilution rate of laser power 3100W and 3200W when the laser incidence angle is 30°

[0058]

[0059] As shown in Table 3, when the laser incidence angle α is 30°, the power is 3100W, and the component dilution rate is appropriate.

[0060] S32. According to the optimal power when the laser incidence angle is 90° and the optimal power value when the laser incidence angle is 30°, the power and laser incidence angle are linearly fitted to narrow the laser power range of the cladding test at other laser incidence angles.

[0061] The following can be obtained,

[0062] ,

[0063] wherein P2 is the predicted power value corresponding to each incident angle, with the unit of watt (W); and a is the laser incident angle, with the unit of degree (°). The values of other incident angles are substituted to obtain Table 4.

[0064] Table 4. Different laser incident angles and their corresponding predicted power values after linear fitting

[0065]

[0066] S33. Cladding tests are performed at the laser incident angles of 30-90° and within the optimized laser power range, and the optimal power values under each laser incident angle are determined according to the optimal composition dilution rate. Specifically, the laser powers are selected within the interval before and after the predicted power value in Table 4 to perform cladding tests, and the absolute value of the difference between the composition dilution rate η2 under each laser incident angle and laser power and the optimal composition dilution rate η1 is calculated using the following formula.

[0067] ,

[0068] wherein η1 is the optimal composition dilution rate; η2 is the composition dilution rate under each incident angle and laser power; and Δη is the absolute value of the difference between the composition dilution rate η2 under each laser incident angle and laser power and the optimal composition dilution rate η1.

[0069] Table 5. Composition dilution rates and absolute value of difference under different laser incident angles and laser powers

[0070]

[0071] The power corresponding to the minimum Δη in each laser incident angle is selected as the optimal power value of each laser incident angle, denoted as P3, as shown in Table 6.

[0072] Table 6. Optimal power values corresponding to different laser incident angles

[0073]

[0074] S4. The optimal power at the laser incident angle of 90° is compared to calculate the attenuation ratio of each laser incident angle, obtain the incident angle-power attenuation ratio formula, and further obtain the power compensation formula of the scanning speed, laser incident angle and power. Specifically, the following steps are included:

[0075] S41. The optimal power compensation value of each laser incident angle is calculated by comparing the optimal power at the laser incident angle of 90°,

[0076] ,

[0077] wherein P3 is the preferred power value of each laser incidence angle, unit: watt (W), P1 is the optimal power when the laser incidence angle is 90°, unit: watt (W), and ΔP is the optimal power compensation value of each laser incidence angle, unit: watt (W).

[0078] S42. The attenuation ratio λ of each laser incidence angle is calculated:

[0079]

[0080] wherein ΔP is the optimal power compensation value of each laser incidence angle, unit: watt (W), and P1 is the optimal power when the laser incidence angle is 90°, unit: watt (W).

[0081] Table 7. The optimal power compensation value and the attenuation ratio of each laser incidence angle

[0082]

[0083] S43. The incidence angle-power attenuation ratio formula is obtained according to the laser incidence angle and the attenuation ratio λ of each laser incidence angle, and the power compensation formula of the scanning speed, the laser incidence angle and the power is obtained in combination with the formula of the linear energy density.

[0084] Specifically, the incidence angle-power attenuation ratio formula is obtained by numerical fitting according to the laser incidence angle α and the attenuation ratio λ of each laser incidence angle,

[0085]

[0086] The power compensation formula of the scanning speed, the laser incidence angle and the power is obtained by using the above incidence angle-power attenuation ratio formula in combination with the formula of the linear energy density, that is:

[0087]

[0088] wherein α is the laser incidence angle, unit: degree (°); v is the scanning speed, unit: millimeter per second (mm / s); E1 is the optimal linear energy density, unit: joule per millimeter (J / mm); and P is the power, unit: watt (W, i.e. J / s).

[0089] S5. Laser cladding is performed on the groove sidewall, the laser incidence angle is changed after each cladding circle, and the cladding power corresponding to each laser incidence angle in the cladding of the groove sidewall is calculated according to the power compensation formula.

[0090] For example, the laser incidence angle is changed to 60° after the first cladding circle, and the cladding power corresponding to the laser incidence angle of 60° is calculated according to the power compensation formula. Figure 1 ​​​For example, the groove side wall cladding track and the cladding head motion track are designed. The groove side wall height is 18 mm, and the width is 15 mm. The horizontal rotary table is used for scanning cladding. After each rotation, the laser cladding head adjusts the posture to the next point. The center of the circular spot moves up 2 mm along the groove side wall. The working distance of the laser cladding head is kept at 25 mm. As the laser cladding head is gradually adjusted, the laser incidence angle gradually increases from point 1 to point 10, as shown in FIG. 8. Figure 2

[0091] According to the designed cladding track, the laser incidence angles are 36.87°, 39.81°, 43.15°, 46.97°, 51.34°, 56.31°, 61.93°, 68.20°, 75.07°, and 82.41°, respectively. In this example, the scanning speed is adjusted according to the incidence angle (16.7 mm / s, 20.05 mm / s, 33.4 mm / s, and 50.1 mm / s) to keep the optimal linear energy density E1 unchanged, and the cladding power is adjusted using the power compensation formula.

[0092] Table 8. Cladding power corresponding to each laser incidence angle calculated according to the power compensation formula

[0093]

[0094] For a laser with a rated power of 8000 W, the cladding efficiency is maximized by selecting appropriate process parameters (cladding power and scanning speed) according to the equipment conditions and the predetermined cladding track, as shown in Table 9.

[0095] Table 9. Process parameters determined according to the laser cladding process optimization method

[0096]

[0097] The coating composition dilution rate is 5.67%, and the hardness is 55.03 HRC, which is obtained by using the process parameters in Table 9 to follow the predetermined cladding track. As shown in FIG. 9, the metallographic picture of the coating can be observed. The coating and the substrate are well combined without pores and linear non-fusion defects. The substrate melting depth is controllable, and the heat affected zone is small. At the same time, the surface after cladding is smooth, the surface after turning is smooth, and the TiC particles are uniformly distributed. Figure 3

[0098] ​​In summary, the present application is directed to the problem of incident angle energy attenuation, using the incident angle power attenuation ratio formula combined with the line energy formula to obtain the power compensation formula. Thus, the actual required laser cladding power corresponding to any incident angle can be calculated a priori before processing, completely eliminating the unpredictability of energy attenuation. In the application process, by dynamically regulating the cladding track of the groove side and the movement track of the cladding head, the incident angle is gradually increased, the energy attenuation is reduced, the energy can be maximized, the cladding efficiency is improved, and the coating quality is maintained. According to the energy compensation strategy, the side wall cladding layer and the substrate can realize metallurgical bonding, and the coating composition dilution rate and coating performance can be accurately controlled.

[0099] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

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. 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.

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.

Images