Research on the causes of the failure of the 2205 double phase stainless steel of the leaf wheel mother material, and protect and enhance the wear -resistant coating through laser melting and laser heavy melting. Study the effects of laser power, scanning speed, and powder delivery speed on the 2205 double -phase stainless steel. Analyze the wear performance of the steel. The results show that when the laser power is 1000W, the scanning speed is 6mm/s, and the powder delivery speed is 1.5R/min, the effect of the melting layer is the best, without obvious cracks and air pores, and the surface hardness of the melting layer is 487.2HV0.2. In this parameter, the laser re -melting test is performed to obtain the process parameters of 1000W of laser power and a scanning speed of 12mm/s. The surface of the heavy melting layer is flat, and the surface hardness of the heavy melting layer is 658.5HV0.2. The substrate wear is 0.0751g, the amount of wear of the melting layer is 0.0350g, and the amount of wear after the melting is 0.0211g. 28.1%. Compared with the original substrate, the melting layer enhances the wear resistance of the substrate surface. After the laser is used to retake the melting treatment, the wear resistance of the melting surface is further improved, which can provide a reference for further repair of the cycle pump leaf wheel.
2205 Double-phase stainless steel is the main material of the impeller. It has high strength, good impact toughness and good corrosion resistance. The elements such as chromium, molybdenum and nitrogen contained in them have strong corrosion resistance [-2]. The complexity and strengthening of failure impeller repair further improved with the development of laser melting technology. Laser melting technology is better than spraying and plating. Spraying is a mechanical combination. Under the action of strong external force, coating is prone to fall off. Electroplating technology has great environmental pollution, while laser melting techniques
There is no pollution, green and environmentally friendly.
Yang Quan and other cuts studied that only considering the unchanged parameters of the laser power unchanged, the width and height of the melting layer increased with the increase in laser power. Sun Mingzhu and others studied on the surface of the dedicated fan of car cleaning to prepare TIC coating. Studies have found that wear resistance is the best when TIC is 20%. Zhang Jie et al. [9 studied the effect of ultrasonic vibration acting on different process parameters on the quality of coating. The silicon particles generated in the single crystal silicon production reaction follow the reaction material and enters into the emergency cold tower cycle pump to circulate, and the surface of the impeller can cause the impeller to fail [1-1]. This article prepares protective coating for the failure impeller, and uses the orthogonal test method to study the effects of laser power, scanning speed, and powder delivery speed on the melting layer performance [2]; The technical means study the tissue and object of the melting layer and the melting layer, and reintegrate the hardness and wear resistance of the protective layer through laser melting.
1 Demuro failure research
After long -term service, the leaf wheels will cause wear and corrosion and failure. Observe the impeller’s macro surface, and find that there are yellow -brown adhesion on the surface of the impeller; it can be seen from the overall macro appearance that the diameter and thickness of the impeller becomes significantly smaller, obvious plastic deformation, and more pillar sulcus appears on the surface of the leaves. The corrosive traces and corrosion were found at the leaf plow ditch.
The chemical composition analysis of the surface of the impeller is performed, and the results are shown in Table 1. It can be seen that only a small amount of S, P, CL, and AL contains less acid corrosion on the surface of the impeller. The main faulty form of the impeller surface is not caused by acid corrosion, but for other reasons.
In summary, it is found that the main factor of the impeller failure is the long -term high -speed impact and washed by the silicon particles, causing the local failure of the surface of the leaf wheel to form a plowing gap, and it is also invalidated by the surface of the impeller caused by comprehensive acid corrosion factors; at the same time, it also The chemical corrosion of the electrical electrical is caused by further failure of the surface of the leaf wheel. This article will be carried out around the failure of the leaf wheel failure.
2 Test materials and methods
2.1 Test materials
The test material uses 100mm × 100mm × 8mm2205 double -phase stainless steel. In order to prevent the substrate 2205 double -phase stainless steel surface oxidation layer and oil stains affect the test results, polish and use water -free ethanol for the surface of the substrate. In order to avoid powder containing moisture and improve the liquidity of the powder, it is insulated at 120 ° C in the drying furnace to achieve the purpose of removing moisture. The experiment uses protective gas and pollination gas as a pillar, which can prevent oxidation reactions during the melting process. The composition of 431 alloy powder is shown in Table 2.
2.2 Test equipment and methods
The laser melting equipment used in the test is ZKZM-20000 fiber high-speed laser melting set equipment, which uses coaxial powder, the wavelength is 1080 μm, the maximum power of the laser is 2kq, the diameter of the light spots is φ2mm, the focus during the test process is 15mm, and the separation amount is 15mm. The overlap rate is 45%, the device has a uniform energy distribution
2.3 orthogonal test design
This experiment uses three factors and four levels of orthogonal test design. L16 (43) with a test of 16 (43). Select the factors of laser power, scanning speed, and powder delivery speed. 3 shown.
3 Test results analysis
3.1 Laser melting macro appearance diagram
The macro appearance of the test results is shown in Figure 2. It can be seen that the surface shape of 1, 2, 4, 6, 11, and 16 is better, and the overall height is uniform. There are no obvious cracks on the surface, and the molding effect is better.
The above sample group uses the HVS-1000 number to display the micro-hardness melter melting layer hardness test. The interval is 80 μm. Each group is taken for 5 points. Finally, the average hardness value of each group is taken. It can be seen that from the R value (pole value) data, the size of the hardness that affects the melting layer is: laser power> pollination speed> sweep the second speed, which shows that the effect of laser power on the overall hardness is more obvious. The appearance and hardness positive intercourse are obtained by the best process parameters.
3.2 Reboning process test
Laser heavy melting technology is a technology that is commonly used to change the surface of the material. Reboning can quickly discharge the gas of the melting layer. Cooling and refining the grains. The test uses the power of 1000W, the scanning speed of 6mm/s, and the powder delivery speed 1.5r/min is used as the basic process of laser heavy melting test. The re -melting process parameters are shown in Table 5.
3.3 Reboning the macro appearance chart
Figure 3 shows the macro map of different laser melting layers. It can be seen that the melting effect of group 2-C has a better melting effect, a relatively flat surface, a good surface appearance, and no obvious cracks. The macro appearance of the 1-C and 3-C group is obviously uneven.
3.4 Analysis of laser melting and laser re -melting hardness analysis
The hardness of the laser melting layer under the best process is shown in Figure 4. It can be seen that the melting layer hardness, thermal influence zone hardness, and substrate hardness, the average micro -hardness of the melting layer is 487.2HV0.2, the overall hardness of the melting layer is not obvious, and the average micro -hardness area of the thermal impact area is 303.9HV0. 2. The average micro -hardness of the substrate is 272.2HV0.2, and the hardness of the items in the melting layer to the thermal impact area is the most obvious. At the binding of the substrate and the melting layer, the tissue distribution is even more uniform due to the continuous losses of the laser energy. Therefore, the hardness of the heat influence is increased, and the hardness of the melting layer is 1.8 times that of the substrate.
The hardness distribution of the laser re-melting group in group 2-C is shown in Figure 5. It can be seen that the average micro -hardness of the heavy melting layer is 658.5HV0.2, the average microscopic hardness of the melting layer is 492.8HV0.2, the average microscopic hardness of the thermal influence area is 348.5HV0.2, the average microscopic hardness of the substrate material 305.4HV0.2, its substrate hardness increases by 33.2HV0.2 compared with the laser melting substrate, and the rapid increase in the temperature of the laser is equivalent to quenching the substrate. The hardness of the substrate is greater than after melting, and the hardness of the melting layer is 2.4 times that of the original substrate. After the laser melting layer is carried out, the microscopic hardness is much greater than the hardness of its melting layer. From the test data, the hardness of the laser retransometer to the increased melting layer is particularly significant. Laser melting makes the melting layer of grains refine, making the tissue more dense, and then enhanced its hardness and wear resistance.
3.5 Laser melting and laser heavy melting micro analysis
During the melting process, the surface of the laser beam is formed by the surface of the substrate. The higher temperature molten pond also accelerates the liquidity of the melting liquid, thereby promoting the interaction between the melting powder and the substrate. Figure 6 shows the micro -appearance of the section of the substrate and the melting layer of the 6th group of gold. The combination of dense, the melting effect is better. Because the laser melting process has rapid melting and rapid cooling characteristics, as shown in the figure, the grain size in the melting layer is significantly smaller than the substrate. At the beginning of the melting, the substrate is at room temperature, so there is a large temperature gradient during the melting process. Laser and substrate effects, the melting material of the first contact with the substrate is quickly cooled, some of the heat spread to the air, and the remaining heat is passed to the inside of the substrate. From the figure, the cell -like crystal tissue is observed from the figure. The size of the particles is basically the same and distributed evenly. As the heat spreads to the top of the melting layer, the temperature gradient gradually decreases, the cooling rate of the melting metal liquid increases rapidly, the branch -shaped crystal structure appears, the distribution direction and horizontal direction of the branch crystal appear. Essence From Figure 6 (b) the deeper part of the lower right corner and the bright part of the bright part is the dividing line of the heavy melting layer and the melting layer. It can obviously observe that the grain size is smaller after the laser is melted and the grain tissue is more dense. This is because the laser melting can fine the grains, the surface of the melting layer is melted, and the melting substance is distributed. After the laser is melted, the micro -tissue structure of the laser melting top layer is also changed. There are rapid heating during the laser process, and the rapid cooling process makes the grains smaller. The surface defects of the melting layer can also disappear after rapid melting and cooling.
Figure 7 shows the melting layer under the best process and the SEM appearance of the heavy melting layer. It can be seen that its objectives are organized into clusters, and the grains are densely distributed and the direction is consistent. And after the laser is melted, the grain tissue is more dense compared to laser melting.
3.6 Analysis of laser melting and laser melting XRD analysis
FIG. 8 is an X-ray diffraction analysis graph of the melting layer and the second-C group under the optimal process. It can be seen that at about 45 °, a relatively obvious diffraction peak appeared in the figure, and lower peak values appeared about 65 ° and 80 °. Compounds can enhance its abrasion resistance and hardness of the melting layer. Due to the existence of high -intensity metal intervertebral compounds, the maximum hardness of the melting layer is 1.8 times that of the substrate, and its material has changed after the laser retake. From Feigni to FESNIZ organization, it increases the hardness of the heavy melting layer. The hardness of the heavy melting layer is 2.4 times that of the original substrate. From the perspective of the diffraction peak, the peak height decreased after the laser was melted, and the laser passed through the laser
After the melting, its diffraction peaks have lowered to varying degrees and generated their new substances. This shows that the laser redemption has a promotion effect on generating new substances, and the new substances generated make it have higher hardness and better abrasion resistance.
3.7 Analysis of laser melting and laser retransometer wear test analysis
Perform the wear test of the substrate, the melting layer, and the melting layer of the best process, clean the samples with alcohol and cleaning agent, and use the electronic balance of 10 to get the last average. It is shown that the amount of substrate wear is 0.0751g, the amount of wear of the melting layer is 0.0350g, and the amount of wear after the melting is 0.0211g. The wear amount is 46.6%of the substrate. 28.1%, the amount of wear is much lower than the substrate. This shows that the abrasion resistance of the melting layer after the laser is more better than the melting layer.
Figure 9 is the wear test diagram of the best process underneath, melting layer, and heavy melting layer. It can be seen that the average friction coefficient of the substrate is 0.3412, the average friction coefficient of the melting layer is 0.2681, and the average friction coefficient of the heavy melting layer is 0.2517. From the friction coefficient, the smaller the friction coefficient, the better its wear resistance, and the stronger its resistance. It can be seen from the friction coefficient diagram that the friction coefficient at the beginning is relatively small, because the wear interface at the beginning has not reached a complete contact and has not been fully grinded. It may also be that the abrasion resistance and abrasion resistance in the melting layer tissue is strong. When the friction sample and the sample are fully grinded, the friction coefficient gradually stabilizes the upper and lower up and down on a horizontal line. At this time, the friction is stable. It can be seen from the friction coefficient diagram of the melting layer that its abrasion resistance is relatively stable, without large fluctuations, and stable wear resistance.
4 The impeller fails repair test
First of all, the invalid impeller fatigue layer is cut and then repaired. This repair uses the same shaft to send powder, protect the gas as the sorbe, the repair process parameters use a laser power of 1000W, the scanning speed of 6mm/s, the powder delivery speed 1.5R/min, 45 use %, The heavy melting process uses a laser power of 1000W and the scanning speed of 12mm/s. After the laser melting and removing melting, the machine processing is restored to the original size, and obvious defects such as no cracks on the surface of the coloring detection surface. The restoration of the impeller is shown in Figure 10. The repair and reinforcement effect is better and fully meet the requirements.
5 conclusions
(1) Analysis of failure impeller is effective for grinding loss. It is a local failure that has been caused by a long -term high -speed sports.
(2) Through the orthogonal test, the laser power has the greatest impact on the hardness of the melting layer. The best laser melting process parameters: laser power 1000W, scanning speed of 6mm/s, and the powder delivery speed 1.5R/min. The best process parameters of the melting: laser power 1000W and scanning speed 12mm/s.
(3) The surface hardness of the melting layer is 487.2HV0.2, and the surface hardness of the heavy melting layer is 658.5HV0.2
(4) The amount of wear of the melting layer is relative to 46.6%of the substrate. The wear of the heavy melting layer is 28.1%of the relative substrate wear, which indicates that the abrasion resistance of the melting layer after the laser retake the melting layer is compared with the melting layer. Strongest.
