| Laser cladding technology has significantly improved the effective utilization of resources in the industrial field and become a key link in green remanufacturing technology.In order to make the prepared cladding coating excellent in performance,it can be studied in terms of process parameters and materials.The application of ultrasonic assist in the foundry industry has acquired certain achievements.Therefore,the application of ultrasonic technology in laser cladding has also been favored by more and more scholars.In the current research,laser cladding with ultrasonic vibration is often carried out under a fixed lap ratio and single cladding layers Further,the comparison of cladding methods is less.In order to obtain the coating with good cladding effect,this article takes Ni60 coating on 45 steel as an example,researching the appropriate lap ratio,and conducts multi-layer cladding,compares the cladding effect of ultrasonic vibration under different scanning modes.Furthermore,seeking the optimal process parameters and methods for the whole cladding period with the assistance of ultrasound.Before multi-layer cladding,it is necessary to obtain a single-layer cladding coating with good cladding effect.Therefore,a finite element model is established,and the temperature field model under three different overlap rates of high,middle,and low is analyzed.Moreover,the simulation results found that the cumulative temperature field of the 66% overlap model was the highest,and it was speculated that the cladding effect was poor at this overlap rate.Furthermore,Verifying the simulation results for this test,the coating with good cladding effect can be trial produced by single-layer and single-pass rough test,and the approximate range of each process parameter can be determined.Within the above parameters,the orthogonal test is designed and carried out,and the optimal basic process parameters are determined according to the established scoring system.In addition,a variable overlap rate cladding tests were performed in above parameters.The test results were consistent with the simulation,and subsequent tests excluded 66% overlap.After determining the appropriate ultrasonic power,conducting experiments with and without ultrasonic assistance were performed at 33% and 50% overlap rates,respectively.The results show that the grain morphology of the coating was relatively complex through comparison but the growth pattern was similar.In general,it can be shown that the grains at the bottom of the coating grow like cells,columnar dendrites grow in the middle of the coating,and equiaxed crystals are distributed at the top.Ultrasonic vibration can refine grains effectively.After the comprehensive comparison of microstructure,abrasion resistance and other factors.What’s more,it was found that the coating performance of 50% overlapped specimens was the best under the assistance of ultrasound.Based on the determined optimal parameters of single-layer cladding,such as overlap rate and ultrasonic power,the multi-layer cladding was carried out,and the contrast tests of ultrasonic vibration applied and ultrasonic vibration not applied were carried out under the mode of line-type and cross-type cladding respectively.The test found that compared with the cross-type cladding,the coating obtained by the line-type cladding method has better performance and fewer defects such as cracks.In addition,through EDS analysis and SEM observation,it can be seen that the cladding process uses ultrasonic assistance,On the one hand,the acoustic flow effect and mechanical vibration energy make the elements and phases in the layer more uniformly distributed.On the other hand,the cavitation effect can effectively crush the grains,reduce the grain size,and then improve the cladding effect and the quality of the coating,and prepare a Ni60 coating with good cladding effect. |
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