| The crack problem is the key to prevent the further application of laser cladding.Therefore,the preparation of crack free coating has been a hot topic in the field of surface engineering and material science.In this paper,a new technology of laser cladding coating with acoustic electro magnetic multi physical field is proposed in this paper.The influence of single physical field and multi physical field on solidification process,cracking tendency of cladding,microstructure and microstructure of cladding coating,microhardness,tribological properties and corrosion resistance of cladding coating were studied by combining theoretical analysis and experimental research.The main contents and conclusions are as follows:Firstly,the research status of laser cladding crack is reviewed.A new method of high performance coating prepared by acoustic electro magnetic multi physical field assisted laser cladding is proposed.The influence of multi physical field on convection,heat transfer and mass transfer in the pool is explored;Secondly,the sound electric magnetic multi physical field experiment device is designed.The experimental device can adjust the parameters of each physical field and realize the coupling and cooperation between the multi physical field and laser cladding equipment,and can quickly,effectively,independently and safely prepare cladding;Thirdly,the difference between the effects of different magnetic field wave on the cladding structure is analyzed.The effects of four magnetic fields on the cracking tendency,microstructure,phase composition,microhardness,tribological properties and corrosion resistance of laser cladding were studied by means of magnetic field device;The mechanism of the effect of magnetic field on the crack and pool of cladding is analyzed.The results show that the introduction of magnetic field can significantly affect the macro morphology of the cladding,refine the structure of the cladding,and further promote the transformation of columnar crystal to equiaxed crystal,but the partial wave magnetic field will lead to the segregation of hard phase of Cr B;The results show that the effect of the disturbance on the cladding pool is as follows: pulse field > alternating pulse magnetic field > alternating field > steady-state magnetic field;Finally,the effects of multi physical field on the cracking tendency,microstructure,phase composition,microhardness,tribological properties and corrosion resistance of the coating were studied.The results show that magnetic,acoustic and electric field affect the macro morphology of the coating,refine its microstructure,even its element distribution,and the tribology and corrosion resistance are improved significantly;The number of cracks in the cladding under the action of multi physical field was 76.92%,30.76%,38.46% and 15.38% lower than that of the non physical field,and the magnetic,acoustic and electric fields respectively;The area of segregation area decreased 39.23%,35.38%,17.26% and 26.49% respectively;The average microhardness was increased by 37.89%,5.72%,20.78% and 13.44% respectively;The average friction coefficient decreased61.96%,12.71%,41.95% and 35.23%,respectively;The average wear loss decreased61.05%,17.89%,48.25% and 21.18% respectively;The corrosion rate decreased 93.01%,52.78%,60.46% and 22.73% respectively.The results show that the application of this method can break through the limit of traditional laser process parameters adjustment,effectively improve the quality and stability of laser cladding technology,improve the efficiency of control of cladding and broaden the application scope of the technology. |
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