Study On Microstructure And Properties Of Fe-Based Laser Cladding Layer On ZL205A Aluminum Alloy Surface

Lightweight transportation equipment plays an important role in saving energy and reducing emissions and improving the overall performance of equipment.As the most important component of transportation equipment,engine occupies a considerable proportion in volume and mass.Using aluminum alloy with lower density instead of cast iron as the cylinder of engine can reduce the weight of engine and promote the process of equipment lightweight.However,the wear resistance of aluminum alloy is poor,and the inner wall of aluminum alloy cylinder can not bear the long-term friction with piston,which eventually leads to cylinder failure.In this paper,aiming at the problem of poor wear resistance of aluminum alloy,three kinds of Fe-based powders,Fe Cr BSi,316L and 18Ni300,were used as cladding materials,and the cladding layer was prepared on the surface of ZL205A aluminum alloy by high-speed laser cladding technology.In order to discuss the effect of additives on improving the properties of cladding layers,eight kinds of cladding layers of 18Ni300+XLa₂O₃/YWC（X=0.5wt.%,1wt.%,1.5wt.%,2wt.%,3wt.%,4wt.%）were prepared in 18Ni300 material with La₂O₃and WC as additives.In order to discuss the stress distribution law of cladding layer and the influence of cooling mode on the stress of cladding layer,the stress field analysis model of single-layer and multi-channel laser cladding layer was established by using sysweld finite element simulation software.The relative error between the calculated value of stress field analysis model and the measured value is between 5.1%and 7.1%,which shows that this analysis model can accurately reflect the actual stress field of cladding layer The residual stress of cladding layer is concentrated in the center of the first cladding layer and multiple cladding layers,and the highest residual stress can reach 381.41MPa;The stress value of each cladding layer fluctuates with the subsequent cladding layer forming,and the highest peak stress is 650.22MPa;Scanning the back of cladding sample with low power laser can significantly reduce the residual stress of cladding layer.Compared with the cladding layer cooled normally,the peak value of residual stress is reduced by 24.8%,and the average residual stress is reduced by 16.1%.It is found that all three Fe-based materials can form metallurgical bonding with the matrix,and a series of Fe-Al intermetallic compounds are formed in the bonding area There are through cracks in Fe Cr BSi cladding layer caused by the uneven distribution of elements such as b and Si and the combined action of tensile stress.there are hot cracks on the surface of 316L cladding layer caused by the separation of liquid film when cooling,while micro cracks exist in the bonding zone of 18Ni300cladding layer,but they do not spread in a large area,and no cracks appear in the cladding layer.Compared with the substrate,the properties of the three cladding layers are greatly improved,but the cracks in Fe Cr BSi cladding layer and 316L cladding layer make them lose their use value as wear-resistant cladding layers,so 18Ni300 is chosen as the basic material for laser cladding of aluminum alloy surface.Under the experimental conditions,the best addition amount of La₂O₃ is 1.5wt.%,and the cladding layer has smooth surface,no cracks and pores inside,and fine grain size.Compared with 18Ni300 cladding layer,the hardness is increased by 47%,the wear loss is reduced by 29%,and the thermal shock resistance is improved by about 41%.The best addition amount of WC is 3wt.%,and the grains of the cladding layer are locally refined,and the strengthening phases such as Fe3W3C and Fe6W6C are formed.The hardness of the cladding layer is increased by 62%,the wear loss is reduced by 43%,but its thermal shock resistance is only increased by 17%,and macroscopic cracks appear on the surface during thermal shock.Therefore,（18Ni300+1.5wt.%La₂O₃）is the most suitable cladding material for improving the wear resistance of aluminum alloy in this study because of its good formability,excellent wear resistance and thermal shock resistance.