Study On The Influence Mechanism Of Wear Resistance Of CeO₂-SiC-Ni60 Coatings With Similar "Pinning" Structure

Aluminum alloys are widely used in industrial manufacturing fields such as aerospace,automotive manufacturing,and shipping due to their advantages of low density,high specific strength,high thermal conductivity,and good formability.However,their application range is limited by factors such as low surface hardness,poor strength,and wear resistance of aluminum alloys.To improve the surface hardness and wear resistance of aluminum alloys,an efficient and economical approach is to prepare metal-ceramic composite coatings.However,the bonding area between high strength coatings and soft metal substrates often becomes a high incidence area for crack initiation,leading to coating cracking.In response to this issue,this article designs three multi step laser processes（laser melting-cladding two-step laser,laser melting-cladding three-step laser,and laser cladding after local laser alloying）to obtain coatings with a"pinning"like structure on the surface of 7075 aluminum alloy.High energy density laser is used to prepare deep melting units with certain spaces that have high strength and hardness,making them present a distribution feature of soft and hard phases with the substrate.This distribution feature utilizes a high plasticity soft aluminum alloy substrate to slow down the stress in the bonding zone and reduce the probability of crack nucleation.At the same time,deep melting units are used to enhance the strength of the bonding zone and its ability to suppress crack propagation,thereby strengthening the bonding between the hard coating and the soft substrate.Through tensile tests,the bonding performance of coatings with similar"pinning"structures and the mechanism of crack propagation inhibition in the bonding zone were deeply explored.Based on wear experiments,the stress distribution characteristics of coatings with similar"pinning"structures during the friction process were further analyzed,and the friction and wear mechanisms of coatings with similar"pinning"structures were elucidated.The main research content is as follows:（1）Research on the strength,toughness,and crack arrest mechanism of coatings with similar"pinning"structures.The effect of Ce O₂content on the strength and toughness of Ce O₂-SiC-Ni60 coatings with a"pinning"structure was studied.The results show that with the addition of Ce O₂the coatings formed are more dense,and the Ce element in rare earth oxides will promote mobility between the melt pools to make them less defective and reduce tissue segregation.Ce also refines the grain size,playing a fine grain strengthening role in the coating.The addition of SiC ceramic particles results in a change in phase composition,forming a hard phase,which plays a dispersion strengthening and second phase strengthening role in the coating,leading to an increase in energy consumption during crack propagation and improving the material’s ability to resist crack propagation.In addition,the deep melting unit is subjected to high energy density laser action,which refines the grain size.The increased grain boundary structure plays a role in suppressing crack propagation in the joint zone between the coating and the substrate with high crack incidence.Compared to the melting deep melting unit,the Ni60 alloying deep melting unit reduces the crack sensitivity in this area by reducing the thermal physical property difference between the coating and the substrate.Under laser action,Ni and Al form stable intermetallic compounds with higher hardness,improving the bonding between the coating and the substrate and further enhancing the bonding strength between the coating and the substrate.（2）Research on the wear resistance and friction wear mechanisms of the"pinning"structural coating.By changing the deep melting unit and coating structure,a Ce O₂-SiC-Ni60 high wear resistant coating with high bonding strength was obtained.The results show that the"pinning"structure coating prepared by the laser melting-cladding three-step laser can further slow down the stress in the bonding zone.As the SiC content increases,its microhardness and friction coefficient also change.The hardness shows a trend of first increasing and then decreasing,while the friction coefficient shows a trend of first decreasing and then increasing.When the SiC content is 30%,the hardness and wear resistance are the best.In addition,the microstructure of the"pinning"structure coating prepared by local alloying of Ni60 is refined,and the hardness is significantly improved compared to the untreated sample.At different wear stages,the wear resistance is improved,extending the service life of the sample.