The failure of mechanical components is mainly caused by three key mechanisms:wear,corrosion,and fatigue.Among these failure modes,wear of mechanical components notably increases energy consumption and leads to substa...The failure of mechanical components is mainly caused by three key mechanisms:wear,corrosion,and fatigue.Among these failure modes,wear of mechanical components notably increases energy consumption and leads to substantial economic losses.Fe-Cr-C-B-Ti-Y wear-resistant cladding metals were prepared by the plasma cladding method.The wear performance of the cladding metals was analyzed using an MLS-23 rubber wheel wet sand wear tester.X-ray diffraction,scanning electron microscope,electron backscatter diffraction,and transmission electron microscope were employed to investigate the phase composition and microstructure of the cladding metals,followed by a discussion of their strengthening and wear mechanisms.The results indicate that the microstructure of Fe-Cr-C-B-Ti-Y cladding metals is composed of austeniteγ-Fe,M_(23)(C,B)_(6)eutectic carbide,and TiC hard phase.As the Y_(2)O_(3)content increases,the hardness and wear resistance of the cladding metal show a trend of first increasing and then decreasing.When the Y_(2)O_(3)content is 0.4wt%,the precipitation of TiC hard phase and M_(23)(C,B)_(6)-type eutectic carbides reaches maximum,and the grain size is the finest.The cladding metal exhibits optimal formability,featuring the smallest wetting angle of 52.2°.Under this condition,the Rockwell hardness value of the cladding metal is 89.7 HRC,and the wear mass loss is 0.27 g.The dominant wear mechanism of cladding metals is abrasive wear,and the material removal process involves micro-cutting and plowing.展开更多
In this study,Fe-C core-shell nanoparticles with identical metal core sizes and C shell thicknesses but varying degrees of graphitization of C shells were fabricated using metal-organic chemical vapor depo-sition and ...In this study,Fe-C core-shell nanoparticles with identical metal core sizes and C shell thicknesses but varying degrees of graphitization of C shells were fabricated using metal-organic chemical vapor depo-sition and subsequent annealing.Due to the identical metal core,these nanoparticles exhibite a similar permeability,but significantly varying permittivity depending on how much C shells have been graphi-tized.It was discovered that proper graphitization of Fe-C nanoparticles annealed at 1350 ℃ can pro-duce excellent microwave absorption(MA),decent dielectric loss tangent in high frequency region,and moderately strong dielectric loss and attenuation properties.Furthermore,the threshold value of 1/ω is discovered to be a crucial parameter in the theoretical analysis of nonlinear behavior of polarization loss,and thus MA performance of the nanoparticles.This research offers a useful method for creating metal-C nanoparticles with various levels of C shell graphitization.It also provides a clear answer to the crucial question of how the level of C shell graphitization affects the MA performance of metal-C nanoparticles.These results may serve as a reference for the development and mechanism analysis of highly effective metal-C based absorbers.展开更多
文摘The failure of mechanical components is mainly caused by three key mechanisms:wear,corrosion,and fatigue.Among these failure modes,wear of mechanical components notably increases energy consumption and leads to substantial economic losses.Fe-Cr-C-B-Ti-Y wear-resistant cladding metals were prepared by the plasma cladding method.The wear performance of the cladding metals was analyzed using an MLS-23 rubber wheel wet sand wear tester.X-ray diffraction,scanning electron microscope,electron backscatter diffraction,and transmission electron microscope were employed to investigate the phase composition and microstructure of the cladding metals,followed by a discussion of their strengthening and wear mechanisms.The results indicate that the microstructure of Fe-Cr-C-B-Ti-Y cladding metals is composed of austeniteγ-Fe,M_(23)(C,B)_(6)eutectic carbide,and TiC hard phase.As the Y_(2)O_(3)content increases,the hardness and wear resistance of the cladding metal show a trend of first increasing and then decreasing.When the Y_(2)O_(3)content is 0.4wt%,the precipitation of TiC hard phase and M_(23)(C,B)_(6)-type eutectic carbides reaches maximum,and the grain size is the finest.The cladding metal exhibits optimal formability,featuring the smallest wetting angle of 52.2°.Under this condition,the Rockwell hardness value of the cladding metal is 89.7 HRC,and the wear mass loss is 0.27 g.The dominant wear mechanism of cladding metals is abrasive wear,and the material removal process involves micro-cutting and plowing.
基金Hunan Provincial Natural Science Foundation of China(Nos.2022JJ40121,2021JJ40153 and 2021JJ50108)Scientific Research Fund of Hunan Provincial Education Department(Nos.21B0657,22A0518).
文摘In this study,Fe-C core-shell nanoparticles with identical metal core sizes and C shell thicknesses but varying degrees of graphitization of C shells were fabricated using metal-organic chemical vapor depo-sition and subsequent annealing.Due to the identical metal core,these nanoparticles exhibite a similar permeability,but significantly varying permittivity depending on how much C shells have been graphi-tized.It was discovered that proper graphitization of Fe-C nanoparticles annealed at 1350 ℃ can pro-duce excellent microwave absorption(MA),decent dielectric loss tangent in high frequency region,and moderately strong dielectric loss and attenuation properties.Furthermore,the threshold value of 1/ω is discovered to be a crucial parameter in the theoretical analysis of nonlinear behavior of polarization loss,and thus MA performance of the nanoparticles.This research offers a useful method for creating metal-C nanoparticles with various levels of C shell graphitization.It also provides a clear answer to the crucial question of how the level of C shell graphitization affects the MA performance of metal-C nanoparticles.These results may serve as a reference for the development and mechanism analysis of highly effective metal-C based absorbers.
