Carbon nanotubes (CNTs) coated on the WC/Co micropunch, with diameter of 150 μm, for prolonging the life of micropunch were investigated. Carbon nanotubes were synthesized by homemade method. Through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the morphology and structure of CNTs were expressed. After the punching test, wherein Ti was used as substrate, the effect of CNTs in prolonging the life of micropunch on the wear loss and the surface morphology of micropunch had been studied through confocal laser, SEM, digital balance, etc. Results show that the wear of CNT-coated micropunch obviously decreased; and that even in the severe wear period, the wear loss is lesser than that of non-CNT-coated micropunch. Compared with the micropunch without CNTs coating, the promising results are due to the formation of a transfer film at the contact region by rubbing of the CNT forest. CNTs produced adhered to the micropunch surface, thereby avoiding direct contact during the punching period and providing lubricant properties to the interface due to their graphitic nature. Moreover, the relevant mechanism was primarily illustrated by movable cellular automaton.
Part of the book: The Transmission Electron Microscope
The fracture variation of liquid-phase-pulse-impact diffusion welding (LPPIDW) welded joints of aluminum matrix composites (ACMs: SiCp/A356, SiCp/6061Al, and Al2O3p/6061Al) was investigated. Results show that under the effect of pulse-impact (i) initial pernicious contact state of reinforcement particles changes from reinforcement (SiC, Al2O3)/reinforcement (SiC, Al2O3) to reinforcement (SiC, Al2O3)/matrix/reinforcement (SiC, Al2O3) and (ii) the fracture of welded joints with optimal processing parameters is the dimple fracture. Meanwhile, scanning electron microscope (SEM) of the fracture surface shows some reinforcement particles (SiC, Al2O3) in the dimples. Moreover, the slight reaction occurs at the interfaces of SiCp/6061Al, which is propitious to improve the property of welded joints because of the release of internal stress caused by the hetero-matches between the reinforcements and matrix. Consequently, aluminum matrix composites (SiCp/A356, SiCp/6061Al, and Al2O3p/6061Al) were welded successfully.
Part of the book: Failure Analysis and Prevention