Papers by Author: H.S. Shen

Abstract: Diamond-coated drawing dies are considered as ideal drawing dies for their unique characteristics, such as high hardness, wear resistance and low friction. In order to utilize the superior characteristics of diamond coatings towards improving the drawing performance, the nonlinear FEM simulation is used to simulate the whole low carbon steel tube hollow sinking process, with 2D axi-symmetric elastic-plastic element. Based on the simulation results, the distributions of the axial stress and radial stress are analyzed, the influence of parameters of drawing dies on the diameter shrinkage is investigated. Optimal die parameters are obtained.

Abstract: Nanocrystalline diamond films were deposited on Co-cemented carbide substrates using CH4/H2/Ar gas mixture by hot filament chemical vapor deposition (HFCVD) technique. The evidence of nanocrystallinity, smoothness and purity was obtained by characterizing the sample with scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), high-resolution transmission electron microscopy (HR-TEM) and selected-area electron diffraction (SAED). A new process was used to deposit composite diamond films by a two-step chemical vapor deposition procedure including first the deposition of the rough polycrystalline diamond and then the smooth fine-grained nanocrystalline diamond. The results show that the film consists of nanocrystalline diamond grains with sizes range from 20 to 80 nm. The Raman spectroscopy, XRD pattern, HR-TEM image and SAED pattern of the films indicate the presence of nanocrystalline diamond. Surface roughness is measured as Ra<100nm by AFM. Smooth nanocrystalline diamond layers can be deposited on conventional microcrystalline diamond layers using a two-step chemical vapor deposition by regulating the deposition parameters. These composite diamond films with the multiplayer (nanocrystalline/microcrystalline) structure have low surface roughness and high adhesive strength on WC-Co substrates. The diamond-coated tools and drawing dies with these composite coatings display excellent performances in the practical application.