Papers by Author: Jia Jing Yuan

Abstract: Chemical vapor deposition nanocrystalline diamond (NCD) film has numerous unsurpassed properties, among them, bulk modulus, hardness; abrasion resistance and thermal conductivity are notable ones like polycrystalline CVD diamond film. The super mechanical properties have made NCD film to be an effective way to improve the resistance performance of the ceramic bearing and extended its life. The contact stress of bearing ball with NCD coating in elastic contact was analyzed. Factors such as substrate material, thickness of NCD coating, load and interlayer material which affect the shear stress distribution of NCD coating on bearing ball were investigated. The results show that substrate with low elastic modulus and heavy load will enlarge the difference of equivalent stress value at NCD/substrate interface. Thick film will make the stress distribution at the interface uniform. Soft interlayer should be inhibited to avoid extra stress in contact status.

Abstract: In this work, the elastic constant and natural frequency of NCD and non-NCD coated AFM probes were simulated using ANSYS. The results indicated that after depositing 1～2μm thick NCD films on the silicon probes, the elastic constant and natural frequency were both increased, yet within the prescribed limit: when the cantilevers had the same total thicknesses (3μm, 3.5μm and 4μm), the elastic constant and the natural frequency of the NCD coated probes were increased by 96%～107% and 28%～30% respectively, compared with the silicon probes.

Abstract: The contact stress of cemented carbide with NCD coating in elastic contact was analyzed using ANSYS. Factors such as elastic modulus and thickness of NCD film and elastic modulus of interlayer which affect the shear stress distribution of NCD film on cemented carbide substrate were investigated. The results show that the maximum shear stress point moves towards the interface with the increase of film elastic modulus. Film thickness has a significant effect on shear stress distribution of NCD film. High shear stress develops in the film layer with the increase of film thickness. Interlayer with low elastic modulus will cause shear stress concentration in NCD film.

Abstract: The present paper describes research on stress in freestanding diamond thick film, diameter of 60mm, prepared on Mo substrate by DC arc plasma jet chemical vapor deposition (DCPCVD) method. The stress in the CVD diamond film was investigated by X-ray diffraction and Raman spectrum. The results show that the stress in the film is compressive. The stress changes little at the same homocentric round. The compressive stress along radial direction is that the stress in the centre of the film is lower than that in the edge at both the final surface and the original surface.