Papers by Author: Jing Lu

Abstract: The path distribution can directly affect the machined workpiece surface quality in lapping and polishing, such as planeness, roughness, etc. In present paper, the influence of rotate speed ratio (RSR) and abrasive position on path distribution was analyzed with a single fixed abrasive. The results show that the RSR and abrasive position has heavy influence on the path distribution. The path distribution with decimal RSR is more intensive and complicate than that with integer RSR, especially complex decimal RSR, and it can be also affected by the abrasive radial and circumferential position, but the shape of path is not changed with different abrasive circumferential position which only affects the initial phase angle of path.

Abstract: Fe-based metal bond has been widely used in fabricating diamond tools recently since the production cost could be greatly reduced for the low price of iron. However, graphitizing elements such as Fe, Co and Ni in the matrix catalyze the transformation of diamond to graphite during high temperature sintering process, which significantly decreases the tool’s efficiency and lifetime. In this paper, Si and Ti coating were coated on diamond grits by quasi atomic layer deposition (QALD) and vacuum slow vapor deposition (VSVD) separately not only to protect diamond from erosion but also to promote the adhesion between diamond grits and the bond. Three-point bending experiment was taken to measure the bending strength of Fe-Cu-Sn-Ni based metal bond diamond blade. In comparison with uncoated diamond blade, the bending strength of coated diamond blade improves dramatically. The theoretic calculation shows that the interface bonding strength between diamond and the metal bond increases by 181.68MPa owing to the Si coating. The effect of Si and Ti coating on interface bonding between diamond and the bond under different sintering temperatures was also illuminated.

Abstract: The adhesion between diamond grits and the bond strongly influence the properties of diamond tools. Since diamond is covalent crystal, the high interfacial energy leads to the poor interface bonding between diamond grits and the bond. Furthermore, the sintering temperature of traditional vitrified bond is also very high because of the high refractoriness of alkalis containing in the bond, resulting in serious thermal damage to diamond grits. In this paper, a low melting point and high strength vitrified bond has been prepared mainly from borate glass, clay and lead glass. The bond is completely glassy above 850°C and the bending strength of the bond sintered at 850°C for 7 minutes is 125.7MPa with a 6.5:3.5 corundum/bond ratio. Moreover, this bond possesses good wettability with diamond abrasive from 600°C to 850°C.

Abstract: Single-phase nanocrystalline diamond composite is very difficult to sinter because of a huge amount of oxygen-containing and nitrogen-containing functional groups adsorbed on the surface of nanocrystalline diamond going against the yielding of diamond-to-diamond bonding. In this paper, silicon film was deposited on nanocrystalline diamond by means of atomic layer deposition (ALD) using silane as precursor, which would promote the sintering of nanocrystalline diamond as the bond. The structure and the morphology of Si-deposited nanocrystalline diamond were thoroughly studied by X-ray diffraction (XRD), high-resolution electron microscopy (HREM) and Fourier transform infrared (FTIR) spectra. The results confirmed that silicon film grew uniformly on every primary particle and functional groups adsorbed on the surface of nanocrystalline diamond were removed by this method.

Abstract: Nanocrystalline diamond compact possesses not only the advantageous performance of polycrystalline diamond but also the high strength and the high toughness of nano-ceramics. However, single-phase nanocrystalline diamond compact is very difficult to sinter because of a huge amount of oxygen-containing and nitrogen-containing functional groups absorbed on the surface of nanocrystalline diamond. In this paper, atomic layer deposition (ALD) method has been used to coat nanocrystalline diamond with titanium, which will promote the bonding of nanocrystalline diamond as the bond in polycrystalline diamond. In vacuum, the H2 and TiCl4 reactants were employed alternately in an ABAB… binary reaction sequence to achieve Ti layer, which reacted with diamond matrix and formed TiC in the coating, realizing strong chemical bonding between the coating and the diamond. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized to study the structure and the morphology of the coating. The results confirmed the formation of titanium carbide at the depositing temperature 500°C. The darker spots and strips observed on nanocrystalline diamond particles by TEM were proved to be TiC and the nucleation and subsequent growth of TiC preferentially occurred in the defects as twin zones and dislocation areas on diamond surfaces.