Papers by Author: Fu Ming Deng

Abstract: In this paper, nanocrystalline diamond with the average grain size of 50nm was prepared under different sintering pressure, temperature and sintering time. The microstructure of the sample was analyzed by SEM, EDS and XRD, and the mechanical properties tested by micro-hardness tester and wear ratio instrument. The results show that the sample sintered under the optimum conditions of oil pressure 87MPa, heating power 4000W and sintering time 120s possessed hardness of 706.41HV and wear ratio of 3280. It indicated that high performance n-PCD sintered from nanodiamond and silicon system can be formed hardly with diamond to diamond bonding but can be formed with diamond to silicon carbide bonding. The poor mechanical properties of the samples were due to the surface adsorption groups and surface graphitization of nanodiamond during high pressure sintering.

Abstract: A new type of sintered diamond reinforced by diamond-MWCNTs composite fibers which were randomly orientated and even distributed in the diamond matrix was synthesized by using 3(wt)% mullti-walled carbon nanotubes(MWCNTs) as starting additive under high pressure of 5.8GPa at temperature of 1500°C for 1 min. A special polycrystalline diamond structure of direct bonding of both diamond to diamond and diamond to diamond-MWCNTs composite fiber was observed. The testing results show that it possesses not only high hardness (49-52GPa) and Young’s modulus (878GPa) but also high bending strength (1320~1540GPa) and fracture toughness (9.0~9.2MPa•M1/2) as it was theoretically predicted. The high performances of the composite were contributed to the fiber strengthening effect and the special structure which can offer more extensive diamond to diamond bonding.

Abstract: GCr15 bearing steel was turned with PCBN cutting tools in a manner of hard and dry cutting, and the characteristics and morphology of rake and flank face of PCBN cutting tools were observed, the element distribution of different regions of rake and flank face of PCBN cutting tools were tested and analyzed by use of EDS, and finally the wear mechanisms of PCBN cutting tools were discussed. The results showed that the wear areas of rake and flank face of PCBN cutting tools were small and mostly concentrated near the tip and sub-chamfering, and the reason was mechanical, oxidation, chemical and phase transition wear, which resulted in the joint action of tool wear.