2825 高純度 cBN 多結晶体の微細構造と切削性能

概要

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High-purity Polycrystalline cBN can be synthesized from hBN by the direct conversion method under HPHT condition without additives or catalyst. Such polycrystalline cBNs under various conditions were prepared and investigated to clarify the effect of impurities and microstructure on cutting performance of the materials. When the amount of the compressed hBN exceeded 0.5%, the cutting performance was found to deteriorate rapidly in high-speed interrupted cutting test of gray cast iron. The tool life of polycrystalline cBN of coarse grade (1-5μm) was found to be shorter than that of fine grade (<0.5μm) by the breakage of the tool edge. From TEM observation, it was found that coarse cBN grains have crystal defects and straight grain boundaries, which are thought to weaken the mechanical strength. It was confirmed that the reduction of remaining compressed hBN (<0.5%) and the suppression of coarsening of cBN grain (<1μ1) are necessary for polycrystalline cBN having excellent performance.
社団法人日本機械学会の論文
2002-09-20