Chang Hsiao-Kuo,1,4, Huang Jow-Lay4, 5, Sung James C.1,2,3
(1. KINIK Company, 64, Chung-San Rd., Ying-Kuo, Taipei Hsien 239, Taiwan)
(2.Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan)
(3.Department of Materials Science and Engineering, National Taipei University
of Technology, Taipei 106, Taiwan)
(4.Department of Materials Science and Engineering, National Cheng Kung
University, Tainan 701, Taiwan)
(5.Department of Polymer Materials, Kun Shan University, Tainan 710, Taiwan)
Abstract As a cutting tool, diamond films made by chemical vapor deposition (CVD) outperformed polycrystalline diamond (PCD) sintered under ultrahigh pressure. For example, the longevity of the CVD tools may be 2~5 times that of PCD inserts. In addition, the former cutting paths are strainghter with less chipping on the edge. However, there have been no report on CVD diamond films that were used as a roller scriber for splitting large glass panels. Our research demonstrated that the CVD diamond film could concentrate the energy in a smaller area (about 1/4), so the glass compressed by the tip of the diamond film was under a larger tensile stress in perpendicular to the direction of compression. The tensile stress then initiated the microcracks that were more in line with the direction of the compression.
The reason that CVD diamond film could concentrate the compressive stress was due to its 100% diamond content. The high diamond content could allow the tip to be polished sharper. In contrast, the PCD cutting tip contained micro grains of cobalt that were softer than glass. As a result, the compressional stress was spreading out due to the larger area of contact. Consequently, the microcracks initiated at the PCD tip were random and they might not propagate along the direction of cutting.