Fabrication and Development of High Bonding Strength Polycrystalline Diamond Compact

• Main Authors: CHEN, WEI-EN, 陳偉恩
• Other Authors: LIN, CHII-RUEY
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/f7dugq

博士 === 國立臺北科技大學 === 機電學院機電科技博士班 === 108 === Polycrystalline composite diamond, also known as PCD or PDC, is commonly used in cutting tools and wear parts applications. Wear resistance is the key property in these applications which thermal stability would be directly related to. In most cases, higher thermal stability provides higher wear resistance. Wear resistance improvement can be achieved by increasing diamond density and reducing cobalt concentration. To increase diamond density and reduce cobalt contained percent can be made by mixing coarse nitrogen contained micron diamond powder with fine boron contained micron powder, ideally will reduce the cobalt contain percentage within the open space between diamond particles up to 50%. Reduced cobalt contain percentage will be replaced by boron micron diamond particles, which will be highly enhanced the weak point of the cutting edge. Due to the slightly electro-conductivity, low chemical reaction, high thermal stability and low friction of boron diamond, this research had following workout: (1) Changing diamond particle size will lead to changing of thermal stable temperature. Boron diamond particle has 100-150℃ higher thermal stable temperature than nitrogen diamond particle. (2) Synthesis 4 grades of PCD with best synthesis tech. and heat in air to observe the difference with SEM. High boron diamond mixed PCD has high thermal stability, which will graphitize until 1100℃. (3) Heat up PCD with placing on high reacted metal to see the changing on the surface. Boron PCD will reduce reaction with metal in high temperature. (4) By the generation of B2O3, boron PCD tips will have low friction force with metal. (5) Wire electrical discharge machining (wire EDM) provides better cutting edge quality with boron diamond contained PCD. (6) Electrical discharge grinding (EDG) with #800 wheels will damage the edge quality made by wire EDM. (7) EDG with #2000 wheels will improve the edge quality made by wire EDM. The innovation of this article is: By replacing fine nitrogen diamond particles with boron diamond particles, PCD will have ultra-high diamond-diamond boundary due to the thermal balance in HPHT process. It solved the problem of fine nitrogen diamond powders transferred into graphite and stopped the sweeping process which will not create diamond-diamond boundary successfully.