超硬合金の銀ろうろう付の強度の向上

抄録

Brazing of cemented carbide with silver filler metal is widely used in manufacturing Polycrystalline Diamond Tools. A cemented carbide chip onto which Polycrystalline Diamond is sintered is then brazed onto a larger cemented carbide base. Sometimes the chip and the base are different widths creating an extended lip. In this case, the strength of the brazed joint is decreased as the brazing material gets thinner and thinner. Previously, the authors developed a method to ensure the optimal brazing thickness using metal spacing powder. Using this method, the static strength of the brazing joint was increased by 50%. The conventional thinking has been that while using a powder can improve static strength, the powder will eventually cause cracking and decrease strength over time. So, in this paper the bending fatigue test was carried out as the next step. Firstly, a bending fatigue tester was developed where the bending load was generated by an electric solenoid actuator. Next, Cantilever bending specimens with a cross section of 4 mm by 4 mm were tested. The specimens were made of cemented carbide. Two brazing methods were tested: the normal furnace brazing method, and the newly developed brazing method using Titanium powder. The bending fatigue strength of the newly developed brazing method was double that of the normal brazing method.