Papers by Author: Rahmi Ünal

Abstract: The performances of metal-bond of diamond cutting tools were investigated by changing the cobalt and bronze ratio conversely as the matrix material. Diamond tools were fabricated by cold pressing and sintering under pressure at the temperature up to 750 °C. Investigation of the microhardness behavior of the segments was showed that increasing the cobalt ratio causes the increase of the hardness of the matrix material. This caused to decrease of the wear rate of the matrix. Because the matrix wears more slowly than the diamonds, the space between the cutting edges and the matrix is constantly reduced. The swarf cannot be carried away properly, and the segment will continuously lose its ability to cut with higher cobalt contents.

Abstract: Diamond segments were fabricated by cold pressing and sintering under pressure at the temperature up to 750 °C. It was obtained from this study that if we increase the cobalt ratio, the hardness of the matrix increases and the wear rate of the segments decreases. But the optimum matrix composition with less wear rate must ensures that the acceptable matrix toughness. Because the harder matrix wears more slowly than the diamonds, the space between the cutting edges and the matrix is constantly reduced. Because the swarf cannot be carried away properly, and the segment will continuously lose its ability to cut. From this point of view, the cobalt ratio in matrix composition for this formulation should not be higher than the 60 wt.% in order to have a good cutting ability.

Abstract: The most important parameter for production of fine powders efficiently is the velocity of the atomizing gas. This can be achieved by increasing the pressure, but this way will not be economic. For that reason, to achieve supersonic velocities different nozzle designs are used in close coupled configuration for an efficient atomization. In this study, a new laval type nozzle was designed and manufactured. Using this nozzle tin powder was produced in close coupled system by using nitrogen gas at different operating conditions. The results showed that the increasing the gas pressure up to 1.47 MPa reduced the mean powder size down to 11.39 microns with a gas/melt mass flow rate ratio of 2.0. Powders are spherical in shape and have smooth surfaces.