New spherical magnetic abrasives with carried diamond particles for internal finishing of capillary tubes

Iron composite powder containing alumina is commercially used as magnetic abrasives for internal finishing of capillary tubes. However, as downsizing and lengthening of capillary tube progress along with sophistication of analytical and testing equipment, the magnetic composite powder with large particle size and irregular shape puts a limit on the finishing performance. In this paper, to break through the limitation and to further improve the finishing performance, spherical iron-based composite powder with carried diamond particles is developed by using a plasma spraying technique. Spherical carbonyl iron powder with 7.2 μm in average and diamond particles with 0.3 μm in average are mechanically mixed and then are plasma-sprayed at various plasma currents, and the spherical iron-based composite powders with carried diamond particles which have a particle size less than 10 μm are obtained. The results of XRD and Raman analysis indicate that the optimal plasma current is 100 A from an oxidation point of iron powder and diamond particles. The abrasive experiment of SUS304 plate shows that the developed composite powder has potential performance as a new magnetic abrasive for internal finishing of capillary tubes.