Surface treatment of steel using non-equilibrium plasma at atmospheric pressure

A mixed gas plasma of argon and hydrogen could be generated by irradiation of a microwave to perovskite-type oxide powders at atmospheric pressure. Th e results of electron and gas temperature measurements showed that this atm ospheric pressure plasma is in a nonequilibrium. By using this plasma, we t ried to remove surface scales, such as a metal oxide layer, on steel produc ts. Consequently, the scales were removed with little damage in a short per iod of time, while it is difficult for the ordinary hydrogen reduction proc ess to remove them. The plasma-treatment effect was advanced with increases in the microwave power and treatment time. Optical emission spectroscopy i ndicated that a large amount of hydrogen radicals existed in the plasma. It is considered that the existence of hydrogen radicals was effective in rem oving the scales rapidly. (C) 1999 Elsevier Science S.A. All rights reserve d.