X-Ray Study of Chromium Plating Layer by Pulse Current Electrolysis

摘要

Several crack-free chromium-plating processes by pulse-current electrolysis have been proposed, but the resulting chromium-plating layers usually have high tensile residual stress and often form macro-cracks after plating operations, especially under high temperature of 373K or more. Therefore, there are few actual industrial applications of this technology.In this study, residual stress is examined for chromium plating layers formed under various pulse plating conditions (pulse-current frequency, duty cycle of pulse-current, and peak current density) from organo-sulfonic acid baths. Residual stress is evaluated by an X-ray stress measurement method. Consequently, a highly compressive residual stress (-300MPa or more) is obtained under certain plating conditions. Furthermore these chromium-plating layers have higher stability under high temperature than chromium plating layers made by conventional pulse current electrolysis or direct current electrolysis.Furthermore, it was cleared that the thermal stability correlates closely with the integral breadth of X-ray diffraction profile.