Papers by Author: Sik Chol Kwon

Abstract: A study on chromium matrix composite plated with nanosized diamond powders was undertaken by employing a standard Sargent bath. Chromium matrix composite plated with nanosized diamond powders manifested super properties. The microhardness was varied from 890 to 920 HV (load 25 g/f), as compared with 801 HV of pure chromium; the wear resistance was increased 3-4 times. The potentiodynamic measurement in a chloride medium showed that the passive current of chromium matrix composite plated with nanosized diamond powder was 6 times as lower as that of pure chromium. Microscopic observation indicated that nano-diamond powders were included in the chromium deposit in the form of single and multi crystalline.

Abstract: The oxidation of Cr-12.7 at.%C coatings electrodeposited on steel was studied at 700 and 800oC in air. The coatings, which consisted of nodular grains having microcracks and pits, had either an amorphous or a microcrystalline structure. They changed to crystalline Cr during oxidation. The oxidation resulted in the formation of Cr2O3, which provided good oxidation resistance to the coating. However, the presence of microcracks and pits in the coating was harmful to oxidation resistance.

Abstract: Chromium chloride (CrCl3) or chromium sulfate(Cr2(SO4)3) content increased trivalent chrome deposition rate. The addition of formic acid and the relative content change of potassium hydroxide decreased the trivalent chrome deposition rate. Industrially applicable trivalent chromium layers with more than 200 µm thick were well prepared at the conditions of pH with the range of 1.3-1.8, electrical current density of 5.0-5.6 A/cm2 and applied voltage of 4.0-5.9V. Average microhardnesses of the chromium layers prepared in the chromium chloride and chromium sulfate solutions are about 803-820 and 700-712 Hv, respectivevly. The wear resistance of the trivalent chromium layers was improved by plating voltage which was related to residual compressive stress on the chomium layer.