Structure of Electrodeposited Chromium on Gun Steel.
Final technical rept.,
ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE CALIBER WEAPON SYSTEMS LAB
Pagination or Media Count:
Scanning and transmission electron microscope examination of electrodeposited chromium has revealed that plating conditions affect the size and orientation of the very fine individual crystallites. Plating at 55 C results in a bright, very hard, 1180 Knoop-hardness number KHN, coating comprised of 0.1 micrometer diameter grains with a strong 111 fiber texture oriented perpendicular to the surface of the base metal. Plating at higher temperatures such as 85 C, or with a well-aged plating solution, produces a much softer deposit 600 KHN composed of 1.5 micrometer grains with a much less pronounced crystallographic texture. High tensile stresses and the resulting crack formation in the deposit appear to be due to the very large and aligned void space associated with the unequilibrated grain boundaries. Heating during firing or annealing results in one or two percent shrinkage of the chromium as the grain boundary void space is eliminated.
- Metallurgy and Metallography
- Fabrication Metallurgy