Grain Orientations in Electrolytic High Contraction and Low Contraction Chromium Deposition

Several electrochemical deposition parameters affect grain orientations, which in turn, affect coating quality and coating performance. An enhanced x-ray pole figure technique has been applied to study grain distribution anisotropy in electrolytic high contraction and low contraction chromium. Temperature and current density are the most important factors controlling grain orientation. Production high contraction (HC) chromium deposited on steel at low temperature and low current density exhibited strong 4 1 l> fiber texture, while low contraction (LC) chromium deposited on steel at high temperature and high current density exhibited near random crystalline orientation. The drastic transition of grain orientation from strongly textured HC chromium to randomly orientated LC chromium on steel is accompanied by marked differences in crack density, hardness, deposition rate, microstructure, thermal behavior upon heating and cooling, and improved wear and erosion performance. Laboratory LC chromium specimens which were deposited on copper plates with and without sample rotation and pulse current plating showed preferred (211) and (222) orientations. Substrate material affects grain orientation, but sample rotation and pulse current plating play a less important role.