Grain Orientations in Electrolytic High Contraction and Low Contraction ChromiumDeposition

摘要

Several electrochemical deposition parameters affect grain orientations, which,in turn, affect coating quality and performance. An enhanced x-ray pole figure technique has been used to study grain distribution anisotropy in electrolytic high contraction (HC) and low contraction (LC) chromium. Temperature and current density are the most important factors controlling grain orientation. Production HC chromium deposited on steel at low temperature and low current density exhibited strong <111> fiber texture, while LC chromium deposited on steel at high temperature and high current density exhibited near random crystalline orientation. The drastic change in grain orientation on steel from strongly textured HC chromium to randomly oriented LC chromium 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 that were deposited on copper plates with and without sample rotation and pulse current plating showed preferred (211) and (222) orientations. Although substrate material affects grain orientation, sample rotation and pulse current plating play a less important role.