MICROSCOPIC CHARACTERIZATION AND ELECTROCHEMICAL-BEHAVIOR OF HIGH-DOSE CARBON-IMPLANTED STAINLESS-STEELS

A study was made of the electrochemical properties and microscopic cha racteristics of types 304 and 430 stainless steel implanted at room te mperature with carbon at a dosed of 10(18) ions cm-2 at 100 keV. The e lectrochemical properties were measured by multisweep cyclic voltammet ry in a solution of H2SO4 + Na2SO4. X-ray diffraction and X-ray photoe lectron spectroscopy were used to analyze the structure, composition d epth profiles and chemical bonding states of carbon-implanted layers. Carbon implantation suppressed the dissolution with transpassivation o f stainless steels without influencing adversely their excellent passi vity. The amorphized carbon-implanted layers were composed of graphiti c solid state carbon, which had a gaussian depth profile corresponding to the distribution of implanted carbon, and metallic carbide with a uniform chemical state in the region containing more than approximatel y 20 at.% carbon. From these investigations, it is proposed that room- temperature carbon implantation at a very high dose can improve the aq ueous corrosion resistance of stainless steels owing to the formation of amorphous layers consisting of graphitic solid state carbon and met allic carbide.