Manufacture, Wet and Dry Corrosion, and Plasma Nitridation of Novel Nanocrystalline Ni-Cr Nanoparticle Nanocomposites: A Brief Review

The paper is a short review of the fabrication, wet and dry corrosion, as well as plasma nitridation of novel Ni-Cr nanocomposites. The nanocomposites, fabricated by co-electrodeposition of Ni and nanometer-sized Cr particles, have the nanocrystalline Ni matrix dispersing the second phase of nanoparticles. They, compared to conventionally coarse-grained Ni-Cr alloys, exhibit dramatically increased resistance to liquid corrosion in a 3.5% NaCl solution, and to hot corrosion under molten salt of Na2SO4-Na2SO4-NaCl at 700oC. The reason for these is correlated with the unique structure of the nanocomposite, which guarantees the fast diffusion of chromium from the composite interior to the corrosion front for the formation of a continuous, protective layer of chromium oxide-rich films severing the composites from environmental corrosive species. During plasma nitridation at 560oC the Ni-Cr nanocomposite forms a thick nitriding layer which cannot be achieved on the conventional alloy counterpart with a comparable composition, due to enhanced nitridation kinetics.