Microstructure and corrosion behavior of high carbon content FeTiNbC alloys in 3.5 wt% NaCl

The aim of the present work is to study the relationship between the microstructure and the corrosion behavior, in a 3.5 wt% NaCl solution, of high carbon content FeNbTiC alloys. Eutectic and mainly primary carbides are formed during the solidification and the carbon content contributes largely to the formation of both of them. The eutectic ones are homogeneous and present a chinese script morphology, which can be avoided with higher carbon amount. The primary particles show essentially a core–shell structure described as a Ti-rich carbide core, surrounded by several layers of niobium (Nb, Ti)C 1-x mixed carbides, where the titanium amount decreases from the core to the shell. The electrochemical tests show is that the higher carbon content better is the corrosion behavior, while a high niobium amount has an adverse effect. A compromise between Ti, Nb and C has been defined to enhance the corrosion resistance of this type of alloys. This type of microstructure, involving ceramic particles, the increasing of (Nb, Ti)C 1-x hardness compared to NbC 1-x and the corrosion resistance of high carbon FeTiNbC could promote them for replacing some iron based alloys such as, cutting tools, tool steels and high speed steel.