The behavior of electroplated hard-chromium on Cr-Mo steel subject to long-term annealing at 250 °C

A hard Cr-deposit was annealed at 250 °C for various periods after electroplating. From the results of the DSC analysis and hardness measurement, the softened microstructure in the Cr-deposit was developed after 30 min annealing. By examining the TEM-cross-sectional annealed specimen, a recrystallization zone of the soften microstructure was found, in which equiaxed grains with relative lower dislocation density were examined from place to place and many voids were found among the triple grain boundary. However, most parts of as-plated Cr-deposit grew slightly and were still in texture after long-term annealing at 250 °C. On the interface between the Cr-deposit and the steel initiated equiaxed grains that grew by merging adjacent grain and small angle grain boundary were observed.