| The process of alloy carbide precipitation in a high cobalt-nickel secondary hardening steel, AF1410 (Fe - 14 wt%Co - 10%Ni - 2%Cr - 1%Mo - 0.16%C) has been studied by FIM and atom probe techniques. The evolution of the alloy carbides has been followed in detail for the standard heat treatment temperature of 510°C. The first evidence of brightly-imaging solute clusters is observed after an ageing time of 1 minute, and the first traces of a rod-like morphology emerge after 30 minutes. Very slow growth of the rod-like carbides takes place between 30 minutes and 5 hours ageing, accompanied by a slow decrease in hardness. This is followed by rapid coarsening and spheroidisation, during which a marked loss of hardness occurs. The size and composition variation of the carbides has been followed throughout the ageing treatment. A model for the growth and coarsening of the particles is presented. |
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