On diffusion and interfacial enrichment of boron in the Laves phase: an in situ TEM-heat-treatment study on newly developed 3Co?3W?9Cr steel

Using in situ transmission-electron-microscopy (TEM) heating and subsequent energy-filtered TEM (EF-TEM) and high-resolution-TEM (HR-TEM) analysis on a newly developed 3Co?3W?9Cr steel, enrichment of boron at the Fe2W and matrix interface has been studied for the first time. The heat treatment has been carried out at a temperature of 770. C. From the EF-TEM analysis, it is confirmed that a stacking-fault-assisted diffusion mechanism is responsible for the enrichment of boron at the interface. From the HR-TEM study, it is ascertained that the diffusion behavior of boron in the Laves phase and the extent of the enrichment at the interface is dependent on the amount of stacking faults in the Laves phase.