Structures of M2C carbides and its influence on strengthening in AerMet100 steel at the typical tempering temperature 482 °C

The structures of M2C carbides in AerMet100 after tempered at 482 °C were finely characterized by high-resolution transmission electron microscopy and its influences on the mechanical properties were studied. The needle-shaped carbides with hexagonal structure are the dominant precipitates, however, the atomic-scale lamellar shaped carbides with orthorhombic structure are newly observed during the tempering process. The orthorhombic carbides are easy to be coarsened against the tempering time. The influence of M2C with different structures on strengthening were evaluated and the results indicated that the orthorhombic-type nano-particles have a lower strengthening efficiency than the hexagonal ones, due to its smaller aspect ratio, and the easy coarsening tendency.