Microstructure Evolution and Pinning of Boundaries by Precipitates in a 9 pct Cr Heat Resistant Steel During Creep

Structural changes in a 9 pct Cr martensitic steel during a creep test at 923 K (720 °C) under the applied stress of 118 MPa were examined. The tempered martensite lath structure (TMLS) was characterized by M23C6-type carbide particles with an average size of about 110 nm and MX-type carbonitrides with a size of 40 nm. The M23C6 particles were located on the packet/block/lath boundaries, whereas the MX precipitates were distributed homogeneously...