Purpose: The purpose of the research was to determine and analyse the changes in
the microstructure and mechanical properties of the Sanicro 25 steel in the as-received
condition and after ageing at 600, 650 and 700°C for up to 10,000 hours.
Design/methodology/approach: The scope of the investigations included: microstructural
investigation – SEM microscopy, analysis of precipitation performed using TEM microscopy,
investigation of mechanical properties, Vickers hardness measurement.
Findings: In the as-received condition, the Sanicro 25 steel was characterised by austenitic
microstructure with annealing twins and numerous primary precipitates. The analysis of
Sanicro 25 steel microstructure after ageing at 600 and 700°C for up to 10,000 hours
revealed significant changes in the microstructure consisting mainly in a tendency to create
unfavourable morphology of secondary precipitates – M23C6 carbides that form continuous
carbide systems along the grain boundaries. The observations have shown that during
long-term ageing the secondary carbides were also precipitated inside the grains and at the
interface of three grain boundaries – σ phase.
Research limitations/implications: The analysis of the microstructure of the examined
steel using SEM and TEM was performed to determine the influence of ageing on the
processes of changes in the precipitate morphology.
Practical implications: The results obtained based on the performed research constitute
a building block for the degradation characteristics of the microstructure and mechanical
properties of the 23/25-type austenitic steels.
Originality/value: The results of the investigation and analysis of the metallographic and
mechanical properties of the Sanicro25 austenitic steel in as-received condition and after
ageing are presented.
Microstructure and mechanical properties of novel TiAl alloys tailored via phase and precipitate morphology
