Instrumented microindentation studies on long-term aged materials: work-hardening exponent and yield ratio as new degradation indicators

Using an instrumented microindentation technique for evaluating tensile properties, the present study was undertaken to determine new mechanical parameters measurable in the field that can indicate time-dependent material degradation. Lab-scale tests performed on a Cr–Ni steel and a Cr–Mo steel, two of the most popular heat-resistant steels for facilities in petrochemical and power plants, showed that the work-hardening exponent and yield ratio could be useful as mechanical parameters indicating degradation. The in-field applicability of these parameters was partly verified.