Nano-indentation study on advanced high Cr heat resisting ferritic steels

A series of nano-indentation tests is performed to investigate the inhomogeneous microstructure in advanced high Cr heat resisting ferritic steels containing more than 4% (W+Re). There are fine Laves precipitates inside the martensite lath in these steels even in the as-tempered state. In response to such a complex microstructure in them, the penetration depth of indenter measured in a maximum load condition varies widely in evry specimen, which still showing dependence on the heat treatment and the alloy compositions. For example, a variation of the penetration depth is enhanced more largely in the aged specimen than in the as-tempered specimen. Also, the maximum penetration tends to become deeper as the Re content increases in the steels. It is found that the nano-indentation test is applicable to the evaluation of the mechanical properties of the nano- and micro-regions in advanced high Cr heat resisting steels.