Evaluation of matrix strength of Fe-C as-quenched and quench-tempered martensite using nanoindentation techniques

Evaluation of the matrix strength of the Fe-C martensite is performed by nanoindentation techniques. As-quenched martensite was examined for five kinds of Fe-C alloys with various carbon contents in the range of 0.1 to 0.8 mass% while quench-tempered martensite was investigated for an Fe-0.4%C alloy. The nanohardness attributed to the matrix strength increases with the carbon content, and decreases with increasing tempering temperature. The ratio of the nanohardness to the macrohardness, H_n/H_v, was much smaller for the Fe-C martensite than those for the single crystals, indicating that there is a significant grain size effect for the martensite.