表面極薄層の硬度評価法の確立およびイオン注入処理された高強度ステンレス鋼の表面硬度評価

抄録

The main aim of this paper is to establish a hardness evaluation method for a ultra-thin surface layer of sub-micron order, and to apply the method to determine the surface hardness of ion implanted 13Cr steel, of which fatigue strength properties were examined previously. First, the microhardness of fully-annealed S25C steel (0.25%C carbon steel) was evaluated to find the optimum loading method and the dispersion of the data was statistically characterized. The controlling condition of the loading process was varied in two ways; constant loading rate and constant loading time. The result reveals that the constant loading time method is preferable for the measurement of a thin surface layer of sub-micron order. The data of the microhardness measurements with 50 repeats under a same condition shows that the indentation depths distribute normally, and that more than 30 measurements are necessary to eliminate the possible measurement errors. Second, the microhardnesses of both ionimplanted and non-implanted 13Cr steel specimens were evaluated using the method established above. The surface layer of sub-micron order is hardened by the ion implantation, and the further increase in hardness can be attained by the post-heat treatment. The hardness-increased depths are consistent with the diffused depths of the ions during the heat-treatment, which is estimated by ion micro analyzation (IMA) in a previous study.