耐熱鋼の研究 (VI) : 微小硬度計による Timken 16-25-6 の析出現象の研究

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The precipitation phenomena of Timken 16-25-6, heat resisting alloy for gas turbine materials, were already reported in author's paper (Tetsu-to-Hagane, August 1954 p.785). In this report, micro-hardness at a point in the middle of the grain, near the boundary and on the boundary, were determined for the purpose of studying the precipitation phenomena. Samples used in this report were the same as those used in the report (V) in this issue. There were three different chemical compositions among the samples. They were solution-treated at 1150℃ (2100°F) for 1 hour, and aged at 700℃ (1290°F), 800℃ (1470°F), and 900℃ (1650°F). The aged sample at each temperature for each time was tested by micro-Vickers hardness and observed through microstructure. Results were as follows : (1) In the case of micro-hardness testing, it is usually said that the micro-hardness at the middle of the grain is observed to be lower than the hardness at a point near the grain boundary, because of the metal flow which is caused by the diamond cone. However, according to the author's tests, this must be more complex, in accordance with crystallography. Because, the samples which were aged and precipitated excessively showed that the micro-hardness at points near the grain boundary, on the grain boundary, and in the middle of the grain had similar hardness, although there were different hardness at points in the middle of the grain, on the grain boundary, and near grain boundary at the stage immediately after solution treatment. (2) Besides, the difference of micro-hardness between points in the middle of the grain and points near the grain boundary was found very often during precipitation process. So, the statistical significance tests were made between them, and most of them showed that the hypothesis was true at level of significance 1%. (3) Sometimes, the different micro-hardness was recognized in one sample, when a different micro-structure, especially a different degree of precipitation, was also found. (4) The relation between the micro-hardness and microstructure was considered. At early stage of the percipitation process, in general, the hardening at points on the middle of the grain was larger than the hardening at points near the grain boundary. At the next stage, when an intertmediate maximum of usual hardness was observed, the micro-hardness at points in the middle of the grain continued to harden in its own place, but the micro-hardness at points near the grain boundary showed an intermediate maximum hardness parallel to the usual hardness. According to this point of view, the phenomena of the intermediate maximum hardness are related with that which depends, on the micro-hardness at points near the grain boundary. In this report, as described above, the information of precipitation phenomena of Timken 16-25-6 alloy made one step forward.
社団法人日本鉄鋼協会の論文
1954-11-25

耐熱鋼の研究 (VI) : 微小硬度計による Timken 16-25-6 の析出現象の研究

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