摩擦表面に発生する硬化層について

抄録

In the previous report, it was shown that the surface of wear test pieces in vacuum is covered by a very hard layer. The cause of such a layer is studied from the following point of view, namely, heat treatment, the constitution of the test pieces and some properties of the layer and wear powder. The cause of the hard layer should be considered in the following three ways; 1. The temperature rise at the surface is very remarkable and the surface layer is particularly well tempered. 2. Chemical reaction occurs even in vacuum. 3. A part of the surface and the wear powder are severely cold-worked. Even in such a low carbon steel as containing only 0.14%C, the hard layer was found. Full ferrite steels, for example, high chromium steel, high aluminum steel, and high silicon steel, also show the hard layer. So the first factor is denied. The nitrogen content in the hard layer was analysed and the microstructure after normalizing in vacuum was examined but the change was not large enough to explain the phenomenon. Hence, it is inferred that the hard layer consists of a compilation of severely and repeatedly cold-worked wear powder. Such a layer is not seen in air test. In vacuum test, the wear powder are believed to attach to the surface from where they were separated once. As the conclusion, the wear should be considered, from the following two points of view; that is, the one is separation from the surface, the other is trace of wear powders after separation.