Cast iron composite brake blocks which include silicon carbide ceramic filters have been developed to enhance the speed of conventional trains and are expected to serve as next generation brake blocks because of their high frictional coefficient characteristics in high speed. However, they cause wheel treads to wear out and heat loads to increase because the filters contained are much harder than cast iron. It is therefore necessary to decrease such impact on wheel treads while maintaining the high frictional coefficient characteristics in high speed. In this study, the number of filters, porosity, and the area fraction of cast iron composite brake blocks were thus changed and tested on a full scale dynamometer. As a result, useful cast iron composite brake blocks with excellent brake performance in high speed and reduced impact on wheel treads and costs were successfully developed.

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  Surface damage caused by the impact of dispersed particles in gas or liquid flow is called “erosion”. Erosion is a serious problem as it occurs in piping systems due to gas-solid flow. This report discusses the evaluation of high manganese spheroidal carbide cast iron which is expected to have high resistance against erosive wear.
  Erosive wear test was performed on flaky graphite cast iron (FC200), spheroidal graphite cast iron (FCD400), white cast iron (WCI), and high manganese cast iron with spheroidal carbides (SCI-VMn) using a shot blast machine. Erosion damage was measured by the removed material volume, defined as erosion rate at impact angle 30°, 60°, and 90°. By way of the mechanism of erosive wear, not only was the surface metal flow in vertical sections observed, but the effect of impact angles, and differences in wear features of specimens were also discussed.
  Results of experiment showed that, the erosion rate for SCI-VMn is about 1/8 of that for FC200, and about 1/6 of that for FCD400. Although the initial hardness of WCI was highest among all specimens, its erosion rate was larger than SCI-VMn. Work hardening effect was seen in all specimens, especially, the surface hardness of SCI-VMn increased from the initial hardness HV530 to HV804 after 3600sec. of blasting. The reason for this maybe that the austenite in the structure undergoes strain induced martensitic transformation which results in surface hardening and lower erosion rate. It was shown that SCI-VMn has excellent erosion resistance and it is expected to be available for wide applications as a wear-resistant material.

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  The strength of salt core comprised of NaCl-Na₂CO₃, KCl-K₂CO₃, KCl-NaCl and K₂CO₃-Na₂CO₃ binary salt systems was investigated in order to develop expendable core for high pressure die casting using 4-point bending test, Vickers hardness measurement, and SEM observation of solidification structures and fracture surfaces. Bending specimens were fabricated from 10K superheated molten salts by the permanent mold method. The results of the bending test showed that the KCl-K₂CO₃ binary system offers quite high strength exceeding about 20MPa. Moreover, especially high strength was obtained for the NaCl-Na₂CO₃ system whose strength value is higher than that of the KCl-K₂CO₃ system. Also, the Vickers hardness of the NaCl-Na₂CO₃ system is higher than that of KCl-K₂CO₃ system. In contrast to these binary systems, salt cores made of KCl-NaCl and K₂CO₃-Na₂CO₃ binary salt systems could not be strengthened by mixing salt, due to phase separation of the solid solution phase crystallized from molten salt.
  In the solidification structures of NaCl-Na₂CO₃ system, dendritic or elliptic shaped primary phase and fine eutectic phase were found. As crack propagation is deflected by both the primary phase and fine eutectic phase, salt cores can be strengthened.

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