• S Seetharamu

      Articles written in Bulletin of Materials Science

    • Significance of structure–property relationship in alumina based porcelain insulators to achieve quality

      Parvati Ramaswamy S Vynatheya S Seetharamu

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      The catastrophic failures of porcelain insulators in power lines can be minimized by understanding the structure–property relationship that governs the performance. A study addressing the materials aspects has been conducted on alumina based porcelain insulators used in 25 kV railway traction lines. This article asserts the controls exercised by chemical composition, crystalline structural phases and microstructure on the functional reliability and durability of the insulators. Influences of the total alumina, 𝛼-Al2O3 (corundum) and 𝛼-quartz contents, microstructural features including morphologies of mullite needles, quartz and corundum grains in the alumino silicate glassy matrix, large inhomogeneities in matrix constituents and composition have been highlighted.

    • Effect of increased manganese addition and mould type on the slurry erosion characteristics of Cr–Mn iron systems

      P Sampathkumaran C Ranganathaiah S Seetharamu Kishore

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      The wear resistance of high chromium iron is well recorded. However, the same is not the case as regards the use of manganese at higher percentages in high chromium irons and its influence on wear behaviour. Hence, this work highlights the slurry wear characteristics of chromium ($\Box$ 16–19%) iron following the introduction of manganese at two levels i.e. 5 and 10%. It is known that the wear properties are dictated by the microstructural features. To alter the structure, the cooling rate of casting has been varied by adopting two different types of moulds (i.e. sand and metal) and subsequently subjecting to thermal treatment. The as-cast and heat treated samples are examined for microstructure and then evaluated for hardness and slurry erosion properties. As the manganese content is increased from 5 to 10%, the hardness showed a decrease in value both in the as-cast and heat treated conditions. The slurry erosion loss, expectedly, showed an increase irrespective of the sample condition (i.e. mould type/heat treatment adopted). The findings are corroborated with the microstructural features obtained through optical and scanning electron microscopy.

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