Investigations of the crack origin in the parts of railway turnouts

Abstract

This diploma thesis deals with origin of hydrogen provoked cracks in the part of railway turnouts. The theoretical part is focused on the description of railway turnouts and examples were given about steel types commonly used in this engineering part . Furthermore, more information is provided about manganese steels and low alloy wear resistance steels in the following chapters. Also, their chemical compositions and mechanical properties were described in detail with supporting documentations in the subchapters. In the last chapter of the theoretical part, factors that cause hydrogen embrittlement formation in steels were given. This documentation includes mechanism of hydrogen embrittlement, source of hydrogen, hydrogen trapping mechanisms and types of hydrogen embrittlement. Within the experimental (practical) part chemical composition analysis, structure analysis, fractography analysis and as a lastly hardness measurements were performed. The special type of wear resistance steels which are used in railway turnouts was delivered to us. For comparison of results all analysis done in the experimental part were applied to sample without damage to obtain reasons that might be cause to hydrogen embrittlement problem in that kind of steels. Closure of the practical part done by under the following chapter as a results and discussions. In the conclusion part, all results and possible reasons causing to this problem were brought up together.