PSI - Issue 13

Marko Katinić et al. / Procedia Structural Integrity 13 (2018) 2040 – 2047 Author name / Structural Integrity Procedia 00 (2018) 000–000

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4. Conclusion As can be seen from this case history and other cases reported in published articles, failure of the moving blades due to the corrosion fatigue still occurs in practice. In order to increase the useful fatigue life of moving turbine blades, further research and development in this area is necessary. In this case, the useful fatigue life of the moving blade elements is increased by applying the following activities: - reduction of steady stress at the blade roots by redesign of the turbine stage and shortening of the blade lengths - replacement of existing blade material with material having a higher tensile strength and fatigue limit In addition to the above mentioned possibilities, the increase of the useful fatigue life of the moving blade elements can be achieved by applying, for instance, certain coats based on nitro-sulphurizing treatment and the use of polymerization resin for erosion protection in a steam with low moisture content. Laboratory experiments show that using this treatment on material Z12CNDV12 increases the fatigue limit by 14 %. Acknowledgements The authors are indebted to the Petrokemija d.d. Kutina for permission to publish this article and for support which made this work possible. References B. Schönbauer, A. Perlega, S. Tschegg, N. Rieger, R. Salzman and D. Gandy, 2012. Influence of Corrosion Pits and Environment on the Fatigue Life of 12% Cr Steam Turbine Blade Steel. Proceedings of ICMFM-XVI, 24-26 Sept. 2012, Brno, pp. 25-32. Salzman R, Gandy D, Rieger N, Schönbauer B, Tschegg S, Zhou S, Turnbull A., 2013. Corrosion-fatigue prediction methodology for 12% Cr steam turbine blades. ASME 2013 Power Conference, Power 2013 (Vol. 98026), Boston B. Schönbauer, S. Tschegg, A. Perlega, R. Salzman, N. Rieger, S. Zhou, A. Turnbull and D. Gandy, 2014. Fatigue life estimation of pitted 12 % Cr turbine blade steel in different environments and at different stress ratios, International Journal of Fatigue, Volume 65, pp. 33-43 M. Katinić, D. Kozak, Ž. Ivandić, 2009. Vibration diagnostic of steam turbine blade breakage, Proceedings of the 1 st International Scientific and

Expert Conference Team 2009, Slavonski Brod, pp. 80-89 Petrokemija d.d. Kutina, 2009: Internal documentation files