Untersuchung des Einflusses von Einschlüssen auf die Schwingfestigkeit von 26NiCrMoV14-5 in Schmiedeteilen für den Schwermaschinenbau

Translated title of the contribution: Analysis of the effects of inclusions on the fatigue strength of 26NiCrMoV14-5 in heavy machinery forgings

Roland Sampl

Research output: ThesisMaster's Thesis

Abstract

This study aims to clarify the cyclic behavior of forged, quenched and tempered 26NiCrMoV14-5 specimens, which is determined at constant stress amplitude at room temperature. The technological size effect was minimised by heat treatment during specimen manufacture due to the large dimensions of the examined forging. The fatigue behaviour of the quenched and tempered steel is characterised under axial tension-compression loading and rotational bending loading and has been carried out to an ultimate number of 10 mio. cycles. This features the fatigue strength characterization for huge heavy-machinery components made of this quenched and tempered steel. An increase in fatigue strength under rotational bending stress is observed in the vibratory-finished series compared to the polished series. When subjected to axial loading, the polished series was also found to have a lower fatigue strength than the vibratory-finished series. The mean stress sensitivity of the vibratory-finished series exceeds the FKM guideline specifications. However, the material shows increased ductile behavior at high stress ratios, especially at the examined stress ratio of 0.5. Fractographic examination of specimens provides parameters for an extreme value model of inclusion size distribution. Examination of the inclusions by SEM and EDX analysis shows that they consist mainly of the oxidic compounds alumina and calcium oxides. Under alternating and pulsating stresses, some specimens exhibit internal fish-eye cracks in the fracture surface. fish-eye lifetime evaluation with the model of Marines-Garcia gives good results with a user-defined parameter set.
Translated title of the contributionAnalysis of the effects of inclusions on the fatigue strength of 26NiCrMoV14-5 in heavy machinery forgings
Original languageGerman
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Stoschka, Michael, Supervisor (internal)
Award date28 Jun 2024
Publication statusPublished - 2024

Bibliographical note

embargoed until 15-05-2029

Keywords

  • heavy machinery
  • quenched and tempered steel
  • fatigue strength
  • non-metallic inclusions
  • fisheye

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