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Root cause analysis of turboprop engine Inconel 713LC turbine blades failure.

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Title: Root cause analysis of turboprop engine Inconel 713LC turbine blades failure.
Authors: Chondrakis, Georgios1 (AUTHOR) geochondrakis@gmail.com, Tzanis, Athanasios1,2 (AUTHOR), Georgiou, Emmanuel3 (AUTHOR), Koutsomichalis, Angelos3 (AUTHOR)
Source: Engineering Failure Analysis. Jul2025, Vol. 176, pN.PAG-N.PAG. 1p.
Subjects: Thermal fatigue, Corrosion fatigue, Fatigue cracks, Failure analysis, Turbine blades
Abstract: • Failure analysis of nickel superalloy turbine blades showed that four successive blades failed first from fatigue. • Protective coating fragmentation due to a synergism of thermal fatigue and pitting corrosion mechanism. • Coating fatigue cracks propagated into the substrate by a combination of creep and fatigue and led to fracture. • These cracks propagated intergranularly during service through creep cavities and continue films of M 23 C 6 carbides. • Incipient melting areas and rafting of γ' phase were detected in the base material. In this paper, the root cause analysis of failed Inconel 713LC superalloy blades with approximately 3500 flight hours since new from the stage Ι of power turbine is presented. A two-stage axial-flow power turbine driving the propeller of an aircraft turboprop engine through an internal shaft, during take-off at altitude of 600 feet experienced an in-flight shutdown. At the time of the incident the rotational speed of power turbine was at 90 % torque rotating at approximately 1,300 rpm, having operating temperatures above 950 °C. The failure occurred after 120 operating hours from the last engine overhaul inspection. To examine the root of this catastrophic failure, both fractographic and metallographic examinations were performed by various means. It was found that four successive blades of the stage Ι turbine disk initially fractured by fatigue mechanism and then by overload. Fatigue initiation sites were observed mainly at the leading edge of those four blades, where coating degradation appears due to a synergism between thermal fatigue cracking and corrosion that extends through the coating and into the blade base material. Microstructural analysis performed at these four blades revealed solutioning and coarsening of the nickel superalloy gamma prime phase and intergranular creep voids, indicating long-term exposure to high temperature. The remaining 62 blades were subsequently fractured by overload due to impact damage from the fragments. From these examinations, it is concluded that the fatigue cracks on the four turbine blades initiated from the combination of thermal fatigue and corrosion. Subsequently, the cracks propagated by a mix of creep and fatigue due to coating and microstructure degradation caused by overheating. [ABSTRACT FROM AUTHOR]
Copyright of Engineering Failure Analysis is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
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  Data: Root cause analysis of turboprop engine Inconel 713LC turbine blades failure.
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  Data: <searchLink fieldCode="DE" term="%22Thermal+fatigue%22">Thermal fatigue</searchLink><br /><searchLink fieldCode="DE" term="%22Corrosion+fatigue%22">Corrosion fatigue</searchLink><br /><searchLink fieldCode="DE" term="%22Fatigue+cracks%22">Fatigue cracks</searchLink><br /><searchLink fieldCode="DE" term="%22Failure+analysis%22">Failure analysis</searchLink><br /><searchLink fieldCode="DE" term="%22Turbine+blades%22">Turbine blades</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: • Failure analysis of nickel superalloy turbine blades showed that four successive blades failed first from fatigue. • Protective coating fragmentation due to a synergism of thermal fatigue and pitting corrosion mechanism. • Coating fatigue cracks propagated into the substrate by a combination of creep and fatigue and led to fracture. • These cracks propagated intergranularly during service through creep cavities and continue films of M 23 C 6 carbides. • Incipient melting areas and rafting of γ' phase were detected in the base material. In this paper, the root cause analysis of failed Inconel 713LC superalloy blades with approximately 3500 flight hours since new from the stage Ι of power turbine is presented. A two-stage axial-flow power turbine driving the propeller of an aircraft turboprop engine through an internal shaft, during take-off at altitude of 600 feet experienced an in-flight shutdown. At the time of the incident the rotational speed of power turbine was at 90 % torque rotating at approximately 1,300 rpm, having operating temperatures above 950 °C. The failure occurred after 120 operating hours from the last engine overhaul inspection. To examine the root of this catastrophic failure, both fractographic and metallographic examinations were performed by various means. It was found that four successive blades of the stage Ι turbine disk initially fractured by fatigue mechanism and then by overload. Fatigue initiation sites were observed mainly at the leading edge of those four blades, where coating degradation appears due to a synergism between thermal fatigue cracking and corrosion that extends through the coating and into the blade base material. Microstructural analysis performed at these four blades revealed solutioning and coarsening of the nickel superalloy gamma prime phase and intergranular creep voids, indicating long-term exposure to high temperature. The remaining 62 blades were subsequently fractured by overload due to impact damage from the fragments. From these examinations, it is concluded that the fatigue cracks on the four turbine blades initiated from the combination of thermal fatigue and corrosion. Subsequently, the cracks propagated by a mix of creep and fatigue due to coating and microstructure degradation caused by overheating. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Engineering Failure Analysis is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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      – Type: doi
        Value: 10.1016/j.engfailanal.2025.109609
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 1
        StartPage: N.PAG
    Subjects:
      – SubjectFull: Thermal fatigue
        Type: general
      – SubjectFull: Corrosion fatigue
        Type: general
      – SubjectFull: Fatigue cracks
        Type: general
      – SubjectFull: Failure analysis
        Type: general
      – SubjectFull: Turbine blades
        Type: general
    Titles:
      – TitleFull: Root cause analysis of turboprop engine Inconel 713LC turbine blades failure.
        Type: main
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            NameFull: Chondrakis, Georgios
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            NameFull: Tzanis, Athanasios
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            NameFull: Georgiou, Emmanuel
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            NameFull: Koutsomichalis, Angelos
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          Dates:
            – D: 01
              M: 07
              Text: Jul2025
              Type: published
              Y: 2025
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              Value: 176
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            – TitleFull: Engineering Failure Analysis
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