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  • 1.  Failure of Austempered Spring Steel Circlip During Assembly

    Posted 28 days ago

    Hi everyone,

    I'm looking for insights into a fracture issue in an austempered spring steel internal circlip observed during mechanical assembly (not in service).

    Background:

    • Material: Austempered spring steel (High Carbon steel)

    • Condition: Hardness and bend test within specification

    • Observation: Fracture occurs during installation; no visible defects before assembly

    • Heat treatment: Verified process consistency; no reported deviations

    Although mechanical and metallurgical test results are within limits, failure happens consistently during assembly.

    I'd appreciate suggestions on how to structure the root cause analysis (RCA). Possible focus areas:

    • Residual or assembly-induced stresses

    • Microstructural issues (e.g., retained austenite, carbide distribution)

    • Edge quality, surface finish, or burrs

    • Hydrogen embrittlement or surface contamination

    • Tolerance or groove fit issues

    • Assembly tool design and application load

    Could anyone share a recommended roadmap for failure investigation or relevant ASM references/case studies for similar spring steel components?

    Thank you in advance for your guidance.



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    Priya Kumari
    Mahindra and Mahindra Limited
    Jhunjhunu
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    IMAT Conference & Expo


  • 2.  RE: Failure of Austempered Spring Steel Circlip During Assembly

    Posted 27 days ago

    Tough to give a full protocol with the limited information you can communicate here. Still, a couple of things need to be evaluated as part of it. You need to characterize the fractography of the clips through visual examination, optical microscopy, and SEM. Confirm the fracture mode (i.e. is it brittle or is there some ductility present? is there intergranular fracture? etc.) You also need to perform EDS analysis on the fracture and outside surfaces to make sure no foreign contaminants are present. Make a cross-section at least through the fracture to make further characterize the fracture nature and the general microstructure of the clip. During examination, focus in on the mechanisms that could make sense to cause your fracture and test accordingly if they might be the issue. Note that hydrogen damage may not be directly visible but could be determined through the process of elimination of other possible mechanisms.



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    Aaron Tanzer
    Consultant - Retired
    Mr. Failure
    Beavercreek OH
    Consultant
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    Original Message
    IMAT Conference & Expo


  • 3.  RE: Failure of Austempered Spring Steel Circlip During Assembly

    Posted 26 days ago
    I can offer this primarily as a retired technician. First i second the observation that some more information would be useful, however that is always the case. I believe you will benefit from first examining the assembly protocol. Whether these are hand assembled or the process is automated it is a challenging operation because they by nature bind or jam on the ID. This just subjects the ring to triaxial stresses that cause brittle overload. Using a lubricant may itself stop the problem because tempering them further likely will cause excessive wear.
    Jeff Brandt
    Sent from my iPhone


    Original Message
    IMAT Conference & Expo


  • 4.  RE: Failure of Austempered Spring Steel Circlip During Assembly

    Posted 26 days ago
    Expanding on what Aaron Tanzer wrote:
    • make sure pieces are stored properly before examination (this is especially important in legal situations - where months or years may elapse before examination. Steel fracture surfaces rust rapidly!)
    • do nondestructive things first!
    • measure the piece carefully
    • look at it by eye, then low power microscope
    • look for possible damage, burrs, corrosion, etc.
    • then do fractography and metallography
    • check hardness if possible

    --
    John Grubb



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  • 5.  RE: Failure of Austempered Spring Steel Circlip During Assembly

    Posted 26 days ago

    Given your list items 3,4, and 6 are where I would start.

    And when asking about the installation tooling and process if you are told 'nothing changed' that means that they changed things that are not recorded or controlled.

    Microstructure, hardness, and dimensions should be easy to verify quickly.  Make sure not only to compare them to you specifications but also to historical values. You wouldn't be first person to find a process that some conditions just don't work together.



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    Edward Blessman
    Plymouth Tube Company
    Mukwonago WI
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    Original Message
    IMAT Conference & Expo