ASM Online Member Community

 View Only

  • 1.  Cracks after Austenitic nitrocarburising of 100Cr6 grade steel

    Posted 09-29-2024 04:21

    Austenitic nitrocarburising has been carried out at 620 deg C with NH3(35% ) , CO2(5%) and N2( 60%) and then tempering at 350 deg C. Cracks are noticed on the inner radius of bend portion. Any recommendation to overcome cracking problem ?



    ------------------------------
    Sandur Ajith Kumar
    Consultant R&D
    TVS Motor Company Ltd
    Anekal
    +919944452591
    ------------------------------


  • 2.  RE: Cracks after Austenitic nitrocarburising of 100Cr6 grade steel

    Posted 09-29-2024 07:54

    Nitrogen austenite has a Ms of 35°C. Thus, it is still austenite upon cooling from nitrocarburazing temperature.

    Upon tempering austenite trasforms to martensite, tends to expand and causes cracks owing to constrained expansion.

    Nitrocarburizing has to be performed below 590°C



    ------------------------------
    Donato FIRRAO FASM
    Professor
    Politecnico di Torino
    TORINO
    +393351494032
    Italy
    ------------------------------



  • 3.  RE: Cracks after Austenitic nitrocarburising of 100Cr6 grade steel

    Posted 10-01-2024 09:31

    Thanks for suggestion.

    How will temperature of processing at 590 deg C , instead of at 620 deg C  will help . Will it be okay to keep same gas ratios ie NH3 ( 35 % ) , CO2 ( 5 % ) and N2 ( 60 % ) even at 590 deg C



    ------------------------------
    Sandur Ajith Kumar
    Consultant R&D
    TVS Motor Company Ltd
    Anekal
    +919944452591
    ------------------------------

    Original Message


  • 4.  RE: Cracks after Austenitic nitrocarburising of 100Cr6 grade steel

    Posted 09-29-2024 16:39

    I am not sure why you are carbonitriding this grade of steel. This grade is a through hardening grade that can reach high hardness without carbonitriding, a process that is very prone to surface cracks. I would recommend that you austemper. If you need further high hardness, it is recommended that part can be nitrided via salt bath, gas or plasma nitriding. The plasma nitriding process has advantage in that it can use very low temperatures for nitriding.

    Ratnesh Dwivedi, Ph.D

    WWW.rkdengg.com



    ------------------------------
    [Ratnesh] [Dwivedi]
    [President]
    [RKD ENGG, LLC]

    www.rkdengg.com
    ------------------------------



  • 5.  RE: Cracks after Austenitic nitrocarburising of 100Cr6 grade steel

    Posted 10-01-2024 09:32

    Thanks.  We don't have salt bath for Austempering



    ------------------------------
    Sandur Ajith Kumar
    Consultant R&D
    TVS Motor Company Ltd
    Anekal
    +919944452591
    ------------------------------

    Original Message


  • 6.  RE: Cracks after Austenitic nitrocarburising of 100Cr6 grade steel

    Posted 09-30-2024 12:43

    This discussion is very confusing. Is the topic austenitic nitrocarburizing or ferritic nitrocarburizing or carbonitriding. They are three completely different heat treat processes.  The can be conducted successfully in gas atmosphere furnaces (and perhaps in vaccum furnaces) at temperatures very much above those mentioned in previous comments.

    Al Swiglo, scssaas67@sbcglobal.net 651-490-7752



    ------------------------------
    A. Alan Swiglo
    Swiglo Metallurgical Consulting
    St. Paul MN
    651-490-7752
    ------------------------------



  • 7.  RE: Cracks after Austenitic nitrocarburising of 100Cr6 grade steel

    Posted 10-01-2024 09:34

    Thanks for your reply.

    We have tried Austenitic Nitrocarburising only at 620 deg C with NH3 ( 35 %) , CO2 ( 5 % ) and N2 ( 60 %)



    ------------------------------
    Sandur Ajith Kumar
    Consultant R&D
    TVS Motor Company Ltd
    Anekal
    +919944452591
    ------------------------------

    Original Message