Published on 28 January 2013
TWI offers premium quality failure investigation and root cause analysis services. TWI has over 50 years of troubleshooting expertise and can provide the right information in the right time frame through the combination of the specialist expertise of its 200 engineers and its access to cutting-edge technology.
Case study: Failed tube made from stabilised stainless steel with a pressurised carburising environment circulating internally at 300-400°C for 1500 hours.
Experimental Approach:
- Fracture face examination using light and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (EDS)
- Microstructure examination on metallographic section,
- Through thickness micro-Vickers,
- Chemical analysis including C, N and S and EDS mapping
- Phase identification and distribution using X-ray diffraction (XRD) and electron backscattered diffraction (EBSD)
- Phase balance using image analysis software and EBSD
- Thermodynamic modelling using ThermoCalc®
Findings:
Failure occurred by a brittle mode due to extensive formation of Fe3C7.
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