Creep Failure of 25Cr-35Ni Centrifugally Cast Reformer Tube

Abstract

Cast 25Cr-35Ni alloys are extensively being used in the petrochemical and petroleum refining industries for high-temperature applications. A typical application of such alloys in the industry is in the manufacture of cast catalyst reformer tubes for the production of hydrogen. The cast 25Cr-35Ni catalyst reformer tubes possess the required mechanical properties, creep resistance, oxidation resistance, and high-temperature stability. Though reformer tubes are designed to give a service life of over 100,000 hours at temperatures beyond 900°C, there are incidents of failure due to creep damage, which is the predominant failure mechanism in reformer tubes. The paper discusses an investigation conducted on the premature failure of a 25Cr-35Ni reformer tube. The investigation involved microstructural assessments and the evaluation of mechanical properties. The microstructure and mechanical properties of the service-exposed reformer tube were also compared with a new tube. The investigation revealed that the failure of the tube was due to creep embrittlement. The creep embrittlement was due to the microstructural degradations that occurred as a result of overheating. Adherence to the design and operational parameters is critical in mitigating creep embrittlement failures.