Matrix replica-based assessment of the microstructure of primary steam piping elbows after long-term operation

Abstract

The degree of degradation of ferritic-pearlitic steels is assessed by describing the size, dispersion and distribution of carbides along the grain boundaries, grain growth and the occurrence of microcracks. The article reports the results of the microstructural assessment of primary steam pipeline elbows made of 13HMF steel. Digital image analysis of matrix replicas was performed. It included the classification of microstructures in terms of pearlite/bainite change classes (fragmentation of cementite plates, spheroidization, coagulation) and the evaluation of carbide precipitation processes and damage processes (presence of isolated oriented creep pores and microcracks). The perlite/ bainite areas were found to disappear completely after long-term operation.

Keywords

• 13HMF steel
• piping elbows
• damage processes
• scanning electron microscopy (SEM)
• phase