Microstructure Characterization of As-cast, Creep-tested and Ex-service Steam-methane Reformer Tube

The main objective of this project is to study the microstructural transformation of a
steam-methane reformer tube material during creep and after long term service by
comparing the microstructures in creep-tested samples, ex-service samples, and as-cast
samples. The creep-tested samples were not completely representative of the actual
creep process during service. The ex-service material represents the material that
underwent actual service condition. The as-cast and creep-tested samples were obtained
from the Schmidt+Clemens (Spain) for preparation and evaluation, while the ex-service
samples were obtained from a methanol plant in North America. The microstructural
comparisons were made in terms of the shape, average particle size, particle area
fraction and percentage. The samples were examined using optical microscope (OM)
and scanning electron microscope (SEM), with secondary electron (SE) and
backscattered electron (BSE) imaging. Energy dispersive spectroscopy (EDS) was
conducted at selected areas of the samples. The average particle size and particle area
percentage of the primary carbides were measured using NIH ImageJ software. The
shape of the primary carbides (M23C6 and NbC) in the ex-service sample is rounder
compared to the creep-tested and finer shape of the as-cast sample with increasing
service time and temperature.