The effect of grain size on the mechanical properties and creep rupture of 253 microalloyed (MA) austenitic stainless steel (ASS) was investigated. The cold rolling process with a 53% reduction in thickness was applied to the steel followed by annealing at 1100 °C over 0, 900, 1800, and 3600 s to obtain grain sizes of 32.4, 34.88, 40.35, and 43.77 µm, respectively. Uniaxial tensile and micro-Vickers hardness tests were carried out to study the effect of grain size on mechanical properties at room temperature. The creep rupture test was performed at 700 °C under a load of 150 MPa. The results showed that there was a correlation between grain size, mechanical properties, and creep rupture time. The fine initial grain size showed relatively good mechanical properties with a short creep rupture time, while the coarse initial grain size produced low mechanical properties with a long creep rupture time. The initial grain size of 40.35 µm was the optimum grain size for a high value of creep rupture time due to the low hardness and elongation values at room temperature and low creep ductility value. The intergranular fracture was found on the initial grain size below 40.35 µm, and a mixed mode of intergranular and transgranular fracture was found on the initial grain size above 40.35 µm after the creep rupture test.
The coal-based steam power plant accounts for the largest electricity generation in Indonesia. Disruption in operation mostly caused by a failure of a component of the system and considered a serious problem and must be prevented. Failure can be originated from operations as well as the design. In the present work, a root cause study was performed on failure elbow in the steam line from the high-pressure heater (HPH) to the deaerator. The failure occurred only after 5 years of operation. The analysis was started with a visual examination, material verification, microstructural investigation, thickness measurement, and computational modelling. The analysis and simulation study showed that the failure of the elbow caused by two-phase flow where steam quality was compromised. The recommendation was to examine the HPH and to find possible leaks of the waterside to the steam side in the HPH system.
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