HIGH TEMPERATURE DEGRADATION OF ASTM A297 GRADE HH CONVECTION PIPE SUPPORT AFTER 24 YEARS OPERATING TIME

• Main Author: Michael Aditya, Dominico
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/55301
• Institution: Institut Teknologi Bandung

Cast austenitic stainless steel (CASS) has been widely used for hightemperature application for a long-term period. However, the behavior of CASS after an extended period of service still lacks investigations which is needed to prevent failure mechanism. Here, we evaluate the chemical composition, microstructure, and CASS grade HH convection pipe support properties operated in 665?-737 for 24 years to determine its behavior. Several characterizations are used, i.e., Optical Emission Spectroscopy (OES), metalografi, Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and Rockwell B hardness test. An average of 29.12% and 7.02% volume fraction of the sigma phase were observed on surface (till the depth of 406.70 ?m) and center of thickness. The Sigma phase on the surface has sphere-like morphology with an average grain diameter of 2.19 ?m. In contrast, the center of thickness is dominated by cellular morphology with an average grain diameter of 3.30 ?m. Unique color gradients are recognized on sigma phase precipitation that infers degradation in chemical composition which supported by EDS data. M23C6 carbide precipitation has wholly evolved with irregular phase boundary. In conclusion, long-term service degrades bulk and precipitates chemical composition with microstructure evolution, resulting in mechanical properties reduction (hardness and strength).