Quantitative Analysis of Microstructure Deformation in Accelerated Creep Fenomena of Ferritic SA-213 T22 and Austenitic SA-213 TP304H Material

Abstract

Abstract

The failure of critical component in fossil fired power plant which operated in creep range (high stress, high temperature and in the long term) depends on its microstructure characteristics. Ferritic low carbon steel (2.25Cr-1Mo) and Austenitic stainless alloy (18Cr-8Ni) is used as a boiler tube in the secondary superheater  outlet header to deliver steam before entering the Boiler. The failure tube is happened in a form of rupture, resulting trip that disrupts the continuity of the electrical generation. The research in quantification microstructure deformation has been done in predicting the remaining life of the tube through interrupted accelerated creep test. For Austenitic Stainless Alloy (18Cr-8Ni), creep test was done in 550°C with the stress 424,5 MPa and for Ferritic Low Carbon Steel (2.25Cr-1Mo) in 570°C with the stress 189 MPa. Interrupted accelerated creep test was done by stopping the observation in condition 60%, 70%, 80% and 90% of remaining life, the creep test fracture was done before. Then the micro hardness test, photo micro, SEM and EDS was taken.  Refers to ASTM E122, microstructure parameter was calculated. The result indicated that there is consistency of increasing of grain size number, micro hardness, and the length of crack or void number per unit area with the decreasing of remaining life. While morphology of grain (stated in parameter α=LV/LH) relatively constant ) for austenitic. But for ferritic the change of morphology shown significant. The quantification of microstructure can be use for predicting remaining life in power plant, refinery or chemical industry. The result is hopefully more accurate than Larson Miller Method or Replica Insitu Method with is used in a large number for predicting remaining life in industry now.

Keywords :accelerated creep, Parameter Larson-Miller, quantification of microstructure, boiler tube, ferritic and austenitic