Figure 12: Optical micrograph of service exposed FPU column (a) base material in as received condition showing ferritic pearlitic structure. (b) base material in crept condition at 78 MPa/ 515°C showing elongated grains of coarse ferrite (white) and dispersed pearlite (dark). (c) base material crept at 98 MPa/ 515°C showing ferritic pearlitic structure. (d) weld material in as received condition showing ferritic pearlitic structure. (e) weld material crept at 78 MPa/ 515oC showing fine grains of ferrite(white) and pearlite (dark) and (f) weld material crept at 98 MPa/ 515°C showing showing fine grains of ferrite(white) and pearlite (dark)[15].