Cast stainless steel may experience embrittlement when it is exposed approximately to 300℃ for a long period. I n the present investigation, the three classes of the thermally-aged C F8M specimen were prepared using an artificially-accelerated aging...
Cast stainless steel may experience embrittlement when it is exposed approximately to 300℃ for a long period. I n the present investigation, the three classes of the thermally-aged C F8M specimen were prepared using an artificially-accelerated aging method. After the specimens were held for 300, 1800 and 3600hrs. at 430℃, respectively, the specimens were quenched in water which is at room temperature. Load versus load line displacement curves and ? - R curves were obtained using the unloading compliance method. ??c values were obtained using the ASTM E 813-87 and ASTM E 813-81 methods. In addition to these methods, ??? values were obtained using the SZW (stretch zone width) method described in JSME S 001-1981. The results of the unloading compliance method are ??=543.9kJ/㎡ for virgin materials. The values of Jlc for the degraded materials at 300, 1800 and 3600hrs. are obtained 369.25kJ/㎡, 311.02kJ/㎡, 276.7kJ/ ㎡, respectively. The results obtained by the SZW method are compared with those obtained by the unloading compliance method. Both results are quite similar. Through the elastic-plastic fracture toughness test, it is found that the value of ??? is decreased with an increase of the aging time.<br/>