摘要
研究了HR3C钢不同运行态过热器管样晶界碳化物M_(23)C_6相参量(面积分数?M_(23)C_6和等效宽度W)的变化与脆化的关系.利用ASTM E112规范奥氏体钢晶粒度评级卡片测算出各级别晶粒度(GL)对应的二维图像晶界总周长(Lgb),并拟合出两者的关系Lgb(GL);利用各管样的扫描电镜二次电子(SEM-SE)像,得到了对应的?M_(23)C_6及W,从而建立了W与GL和?M_(23)C_6的关系(W(GL,?M_(23)C_6));再结合Charpy冲击实验,获得了冲击值(aKV)与W的关系(aKV(W));此外,利用纳米压痕仪测定了晶界的弹性模量(Er).结果表明,所有管样冲击断口均呈沿晶断裂形貌;当?M_(23)C_6一定时,GL越小,W越大,其Er也越大,对应的aKV越小,即晶界脆化倾向越大.揭示了晶界M_(23)C_6片等效宽度的增大(粗化)导致脆化的实质.
The relationship of the evolution of the phase parameters （area fraction ФM23C6 and equivalent width W） of grain boundary M23C6 plates with the embrittlement of HR3C super-heater tube samples in service was studied. Based on the ASTM E1 12 standard charts, the total length of two dimensional austenite grain boundaries （Lab） corresponding to each grain size number （GL） was determined in the observed area of the metallographic imag- es and expressed as Lgb （GL）. Making use of the SEM-SE images of the samples, the ФM23C6 and W were determined. The relationships of W with GL and ФM23C6 were established as W（GL, ФM23C6）. Combined with the result from a Charpy impact test, the function of the impact value （aKV） as the W was obtained. In addition, the grain boundary elastic modulus （Er） was measured by a nano-hardness test. The result shows that intergranular fracture occurred on all the room temperature impact test specimens taken from the super-heater tubes exposed under the operating con- ditions. The W was increased with the decrease of GL and the increase of Er at a constant ФM23C6, causing a corr- esponding decrease of aKV, and hence promoting the embrittlement of the HR3C super-heater tubes. The related mechanism for the intergranular fracture caused by the increase of the equivalent width W of grain boundary car- bides （carbide coarsening） can be explained through the application of the proposed method.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第11期1325-1332,共8页
Acta Metallurgica Sinica
