研究了HR3C钢不同运行态过热器管样晶界碳化物M₂₃C₆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(G_L)对应的二维图像晶界总周长(L_gb), 并拟合出两者的关系L_gb(G_L); 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G_L和 ? M 23 C 6 的关系(W(G_L, ? M 23 C 6 )); 再结合Charpy冲击实验, 获得了冲击值(a_KV)与W的关系(a_KV (W)); 此外, 利用纳米压痕仪测定了晶界的弹性模量(E_r). 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, G_L越小, W越大, 其E_r也越大, 对应的a_KV越小, 即晶界脆化倾向越大. 揭示了晶界M₂₃C₆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 ? M 23 C 6 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 E112 standard charts, the total length of two dimensional austenite grain boundaries (L_gb) corresponding to each grain size number (G_L) was determined in the observed area of the metallographic images and expressed as L_gb (G_L). Making use of the SEM-SE images of the samples, the ? M 23 C 6 and W were determined. The relationships of W with G_L and ? M 23 C 6 were established as W(G_L, ? M 23 C 6 ). Combined with the result from a Charpy impact test, the function of the impact value (a_KV) as the W was obtained. In addition, the grain boundary elastic modulus (E_r) 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 conditions. The W was increased with the decrease of G_L and the increase of E_r at a constant ? M 23 C 6 , causing a corresponding decrease of a_KV, 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 carbides (carbide coarsening) can be explained through the application of the proposed method.