通过DL-EPR试验研究了混晶和晶粒均匀对C-HRA-5奥氏体耐热钢晶间腐蚀性能的影响,采用金相显微镜、SEM、EBSD等分析了晶粒尺寸、特殊晶界、碳化物析出相和晶间腐蚀特征等。结果表明:晶粒均匀组织试样的耐晶间腐蚀性能高于混晶组织试样;两种试样都含有Σ3占主导的低ΣCSL特殊晶界,前者的特殊晶界含量为54.2%,远高于后者29.5%;可认为晶粒均匀组织试样高耐蚀性的原因是高含量的特殊晶界打断了大角度晶界网络的连通性,对富Cr的M₂₃C₆的析出具有一定的抑制作用,改善部分晶界的贫Cr现象。

The influence of mixed grain structure (MGS) and uniform grain size structure (UGS) on the intergranular corrosion performance of C-HRA-5 austenitic heat-resistant steel was studied through DL-EPR experiments. Grain size, special grain boundaries, carbide precipitation phases, and intergranular corrosion characteristics were analyzed using metallographic microscopy, SEM, EBSD, etc. The results showed that the intergranular corrosion resistance of samples with uniform grain size (microstructure) was higher than that of samples with mixed grain size microstructure. Both UGS and MGS samples contained low ΣCSL special grain boundaries mainly Σ3 boundaries. The special grain boundary content of UGS samples was 54.2%, which was much higher than that of MGS samples (29.5%). The reason for the high resistance of UGS to the corrosion could be regarded as the high content of special grain boundaries interrupted the connectivity of the large angle grain boundary network, which had a certain inhibitory effect on the precipitation of Cr rich M₂₃C₆ and improved the phenomenon of Cr deficiency in some grain boundaries.