T23 steel (2.25Cr–1Mo–1.6W–0.24V–0.05Nb, in wt.%) has been widely used as water walls in ultra-supercritical (USC) power plants. However, high reheat cracking susceptibility of T23 steel hazarded the safety of USC power plants. It is aimed to improve the reheat cracking susceptibility of T23 steel from the perspective of modifying chemical composition. Gleeble-3800 thermal simulator was used to simulate the coarse-grained heat-affected zone (CGHAZ) in T23 and modified T23 steels via thermal simulation of welding, and then evaluate the reheat cracking susceptibility in CGHAZ of T23 and modified T23 steels by the isothermal slow strain rate tensile test. The microstructure was systematically investigated by optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show that the reheat cracking susceptibility of modified T23 steel is extremely improved. Compared with T23 steel, there are fewer M₂₃C₆ particles at the grain boundaries in modified T23 steel, and the degree of intergranular weakening is smaller. At the same time, not only MX in the grain interiors but also the solid-solutioned C and W in the matrix decrease in modified T23 steel, leading to the decline of intragranular strengthening. In addition, small grain size is beneficial to the improvement of the reheat cracking susceptibility of modified T23 steel. The decreased number of M₂₃C₆ at grain boundaries helps to retard the formation and propagation of reheat cracks because of decreased denuded zones.

T23钢（2.25Cr–1Mo–1.6W–0.24V–0.05Nb，以重量％计）已被广泛用作超超临界（USC）电厂的水冷壁。但是，T23钢的高再热开裂敏感性会危及USC电厂的安全。从改变化学成分的角度出发，旨在提高T23钢的再热裂纹敏感性。利用Gleeble-3800热模拟机通过焊接热模拟对T23和T23改性钢中的粗晶粒热影响区（CGHAZ）进行了模拟，然后通过等温法对T23和T23改性钢的CGHAZ中的再热开裂敏感性进行了评估。慢应变速率拉伸试验。通过光学显微镜，扫描电子显微镜和透射电子显微镜系统地研究了显微组织。结果表明，改性T23钢的再热开裂敏感性大大提高。与T23钢相比，M少在改性T23钢中，晶界处存在₂₃ C ₆颗粒，且晶界弱化程度较小。同时，改性T23钢不仅晶粒内部的MX，而且基体中的固溶碳和钨均降低，导致晶粒内强化下降。另外，较小的晶粒尺寸有利于改善改性T23钢的再热裂纹敏感性。M ₂₃ C ₆在晶界的减少有助于减少再热裂纹的形成和传播，因为减少了剥蚀区。