Modified 9 Cr–1 Mo is an ideal candidate preferred for high temperature applications in power plants. In this study, three P91 welds of 12 mm thickness are produced using Gas Tungsten Arc Welding (GTAW), Cold Metal Transfer (CMT) and Pulsed-CMT (P-CMT) processes. The impact toughness is evaluated in the as-welded as well as in the PWHT (760 °C-2 h) condition. It is found that P-CMT process resulted in the highest toughness in both the conditions. The heat input was maximum in the case of GTAW (800 J/mm) welds and minimum in CMT (330 J/mm). Even though P-CMT (380 J/mm) has heat input slightly above CMT, the former is compensated by higher welding speeds. Electron microscopy analysis revealed the presence of fine M₂₃C₆ and MX precipitates. Among the welds, P-CMT had minimal amount of the precipitates whereas GTAW welds had the maximum. The dimple morphology observed in the ruptured surface significantly varied and P-CMT process had finer dimples indicating finer weld microstructures and enhanced mechanical properties.

改性的9 Cr–1 Mo是发电厂高温应用的理想选择。在这项研究中，使用钨极氩弧焊（GTAW），冷金属转移（CMT）和脉冲CMT（P-CMT）工艺生产了三种12 mm厚的P91焊缝。在焊接状态和PWHT（760°C-2 h）条件下评估冲击韧性。发现在两种条件下，P-CMT工艺均具有最高的韧性。对于GTAW（800 J / mm）焊缝，热量输入最大，而对于CMT（330 J / mm）焊缝，热量输入最小。即使P-CMT（380 J / mm）的热量输入略高于CMT，但前​​者可通过更高的焊接速度来补偿。电子显微镜分析表明存在细M ₂₃ C ₆和MX沉淀。在焊缝中，P-CMT的析出物最少，而GTAW焊缝的析出物最多。在破裂表面观察到的凹痕形态显着变化，P-CMT工艺具有更精细的凹痕，表明更精细的焊接微观结构和增强的机械性能。