Abstract: The effect of high temperature and pressurized hydrogen on the mechanical properties and failure morphology for stainless steel weld overlay cladding of 309L and 347L，in the original specimens and the specimens thermally charged with hydrogen was investigated.The results of slow strain rate testing (SSRT) indicated that：ⅰ) Fracture stress and plasticity decreased obviously after thermal charging with hydrogen：ⅱ)For the original specimens the fracture of both smooth and notched specimens occurred in the 347L region (except the specimen with notch in 309L region)，but if the specimens were thermally charged with hydrogen the fracture occured in the 309L region (except the specimen with notch in the 347L region).After thermally charging with hydrogen the fracture stress dropped from 885MPa to 478MPa for 309L and from 799.9MPa to 564MPa for 347L respectively.The characteristics of low frequency fatigue with short-crack was also investigated.The propagation rates(da/dN) in three stages and the conditional threshold value (ΔJ_th) of the fatigue crack was calculated.The results showed that the ΔJ_th of specimen after thermally charging with hydrogen dropped obviously while the da/dN of specimen increased.In addition，the fracture morphology of SSRT and different crack propagation mechanism of low frequency fatigue in three propagation stages were observed with SEM.

摘要： 研究了在模拟加氢反应器工况条件下，国产加氢反应器壁材料2(1/4)Cr-1Mo内壁上的309L和347L不锈钢堆焊层的力学性能和断裂形貌.结果表明：热渗氢后，明显降低了其断裂应力(σ_f)和塑性.对于309L和347L堆焊层，未经热渗氢的光滑试样与缺口试样(除缺口位置在309L区域试样外)均断裂在347L区域内.而经渗氢后，无论是起裂于2(1/4)Cr-1Mo和309L的熔合线，还是309L和347L的熔合线处，最后都断在309L区域内(除缺口位置在347L区域试样外).在对短裂纹的低周疲劳特性研究中，计算了裂纹扩展速率(da/dN)和门槛值(ΔJ_th).经热渗氢后，ΔJ_th有明显下降，da/dN-ΔJ曲线也向左移，提高了da/dN.SEM断口分析结果与上述结论一致，裂纹扩展以穿晶为主，热渗氢后有二次裂纹存在，说明热渗氢降低了其力学性能，增加了加氢反应器壁材料的断裂敏感性.