Near-threshold fatigue crack growth of an electron beam weldment in AISI 4130 steel is studied. To increase the fatigue resistance ability, two different post-weld heat treatment processes are adopted to compare the near-threshold fatigue crack growth data with that of an as-welded specimen. The electron beam tempering in the vacuum chamber immediately after the welding and the traditional furnace tempering treatment are chosen for comparison. Strength of the welded joints is evaluated by a tensile test and near-threshold fatigue properties are investigated by K-decreasing method. The resistance to near-threshold fatigue crack growth is improved with post-weld heat treatment, due to the residual stress relief effect and existence of a toughened tempered structure. For electron beam post-weld heat treatment with 6 mm dot pattern width, the threshold stress intensity factor range increases by 14% compared to that of an as-welded specimen and the data of furnace post-weld heat treatment at 550-degrees-C can be improved by as much as 26%.
