Effects of interpass temperature on crack propagation energy in deposited metal of 690 MPa grade HSLA steel

Instrumented impact test was conducted on the deposited metal of 690 MPa grade HSLA steel when the interpass temperature was 80℃ and 200℃, respectively.The factors to hinder crack propagation were discussed with optical microscope(OM), scanning electron microscope(SEM) and electron backscatter diffraction(EBSD) combining with load-distance curve.The results showed that the impact energy of the deposited metals made with interpass temperature of 80℃ and 200℃ was 103.9 J and 63.2 J, respectively.The gap between crack initiation energy and propagation energy was 6.7 J and 34 J for two interpass temperatures, respectively.The difference of impact energies was mainly attributed to the propagation energy.During the crack propagation, the maximum propagation distance of the dimple area was 1.68 mm and 0.6 mm for 80℃ and 200℃ of interpass temperature, respectively.The fractography of the brittle fracture areas was mainly of cleavage, but dimple bands were observed in the deposited metal with interpass temperature of 80℃.It was concluded that the proportion of high angle grain boundaries of 55°-60° determining the impact energy.