An experimental steel billet of SA508 reactor pressure vessel material was manufactured by the additive forging method, and microstructure and mechanical properties of the hot-compression bonding interface were systematically investigated. The result indicated that oxidation levels of bonding interfaces were well controlled using vacuum electron beam welding. It was easy to discriminate interfaces from base materials during the optical microstructure observation, since interfaces were characterized by grain or phase boundaries in a straight line. Test results of uniaxial tensile experiments (at 20 and 350 °C) and Charpy V-notched impact tests (at 0 and 20 °C) showed that fracture behaviour of all those samples appeared at the base material, and bonding interfaces showed advantage of strength and toughness at the forge bonding state.

An experimental steel billet of SA508 reactor pressure vessel material was manufactured by the additive forging method, and microstructure and mechanical properties of the hot-compression bonding interface were systematically investigated. The result indicated that oxidation levels of bonding interfaces were well controlled using vacuum electron beam welding. It was easy to discriminate interfaces from base materials during the optical microstructure observation, since interfaces were characterized by grain or phase boundaries in a straight line. Test results of uniaxial tensile experiments (at 20 and 350 °C) and Charpy V-notched impact tests (at 0 and 20 °C) showed that fracture behaviour of all those samples appeared at the base material, and bonding interfaces showed advantage of strength and toughness at the forge bonding state.