Microstructures and mechanical properties of friction hydro-pillar processing overlap welding in API 5L X65 pipeline steel

摘要

Abstract This paper exhibits a novel in situ remediation technique named friction hydro-pillar process overlap welding (FHPPOW) to repair the through crack of the structures and components in the harsh environments. In the present work, the effects of welding parameters on the microstructures and mechanical properties of the welding joints are investigated. The defect-free joints can be obtained in a large process window with the rotational speed of 6000–7000?rpm and welding force of 20–40?kN. In the heat-affected zone (HAZ), the interface between the substrate and lap plate can be clearly distinguished. The microstructure of the weld is mainly consisted of the upper bainite. The hardness value in the welding zone is highest and is the lowest in the base material. The pull-out tests of all welds are failure in the stud. Results indicate that the good welding quality can be obtained in these welding conditions. The best results of the cruciform uniaxial tensile and the shear tests are 662.8 and 552?MPa, respectively. The favorable Charpy impact absorbed energy is 68.75?J at 0?°C. The fracture characteristic of Charpy impact tests is brittle fracture with a large area of cleavage.