Microstructure and mechanical properties of thin-walled ODS ferritic steel tubes fabricated by a near-net forming method

Abstract

This research successfully applied a new near-net forming process for producing thin-walled ODS ferritic steel tubes. The process involves hot isostatic pressing (HIP), hot extrusion (HE), and Pilger-rolling (PR). The tubes produced have a length of 2800 mm and a thickness of ∼1 mm. The microstructural analysis shows that the thin-walled tubes have partially elongated grains and a γ-fiber {111} texture. The precipitated nano-oxide particles in the thin-walled tubes are Y4Zr3O12 and Y2(Zr0.6Ti0.4)2O7, with an average size of 7.21 nm and a number density of 4.3 × 1023 m−3. The tubes have an ultimate tensile strength (UTS) of 908.3 MPa at ambient temperature and 186.2 MPa at 800 °C along the hoop direction. These values are comparable to those reported for ODS steel tubes produced by conventional methods, including powder hot extrusion, drilling machining, and Pilger-rolling. Based on the results, this near-net forming method effectively produces high-performance thin-walled ODS steel tubes. In addition, compared to conventional methods, the manufacturing process has a high material utilization rate of over 90%, which is a significant improvement.