Friction Welding of Oxide Dispersion Strengthened Steels and Its Tensile Properties for High Temperature Service Applications

Abstract

In this study Friction welding was employed to join oxide dispersion strengthened steels and ferritic/martensitic steel, and mechanical properties of the joints were investigated. 12Cr ODS steel was successfully friction welded under several welding pressures with similar ODS steel and ferritic/martensitic HT9 steel. Optical microscopic observation revealed that sound joints without any inclusions or micro- cracks at the welding interface, or degradation in the base metals. The microstructure observed by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) also reassured the sound joining condition within the welded materials. At room temperature, the joint had nearly the same tensile strength as that of the base metal, ferritic/martensitic steel. However, total elongation of the joint region significantly decreased, but reached 70% of the base metal, though a ductile fracture occurred far from the welding interface. The Vickers hardness test showed reasonable results for the welded specimens. Nano oxide particle distribution within the welded materials has been measured from the STEM microstructure and showed homogenous nano oxide particle distribution within the welded zone compared to the base metal. Therefore, it is considered that friction welding between ODS steel and F/M steel can be a very useful joining method to fabricate components in high temperature service applications.