Transient liquid phase bonding of ODS ferritic steel with a physical vapor deposited boron thin layer

Abstract

Transient liquid phase bonding (TLBP) was employed to join high-Cr oxide dispersion strengthened (ODS) ferritic steels under a high vacuum atmosphere using a uni-axial compressive hot press, and microstructural evolutions and mechanical properties of the joints were investigated. As insert material, pure boron thin layer was employed and fabricated by an electron beam assisted physical vapor deposition (EBPVD). The ODS ferritic steels with an EBPVD boron layer were successfully diffusion bonded at 1200 °C for 1 h under a pressure of 10 MPa. The microstructural observation and elemental analysis revealed that the TLBP with EBPVD boron shows a very narrow joint region and minimizes the microstructural degradation of base metals in comparison with the joint with an amorphous insert foil. Nevertheless, it was inevitable that the nano-oxide particle at the joint region was agglomerated by temporarily and partially melting of the base metal at the bonding interface by boron diffusion during the TLPB process. However, the joint presented comparable tensile properties with those of the base metal at room and elevated temperatures. It also has a more favorable ductility than TLPB with an amorphous insert foil.