Influence of Ti Addition on the Microstructure and Mechanical Properties of High Boron Stainless Steels

High boron stainless steels with 2.0 and 3.0 wt % B, respectively, were prepared by vacuum induction melting method. Ti was added to the alloys to optimize the microstructure and improve the comprehensive mechanical properties. The borides are identified as TiB2 in the both alloys. In the alloy with 2.0 wt % B under as-cast state, the borides present by themselves rod-like or crystallographically faceted shape, with a size about 10 μm for the rod-like borides. When the boron content increases to 3.0 wt %, the amount of the rod-like borides increases, and some of these borides grow to 20 μm. After hot rolling, the borides transform to small particles with an average size below 3 μm, evenly distributing in the matrix for the 2.0 wt % B alloy. As the boron content rises to 3.0 wt %, some borides exhibit slender shape with a length less than 10 μm. The yield strength and the ultimate tensile strength improve from 381 and 732 MPa to 423 and 820 MPa, respectively, while the elongation declines from 11.2 to 4.6% when the content of boron increases from 2.0 to 3.0 wt %.