Effect of annealing on mechanical properties and microstructure evolution of borated stainless steels

A borated stainless steel based on the composition of type 304 stainless steel containing different amount of boron was fabricated through a conventional ingot metallurgy-hot working process, and the relationship between the microstructure and mechanical properties was investigated. As the content of boron increases, the volume fraction of (Fe,Cr)(2)B increases, as predicted by thermodynamic equilibrium calculations. As the annealing proceeds at 1180 degrees C, the plate-like shape of (Fe,Cr)(2)B turned into a spherical shape. In addition, brittle fracture of the boride was dominant before the heat-treatment, but ductile mode due to the formation of dimples in the austenite was dominant after heat-treatment. In the specimen containing 1.78 wt% of boron, the Cr and Ni contents of the austenite matrix were homogenized after annealing at 1180 degrees C for 192 h, and the strength and ductility were simultaneously improved. (C) 2018 Elsevier B.V. All rights reserved.