Boron and Carbon Segregation to a Prior Austenite Grain Boundary in Tempered Martensitic Steel

Abstract

Controlling the solute segregation to prior austenite grain boundaries (PAGBs) is an important factor in enhancing the mechanical properties of martensitic steels. This study investigates the use of ultrawide field-of-view atom probe to characterize boron and carbon segregation at the PAGB in a tempered martensitic steel cooled at 10 K/s from austenitizing temperature. Clear differences could be observed between the inhomogeneous distribution of boron and carbon at the PAGB, where carbon appears to segregate during tempering to concentrate at the intersections of PAGB with low angle grain boundaries, and does not indicate site competition with boron, which appears to follow an equilibrium diffusion mechanism. These findings can aid in the development of tempered martensitic steels with optimal compositions and heat treatment profiles.

Keywords: Martensitic steel, Prior austenite grain boundary, Carbon, Boron