Carbide Precipitation in a Low Alloyed Steel during Aging Studied by Atom Probe Tomography and Thermodynamic Modeling

Abstract

Carbide precipitation in martensitic low alloyed steels contributes to the mechanical properties through precipitation hardening. A high number density of carbides is desired to maximize the hardening effect, which is achieved through the precipitation of carbides on the dislocations in the martensitic structure. In this study, the nucleation, growth, and coarsening of vanadium and molybdenum carbides during aging at 600 °C for periods up to four weeks were investigated. The work covers characterization with atom probe tomography, which showed that the nucleation of V and Mo rich MC/M2C carbides takes place on dislocations. The growth of these carbides proceeds by the diffusion of elements to the dislocations, which has been modeled using Dictra software, confirming the rate of the reaction as well as the depletion of carbide formers in the matrix. For longer aging times, particle coarsening will decrease the number density of particles with a transition from dislocation-based carbides to separate rounded carbides.

Simultaneously Improving Microstructures and Wear Properties of Ni60 Coating by Heat Treatment

“…It is obvious that the diffraction peak intensity of Cr 7 C 3 , Cr 23 C 6 , and Cr 2 Ni 3 of the four composite coatings after heat treatment at 500 • C for 1 h is higher than that of other heat-treatment temperatures (Figure 1A 2 ). This can be attributed to the fact that laser cladding is a rapid non-equilibrium solidification process [20,21]. During the laser-cladding process, parts of boron atoms do not have enough time to combine with carbon or nickel atoms or the solute in the unstable supersaturated solid solution (Ni,Fe) in the molten pool [22].…”

Evolution of iron carbides during tempering of low-alloy tool steel studied with polarized small angle neutron scattering, electron microscopy and atom probe

“…Carbon has a strong impact on the strength of martensitic steel grades [5]. In quenched-hardened steel, carbon can be in the form of carbides like AT carbides or segregated into solid solution clouds (Cottrell atmospheres) [6]. Cementite precipitates in most steels below 700 • C, i.e.…”