Map of surface hardening of the DP600 steel using the Yb:fiber laser, and force spectroscopy characterization

Abstract

In dual-phase (DP) steels, the morphology, distribution, and volume fraction of the martensite phase affect several properties of the metal. In this work, the DP600 steel was laser treated using an Yb:fiber laser with different process parameters. The objective was to map the laser surface hardening and construct a process chart. Additionally, force spectroscopy was proposed to evaluate microstructural phases stiffness. The elastic constant of ferrite from both the base material and the laser treated area was approximately the same, about 20% lower than that of martensite from the treated area. From the processes chart, conclusion was more intense hardening, with needle-like structures, but in thinner layers, requires specific energies of about 2.0 kJ/cm2, while greater volume of martensitic phase is accomplished at 4.0 kJ/cm2. Tensile yield increased 30%, though tensile strength augmented 5–10%. In addition, lower laser scanning velocities was more suitable to obtain greater volumes of martensite.