Interface engineering of additively manufactured maraging steel-H13 bimetallic structures

Abstract

This paper presents a study that aims to modify the interfacial characteristics of maraging steel-H13 bimetal structures through heat treatment procedures. Laser powder bed fusion (LPBF) was used to deposit maraging steel powder (MS1) on H13 hot work tool steel blocks. Subsequently, printed samples went through two different treatment cycles: (i) solution treatment, and (ii) aging treatment recommended for maraging steel. The microstructure, grain morphology, and mechanical response of MS1-H13 bimetals were assessed and compared with the as-built condition. Scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) techniques were used to analyze the interfacial modification upon heat treatment. Using uniaxial tensile testing and microhardness measurements along with 2D nanoindentation mapping, the mechanical properties of bimetal structures were correlated to the microstructural evolution of the samples during different heat treatments. Although the aging treatment was not effective to induce tangible microstructure changes, the solution treatment succeeded in the modification of MS1-H13 interface. A fully lath martensitic morphology was promoted across the interface, eliminating microstructure and hardness inhomogeneity as well as interface distinction between both sides. Finally, the solution treatment enhanced the mechanical properties of MS1-H13 bimetal structure by tripling the ultimate tensile strength.