Time and temperature dependent softening of a novel maraging steel fabricated by laser metal deposition

Artikel i vetenskaplig tidskrift, 2022

Durability is a critical factor for hot stamping dies from an economic point of view. Refurbishing the dies by depositing new material instead of replacement is a promising method to reduce the cost. For this reason, a newly developed maraging steel (NMS) was cladded on a hot work tool steel by means of directed energy deposition. After an optimized tempering, exposures at high temperatures were carried out on the cladded NMS in order to examine the softening resistance. The microstructural evolution of the material was systematically characterized using a combination of optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). The precipitate in the cladded steel was identified as Laves phase. The coarsening of this phase is considered as the main reason for the thermal softening of the steel at high temperatures. The coarsening behavior was also simulated by using the revised Langer-Schwartz-Wagner (LSW) model, which was in good agreement with experimental observations. Moreover, a mathematical model of precipitate strengthening was successfully applied to evaluate the softening behavior of the steel. This model can be used to predict the hardness/strength evolution of the investigated tool steel during its high-temperature service.