Maraging steel

About: Maraging steel is a research topic. Over the lifetime, 1728 publications have been published within this topic receiving 19886 citations. The topic is also known as: martensitic ageing steel.

Laser surface melting: A suitable technique to repair damaged surfaces made in 14 Ni (200 grade) maraging steel

Abstract: A high power solid Nd-YAG laser, operating in continuous mode, was used to re-melt the surface of a maraging steel, 14 Ni (200 grade), in different heat treatment conditions. Processing parameters were optimized for the employment of this technique as a repairing procedure of damaged surfaces to increase the useful life of tools made in maraging steels. Different zones can be found in laser-heated material. In addition, the absence of austenite reversion, consistent with the low nickel content of this steel, was found with the exception of a few very small pools of austenite found in a narrow layer in the heat-affected zone of samples corresponding to one of the studied heat treatment conditions of steel. Laser surface melting (LSM) combined with aging heat treatment causes a significant rise in the hardness (from 325 to more than 520 HV0.1) and in the wear resistance of the surface layer (with a decrease in the volume of lost material from 0.52 mm3 in the steel in the laser surface melted condition to 0.28 mm3 in the steel in laser surface melted and finally peak age hardening condition).

On the role of the powder stream on the heat and fluid flow conditions during Directed Energy Deposition of maraging steel—Multiphysics modeling and experimental validation

Abstract: The Directed Energy Deposition (DED) process of metals, has a broad range of applications in several industrial sectors. Surface modification, component repairing, production of functionally graded materials and more importantly, manufacturing of complex geometries are major DED’s applications. In this work, a multi-physics numerical model of the DED process of maraging steel is developed to study the influence of the powder stream specifications on the melt pool’s thermal and fluid dynamics conditions. The model is developed based on the Finite Volume Method (FVM) framework using the commercial software package Flow-3D. Different physical phenomena e.g. solidification, evaporation, the Marangoni effect and the recoil pressure are included in the model. As a new feature, the powder particles’ dynamics are modeled using a Lagrangian framework and their impact on the melt pool conditions is taken into account as well. In-situ and ex-situ experiments are carried out using a thermal camera and optical microscopy. The predicted track morphology is in good agreement with the experimental measurements. Besides, the predicted melt pool evolution follows the same trend as observed with the online thermal camera. Furthermore, a parametric study is carried out to investigate the effect of the powder particles incoming velocity on the track morphology. It is shown that the height-to-width ratio of tracks increases while using higher powder velocities. Moreover, it is shown that by tripling the powder particles velocity, the height-to-width ratio increases by 104% and the wettability of the track decreases by 24%.

Effect of build orientation on microstructure and tensile behaviour of selectively laser melted M300 maraging steel

Abstract: Additive Manufacturing (AM) is an emerging technology for fabrication of structural components, which refers to the processing through layer by layer addition of material using sliced CAD model of the desired geometry. Maraging steels are especially used in aerospace and tool industries due to their excellent combination of strength and fracture toughness. The present work aims at studying the effect of build orientation on microstructure and tensile behaviour of maraging steel (M300) processed by one of the AM techniques, namely, Selective Laser Melting (SLM). Initially, AM plates were processed in orientations of 0°, 45° and 90° and were further given solution treatment and aging. Measurement of density, surface roughness, hardness, residual stress and microstructural characterization of all samples were carried out and compared with those of conventionally melted (CM) samples. Transmission Electron Microscopy (TEM) confirmed the presence of Ni3Ti needle shaped precipitates and Fe2Mo globular precipitates after AM processing and also after heat treatment. Tensile testing of samples was conducted at a strain rate of 1 × 10−3 s−1. Better strength with reasonable ductility was observed in the samples built in 45° orientation compared to those at other build orientations and the properties in CM conditions. Solution treatment followed by aging decreased microstructural anisotropy caused by layer-wise effect due to laser processing. Surprisingly, most of the AM samples after heat treatment showed increase in strength without significant loss of ductility. Larger degree of work hardening and reversion of martensite to austenite might be the reasons for the observed behaviour. Typical ductile fracture featuring dimples due to microvoid coalescence were observed in all samples. Heat treatment not only improved tensile properties but also reduced anisotropy and residual stresses introduced during material processing.