Abstract
In this work, a new approach for compaction of the gas-atomized 18Ni300 maraging steel at two different temperatures of 1050 °C and 1150 °C using a progressive SPS technology is studied. Moreover, the influence of two heat treatments combining solution annealing and aging (SAT) and simply aging treatment (AT) on the microstructure and mechanical properties is investigated. It is found that samples compacted at 1050 °C had higher porosity compared to the almost non-porous material produced at 1150 °C. In addition, the difference of 100 °C for the compaction temperature successfully reduces the porosity from 0.86% down to 0.08%. Additionally, we discovered that the higher the compaction temperature, the higher the amount of retained γ-Fe which positively affects the ductility of the samples. The subsequential heat treatment results in precipitation strengthening via the Ni3Mo precipitates. Microhardness of the SPS1050 and SPS1150 samples increase from 303 ± 13 HV0.1 and 360 ± 5 HV0.1 to 563 ± 31 HV0.1 and 606 ± 17 HV0.1, respectively. The sample compacted at 1150 °C shows the highest ultimate tensile strengths reaching up to 1940 ± 6 MPa, while also showing 4% ductility.
Highlights
Maraging steels are ultra-high-strength martensitic steels with a very low carbon content
The Spark plasma sintering (SPS) compaction method was used as an alternative to producing bulk semi-samples, which mechanical properties may outperform those prepared by additive manufacturing
The present work demonstrates a novel approach for the compaction strategy for the maraging steels using an SPS to produce almost non-porous material
Summary
Maraging steels are ultra-high-strength martensitic steels with a very low carbon content (generally ≤0.03 wt.%). The main reason for such good mechanical properties of the maraging steels is the precipitation hardening during heat treatment, allowing to form a few types of nano-sized precipitates (Ni3(Mo, Ti), Fe2Mo) homogeneously dispersed within the material volume [5,6,7]. Due to their admirable properties, these steels have a wide range of applications, e.g., can be used for tooling components, aerospace and hydrospace industry, as well as for motor racing applications [4,8,9,10]. Considering the good weldability, maraging steels are suitable for production via classical methods and by way of modern processes, such as additive manufacturing [4,9,11,12] and powder metallurgy [13,14]
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