Contribution to Improving the Surface Treatment of M300 Maraging Steel Components Fabricated by Selective Laser Melting

Abdesselam Mechali

Doctoral thesis

Abstract:

Additive manufacturing (AM) is now a popular manufacturing technology that allows the production of complex structures while reducing material and increasing flexibility. A specific AM technology for metals, selective laser melting (SLM), is often used to produce robust metal parts. The widespread use of SLM in industry is limited due to increased production costs, lower surface quality, powder recycling, and worker safety. In order to achieve better performance, safety and economical and environmentally friendly manufactured components with SLM, we must avoid the above difficulties. In this dissertation, we analyze the effect of powder recycling, post-processing methods, and surface modification on the surface integrity and functional properties of M300 maraeenza steel parts produced by the SLM method (precipitation-hardable, ultra-high-strength steel widely used in the aerospace, automotive, tooling, and defense industries). Emphasis is placed on the simultaneous use of heat treatment, mechanical surface treatment (centrifugal tumbling) and electroplating (nickel plating). Experiments prove that repeated recycling of the powder causes tangible changes in the morphology of the powder and its properties, which can be prevented with the right post-processing steps. Heat treatment effectively preserves porosity and helps maintain microstructural stability, while mechanical tumbling significantly reduces surface roughness, with centrifugal tumbling being more effective at creating a more uniform surface morphology. The application of nickel coating to reclaimed surfaces provides much greater wettability uniformity and good corrosion resistance, especially for components made from recycled powder. This research provides a framework with improved post-processing and coating processes to improve the surface quality and functional properties of M300 martensitic steel components manufactured using the SLM method, and contributes to the knowledge of powder recycling and surface engineering in metal additive manufacturing. This provides an effective strategy for the economical and environmentally friendly production of metal parts for demanding industrial applications.

Abstract:

Additive Manufacturing (AM) is now a popular manufacturing technology and allows the fabrication of complex structures while reducing material and increasing flexibility. A specific metal AM technology, Selective Laser Melting (SLM), is frequently employed to fabricate robust metal parts. The extended use of SLM in industries is restricted due to increased production costs, lower surface quality, powder recycling, and worker safety. To attain enhanced performance, safety, and economical and environmentally friendly manufactured components with SLM, we need to avoid the aforementioned difficulties. In this dissertation we analyze the effects of powder recycling, post-processing methods, and surface modification on the surface integrity and functional properties of SLM-produced M300 maraging steel parts (precipitation hardenable, ultra-high-strength steel widely used in aerospace, automobile, tooling, and defence industries). The emphasis is placed on the simultaneous use of heat treatment, mechanical surface finishing (centrifugal tumbling), and electroplating (nickel). Experiments prove that repetitive powder recycling brings about tangible changes in powder morphology and surface features, which can be prevented using proper post-processing steps. Heat treatment effectively preserves porosity and helps in microstructural stability, while mechanical tumbling significantly reduces the surface roughness, with centrifugal tumbling being more effective in producing more uniform surface morphology. Applying a nickel coating on the tumbled surfaces provides much more uniformity in wettability and good corrosion resistance, especially on the component fabricated from recycled powder. This research presents a framework with improved post-processing and coating processes to enhance the surface quality and functional features of M300 maraging steel components manufactured via SLM and contributes to the knowledge on powder recycling and surface engineering in metal AM. This provides an effective strategy towards economic and green manufacturing of metal parts for demanding industrial applications

Keywords

Additive manufacturing, SLM, recycled martensitic steel M300, nickel coating, surface treatment, heat treatment, steel

Keywords

additive manufacturing, SLM, recycled M300 maraging steel, nickel coating, surface modification, heat treatment, steel blackening

Language used: English

Date on which the thesis was submitted / produced: 13. 8. 2026

Thesis defence

• Supervisor: Jana Petrů
• Reader: Juraj Beniak, Peter Pokorný, Aleš Mizera

VSB – Technical University of Ostrava

Fakulta strojní

Doctoral programme:
Strojírenská technologie