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<p>The effect of heat treatment and ionic nitriding on the microstructure and surface performance of a newly developed precipitation-hardenable martensitic steel designed for laser powder bed fusion (L-PBF)&#xa0;was investigated. The alloy, formulated without cobalt or molybdenum and with reduced nickel content (~7&#xa0;wt.%), exhibits a refined cellular microstructure in the as-built state, with localised elemental segregation and nanoscale precipitation. A full factorial experimental design was applied to assess the individual and interactive effects of austenitisation, ageing, and nitriding on hardness, adhesive wear resistance, and corrosion behaviour. Ageing promoted Ni<sub>3</sub>Ti-type precipitation and increased hardness by 82% relative to the as-built state. Ionic nitriding produced a ~30&#xa0;µm hardened layer, enhanced surface hardness (HV10, test force of approximately 98.1 N), and reduced wear by up to 97%. However, this treatment significantly impaired corrosion resistance, lowering polarisation resistance by 89% and increasing the corrosion current density by a factor of 4.6. The absence of protective titanium oxides and the presence of nitriding-induced microcracks were identified as the main contributors to this degradation. These results suggest that ageing alone offers the most balanced post-processing strategy when wear and corrosion coexist, whereas nitriding should be restricted to applications dominated by surface wear.</p>

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Microstructural and functional impact of nitriding and heat treatments on an L-PBF-processed precipitation-hardenable martensitic steel

  • 期刊论文

  • 发表日期：

    2026年1月26日

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  • I.P. Gonzalo,
  • A.G. Pociño,
  • F.A. Antolin

摘要

The effect of heat treatment and ionic nitriding on the microstructure and surface performance of a newly developed precipitation-hardenable martensitic steel designed for laser powder bed fusion (L-PBF) was investigated. The alloy, formulated without cobalt or molybdenum and with reduced nickel content (~7 wt.%), exhibits a refined cellular microstructure in the as-built state, with localised elemental segregation and nanoscale precipitation. A full factorial experimental design was applied to assess the individual and interactive effects of austenitisation, ageing, and nitriding on hardness, adhesive wear resistance, and corrosion behaviour. Ageing promoted Ni3Ti-type precipitation and increased hardness by 82% relative to the as-built state. Ionic nitriding produced a ~30 µm hardened layer, enhanced surface hardness (HV10, test force of approximately 98.1 N), and reduced wear by up to 97%. However, this treatment significantly impaired corrosion resistance, lowering polarisation resistance by 89% and increasing the corrosion current density by a factor of 4.6. The absence of protective titanium oxides and the presence of nitriding-induced microcracks were identified as the main contributors to this degradation. These results suggest that ageing alone offers the most balanced post-processing strategy when wear and corrosion coexist, whereas nitriding should be restricted to applications dominated by surface wear.