Mechanical Properties and Microstructure Analysis of Additive/ Conventional Manufactured 13cr-4ni Soft Martensitic Steel
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2023-10-11
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Working Paper
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yes
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Abstract
Additive manufacturing (AM) opens new possibilities to manufacture metallic, complex, and customized parts. However, AM also faces geometrical and economical limitations especially in material quality and residual stresses. Joining AM parts with conventionally manufactured (CM) parts will be necessary in order to produce cost-efficiently the vast variety of products and might overcome those limitations. A few studies investigated part segmentation between AM/CM parts but none of them used martensitic steel with its complex microstructure. The analysed material is a soft martensitic stainless steel due to its low carbon content of 0.03 % C and Ni content of 4%. Its metallurgy is characterised by the prior austenite grains, packets, blocks, and laths. In this study, the grain size distribution of martensitic steel is correlated with the mechanical properties of different segments based on the Hall-Petch relationship. The AM segments are produced by direct energy deposition (DED), the CM segment by hot forming (HF), and the joint by laser welding (LW). The mechanical properties and microstructure are examined by Vickers micro hardness measurements, optical microscopy, Electron Backscatter Diffraction (EBSD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX). Hybrid specimens fail in the HF segment and show a limited elongation due to the laser weld. The best results in terms of ultimate tensile strength and elongation are achieved by the heat treated homogeneous DED specimens. Ultra fine grains are present in the LW segment after heat treatment which implies recrystallisation. Si- and Mn-oxides are present in the LW and DED segments. The martensitic grain size is defined by the length and width of the blocks separated by high-angle-boundaries. The correlation between grain size and hardness does not follow the Hall-Petch relationship. This means that other hardening mechanisms than grain boundary strengthening are dominant in soft martensitic steels.
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published
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4598646
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Social Science Research Network
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v1
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Subject
laser welding; Direct Energy Deposition; Martensitic Steel; Grain size measurement; Hall-Petch relationship
Organisational unit
03641 - Wegener, Konrad (emeritus) / Wegener, Konrad (emeritus)
02891 - ScopeM / ScopeM