PSI - Issue 53

Mariana Cunha et al. / Procedia Structural Integrity 53 (2024) 386–396 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 9 Microhardness profile of the cross-section of multi-layered volume

Localized SEM-EDS analysis was conducted to identify the dark particles observed during optical microscopy (Figure 10). The analysis confirmed that Z1, Z2, Z3, Z6 and Z7 correspond to oxides due to high concentrations of oxygen content. Notably, these spectra manifest elevated concentrations of chromium and manganese, clearly indicating the presence of corresponding oxides – specifically chromium oxide and manganese oxide eventually leading to depletion of Cr and Mn in the matrix as revealed in Figure 8.

Figure 10 - SEM BEI images from the top surface of the deposited AISI P20+Ni material

As previous stated, in proximity to the substrate, a prevalence of martensite is observable, signifying elevated hardness values within that region. The diminution of hardness values along the build direction can be attributed to two principal factors. First, the decrease in the fraction of martensite in the material, as the build progresses. Secondly, the depletion of alloying elements (Cr, Mn) via oxidation (as observed in Figure 8 & Figure 10), along the building direction of the printed material. 5. Conclusions The study aimed to develop sustainable metal powders for additive manufacturing (AM). AISI P20+Ni tool steel powder was successfully produced through disc milling yielding irregular and flake-like powder particles. An optimized disc milling procedure (PND 1) with a 75-minute duration was utilized for this study. Particle in size range 38-212 µm showed higher densities and better flowability than that of 53-150 µm. The mechanical milling in non controlled atmosphere did change the chemical composition of the milled particles. After printing the selected feedstock, lack of fusion was observed at the substrate-dilution interface. The residual heat accumulation from the bottom layers affected the microstructural evolution from martensitic to ferritic reaching the top most region.