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Metals 2019, 9(2), 199; https://doi.org/10.3390/met9020199

Advanced Mechanical Strength in Post Heat Treated SLM 2507 at Room and High Temperature Promoted by Hard/Ductile Sigma Precipitates

1
Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-97187 Luleå, Sweden
2
Department of Ceramics, Institute of Mater. Res. of the Slovak Academy of Sciences, Watsonova 47, Košice, Slovakia
*
Author to whom correspondence should be addressed.
Received: 21 January 2019 / Accepted: 31 January 2019 / Published: 8 February 2019
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Abstract

Duplex stainless steel, 71 wt.% austenite, 13 wt.% ferrite and 16 wt.% sigma, was made upon heat treating of fully ferritic as-built selective laser melted (SLM) 2507 stainless steel at 1200 °C. Formation of sigma phase in the heat treated SLM 2507 was investigated using optical microscopy and scanning electron microscopy (SEM). The heat treated SLM 2507 demonstrated a yield strength of 686 MPa, ultimate tensile strength of 920 MPa and an elongation of 1.8% at room temperature with a brittle fracture morphology. Precipitation of sigma phase during heat treatment and slow cooling improved the mechanical and wear properties at high temperatures (1200 °C and 800 °C, respectively). The tensile strength and elongation of the heat treated SLM 2507 was measured 400 MPa and 20% as compared to casted duplex steel with 19 MPa and 30% elongation at 1200 °C. The 20 times higher mechanical strength as compared to casted duplex steel was attributed to sigma precipitates. Tribological behaviour of heat treated duplex SLM 2507 containing sigma at 800 °C showed very low wear rate of 4.5 × 10−5 mm3/mN compared to casted duplex steel with 1.6 × 10−4 mm3/mN. View Full-Text
Keywords: selective laser melting; duplex stainless steel; heat treatment; mechanical properties selective laser melting; duplex stainless steel; heat treatment; mechanical properties
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Saeidi, K.; Alvi, S.; Lofaj, F.; Petkov, V.I.; Akhtar, F. Advanced Mechanical Strength in Post Heat Treated SLM 2507 at Room and High Temperature Promoted by Hard/Ductile Sigma Precipitates. Metals 2019, 9, 199.

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