Comparative investigations into microstructural and mechanical properties of as‐cast and laser powder bed fusion (LPBF) fabricated duplex steel (1.4517)

Abstract

A methodology is presented that compares the microstructural and mechanical properties of as-cast and additive-made ferritic-austenitic duplex steel 1.4517. Microstructure of approximately equal amounts of ferrite and austenite measured in as-cast material could not be replicated in post heat-treated laser powder bed fusion samples after 30 min and 60 min of post heat treatment. This is attributed to nitrogen loss during powder atomization which left fewer austenite formers. Postheat treated laser powder bed fusion samples of duplex structure had its austenite content repeatedly adjusted between 38 % and 40 %. As-built laser powder bed fusion tensile specimens which had a ferritic microstructure recorded high tensile and yield strength but had very poor elongation. Post heat-treated duplex laser powder bed fusion tensile specimen built in both horizontal and vertical orientations had good tensile and yield strength comparable to conventional casting processes; Tensile strength -739 MPa (horizontal), 759 MPa (vertical); Yield strength (R p0.2 ) -489 MPa (horizontal), 525 MPa (vertical). The horizontally built duplex specimen had a very high elongation of 32 % than the vertical (11 %) or conventionally reported (22 %). This work establishes the 1.4517 duplex steel as a good candidate with good mechanical properties when processed by additive manufacturing.Keywords: Duplex-steel / additive manufacturing / microstructure / tensile test / Calphad method Schlüsselwörter: Duplex-Stahl / additive Fertigung / Mikrostruktur / Zugversuch /

A Comparative Investigation of Duplex and Super Duplex Stainless Steels Processed through Laser Powder Bed Fusion

“…It has been reported that phases with concentrations below 5%, including chromium nitrides, micro-crystalline austenite, and process-related defects, such as pores and cracks, are identified by the EBSD detector as a fraction of zero solutions. Therefore, they are excluded from the calculation of the ferrite and austenite phase fraction [18]. The crystallographic orientation is influenced by the LPBF process parameters [34].…”

“…The crystallographic orientation is influenced by the LPBF process parameters [34]. Therefore, they are excluded from the calculation of the ferrite and austenite phase fraction [18]. In this case, the DSS and SDSS process parameters of optimum samples were almost identical in terms of laser power, scan speed, and hatch distance.…”

“…Studies can be found in the literature where the process optimization of commercially available duplex and super duplex stainless steel powders is presented [16,17]. In some studies, the focus is on the analysis of the microstructure and the impact on mechanical properties [18][19][20], and in others, research is performed to quantify phases and their effect on corrosion resistance [21,22]. Different methodologies for the parameter optimization of DSS and SDSS LPBF processing were based on experiments exploring a wide range of the processing parameters combined with statistical analyses, or on thermodynamic calculations studying the formation of embrittling phases upon laser processing or post-AM heat treatment [9,[15][16][17][18]20,22].…”

“…In some studies, the focus is on the analysis of the microstructure and the impact on mechanical properties [18][19][20], and in others, research is performed to quantify phases and their effect on corrosion resistance [21,22]. Different methodologies for the parameter optimization of DSS and SDSS LPBF processing were based on experiments exploring a wide range of the processing parameters combined with statistical analyses, or on thermodynamic calculations studying the formation of embrittling phases upon laser processing or post-AM heat treatment [9,[15][16][17][18]20,22]. Other studies correlated microstructure evolution and second-phase precipitation with mechanical properties (ultimate tensile strength, elongation at break, microhardness) and/or corrosion behavior [15,20,23,24].…”

Effects of Powder Characteristics and Chemical Composition on the Properties of 25Cr7Ni Stainless Steel Fabricated by Laser-Powder Bed Fusion and Evaluation of Process Simulation

“…The corrosion resistance of the alloy system is heavily governed by the Cr, Mo, and N content [12,13]. Few studies have been conducted to establish the influence of the powder attributes and chemical composition of the starting powder on the mechanical properties and microstructure of L-PBF fabricated 25Cr7Ni stainless steel [14][15][16][17], and there has been no qualification of corrosion properties of the fabricated parts. The present study seeks to address this research gap.…”