Institute of Fundamental Technological Research
Polish Academy of Sciences

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Ahmad Serjouei

University of Derby (GB)


Recent publications
1.  Wood P., Libura T., Kowalewski Z.L., Williams G., Serjouei A., Influences of horizontal and vertical build orientations and post-fabrication processes on the fatigue behavior of stainless steel 316L produced by selective laser melting, Materials, ISSN: 1996-1944, DOI: 10.3390/ma12244203, Vol.12, No.24, pp.4203-1-19, 2019

Abstract:
In this paper, the influences of build orientation and post-fabrication processes, including stress-relief, machining, and shot-peening, on the fatigue behavior of stainless steel (SS) 316L manufactured using selective laser melting (SLM) are studied. It was found that horizontally-built (XY) and machined (M) test pieces, which had not been previously studied in the literature, in both stress-relieved (SR) or non-stress-relieved (NSR) conditions show superior fatigue behavior compared to vertically-built (ZX) and conventionally-manufactured SS 316L. The XY, M, and SR (XY-M-SR) test pieces displayed fatigue behavior similar to the XY-M-NSR test pieces, implying that SR does not have a considerable effect on the fatigue behavior of XY and M test pieces. ZX-M-SR test pieces, due to their considerably lower ductility, exhibited significantly larger scatter and a lower fatigue strength compared to ZX-M-NSR samples. Shot-peening (SP) displayed a positive effect on improving the fatigue behavior of the ZX-NSR test pieces due to a compressive stress of 58 MPa induced on the surface of the test pieces. Fractography of the tensile and fatigue test pieces revealed a deeper understanding of the relationships between the process parameters, microstructure, and mechanical properties for SS 316L produced by laser systems. For example, fish-eye fracture pattern or spherical stair features were not previously observed or explained for cyclically-loaded SLM-printed parts in the literature. This study provides comprehensive insight into the anisotropy of the static and fatigue properties of SLM-printed parts, as well as the pre- and post-fabrication parameters that can be employed to improve the fatigue behavior of steel alloys manufactured using laser systems.

Keywords:
selective laser melting, stainless steel 316L, fatigue, defect, fracture

Affiliations:
Wood P. - University of Derby (GB)
Libura T. - IPPT PAN
Kowalewski Z.L. - IPPT PAN
Williams G. - University of Derby (GB)
Serjouei A. - University of Derby (GB)

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