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Mechanical properties and microstructural characterization of selective laser melted 17-4 PH stainless steel

Mohamad Mahmoudi (Department of Industrial & Systems Engineering, Texas A&M University, College Station, Texas, USA)
Alaa Elwany (Department of Industrial & Systems Engineering, Texas A&M University, College Station, Texas, USA)
Aref Yadollahi (Department of Mechanical Engineering, Mississippi State University, Starkville, Mississippi, USA)
Scott M. Thompson (Department of Mechanical Engineering, Mississippi State University, Starkville, Mississippi, USA)
Linkan Bian (Department of Industrial and Systems Engineering, Mississippi State University, Starkville, Mississippi, USA)
Nima Shamsaei (Department of Industrial and Systems Engineering, Mississippi State University, Starkville, Mississippi, USA, and Center for Advanced Vehicular Systems (CAVS), Mississippi State University, Starkville, Mississippi, USA)

Rapid Prototyping Journal

ISSN: 1355-2546

Article publication date: 20 March 2017

2638

Abstract

Purpose

The purpose of this paper is to understand the effect of four different factors: building orientation, heat treatment (solution annealing and aging), thermal history and process parameters on the mechanical properties and microstructural features of 17-4 precipitation hardening (PH) stainless steel (SS) parts produced using selective laser melting (SLM).

Design/methodology/approach

Various sets of test samples were built on a ProX 100™ SLM system under argon environment. Characterization studies were conducted using mechanical tensile and compression test, microhardness test, optical microscopy, X-ray diffraction and scanning electron microscopy.

Findings

Results indicate that building orientation has a direct effect on the mechanical properties of SLM parts, as vertically built samples exhibit lower yield and tensile strengths and elongation to failure. Post-SLM heat treatment proved to have positive effects on part strength and hardness, but it resulted in reduced ductility. Longer inter-layer time intervals between the melting of successive layers allow for higher austenite content because of lower cooling rates, thus decreasing material hardness. On the other hand, tensile properties such as elongation to failure, yield strength and tensile strength were not significantly affected by the change in inter-layer time intervals. Similar to other AM processes, SLM process parameters were shown to be instrumental in achieving desirable part properties. It is shown that without careful setting of process parameters, parts with defects (porosity and unmelted powder particles) can be produced.

Originality/value

Although the manufacturing of 17-4 PH SS using SLM has been investigated in the literature, the paper provides the first comprehensive study on the effect of different factors on mechanical properties and microstructure of SLM 17-4 PH. Optimizing process parameters and using heat treatment are shown to improve the properties of the part.

Keywords

Acknowledgements

Authors appreciate the funding and support from Mississippi State University’s Office of Research and Economic Development (ORED) and Center for Advanced Vehicular Systems (CAVS). The current affiliation for Scott Thompson and Nima Shamsaei Laboratory for Fatigue and Additive Manufacturing Excellence (FAME), Department of Mechanical Engineering, Auburn University, Auburn, Alabama.

Citation

Mahmoudi, M., Elwany, A., Yadollahi, A., Thompson, S.M., Bian, L. and Shamsaei, N. (2017), "Mechanical properties and microstructural characterization of selective laser melted 17-4 PH stainless steel", Rapid Prototyping Journal, Vol. 23 No. 2, pp. 280-294. https://doi.org/10.1108/RPJ-12-2015-0192

Publisher

:

Emerald Publishing Limited

Copyright © 2017, Emerald Publishing Limited

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