Prediction of Solidification Phases in Cr-Ni Stainless Steel Alloys Manufactured by Laser Based Powder Bed Fusion Process

Published

March 1, 2018

Author(s)

Gregor Jacob

Abstract

The knowledge of material phases in chromium (Cr), nickel (Ni) stainless steel alloys is sometimes important during parts and structures fabrication processed with additive manufacturing (AM) technologies. Laser-based powder bed fusion (LPBF) is one of these AM- process, which allowed to manufacture parts out of Cr-Ni stainless steel alloys. Mechanical behavior and microstructure of these LPBF manufactured steels are strongly dependent on their chemical composition and thermal conditions during the LPBF process as well as during the post process treatment. This current work is for users of laser-based PBF process to predict the material microstructure in Cr-Ni stainless steel alloys manufactured in a PBF process and help to develop guidelines for optimizing the microstructure in Cr-Ni stainless steel alloys and help to develop and to improve their manufacture process. This work outlines the use of established methods to predict the material microstructure of stainless steel weld metals for Cr-Ni stainless steel alloys manufactured by laser based Powder Bed Fusion Process. Predictions to the phase solidification in Cr-Ni stainless steel alloys were shown with the calculation of the ration between the chromium and nickel equivalent and inscribe these values into the phase reaction diagram helps to predict whether the solidification in a Cr-Ni stainless steel occurs either primary ferritic of austenitic. Inscribing these values of the chromium and nickel equivalent into the Schaeffler and DeLong diagram showed a strong effect of the nitrogen content, which led to a higher amount of retained austenite in the material microstructure, when the nitrogen content in the additively manufactured S17-4 PH increased. The stability of this retained austenite to decompose into the Cr-Ni stainless steel phase, such as martensite and cementite could be quantified with the calculation of the Md30 temperature and shown with the increase of the hardness after the as manufactured

Citation

Advanced Manufacturing Series (NIST AMS) - 100-14

Report Number

100-14

NIST Pub Series

Advanced Manufacturing Series (NIST AMS)

Pub Type

NIST Pubs

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DOI Link

Keywords

Additive Manufacturing, Austenite, Chromium, Cryogenic, Delong Diagram, Equivalent, Heat treatment, Precipitation Hardening, Stainless Steel, Martensite, Nickel Equivalent, Powder Bed Fusion, Schaeffler Diagram, Selective Laser Melting, and Sub-zero

Citation

Jacob, G. (2018), Prediction of Solidification Phases in Cr-Ni Stainless Steel Alloys Manufactured by Laser Based Powder Bed Fusion Process, Advanced Manufacturing Series (NIST AMS), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.AMS.100-14 (Accessed December 11, 2024)