Additive Manufacturing of 17-4 PH Stainless Steel: Post Processing Heat Treatment to Achieve Uniform Reproducible Microstructure

Published

December 21, 2015

Author(s)

Sudha Cheruvathur, Eric Lass, Carelyn E. Campbell

Abstract

17-4 precipitation hardenable (PH) stainless steel is a useful material when a combination of high strength and good corrosion resistance up to about 315 °C is required. In the wrought form this steel has a fully martensitic structure that can be strengthened by precipitation of fine Cu-rich FCC precipitates upon aging. When fabricated via additive manufacturing (AM), specifically laser powder-bed fusion, 17-4 PH exhibits a dendritic structure containing a substantial fraction of nearly 50 % of retained austenite along with BCC/martensite and fine niobium carbides preferentially aligned along interdendritic boundaries. The effect of post-build thermal processing on the material microstructure is studied in comparison to that of conventionally produced wrought 17-4 PH with the intention of creating a more uniform, fully martensitic microstructure. The recommended stress relief heat treatment currently employed in industry for post processing of AM 17-4 PH steel is found to have little effect on the as-built, dendritic microstructure. It is found that by implementing the recommended homogenization heat treatment regimen of Aerospace Materials Specification (AMS) 5355 for, CB7Cu-1, a casting alloy analog to 17-4 PH, the dendritic solidification structure is destroyed, resulting in a microstructure containing about 90 % martensite with 10 % retained austenite.

Citation

JOM Journal of the Minerals Metals and Materials Society

Volume

68

Issue

3

Pub Type

Journals

Download Paper

DOI Link

Keywords

additive manufacturing, stainless steel, microstructure, microstructural

Citation

Cheruvathur, S. , Lass, E. and Campbell, C. (2015), Additive Manufacturing of 17-4 PH Stainless Steel: Post Processing Heat Treatment to Achieve Uniform Reproducible Microstructure, JOM Journal of the Minerals Metals and Materials Society, [online], https://doi.org/10.1007/s11837-015-1754-4 (Accessed April 19, 2024)