Effects of additive manufacturing processes and isothermal aging on the microstructure and properties of 13-8 Mo precipitation hardening martensitic stainless steel

Authors

M. J. Benoit, University of British Columbia Okanagan
S. Tabaie, University of British Columbia Okanagan
T. Waqar, University of British Columbia Okanagan
T. Ganton, University of British Columbia Okanagan
B. S. Amirkhiz, CanmetMATERIALS
A. Hadadzadeh, University of MemphisFollow
A. Nasiri, Dalhousie University

Abstract

The objective of this study is to evaluate the effect of AM process on the microstructure and properties of PH 13-8 Mo steel in the as-printed and aged conditions. Samples were produced by both laser powder bed fusion (L-PBF) and arc directed energy deposition (arc-DED) and characterized in both the as-printed and direct aged (530 °C, 3 h) conditions. The as-printed L-PBF sample was characterized by a nearly fully martensitic microstructure, while the as-printed arc-DED microstructure included coarser lath martensite, 2.3 vol % retained austenite, and δ-ferrite. However, the hardness of the as-printed arc-DED sample (401.0 HV1) was greater than the as-printed L-PBF (347.7 HV1), due to precipitation of β-NiAl particles in the as-printed arc-DED condition. Aging of the L-PBF sample resulted in microstructure refinement, precipitation of β-NiAl particles, and a corresponding increase in hardness to 508.3 HV1. Conversely, aging the arc-DED sample resulted in the formation of a large amount of reverted austenite (7.2 vol %), Cr23C6 particles, as well as β-NiAl particles, but was unable to remove the δ-ferrite grains. Consequently, the hardness of the aged arc-DED sample was similar to the as-printed value (428.3 HV1). It is concluded that the selection of the AM process has an important effect on the microstructure and properties of PH 13–8 Mo steel, and that a single-step direct aging heat treatment is suitable for samples produced by L-PBF but not arc-DED.

Publication Title

Additive Manufacturing

Recommended Citation

Benoit, M., Tabaie, S., Waqar, T., Ganton, T., Amirkhiz, B., Hadadzadeh, A., & Nasiri, A. (2023). Effects of additive manufacturing processes and isothermal aging on the microstructure and properties of 13-8 Mo precipitation hardening martensitic stainless steel. Additive Manufacturing, 72 https://doi.org/10.1016/j.addma.2023.103615