In situ tempering of martensite during laser powder bed fusion of Fe-0.45C steel
(2022) In Materialia 23.- Abstract
During laser powder bed fusion (L-PBF), materials experience cyclic re-heating as new layers are deposited, inducing an in situ tempering effect. In this study, the effect of this phenomenon on the tempering of martensite during L-PBF was examined for Fe-0.45C steel. Detailed scanning electron microscopy, transmission electron microscopy, atom probe tomography, and hardness measurements indicated that martensite was initially in a quenched-like state after layer solidification, with carbon atoms segregating to dislocations and to martensite lath boundaries. Subsequent tempering of this quenched-like martensite was the result of two in situ phenomena: (i) micro-tempering within the heat affected zone and (ii) macro-tempering due to heat... (More)
During laser powder bed fusion (L-PBF), materials experience cyclic re-heating as new layers are deposited, inducing an in situ tempering effect. In this study, the effect of this phenomenon on the tempering of martensite during L-PBF was examined for Fe-0.45C steel. Detailed scanning electron microscopy, transmission electron microscopy, atom probe tomography, and hardness measurements indicated that martensite was initially in a quenched-like state after layer solidification, with carbon atoms segregating to dislocations and to martensite lath boundaries. Subsequent tempering of this quenched-like martensite was the result of two in situ phenomena: (i) micro-tempering within the heat affected zone and (ii) macro-tempering due to heat conduction and subsequent heat accumulation. Hardness measurements showed that although both influenced martensite tempering, micro-tempering had the most significant effect, as it reduced martensite hardness by up to ∼380 HV. This reduction was due to the precipitation of nano-sized Fe3C carbides at the previously carbon-enriched boundaries. Lastly, the magnitude of in situ tempering was found to be related to the energy input, where increasing the volumetric energy density from 60 to 190 J/mm3 reduced martensite hardness by ∼100 HV. These findings outline the stages of martensite tempering during L-PBF and indicate that the level of tempering can be adjusted by tailoring the processing parameters.
(Less)
- author
- Hearn, William ; Lindgren, Kristina ; Persson, Johan LU and Hryha, Eduard
- organization
- publishing date
- 2022-06
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Additive manufacturing, Carbon steel, In situ tempering, Intrinsic heat treatment, Laser powder bed fusion, Martensite
- in
- Materialia
- volume
- 23
- article number
- 101459
- publisher
- Elsevier
- external identifiers
-
- scopus:85131084562
- ISSN
- 2589-1529
- DOI
- 10.1016/j.mtla.2022.101459
- language
- English
- LU publication?
- yes
- id
- 5a57fd34-b2ce-4e7c-8aaf-f7f6ef0a4625
- date added to LUP
- 2022-12-28 08:35:51
- date last changed
- 2023-01-20 09:20:56
@article{5a57fd34-b2ce-4e7c-8aaf-f7f6ef0a4625,
abstract = {{<p>During laser powder bed fusion (L-PBF), materials experience cyclic re-heating as new layers are deposited, inducing an in situ tempering effect. In this study, the effect of this phenomenon on the tempering of martensite during L-PBF was examined for Fe-0.45C steel. Detailed scanning electron microscopy, transmission electron microscopy, atom probe tomography, and hardness measurements indicated that martensite was initially in a quenched-like state after layer solidification, with carbon atoms segregating to dislocations and to martensite lath boundaries. Subsequent tempering of this quenched-like martensite was the result of two in situ phenomena: (i) micro-tempering within the heat affected zone and (ii) macro-tempering due to heat conduction and subsequent heat accumulation. Hardness measurements showed that although both influenced martensite tempering, micro-tempering had the most significant effect, as it reduced martensite hardness by up to ∼380 HV. This reduction was due to the precipitation of nano-sized Fe<sub>3</sub>C carbides at the previously carbon-enriched boundaries. Lastly, the magnitude of in situ tempering was found to be related to the energy input, where increasing the volumetric energy density from 60 to 190 J/mm<sup>3</sup> reduced martensite hardness by ∼100 HV. These findings outline the stages of martensite tempering during L-PBF and indicate that the level of tempering can be adjusted by tailoring the processing parameters.</p>}},
author = {{Hearn, William and Lindgren, Kristina and Persson, Johan and Hryha, Eduard}},
issn = {{2589-1529}},
keywords = {{Additive manufacturing; Carbon steel; In situ tempering; Intrinsic heat treatment; Laser powder bed fusion; Martensite}},
language = {{eng}},
publisher = {{Elsevier}},
series = {{Materialia}},
title = {{In situ tempering of martensite during laser powder bed fusion of Fe-0.45C steel}},
url = {{http://dx.doi.org/10.1016/j.mtla.2022.101459}},
doi = {{10.1016/j.mtla.2022.101459}},
volume = {{23}},
year = {{2022}},
}