Effect of the process control agent in the ball-milled powders and SPS-consolidation temperature on the grain refinement, density and Vickers hardness of Fe14Cr ODS ferritic alloys

Fe-14Cr-0.4Ti-0.25Y2O3 ferritic steels were produced by varying the amount of residual process control agent, PCA (ethanol), in the ball-milled powders and changing the spark-plasma-sintering, SPS, temperature. Near theoretical density (99.3%), high Vickers hardness (501–920 HV, measured by applying...

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Bibliographic Details
Published in:Powder technology 2019-04, Vol.347, p.103-113
Main Authors: Mihalache, V., Mercioniu, I., Velea, A., Palade, P.
Format: Article
Language:English
Subjects:
Ball milling
Consolidation
Diamond pyramid hardness
Dispersion hardening alloys
Dispersion hardening steels
Ethanol
Fe14Cr ODS ferritic steel
Ferritic stainless steels
Grain refinement
Grain size
Hardness
Heating
MA powder
Process control
Process controls
Residual process control agent
Spark plasma sintering
SPS densification
Temperature
Temperature effects
Theoretical density
Ultra-fine grains
Vickers hardness
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Summary:Fe-14Cr-0.4Ti-0.25Y2O3 ferritic steels were produced by varying the amount of residual process control agent, PCA (ethanol), in the ball-milled powders and changing the spark-plasma-sintering, SPS, temperature. Near theoretical density (99.3%), high Vickers hardness (501–920 HV, measured by applying a load of 100 g for 5 s) and fine grain size (26–36 nm), very stable against heating, can be achieved on ODS ferritic steels, consolidated from powders with a low amount of PCA and processing temperature in the range of 1000 °C–1100 °C. Additional grain refinement occurs near α → γ transition which is generated by the reaction of the traces of PCA with the ferritic matrix upon heating. High local temperatures and the evolved thermally activated processes, at the contact points between particles/at the particle surfaces during SPS-consolidation, were demonstrated to be the main factors responsible for improved densities and hardness. The role of PCA in the sintering, thermal and microstructure particularities and its impact on the quality of the final steel was thoroughly analysed throughout the work. [Display omitted] •Highly dense ultra-fine grained Fe14Cr ODS ferritic steel with high hardness was produced.•Density and Vickers hardness are determined by the amount of residual PCA in MA powders.•PCA dissolved upon heating within the Fe14Cr alloy promoted α → γ transformation.•Rapid cooling from the C- enriched regions caused grain refinement and hardening.•Post SPS treatment - stable nano-sized grains, reduction of (Fe,Cr)2O3 and M7C3.
ISSN:0032-5910
1873-328X
DOI:10.1016/j.powtec.2019.02.006