The Effect of Nb-Content on the Microstructures and Corrosion Properties of CrFeCoNiNbx High-Entropy Alloys
Abstract
:1. Introduction
2. Experimental Section
3. Results and Discussion
4. Conclusions
- The CrFeCoNi alloy had an fcc granular structure. The microstructures became dual-phased dendritic microstructures after adding niobium. The CrFeCoNiNb0.2 and CrFeCoNiNb0.4 alloys were hypereutectic alloys; their dendrites were fcc phases, and the interdendrites were eutectic structures of fcc and Laves phases (hcp). The CrFeCoNiNb0.6 and CrFeCoNiNb alloys were hypoeutectic alloys; their dendrites were a Laves phase, and the interdendrites were still eutectic structures of fcc and Laves phases.
- The lattice constants of fcc and Laves phases in these CrFeCoNiNbx alloys increased with increasing Nb-content due to solid-solution strengthening. Increasing Nb-content also resulted in increasing the hardness of CrFeCoNiNbx alloys. The hardness increased from HV144 of CrFeCoNi alloy to HV652 of CrFeCoNiNb alloy.
- The corrosion resistance of CrFeCoNiNbx alloys slightly decreased after adding niobium because of their dual-phased dendritic microstructures. In addition, adding niobium into CrFeCoNiNbx alloys could stabilize and expand the passivation regions of these alloys in these two solutions. The fcc phase of each CrFeCoNiNbx alloy was more severely corroded than the Laves phase after polarization tests in 1 M deaerated H2SO4 and 1 M deaerated NaCl solutions.
- The CrFeCoNiNbx alloys possessed good corrosion resistance, and their hardness changed with Nb-content. This work thus provides a method to design a CrFeCoNiNbx alloy with suitable hardness and good corrosion resistance for different commercial applications.
Author Contributions
Funding
Conflicts of Interest
References
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Alloys (at.%) | Compositions (wt.%) | ||||
---|---|---|---|---|---|
Cr | Fe | Co | Ni | Nb | |
CrFeCoNi | 23.06 | 24.77 | 26.13 | 26.04 | N/A |
CrFeCoNiNb0.2 | 21.31 | 22.88 | 24.14 | 24.05 | 7.62 |
CrFeCoNiNb0.4 | 19.80 | 21.26 | 22.44 | 22.35 | 14.15 |
CrFeCoNiNb0.6 | 18.49 | 19.86 | 20.95 | 20.88 | 19.82 |
CrFeCoNiNb | 16.33 | 17.54 | 18.51 | 18.44 | 29.18 |
Alloys | fcc (Å) | Laves Phase (hcp) (Å) |
---|---|---|
CrFeCoNi | 3.577 | N/A |
CrFeCoNiNb0.2 | 3.578 | a = 4.773; c = 7.818 |
CrFeCoNiNb0.4 | 3.581 | a = 4.773; c = 7.831 |
CrFeCoNiNb0.6 | 3.590 | a = 4.798; c = 7.841 |
CrFeCoNiNb | 3.590 | a = 4.802; c = 7.848 |
Alloys | Compositions (Atomic Percent) | ||||
---|---|---|---|---|---|
Cr | Fe | Co | Ni | Nb | |
CrFeCoNi | |||||
Overall | 23.1 | 24.8 | 26.1 | 26.0 | N/A |
Cr-rich precipitate | 53.8 | 16.1 | 15.9 | 14.2 | N/A |
CrFeCoNiNb0.2 | |||||
Overall | 23.4 | 23.5 | 23.3 | 22.3 | 7.4 |
fcc | 24.2 | 26.5 | 24.3 | 23.2 | 1.8 |
hcp | 19.4 | 18.2 | 23.1 | 21.2 | 18.1 |
CrFeCoNiNb0.4 | |||||
Overall | 22.7 | 21.6 | 22.3 | 21.6 | 11.8 |
fcc | 25.2 | 24.3 | 22.2 | 24.9 | 3.5 |
hcp | 21.3 | 19.3 | 19.8 | 19.1 | 20.5 |
CrFeCoNiNb0.6 | |||||
Overall | 21.4 | 20.6 | 21.5 | 19.3 | 17.2 |
fcc | 25.1 | 24.4 | 21.8 | 23.0 | 5.7 |
hcp | 16.5 | 18.4 | 22.3 | 15.9 | 26.9 |
CrFeCoNiNb | |||||
Overall | 19.8 | 19.8 | 19.0 | 19.4 | 22.0 |
fcc | 26.7 | 24.3 | 18.4 | 25.5 | 5.1 |
hcp | 17.1 | 18.1 | 19.7 | 14.8 | 30.3 |
precipitate | 16.7 | 16.7 | 19.1 | 15.7 | 31.8 |
Alloys | Ecorr (VSHE) | icorr (A/cm2) | Epp (VSHE) | icrit (A/cm2) |
---|---|---|---|---|
CrFeCoNi | −0.086 | 35.1 | 0.014 | 120 |
CrFeCoNiNb0.2 | −0.084 | 15.8 | 0.082 | 47.1 |
CrFeCoNiNb0.4 | −0.082 | 52.1 | 0.183 | 64.4 |
CrFeCoNiNb0.6 | −0.078 | 10.1 | 0.122 | 41.9 |
CrFeCoNiNb | −0.068 | 22.3 | 0.132 | 28.0 |
304SS | −0.101 | 30.0 | 0.082 | 930 |
Alloys | Ecorr (VSHE) | icorr (μA/cm2) | Epp (VSHE) | icrit (μA/cm2) |
---|---|---|---|---|
CrFeCoNi | −0.081 | 0.28 | 0.049 | 17.3 |
CrFeCoNiNb0.2 | −0.192 | 12.3 | −0.086 | 33.2 |
CrFeCoNiNb0.4 | −0.207 | 21.1 | −0.006 | 58.1 |
CrFeCoNiNb0.6 | −0.212 | 72.5 | 0.152 | 46.7 |
CrFeCoNiNb | −0.221 | 12.0 | N/A | N/A |
304SS | −0.638 | 12.9 | N/A | N/A |
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Tsau, C.-H.; Yeh, C.-Y.; Tsai, M.-C. The Effect of Nb-Content on the Microstructures and Corrosion Properties of CrFeCoNiNbx High-Entropy Alloys. Materials 2019, 12, 3716. https://doi.org/10.3390/ma12223716
Tsau C-H, Yeh C-Y, Tsai M-C. The Effect of Nb-Content on the Microstructures and Corrosion Properties of CrFeCoNiNbx High-Entropy Alloys. Materials. 2019; 12(22):3716. https://doi.org/10.3390/ma12223716
Chicago/Turabian StyleTsau, Chun-Huei, Chen-Yu Yeh, and Meng-Chi Tsai. 2019. "The Effect of Nb-Content on the Microstructures and Corrosion Properties of CrFeCoNiNbx High-Entropy Alloys" Materials 12, no. 22: 3716. https://doi.org/10.3390/ma12223716