Hot Corrosion Behavior of CoCrNi Medium-entropy Alloys Fabricated by Laser Powder Bed Fusion

doi:10.11902/1005.4537.2025.170

Journal of Chinese Society for Corrosion and protection

2026, Vol. 46

Issue (1): 115-125 DOI: 10.11902/1005.4537.2025.170

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Hot Corrosion Behavior of CoCrNi Medium-entropy Alloys Fabricated by Laser Powder Bed Fusion

ZHOU Xiaobao¹, WANG Ziteng², REN Yanjie¹^,²(

), DONG Shaoyang², GAN Lang², LI Cong²

^1.School of Intelligent Manufacturing and Energy Engineering, Zhejiang University of Science and Technology, Hangzhou 310023, China
^2.Department of Energy and Power Engineering, Changsha University of Science and Technology, Changsha 410076, China

Cite this article:

ZHOU Xiaobao, WANG Ziteng, REN Yanjie, DONG Shaoyang, GAN Lang, LI Cong. Hot Corrosion Behavior of CoCrNi Medium-entropy Alloys Fabricated by Laser Powder Bed Fusion. Journal of Chinese Society for Corrosion and protection, 2026, 46(1): 115-125.

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Abstract

Herein, the corrosion behavior of two CoCrNi medium entropy alloys (MEA) with the same chemical composition, but prepared by laser powder bed fusion (LPBF) and rolling respectively, was comparatively investigated beneath a molten mixed salt film of 50%KCl + 50%Na₂SO₄ (mass fraction) at 650 ^oC by means of electrochemical impedance spectroscopy. The results reveal that the LPBF-fabricated alloy exhibits a double capacitive response, whereas the rolled alloy displays a transition from double capacitive characteristics to diffusion-dominated behavior with increasing corrosion time. Microscopic characterization shows that the LPBF-fabricated alloy surface forms a layered multi-product consisting of Co₃O₄, NiO, Ni₃S₂ and Cr₂O₃, while the rolled alloy surface generates only a single Cr₂O₃, accompanied by severe internal oxidation. The distinct corrosion behavior may be attributed to the influence of grain boundary density and grain boundary distribution characteristics on the metal atom diffusion and corrosive medium permeation, thereby affecting the characteristics of electrochemical impedance spectra and the composition and structure of corrosion product films.

Key words: hot corrosion laser powder bed fusion CoCrNi MEA electrochemical impedance spectroscopy microstructure

Received: 06 June 2025 32134.14.1005.4537.2025.170

ZTFLH:

TG174

Fund: National Natural Science Foundation of China(52171066);National Natural Science Foundation of China(52175129)

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	ZHOU Xiaobao
	WANG Ziteng
	REN Yanjie
	DONG Shaoyang
	GAN Lang
	LI Cong

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https://www.jcscp.org/EN/10.11902/1005.4537.2025.170 OR https://www.jcscp.org/EN/Y2026/V46/I1/115

Fig.1 Morphology of CoCrNi MEA powder for LPBF (a), particle size distribution (b) and schematic illustration of the scanning strategy (c)

Fig.2 Schematic of electrochemical test system

Fig.3 LPBF CoCrNi MEA at low magnification (a), LPBF CoCrNi MEA at high magnification (b), rolled CoCrNi MEA at low magnification (c) and XRD profiles of LPBF and rolled CoCrNi MEAs (d)

Fig.4 EBSD characterization of LPBF and rolled CoCrNi MEAs: (a1, b1) grain orientation maps and inverse pole figures,(a2, b2) grain boundary misorientation distribution histograms, (a3, b3) Kernel average misorientation (KAM) mappings

Fig.5 Nyquist plots (a) and Bode plots (b) of EIS spectrum of LPBF CoCrNi MEAs under salt film corrosion

Fig.6 Nyquist plots (a) and Bode plots (b) of EIS spectrum of rolled CoCrNi MEAs under salt film corrosion

Fig.7 Equivalent circuits representing the corrosion of LPBF CoCrNi MEAs and rolled CoCrNi MEAs beneath a molten 50%KCl + 50%Na₂SO₄ film at 650 ^oC in air: (a) when the alloy is covered with a complete and dense protective salt layer, (b) when the alloy is covered with a loose, porous and uneven protective salt layer, (c) when the alloy is under charge transfer and diffusion control

Table 1 Fitting parameters for electrochemical impedance spectra of LPBF and rolled CoCrNi MEAs under high temperature salt film corrosion

Fig.8 XRD pattern of LPBF CoCrNi MEA (a) and rolled CoCrNi MEA (b) corrosion in the presence of 50%KCl + 50% Na₂SO₄ film for 48 h

Fig.9 Cross-section morphologies of LPBF CoCrNi MEA of corrosion in the presence of 50%KCl + 50%Na₂SO₄ film for 48 h: (a) low magnification, (b) high magnification, (c) element EDS map

Fig.10 Cross-section morphologies of rolled CoCrNi MEA of corrosion in the presence of 50%KCl + 50%Na₂SO₄ film for 48 h: (a) low magnification, (b) high magnification, (c) element EDS map

Fig.11 Schematic diagram illustrating the corrosion mechanisms of LPBF and rolled CoCrNi MEAs under a 50%KCl-50% Na₂SO₄ molten salt film

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