TY - JOUR
T1 - Passive film formation and corrosion resistance of laser-powder bed fusion fabricated NiTi shape memory alloys
AU - Liu, Ming
AU - Zhu, Jia Ning
AU - Popovich, V. A.
AU - Borisov, E.
AU - Mol, J. M.C.
AU - Gonzalez-Garcia, Y.
PY - 2023
Y1 - 2023
N2 - Electrochemical tests and surface analysis measurements were performed to study the corrosion behavior in a 0.9 wt.% NaCl solution at 37 °C of three NiTi shape memory alloys fabricated by laser-powder bed fusion (L-PBF). The passive film characteristics and corrosion resistance of L-PBF NiTi showed different features as a function of their preparation process settings. The passivation rate for L-PBF NiTi surfaces including defects, such as keyhole pores and cracks which showed high electrochemical activity accelerating the passivation reaction process, was higher in the early stages of immersion, but the corrosion resistance provided by such a rapidly formed passive film containing higher defect density is lower than that for an initially defect-free surface. The thickness of the passive film including a higher defect density does not necessarily relate to the corrosion resistance. The L-PBF NiTi prepared at a linear energy density of 0.2 J/m and volumetric energy density of 56 J/mm3 shows the least defects. Also, an outer Ti-rich and inner Ni-rich dense and corrosion protective passive film could be obtained for these L-PBF NiTi samples, which also results in a relatively low Ni ion release rate. A passive film model based on thickness, composition and defect density properties as a function of processing conditions is proposed to explain the difference in corrosion resistance of the various L-PBF NiTi.
AB - Electrochemical tests and surface analysis measurements were performed to study the corrosion behavior in a 0.9 wt.% NaCl solution at 37 °C of three NiTi shape memory alloys fabricated by laser-powder bed fusion (L-PBF). The passive film characteristics and corrosion resistance of L-PBF NiTi showed different features as a function of their preparation process settings. The passivation rate for L-PBF NiTi surfaces including defects, such as keyhole pores and cracks which showed high electrochemical activity accelerating the passivation reaction process, was higher in the early stages of immersion, but the corrosion resistance provided by such a rapidly formed passive film containing higher defect density is lower than that for an initially defect-free surface. The thickness of the passive film including a higher defect density does not necessarily relate to the corrosion resistance. The L-PBF NiTi prepared at a linear energy density of 0.2 J/m and volumetric energy density of 56 J/mm3 shows the least defects. Also, an outer Ti-rich and inner Ni-rich dense and corrosion protective passive film could be obtained for these L-PBF NiTi samples, which also results in a relatively low Ni ion release rate. A passive film model based on thickness, composition and defect density properties as a function of processing conditions is proposed to explain the difference in corrosion resistance of the various L-PBF NiTi.
KW - Auger electron spectroscopy
KW - Corrosion
KW - Laser-powder bed fusion
KW - NiTi
KW - Passivation
KW - Shape memory alloys
KW - X-ray photoelectron spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=85150286523&partnerID=8YFLogxK
U2 - 10.1016/j.jmrt.2023.01.204
DO - 10.1016/j.jmrt.2023.01.204
M3 - Article
AN - SCOPUS:85150286523
SN - 2238-7854
VL - 23
SP - 2991
EP - 3006
JO - Journal of Materials Research and Technology
JF - Journal of Materials Research and Technology
ER -