In situ alloying of NiTi: Influence of laser powder bed fusion (LBPF) scanning strategy on chemical composition

Chmielewska, Agnieszka; Wysocki, Bartłomiej; Buhagiar, Joseph; Michalski, B.; Adamczyk‐Cieślak, Bogusława; Gloc, Michał; Święszkowski, Wojciech

doi:10.1016/j.mtcomm.2021.103007

Cited by 17 publications

(23 citation statements)

References 33 publications

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“…Moreover, the number of melt runs and Ni evaporation can also affect the changes in martensitic and austenitic transformation temperatures of NiTi. These differences were described by Chmielewska et al (2021).…”

Section: Resultsmentioning

confidence: 90%

“…The highest decrease in nickel content was observed after the first melting (1.6 Wt.%), and each subsequent melt run resulted in a smaller reduction in the amount of nickel, which was 0.6 Wt.% and 0.4 Wt.% for the first and second remelting, respectively. The decrease in the amount of evaporated nickel might be due to the fact that pure elements were alloyed after first melting (no peaks of pure Ti and Ni were detected on XRD) and were more thoroughly blended after each melt run, and the evaporation of nickel from NiTi alloy is less than that of pure nickel (Chmielewska et al , 2021). Moreover, the number of melt runs and Ni evaporation can also affect the changes in martensitic and austenitic transformation temperatures of NiTi.…”

Section: Resultsmentioning

confidence: 99%

“…In the first set of the parameters, SM of each layer was performed with a wide range of energy densities (17–198 J/mm 3 ), and low laser powers in a range of 32.5 W–42.5 W. The low laser powers are, in our experience, beneficial for the defect free fabrication of the titanium alloys that was described in our previous study (Chmielewska et al , 2021). While a few parameters form the set of Parameters no.…”

Section: Parameters Nomentioning

confidence: 99%

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Laser powder bed fusion (LPBF) of NiTi alloy using elemental powders: the influence of remelting on printability and microstructure

Chmielewska

Wysocki

Gadalińska

et al. 2022

RPJ

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Purpose The purpose of this paper is to investigate the effect of remelting each layer on the homogeneity of nickel-titanium (NiTi) parts fabricated from elemental nickel and titanium powders using laser powder bed fusion (LPBF). In addition, the influence of manufacturing parameters and different melting strategies, including multiple cycles of remelting, on printability and macro defects, such as pore and crack formation, have been investigated. Design/methodology/approach An LPBF process was used to manufacture NiTi alloy from elementally blended powders and was evaluated with the use of a remelting scanning strategy to improve the homogeneity of fabricated specimens. Furthermore, both single melt and up to two remeltings were used. Findings The results indicate that remelting can be beneficial for density improvement as well as chemical and phase composition homogenization. Backscattered electron mode in scanning electron microscope showed a reduction in the presence of unmixed Ni and Ti elemental powders in response to increasing the number of remelts. The microhardness values of NiTi parts for the different numbers of melts studied were similar and ranged from 487 to 495 HV. Nevertheless, it was observed that measurement error decreases as the number of remelts increases, suggesting an increase in chemical and phase composition homogeneity. However, X-ray diffraction analysis revealed the presence of multiple phases regardless of the number of melt runs. Originality/value For the first time, to the best of the authors’ knowledge, elementally blended NiTi powders were fabricated via LPBF using remelting scanning strategies.

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Section: Resultsmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Parameters Nomentioning

confidence: 99%

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Laser powder bed fusion (LPBF) of NiTi alloy using elemental powders: the influence of remelting on printability and microstructure

Chmielewska

Wysocki

Gadalińska

et al. 2022

RPJ

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“…The parameters of both the melting and the remelting steps used for manufacturing NiTi and Ni+Ti parts are given in Table 4. The manufacturing procedure has been previously described in detail [53]. To homogenise chemical and phase composition, Ni+Ti materials were subjected to a solution heat treatment composed of a two-step vacuum heat treatment performed at 900 • C for 24 h followed by solutionising at 1150 • C for another 24 h and subsequent immediate quenching in water.…”

Section: Materials and Fabrication Proceduresmentioning

confidence: 99%

Biological and Corrosion Evaluation of In Situ Alloyed NiTi Fabricated through Laser Powder Bed Fusion (LPBF)

Chmielewska

Dobkowska

Kijeńska‐Gawrońska

et al. 2021

IJMS

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In this work, NiTi alloy parts were fabricated using laser powder bed fusion (LBPF) from pre-alloyed NiTi powder and in situ alloyed pure Ni and Ti powders. Comparative research on the corrosive and biological properties of both studied materials was performed. Electrochemical corrosion tests were carried out in phosphate buffered saline at 37 °C, and the degradation rate of the materials was described based on Ni ion release measurements. Cytotoxicity, bacterial growth, and adhesion to the surface of the fabricated coupons were evaluated using L929 cells and spherical Escherichia coli (E. coli) bacteria, respectively. The in situ alloyed NiTi parts exhibit slightly lower corrosion resistance in phosphate buffered saline solution than pre-alloyed NiTi. Moreover, the passive layer formed on in situ alloyed NiTi is weaker than the one formed on the NiTi fabricated from pre-alloyed NiTi powder. Furthermore, in situ alloyed NiTi and NiTi made from pre-alloyed powders have comparable cytotoxicity and biological properties. Overall, the research has shown that nitinol sintered using in situ alloyed pure Ni and Ti is potentially useful for biomedical applications.

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“…However, these phases or precipitates generally do not affect the shape memory effect (SME) directly, instead it changes the composition of the matrix [5]. At times, the distribution of Ni and Ti could be non-uniform in indicated by a number of additional small peaks in DSC curves which can adversely affect the shape recovery [47].…”

Section: Transformation Temperaturesmentioning

confidence: 99%

Control of Ni-Ti Phase Structure, Solid-State Transformation Temperatures and Enthalpies Via Control of L-Pbf Process Parameters

et al. 2021

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In situ alloying of NiTi: Influence of laser powder bed fusion (LBPF) scanning strategy on chemical composition

Cited by 17 publications

References 33 publications

Laser powder bed fusion (LPBF) of NiTi alloy using elemental powders: the influence of remelting on printability and microstructure

Laser powder bed fusion (LPBF) of NiTi alloy using elemental powders: the influence of remelting on printability and microstructure

Biological and Corrosion Evaluation of In Situ Alloyed NiTi Fabricated through Laser Powder Bed Fusion (LPBF)

Control of Ni-Ti Phase Structure, Solid-State Transformation Temperatures and Enthalpies Via Control of L-Pbf Process Parameters

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