Effect of process parameters and electropolishing on the surface roughness of interior channels in additively manufactured nickel-titanium shape memory alloy actuators

Mingear, Jacob; Zhang, Bing; Hartl, Darren J.; Elwany, Alaa

doi:10.1016/j.addma.2019.03.027

Cited by 34 publications

(26 citation statements)

References 24 publications

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“…To the best of our knowledge, there are no studies explaining the effect of electropolished samples after being laser marked. However, there are many experimental works that have studied the response of surfaces being treated with electropolishing after laser cutting [ 38 , 39 ], laser sintering [ 40 ] or have used electropolishing as an alternative method to engrave surfaces as laser technologies [ 41 ]. Further studies should be performed to study the different surface topographies and their biological response.…”

Section: Discussionmentioning

confidence: 99%

Laser Surface Texturing and Electropolishing of CoCr and Ti6Al4V-ELI Alloys for Biomedical Applications

2020

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The interplay between a prosthetic and tissue represents an important factor for the fixation of orthopedic implants. Laser texturing tests and electropolishing were performed on two materials used in the fabrication of medical devices, i.e., CoCr and Ti6Al4V-ELI alloys. The material surface was textured with a diode-pumped solid state (DPSS) laser and its effect on the surface quality and material modification, under different combinations of laser power and marking speed, were investigated. Our results indicate that an increment of energy per unit length causes an incremental trend in surface roughness parameters. Additionally, phase transformation on the surface of both alloys was achieved. Chemical analysis by energy dispersive X-ray spectrometer (EDX) shows the formation of (Co(Cr,Mo)) phase and the M23C6 precipitate on the CoCr surface; while quantitative analysis of the X-ray diffractometer (XRD) results demonstrates the oxidation of the Ti alloy with the formation of Ti2O and Ti6O from the reduction of the α-Ti phase. The behaviors were both related with an increase of the energy per unit length. Control of the final surface roughness was achieved by an electropolishing post-treatment, minimizing the as-treated values. After polishing, a reduction of surface roughness parameters was obtained in a range between 3% and 44%, while no changes in chemical composition or present phases were observed.

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Section: Discussionmentioning

confidence: 99%

Laser Surface Texturing and Electropolishing of CoCr and Ti6Al4V-ELI Alloys for Biomedical Applications

2020

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“…The overhang angle (θ, measured with respect to the build direction) is a crucial parameter that affects the warp deflection of overhang regions as well as the surface roughness (Kamat and Pei 2019;Mingear et al 2019). An overhang angle of θ ∼ 45°is generally agreed upon as the critical value up to which overhang regions can be printed without support structures (Pakkanen et al 2016;Kadirgama et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigation of the origin of surface roughness in laser powder bed fused overhang regions

Feng

Kamat

Sabooni

et al. 2021

Virtual and Physical Prototyping

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Surface roughness of laser powder bed fusion (L-PBF) printed overhang regions is a major contributor to deteriorated shape accuracy/surface quality. This study investigates the mechanisms behind the evolution of surface roughness (R a) in overhang regions. The evolution of surface morphology is the result of a combination of border track contour, powder adhesion, warp deformation, and dross formation, which is strongly related to the overhang angle (θ). When 0°≤ θ ≤ 15°, the overhang angle does not affect R a significantly since only a small area of the melt pool boundaries contacts the powder bed resulting in slight powder adhesion. When 15°< θ ≤ 50°, powder adhesion is enhanced by the melt pool sinking and the increased contact area between the melt pool boundary and powder bed. When θ > 50°, large waviness of the overhang contour, adhesion of powder clusters, severe warp deformation and dross formation increase R a sharply.

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“…In detail, SLM often requires the adoption of post-processing treatments, not only for inducing tailored microstructures through heat treatments but also surface modifications [19,20], due to high roughness values and relevant dimensional errors [21,22]. The literature reports some works regarding the performances of conventional treatments, like electropolishing [23,24], and advanced finishing post-processing, like laser shock peening [25,26] and ultrasonic nanocrystal surface modification (UNSM) [27,28,29], on NiTinol samples. The main achievements obtained during the surface modification processing were good surface roughness values and improved surface responses, such as wear resistance, fatigue behavior, and biological response.…”

Section: Introductionmentioning

confidence: 99%

“…So far, only a few of these works have focused on SLMed NiTi parts [24,29]. As the initial surface condition and the mechanical properties of a rolled NiTi tape or wire are pretty different from the ones of an SLMed component, the performances of the post-processing treatments should be revised for the AMed NiTi alloys.…”

Section: Introductionmentioning

confidence: 99%

“…As the initial surface condition and the mechanical properties of a rolled NiTi tape or wire are pretty different from the ones of an SLMed component, the performances of the post-processing treatments should be revised for the AMed NiTi alloys. In fact, in a previous work the effect of the main SLM process parameters on the performances of electropolishing on NiTi samples containing interior channels was studied [24]. It was found that electropolishing can decrease the roughness only for low power densities, thanks to the smaller melt pools and columnar structures.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Ultrasonic Nanocrystal Surface Modification on the Microstructure and Martensitic Transformation of Selective Laser Melted Nitinol

et al. 2019

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Nitinol has significant potential for biomedical and actuating-sensing devices, thanks to its functional properties. The use of selective laser melting (SLM) with Nitinol powder can promote novel applications aimed to produce 3D complex parts with integrated functional performances. As the final step of the production route, finishing processing needs to be investigated both for the optimization of the surface morphology and the limit alteration of the Nitinol functional properties. In this work, the effect of an advanced method of surface modification, ultrasonic nanocrystal surface modification (UNSM), on the martensitic transformation and microstructure of SLM built Ni50.8Ti49.2 (at.%) was investigated. Scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry indicated that the UNSM process can generate stress-induced martensite, at least partially suppressing the martensitic transformation. The microhardness profile indicates that the UNSM process can affect the mechanical properties of the SLMed Nitinol sample in a range of up to approximately 750 μm in depth from the upper surface, while electron backscatter diffraction analysis highlighted that the initial austenitic phase was modified within a depth below 200 μm from the UNSMed surface.

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Effect of process parameters and electropolishing on the surface roughness of interior channels in additively manufactured nickel-titanium shape memory alloy actuators

Cited by 34 publications

References 24 publications

Laser Surface Texturing and Electropolishing of CoCr and Ti6Al4V-ELI Alloys for Biomedical Applications

Laser Surface Texturing and Electropolishing of CoCr and Ti6Al4V-ELI Alloys for Biomedical Applications

Experimental and numerical investigation of the origin of surface roughness in laser powder bed fused overhang regions

Effect of Ultrasonic Nanocrystal Surface Modification on the Microstructure and Martensitic Transformation of Selective Laser Melted Nitinol

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