Novel Laser Technology to Enhance the Wear Resistance of Shape Memory NiTi Alloy for Total Joint Replacement Applications

NiTi shape memory alloys (SMAs) have the best combination of properties among the different SMAs. However, the limitations of conventional manufacturing processes and the poor manufacturability of NiTi have critically limited its full potential applicability. Thus, additive manufacturing, commonly known as 3D printing, has the potential to be a solution in fabricating complex NiTi smart structures. Recently, a number of studies on Selective Laser Melting (SLM) of NiTi were conducted to explore the various aspects of SLM-produced NiTi. Compared to producing conventional metals through the SLM process, the fabrication of NiTi SMA is much more challenging. Not only do the produced parts require a high density that leads to good mechanical properties, strict composition control is needed as well for the SLM NiTi to possess suitable phase transformation characteristics. Additionally, obtaining a good shape memory effect from the SLM NiTi samples is another challenging task that requires further understanding. This paper presents the results of the effects of energy density and SLM process parameters on the properties of SLM NiTi. Its shape memory properties and potential applications were then reviewed and discussed.

Nickel titanium

Selective Laser Melting

Smart material

Pseudoelasticity

10.3390/ma11040519

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Investigation on laser assisted welding of NiTi shape memory alloy

Vivek Kumar I. A. Palani

Nickel titanium

Source

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Generation of NiTi-SMA-micro parts using two step laser sintering

S. Dudziak Oliver Meier Henrik Mewes Andreas Ostendorf

Due to special properties like superelasticity and reversible temperature induced deformation shape memory materials offer a unique potential in various fields of application. In medical engineering the shape memory effect, e.g. of NiTi alloys, realized on human body temperature, is in focus. Whilst the application of NiTi based products in cardiology is the most-known one, shape memory alloys can be found nowadays in trauma and reconstructive surgery as well. Surgeons demand for micro grippers to design active micro catheters for cerebric surgery. Furthermore, it is the idea to create NiTi micro actors for the directed stimulation of nerves. Because of its material properties resulting in adverse machinability, there are no machining methods for the production of NiTi micro parts. The generation of micro scale NiTi samples using two step laser sintering could recently be achieved at Laser Zentrum Hannover. As base material, spherical NiTi powders are used. The laser beam source is a 50 W fibre laser. Varying the compression of the powder bed as well as process parameters, micro parts of different density with a minimal width of <100 µm could be generated. Thereby, the special material properties are preserved: The sintered structures show the one way shape memory effect.

Nickel titanium

Machinability

Pseudoelasticity

Selective laser sintering

10.2351/1.5061148

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