Passive film formation and corrosion resistance of laser-powder bed fusion fabricated NiTi shape memory alloys

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...

Superelastic response and damping behavior of additively manufactured Nitinol architectured materials

In energy absorption applications, architectured metallic materials generally suffer from unrecoverable deformation as a result of local yield damage or inelastic buckling. Nitinol (NiTi) offers recoverable deformation and energy dissipation due to its unique superelasticity, which can change the way we design and additively manufacture...

Achieving superelasticity in additively manufactured Ni-lean NiTi by crystallographic design

Superelastic metallic materials possessing large recoverable strains are widely used in automotive, aerospace and energy conversion industries. Superelastic materials working at high temperatures and with a wide temperature range are increasingly required for demanding applications. Until recently, high-temperature superelasticity has only...

Corrosion and passive film characteristics of 3D-printed NiTi shape memory alloys in artificial saliva

Electrochemical tests and surface analysis were applied to study the corrosion behavior and passive film characteristics of three-dimensional-printed NiTi shape memory alloys fabricated by laser-powder bed fusion (L-PBF) in artificial saliva at 37 °C. The passivity of L-PBF NiTi shows to be influenced by the process parameters and resulting...

Effect of heat treatment on microstructure and functional properties of additively manufactured NiTi shape memory alloys

Additive manufacturing of NiTi shape memory alloys has attracted attention in recent years, due to design flexibility and feasibility to achieve four-dimensional (4D) function response. To obtain customized 4D functional responses in NiTi structures, tailorable phase transformation temperatures and stress windows as well as one-way or two-way...

Healing cracks in additively manufactured NiTi shape memory alloys

The pursuit of enhancing NiTi superelasticity through laser powder bed fusion (L-PBF) and [001] texture creation poses a challenge due to increased susceptibility to hot cracking in the resulting microstructure with columnar grains. This limitation restricts NiTi's application and contributes to material waste. To overcome this, we introduce...

Additive manufacturing of functionally graded inconel 718: Effect of heat treatment and building orientation on microstructure and fatigue behaviour

This paper addresses the effect of the post-process heat treatments on the microstructure and fatigue crack growth behaviour of the functionally graded (FG) laser powder bed fusion (L-PBF) Inconel 718 (IN718) superalloy. Sets of samples were additively manufactured (AM) altering the process parameters, namely the laser power, the laser...

Controlling microstructure evolution and phase transformation behavior in additive manufacturing of nitinol shape memory alloys by tuning hatch distance

Laser powder bed fusion (L-PBF), categorized as additive manufacturing technique, has a capability to fabricate NiTi (Nitinol) shape memory alloys with tailorable functional properties and complex geometries. An important processing parameter, hatch distance (h), is often related to macroscale structural defects; however, its role on...

Effect of Hot Isostatic Pressing on the Microstructure of Directionally Solidified Nickel Alloy After SLM

The paper investigates the effect of hot isostatic pressing of single-crystal nickel-based alloy manufactured by selective laser melting (SLM) with a high-temperature substrate preheating. A study of the structure and phase composition of the material before and after treatment has been carried out. It was found that as a result of such...

Effect of microstructure induced anisotropy on fatigue behaviour of functionally graded Inconel 718 fabricated by additive manufacturing

In this paper, the effect of microstructural anisotropy on the fatigue crack growth behaviour of the functionally graded Inconel 718 fabricated through laser powder bed fusion (L-PBF) is investigated. Different manufacturing parameters, including low and high laser powers, were used to produce a variety of non-graded (NG) and functionally...

Heat treatment effect on the structure formation of directionally solidified nickel alloy after SLM

The aim of this study was to determine the influence of heat treatment on the microstructure of single-crystal nickel-based alloy manufactured by selective laser melting with a high-temperature substrate preheating. The change of gamma/gamma prime -phases ratio was established as a result of various heat treatment modes.

Predictive analytical modelling and experimental validation of processing maps in additive manufacturing of nitinol alloys

Nitinol (NiTi) shape memory alloys fabricated by Laser Powder Bed Fusion (L-PBF) Additive Manufacturing (AM) have attracted much attention in recent years, as compared with conventional manufacturing processes it allows to produce Nitinol parts with high design complexity. Avoidance of defects during L-PBF is crucial for the production of...

Cracks formation in nickel-based single crystal alloy manufactured by selective laser melting

The aim of this study was to determine the influence of selective laser melting (SLM) process parameters on the formation of cracks in nickel-based single crystal alloy. Several sets of laser scanning parameters, with varied laser power, scanning speed and hatch distance, thus resulting in different volumetric and linear energy densities,...

Continuous and pulsed selective laser melting of Ti6Al4V lattice structures: Effect of post-processing on microstructural anisotropy and fatigue behaviour

Additive manufacturing technologies in general and laser powder bed fusion (L-PBF) in particular have been on the rise in different applications, including biomedical implants. The effects of the various L-PBF process parameters on the microstructure and properties of Ti6Al4V lattice structures have been studied before. However, the...

Simplified methods for calculation of damping using records of free nonlinear rolling with large amplitude decay