Deposition and characterization of cold sprayed nanocrystalline NiTi

Binary 50Ni–50Ti mixture was prepared by mechanical alloying from elemental powders. After 48 h of milling, the nanocrystalline B2-NiTi powder was produced. Then, this as-milled powder was deposited by cold spraying in order to produce a target which can be used to create thin films by magnetron sputtering technique. The objective is to improve the electrical characterizations of the NiTi/SiO2/Si M.O.S structures. The morphology evolution of the powder particles, the phase identification and the alloying evolution process as function of milling time were studied using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. In addition, the target was also characterized using X-ray diffraction, Scanning electron microscopy, and microhardness measurements. The milling of powders leads to the formation of disordered nanocrystalline B2-NiTi with a crystallite size of about 12 nm and a microstrain of level 2.10%, after 48 h of milling. The microstructure, the composition and grain size of the milled powders for 24 h and 48 h characterized by TEM are heterogeneous. The as-deposited intermetallic NiTi can be retained in the coating with a lattice parameter of 0.3 nm, crystallite size of 14 nm, microstrain and high microhardness of 2% and 694 Hv0.25, respectively.

Graphical abstractThe structural parameters of nanocrystalline NiTi obtained by mechanical alloying process was reported. The structural evolution as well as the phase identification and microstructural parameters such as lattice parameter a, crystallite size and microstrain have been investigated. After 48 h of milling, the nanocrystalline B2-NiTi powder was produced. Then, this as-milled powder was deposited by cold spraying in order to produce a target which can be used to create thin films by magnetron sputtering technique.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch Highlights► B2-NiTi phase formation after 48 h of milling. ► Deposited of the nanocrystalline B2-NiTi by cold spray. ► Structural, microstructural and microhardness of the coating were compared with the milled powder for 48 h.