Abstract
Bulk NiTi is used to make parts, such as couplings and bearings, that can be found in many industries such as the automotive, aerospace and medical sectors. Forming and machining bulk superelastic NiTi is a very difficult and costly process; however, applying NiTi as a surface coating will provide an alternate manufacturing method that will minimize machining processes. The objective of this study is to produce a superelastic NiTi-based surface coating that exhibits denting, impact and wear resistance. Superelastic NiTi has been successfully produced through vacuum deposition processes, despite this, there is a lack of a full and comprehensive study on the formation of the NiTi phase during coating development. In this study, the NiTi phase is fabricated through the annealing of sputtered deposited Ti and Ni layers in a coating. To confirm the presence of the intermetallic phases, X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) analysis were performed. The erosion behavior of the coating is evaluated through single particle erosion testing, which resulted in the coatings that contained the NiTi precipitates to exhibit the best damage resistance compared to the other nanolaminates. This indicates that the superelastic NiTi phase increases the resistance to impacting particles. Microstructural evolution and NiTi formation during annealing is discussed and related to the observed damage resistance of the coatings.
Highlights
The erosion of working parts cost industries millions of dollars each year
The erosion behavior of the coating is evaluated through single particle erosion testing, which resulted in the coatings that contained the NiTi precipitates to exhibit the best damage resistance compared to the other nanolaminates
The single particle erosion test in this study evaluates the coatings’ response to denting by high velocity particle at different impact angles
Summary
The erosion of working parts cost industries millions of dollars each year. The effects of erosion can lead to a loss of process efficiency, plant shutdowns and safety risks [1]; causing production delays which result in a significant increase in costs. A common method to prevent erosion is to protect the material by applying a surface coating that can withstand erosion. Erosion occurs when particles impact a solid surface and the kinetic energy is transferred to the material [2,3]. Erosion is influenced by operational properties, such as particle velocity, impact angle and the impacting particle, such as hardness, size and shape [4]. The kinetic energy can be totally or partially dissipated in the material through ductility, phase transformations and heat [2]
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