Abstract
The cold spraying of ceramic materials is widely acknowledged as a difficult process because it necessitates the feedstock powder particles experiencing a plastic deformation for deposition on a substrate. The problem arises due to the brittle properties of ceramic powder feedstock such as titanium dioxide (TiO2), combined with a lack of understanding of the bonding mechanisms. In this study, TiO2 coatings were deposited onto copper and aluminum substrates and the adhesion strength was evaluated to investigate the bonding mechanism. The influence of substrate hardness and remaining surface oxide layer was investigated by annealing the substrates with various temperatures. The results showed that the adhesion strength of the coatings on the aluminum substrate was higher than the copper substrate. Furthermore, the adhesion strength was decreased with increasing the annealing temperature on both substrate materials. These results indicate that a softer aluminum substrate was advantageous for adhesion. Annealing led to thermal softening the substrate; however, the thickness of the surface oxide layer was increased. Therefore, bonding occurred between the cold-sprayed TiO2 particle and newly deform substrate surface, which yielded the higher adhesion strength. The main bonding mechanism is metallurgical, similarly to the cold-sprayed metallic coatings.
Highlights
A de Laval nozzle accelerates powder feedstock towards a substrate to deposit a coating, which is known as the cold-spraying process
By using focused ion beam (FIB) milling equipment, thin membrane films for transmission electron microscopy (TEM) testing were thoroughly prepared from collected titanium dioxide particles at room temperature and mirrored pure metal substrates annealed at 400 ◦C (FEI Helios Dual Beam 650)
Our experiment is consistent with the results of Ichikawa et al, where substrate deformation existed on both pure metals annealed at 400 ◦C, but the adhesion strength was lowest at this annealing temperature due to the oxide film remaining on the substrate surface after impact from cold-sprayed TiO2 particles
Summary
A de Laval nozzle accelerates powder feedstock towards a substrate to deposit a coating, which is known as the cold-spraying process. Winnicki et al used amorphous and crystalline TiO2 powders cold-sprayed onto aluminum and steel substrates with varying surface roughness values They discovered that the grit-blasted substrate enabled them to reduce defects caused by differences in metallic substrates and ceramic coating properties, which were influenced by the thermal expansion coefficient. Gutzmann et al investigated the deposition of various particles on substrates of different temperature and gained a better understanding of the impact morphology of single TiO2 particles They demonstrated that concentric rings, such as in the shear instability zone, existed on the impacted substrates. Gardon et al reported that between the particles and a stainlesssteel substrate, chemical bonding caused TiO2 formation on the substrate during the cold-spraying procedure They demonstrated that the existing layer of titanium suboxide provides the substrate with the required surface coarseness for TiO2 particles to form a coating. The powder feed rate was three grams per minute, and the pass number was one
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
