Abstract
The surface of most metals is covered with thin native oxide films. It has generally been believed that to achieve bonding, the oxide covering the surface of metallic particles or metal substrates must be broken and removed by adiabatic shear instability (ASI), whether induced at the particle–substrate interface or at the particle–particle interface. The aim of the present research is to investigate the correlation between the remaining oxide amorphous layer and substrate-deformation with the adhesion strength of cold-sprayed TiO2 coatings towards the bonding mechanism involved. Relevant experiments were executed using stainless steel (SUS 304), subjected to various annealing temperatures and cold-sprayed with TiO2 powder. The results indicate an increasing trend of coating adhesion strength with increasing annealed substrate temperature. The influence of substrate plastic deformation and atomic intermixing at the remaining amorphous oxide layer is discussed as the factors contributing to the increasing adhesion strength of cold-sprayed TiO2 coatings.
Highlights
Cold spraying is a process in which the powder particles are used to form a coating by means of ballistic impingement upon a suitable substrate
This study investigated the correlation between the adhesion strength of cold-sprayed TiO2 on the SUS 304 stainless steel—annealed at temperatures ranging from room temperature to 1000 ◦ C
The annealing process plays an important role in the induced ductility of the austenitic stainless steel, SUS 304 especially when annealed at a high temperature such as 1000 ◦ C
Summary
Cold spraying is a process in which the powder particles are used to form a coating by means of ballistic impingement upon a suitable substrate. Gardon et al reported that the mechanism responsible for the deposition of TiO2 on the stainless steel substrate in the cold-spraying process is the chemical bonding between the particles and the substrate. They have shown that the previous layer of titanium sub-oxide prepares the substrate with the appropriate surface roughness needed for the deposition of the TiO2 particle. To further understand the correlation between the remaining oxide amorphous phases after cold spraying, and their impactsthe on bonding mechanism of cold-spraying TiO2 onto metal substrates, in this study, we investigated the particle/substrate interface toward the amorphous adhesion strength agglomerated nano-TiO. Steel after annealing at higher temperature, we expect better bonding between the TiO2 coating and the SUS 304 annealed stainless steel
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