Impact of Gas Pressure on the Adhesion Process of Cold-sprayed Titanium Dioxide layers on Unalloyed Metals

Abstract

Applying ceramic materials like TiO2 through cold spraying is acknowledged as a complex procedure. The intricacy stems from the need for feedstock particles to undergo plastic deformation to bond with the substrate during cold spraying. However, inducing such deformation in ceramics, known for their hardness and brittleness, is not straightforward. Additionally, the underlying bonding mechanism is not fully clear. This study sought to understand the effects of different substrates and gas pressures on the TiO2 application method. We experimented with TiO2 particles and metals such as copper and aluminum, exposing them to varied gas pressures to delve deeper into the dynamics of cold spraying ceramics onto metallic surfaces. We utilized sophisticated instruments like the focused ion beam and the transmission electron microscope to scrutinize the interfacial structures of TiO2 particles with pure copper (C1020) as well as pure aluminum (AA1050). The data revealed that as we adjusted the gas pressure from 0.7 to 3.0 MPa, there was a corresponding increase in the coating\'s bond strength, registering between 1.52 to 3.46 MPa for C1020 and 0.45 to 4.15 MPa for AA1050. An ultra-thin amorphous oxide layer, under 5 nm in thickness, was detected at the juncture of TiO2 with both metals. The shift in process gas pressure emerged as a pivotal element affecting the bond strength of the TiO2 layer.