By combining lightweight metal alloys with ceramics it is possible to adapt material properties on stressed parts and thus increase stiffness and/or change the thermal resistance: yet joining such materials is problematic due to the poor wettability of ceramics by molten metals. In this work the technique of friction surfacing is used to connect alumina (Al2O3) with an aluminium alloy (EN-AW 5083). Despite the fact that Al2O3 has a relatively high coefficient of thermal expansion and a low thermal shock resistance, specimens have been produced showing encouraging results. In order to compensate for these material properties the substrate was preheated to a minimum of 150°C. In tests bonding strengths reached 47.8 MPa and coating thicknesses of 213 μm were achieved; results which are comparable with conventional thermally sprayed coatings. Bonding strengths were determined by using a pull-off adhesion tester and the coating thickness was measured with a laser scanning microscope. Analysis of the joint zone shows no clear evidence of chemical reactions (inter-metallic compounds) or diffusion. Mechanical interlocking can only be shown to be accountable for 16% of the bonding strength with investigations turning towards van der Waals forces and their contribution to adhesion
|Journal||Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications|
|Publication status||Accepted/In press - 25 Jun 2020|
Atil, H., Leonhardt, M., Grant, R., & Barrans, S. (Accepted/In press). Microstructure and mechanical properties of aluminium alloy coatings on alumina applied by friction surfacing. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications.