Effect of the Substrate Surface Profile on the Bonding Strength of the Aluminum Thermal Sprayed on the Low Carbon Steel

Abstract

The contact surface of thermal spray significantly affected bonding strength and coating elasticity. This work aimed to evaluate the effects of contact surface conditions characterised by substrate surface profile and spray pressure on the bonding and buckling strength of aluminium thermal sprayed on the low-carbon steel substrate. The SS400 low-carbon steel substrate was profiled using the milling process to form the V, small V, U, and flat profiles that were subsequently roughed by employing the sandblasting process. A coating comprising 99% aluminium was sprayed onto the substrate surface with different spraying pressures of 3.5, 4.5, and 5.5 bar. Pull-off and buckling tests were performed for determining thermal spray characteristics. The results of this work showed that the optimal bonding strength of the coating was obtained for the thermal spray specimen that had a flat substrate surface, and the spraying pressure was set to 5.5 bar. Generally, low spraying pressure lead to be low bonding strength and vice versa. Profiled surface was not profitable on the mechanic properties of thermal spray bonding.