Effects of Al<sub>2</sub>O<sub>3</sub>-13% TiO<sub>2</sub> Coating Particle Size on Commercial Mild Steel via Plasma Spray Method

Abstract

This paper discusses the effect of Al2O3-13% TiO2 agglomerated nanoparticle powders ranging from 20 to 60 m and microparticle powders ranging from 10 to 25 m on commercial marine grade mild steels using a plasma spray technique. Prior to coating, the nanoparticle powders were subjected to a 2 level factorial design of experiment to give a careful control and optimise the operational spray parameters as well as process by using the statistical methods. The method was focused on the primary gas pressure, carrier gas pressure and powder feed rate of the spray parameters. The optimum properties of wear rate, surface roughness and microhardness were identified by using the lowest primary and carrier gas pressure together with the highest powder feed rate. As for the microparticle powders, they were subjected to an optimum properties by using 35 kW plasma spray power. In this study, the plasma spray power for microparticle varied from 20 kW to 40 kW, while the other parameters such as primary gas pressure, carrier gas pressure, powder feed rate and spray distance were held constant. It was found that microparticle powders exhibited denser coating microstructure s and improved both surface roughness and microhardness. On the other hand, the nanoparticle powder coating gave a greater wear resistance than those of micro particle powders, which may likely due to the strengthening effect of both fully and partially melted region.