Optimization of plasma spray parameters on the mechanical properties of agglomerated Al2O3–13%TiO2 coated mild steel

This paper discusses the effect of plasma spray parameters of deposited agglomerated nano Al2O3-13%TiO2 powders on commercial marine-grade mild steels. Prior to the coating work, the nanopowders were subjected to a two-level factorial design of experiment to optimize the operational spray parameters, namely, the primary gas pressure, the carrier gas pressure, and the powder feed rate. These operational spray parameters potentially affect the following responses of the coatings: microhardness, wear rate, and surface roughness. The significant effect on surface roughness is due to the interaction factor with the carrier gas pressure. However, by changing the carrier gas pressure and the powder feed rate, an insignificant effect on the microhardness and wear rate is noted. In general, agglomerated Al2O3-13%TiO2 nanopowder-coated steels, with the lowest primary pressure of 40 psi, carrier gas pressure of 20 psi, and the highest powder feed rate of 3 rpm, are most preferred.

► Optimum properties of coatings were achieved using a statistical approach.
► Deposited coatings of a bi-modal structure provide better mechanical properties.
► Low microhardness and high wear rates were due to the weak partially melted regions.
► Increased primary gas pressure decreases microhardness and increased wear rate of coatings.