Tribological behavior of novel Al2O3-La2O3 HVOF composite coatings

Abstract

The development of new coatings materials, particularly ceramic based has gained attention for increasing the component durability of sliding component under varied environments. In this work lanthanum oxide (La2O3), a rare earth oxide as a reinforcing material in Al2O3 coatings in different weight percentages of 1.4%, 1.6%, and 1.8% respectively developed through High Velocity Oxy Fuel (HVOF) surface modification technique with SS304 as substrate. The porosity, hardness and chemical composition of the developed coatings was studied. Further, reciprocating tribological testing of the coatings was carried out at two loads (5 N and 15 N) under dry sliding conditions. The testing revealed that addition of La2O3 up to 1.6% lowers the porosity upto 40% and improves hardness by 10% when compared to 100%Al2O3 coating. The coating with 1.6 wt% Al2O3exhibited the least coefficient of friction amongst all developed coatings at both the loads. Further, with increase in load the coefficient of friction decreases for all the developed coatings. Further, the addition of La2O3 in the coating led to a decrease in wear, with 1.6 wt% La2O3 coating exhibiting the lowest wear at both the loads. At high load the wear increases for all developed coatings. SEM, EDS and XRD analysis of the worn surfaces revealed the role of La2O3 in improving the friction behaviour due to formation of oxides such as α-Al2O3 and Al22La2O36, change in wear modes and size of the wear debris. The developed composite coatings shall serve to exploit the potential of Al2O3 coatings for advanced industrial applications.