Oil-in-water emulsions containing titanium dioxide nanoparticles: A tribological study on forged steel-steel surfaces

The article aims to explore the tribological behaviour of TiO2 nano-additive oil-in-water emulsion. Tribological tests were conducted under a 70 N load for 10 min using nanofluids prepared through a dual-step method at varying concentrations (wt%) of 0.05, 0.1, 0.3, 0.5, and 1.0. Pins were made from IS 2062 E350 grade steel, while discs were made from high-strength forged steel containing 2 % chromium. Surface characterization of pin wear surface was performed through FESEM and a non-contact type profilometer. 0.1 wt% nano-concentration showed excellent tribological efficacy with a 65 % friction force reduction and better surface morphology than the conventional emulsion. The reasonably lower surface roughness (0.101 mu m) was also detected. Nanoemulsion witnessed slightly higher wear than the without nanoparticle emulsion. Wear Scar Diameter increased due to the increment in nano-concentrations. The WSDs for base emulsion and optimised 0.1 wt% nano-suspension are 1112 mu m and 1684 mu m, respectively. Simultaneously, the nano-suspension has a good polishing effect by reducing surface roughness. The inflation in concentration increased the thermal conductivity and wettability. With the increased concentration in the base, the emulsion showed a minimal increase in viscosity. Hence, the nano-additive oil-in-water emulsion carries the potential to substitute conventional oil emulsions.