Optimization of Synergistic Coatings on Piston Crown and Cylinder Liner: Electroless Ni–P–Nano–TiO₂ Underlayer with Plasma YSZ Overlay in CI Engines

This study investigates the optimization of duplex coatings on piston crown and cylinder
linersurfaces in compression ignition (CI) engines to improve thermal and tribological
performance. A dual-layer system was developed, comprising an electroless Ni–P–Nano–
TiO₂ underlayer and a plasma-sprayed yttria-stabilized zirconia (YSZ) overlay. The Ni–P–
Nano–TiO₂ layer provided high hardness, uniform deposition, and wear resistance, while the
YSZ layer acted as a thermal barrier due to its low thermal conductivity and excellent hightemperature
stability. Process parameters were optimized to ensure strong adhesion, reduced
porosity, and improved structural integrity of the coatings. Characterization results confirmed
the synergistic interaction between the two layers, with enhanced hardness, adhesion strength,
and thermal resistance compared to single-layer coatings. Engine performance tests
demonstrated reduced heat transfer to the cylinder walls, better combustion stability, and
lower fuel consumption. Tribological evaluations indicated a lower coefficient of friction and
improved scuffing resistance under high load andtemperature conditions. The optimized
duplex coating system effectively enhanced both durability and efficiency of the engine
components. The results highlight the potential of electroless Ni–P–Nano–TiO₂ combined
with plasma-sprayed YSZ as a reliable surface engineering solution for next-generation CI
engines, supporting improved fuel efficiency, durability, and emission reduction.