Wear and scratch behaviour of electroless Ni-P-nano-TiO2: Effect of surfactants

• Electroless Ni-P-nano-TiO2 coatings were obtained in presence of surfactants.
• Sodium dodecyl sulphate (SDS), dodecyl trimethyl ammonium bromide (DTAB) were used.
• Composite coatings showed higher scratch resistance for DTAB surfactant than SDS.
• At critical micelle concentration (CMC), DTAB exhibited maximum wear resistance.

This paper investigates the effects of surfactants on microhardness, scratch, wear and friction behaviour of the Ni-P-nano-TiO2 composite coatings. Nano TiO2 particles were co-deposited with electroless Ni–P coating on low carbon steel substrates in the presence of anionic and cationic surfactants-sodium dodecyl sulphate (SDS) and dodecyl trimethyl ammonium bromide (DTAB) respectively. Results revealed that at an optimum concentration of the surfactants, the coatings obtained a smoother surface, low frictional coefficient, enhanced microhardness and high wear resistance. The findings of scratch test showed that the composite coatings with surfactants exhibited the ability to withstand higher critical load and lower penetration depth. This can be ascribed to the reinforcing action of co-deposited TiO2 nanoparticles in the composite coatings. The cationic surfactant DTAB contributed to the increase in weight percentage of TiO2 in the Ni–P matrix considerably. At critical micelle concentration (CMC) value of the DTAB surfactant, the coatings had the highest weight percent of incorporated TiO2 and showed a better homogenous distribution.