Fabrication of Alumina-Silicate nanocomposite coating on titanium substrate via micro arc oxidation method and investigation of current density effect on the wear behavior of coating

Titanium and its alloys have wide applications in industry. Main reasons are unique features of titanium such as biological behavior, corrosion resistance and high strength to weight ratio. The fundamental problem of titanium is its low wear resistance that leads to be worn in industrial applications. One of thebest solutions for this problem is coating. Micro arc oxidation (MAO) is a novel method to create ceramic coatings on metals. In this research, nano alpha alumina particles were added to a silicate base electrolyte to coat and alumina-silicate nanocomposite. Three samples with 0.1, 0.15 and 0.2 A/cm2 current densityand with constant parameters of bipolar condition, 30 min process time, 50% duty cycle and 50Hz frequency were prepared. Wear properties of alumina-silicate nanocomposite and simple silicate coatings were investigated by pin on disk method. Moreover friction coefficient and weight changes were calculated. SEM, EDS, eddy current tests and optic microscope were used to study the microstructure,chemical composition, thickness and wear route of coatings, respectively. Investigations revealed that coating mechanism with nano particles in electrolyte was combination of cataphoretic effect and spark ignition. Results showed that nano alpha-alumina particles with high hardness had a significant role inimproving the wear properties of coating. With increasing current density, energy of discharge channels increases and more nano particles adhere to the coating, resulting in higher wear resistance of coating. Moreover, coefficient of friction was increased by rising current density due to increase in amount of alumina nano particles in the coating and increase in surface roughness.

کلیدواژه ها:

Micro Arc Oxidation ، Titanium ، Nano alpha alumina ، Nanocomposite coating ، wear