Wear properties of Al2O3/MoS2 nanocomposite coatings created by electro spark deposition and oxidation on the surface of Ti-6Al-4V alloy

In this research, the synthesis of Al2O3/MoS2 nanocomposite coating by electro spark deposition method for its wear properties are investigated. Ti-6Al-4V alloys have been noted for theirs high strength to weight ratio. But there have low wear resistance. Various coatings have been used to improve this weakness. There are a variety of ways to apply these coatings. One of these methods is the ESD method. In this method, the coating usually forms a strong metallurgical bond with the substrate. MoS2 due to self-lubricant properties and Al2O3 due to high hardness can be a good option to improve the tribological properties of Ti-6Al-4V. Grade 5 titanium alloy sheet containing 6.12 % Al, 4.06 % V, 0.19% Fe and 0.05 % Ni was used as a substrate. An Al/MoS2 composite electrode includes 95% aluminum and 5% molybdenum disulfide in the form of a cylindrical rod was used for coating. The coating operation was performed in three frequencies of 5, 8, and 11 kHz, three current limits of 15, 25, and 35 amps, and three duty cycles of 50, 60, and 70%. In order to form an Al2O3/MoS2 coating, the Al/MoS2 coated samples were kept in a normal atmosphere furnace at 600 ° C for 2 hours. AFM analyze was used to study the topography, morphology and calculation of roughness. The adhesive strength of the final coating was evaluated to the adhesion strength of coating films on a metal background using glue tape The samples were then subjected to hardness testing. Wear test was performed by pin on disk method to determine the wear resistance of the samples. XRD test was performed to identify the phases in the surface of the coated samples. SEM was used to examine the microstructure of the coating after oxidation and after wear test and to determine the wear mechanism. XRD results confirmed the formation of a Al2O3/MoS2 composite coating after oxidation. SEM images showed oxidation caused the closing of surface cracks in the coating. The results of adhesion test showed that all the coatings created had the highest adhesion strength. The surface hardness of all specimens increased with increasing spark energy up to 700 Vickers. The AFM result showed an increase in surface roughness due to the coating. Roughness values after oxidation range from 18.3 nm for the reference sample to 289.3 nm for the 351170 sample. Abrasion test results showed that after oxidation, the coefficient of friction decreased by approximately 12% and weight loss by approximately 20%. The wear mechanism in coated samples is the scratching mechanism.