Improve the mechanical properties and wear resistance of Cr-C thin films by adding Al2O3 particles

In this study, alumina particles with various contents of 5, 10, 15, and 20 g/L in bath are co-deposited within Cr-C matrix by electrodeposition from a trivalent chromium bath. The electrodeposition is performed at a current density of 10, 15, 20 and 25 A/dm2, respectively, for 30 min. The influences of plating parameters including alumina concentration in the plating bath and current density on the volumetric percent of co-deposited particles in coating, deposition rate, morphology, hardness, corrosion resistance and wear behavior of electrodeposited Cr-C/Al2O3 composite coatings are evaluated and compared with that of electrodeposited Cr-C coatings. Our result shows that the codeposited particles percent, a determinant factor governing the hardness, corrosion resistance, and wear resistance of the coating, is influenced by concentration of alumina in bath and the current density. The maximum content of Al2O3 particles of 21.1 vol% is achieved at an Al2O3 concentration of 15 g/L in bath and a current density of 20 A/dm2. An increase of Al2O3 particles content in deposits increases the hardness of the coatings and significantly increases the corrosion as well as the wear resistance of the coatings, whereas the average friction coefficient decreases. The highest hardness approximately at 1075 HV is obtained from the Cr-C/Al2O3 composite coating with Al2O3 content of 21.5 vol%.