Effect of Duty Cycle on the Microstructure and Mechanical Properties of Micro - Arc Deposited Al₂O₃ - TiO₂ Coating on the Surface of Ti Alloy for Engine

Abstract

In order to improve the comprehensive properties of titanium alloys to meet the requirements for the production of engines, the micro - arc deposition technology was used to modify the surface of titanium alloys for engines. Three different micro - arc deposited Al2O3 - TiO2 coatings were prepared with different pulse duty cycles (30%, 40% and 50%). The surface morphology of coatings was observed by field emission electron microscope, the thickness of coatings was measured by metallographic microscope, the surface roughness of coatings was measured by laser confocal microscope, the elastic modulus and hardness of coatings were measured by nanoindenter, and the effect of duty cycle on the structure and mechanical properties of micro - arc deposited Al2O3 - TiO2 coatings on titanium alloys for engines were investigated systematically. Results showed that the average thickness of the Al2O3 - TiO2 coating increased as the duty cycle increased from 30% to 40% and 50%. With the increase of pulse duty cycle, the surface roughness (Ra) of the as - deposited coating decreased, which reached the minimum of about 2 μm under the duty cycle of 50%. When the pulse duty ratio changed from 30% to 50%, the number of micropores on the surface of the Al2O3 - TiO2 micro - arc deposition coating gradually increased, the radius of the micropores decreased, and the surface was more uniform. When the pulse duty cycle was 50%, the prepared Al2O3 - TiO2 coating had the highest hardness and elastic modulus.

Keywords

• micro - arc deposition|titanium alloy|pulse duty cycle|microstructure|mechanical properties