Characterization. Performance and Microstructural Enhancement of Additive Manufactured AI-Si-Sn-Cu/Ti -6A1-4 V Composite Coatings

Abstract

The paper is focused in enhancing the hardness property of the titanium alloy by direct laser metal deposition using quaternary (AI-Si-Sn-Cu) reinforcement coatings. The procedure of the experimental work was done in South Africa at National Laser Center using Ytterbium Laser System that has capacity of 3000 W. Multiple tracks was employed with length of track stood at 65 mm and the laser beam diameter at 2 mm. Standard procedure was followed for materials characterization. L4 orthogonal design of experiment was used for the optimization of the process parameters. Varied laser power, powder feed rate and scan speed were used as process parameters. From the results gotten, copper weight percent increase contributed to the enhanced tensile strength and yield strength and hardness property as a result of formation of titanium-aluminium (Ti3AI). copper is classified as beta stabilizing element. Moreover, during solidification, copper atomic movement resulted in the formed beta-titanium phase. The thin columnar and elongated grains formed came from the refined grains as a result of added layers. Finer grains were produced in the microstructure with increased scanning speed because of faster cooling rate. Phases such as SiTi, Cu <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T$</tex> i2, Ti3AI, AISi3Ti2, A10.25Sn0.75V3 and AITi0.6V0.4, contributed to the enhanced hardness of the composites. The microstructures became well distributed and homogeneous. When the weight percent of copper was increased from 5 to 10%, there was increase in hardness value from 451 HV to 568 HV at the same scan speed but different laser power. This is about 25% increase in hardness. Also, at scan speed of 1.2 m/min, when the weight percent of copper was increased from 5 to 10%, there was increase in hardness value from 498 HV0.1 to 602 HV0.1 at the same scan speed but different laser power. This is about 21 % increase in hardness. But compared to the base metal, 88.13% increase in the hardness was seen for sample 4. The least hardness value shown by sample 1 is equivalent to 40.94 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup> increase in hardness as compared to the base metal