Microstructure and properties of Ti-Al coating and Ti-Al-Si system coatings on Ti-6Al-4V fabricated by laser surface alloying

In order to improve surface properties of Ti-6Al-4V titanium alloy, Ti-Al-Si coatings with different Si content were fabricated on Ti-6Al-4V titanium alloy by laser surface alloying. In order to compare properties of Ti-Al-Si system coatings, Ti-Al coating was simultaneously fabricated. The microstructures, hardness and high-temperature oxidation behaviors of the coatings were analyzed. The results show that the coatings exhibit excellent metallurgical bonding with the substrate. There were no obvious cracks observed in Ti-Al-Si system coatings. However, there were some penetrating cracks that formed in Ti-Al coatings. Ti-Al-Si system coatings have a higher hardness due to the formation of Ti5Si3 reinforced phase. Both Ti-Al coating and Ti-Al-Si system coatings exhibit excellent, high-temperature oxidation resistance compared with the substrate at 800 °C for 1000 h. The higher Al and Si content in Ti-Al-Si system coatings, the more excellent, high-temperature oxidation resistance was achieved. There is also a discussion of the mechanism of Si on mechanical properties and high-temperature oxidation in Ti-Al-Si system coatings.