Microstructural analysis, micro-hardness and wear resistance properties of quasicrystalline Al–Cu–Fe coatings on Ti-6Al-4V alloy

Abstract

The need for engineering components with suitable functionality under harsh wear and aggressive environment subjected to high risk of deterioration, has led to the demand for surface treatment processes and high-performance materials. Ti-6Al-4V is one of the mostly used titanium alloys with more than 70% of the industrial applications in the aerospace, marine and automotive industries. Despite the exceptional properties of Ti-6Al-4V alloy, their low hardness, high susceptibility to corrosion, poor thermal stability and poor tribological properties have limited their viability in the field of engineering. In this research, laser metal deposition technique by incorporating quasicrystalline Al–Cu–Fe coatings can be very beneficial in enhancing the surface properties of Ti-6Al-4V alloy. A 3 kW continuous wave ytterbium laser system (YLS) attached to a KUKA robot which controls the movement of the cladding process was utilized for the fabrication of the coatings. The titanium alloy cladded surfaces were investigated for its microstructure, mechanical and wear resistance properties at different laser processing conditions. The obtained results illustrated that geometrical properties height and width of the deposit increase with an increase in laser power. Increase in scanning speed results in a decrease in the geometrical properties. Ti reacted with increased amount of Al and Fe and less amount of Cu powders to form Al2Ti, Fe0.975Ti, Al0.9Fe3.1Ti0.025 and AlCu2Ti. The optimum performances were obtained for an alloy composition of Ti-6A-4V/Al-Cu-5Fe composite, at laser power of 800 W and scanning speed of 1.0 m min−1. Its performance enhancement compared to the unprotected substrate comprised a significant increase in hardness from 302 to 2740 HV which translates to 89.14% in hardness values above that of the substrate. Coatings with higher hardness levels were achieved mainly due to the larger fraction of hard-intermetallic phases at lower laser scanning speeds. Finally, Ti-6Al-4V/Al-Cu-5Fe coating at laser power of 800 W and scanning speed of 1.0 m min−1 shows the highest wear resistance performance compared to the substrate. Ti-6Al-4V/Al-Cu-5Fe coating was 2.8 times the wear resistance performance of the substrate.