High-temperature oxidation performance of laser-cladded amorphous TiNiSiCrCoAl high-entropy alloy coating on Ti-6Al-4V surface

To enhance the high-temperature oxidation performance of Ti-6Al-4V alloy, we successfully prepared a TiNiSiCrCoAl high-entropy alloy coating on its surface via laser cladding technology. X-ray diffraction, scanning electron microscopy, and electron probe microanalysis were used to characterize the microstructure, elemental distribution, and high-temperature oxidation resistance of the coating. The results indicated that the microstructure of the coating was composed of a matrix and a σ phase. Owing to the rapid cooling via laser processing and the matched δ, ∆Hmix, and Ω, the matrix phase was an amorphous structure rich in Ti, Si, Cr, and Co, and the σ phase was an FCC structure rich in Ti, Ni, Co, and Al. The volume fraction of the amorphous-structured matrix in the coating increased with increasing laser scanning speed. The section after the oxidation treatment was composed of an oxide layer, a transition layer, and a coating matrix. The oxide layer was composed of TiO2, Al2O3, and NiAl2O4, and the transition layer was rich in Si, Ni, and Co. The amorphous-structured matrix exhibited a higher oxidation resistance than the FCC-structured σ phase. Compared with the Ti-6Al-4V substrate, the oxidation resistance of the coating increased by 10.7, 28.1, 40.5, and 65.1 times at different laser scanning speeds under oxidation at 800 °C for 48 h, which indicates that the coating has better oxidation resistance than the Ti-6Al-4V alloy at high temperatures.