Nanocrystallization of a Ti40 cladding layer by ultrasonic impact to improve burn resistance

With the wide application of titanium alloys in the aerospace industry, the burn resistance properties and surface strengthening processes of titanium alloys have been received increasing attention. In this study, Ti40 burn-resistant titanium alloy was cladded on the surface of TC4 by electron beam cladding, and the surface layer of the nanostructure was prepared by ultrasonic impact treatment (UIT). The nanostructure layer was examined by pulse laser ablation. The results showed that when the moving speed was 16 mm/s, the maximum thickness of the plastic deformation zone of the UIT Ti40 cladding layer reached 150 μm. The highest hardness value was 531 HV, which was approximately 43.5% higher than the original microstructure of the Ti40 cladding layer without UIT. Moreover, the surface microstructure of the Ti40 burn resistant titanium alloy cladding layer was nanocrystalline with uniform distribution and random orientation, and the average grain size was 50 nm. The UIT process can effectively increase the relative content of burn-resistant alloy elements on the surface of the Ti40 cladding layer and increase the content of dense oxidation protective films after laser ablation, which hinders the diffusion and migration of oxygen elements to the matrix alloy in the process of ablation and then improves the burn resistance of the Ti40 cladding layer.