Titanium alloy has low hardness and poor wear resistance. When used as flow passage components such as ship propeller blades, turbine blades, turbines, draft tubes, pumps, and valves, it is very easy to cause cavitation of components due to the pressure change zone in the fluid. When cavitation bubbles collapse near the solid boundary, the surface of solid materials will peel off, resulting in the reduction of equipment performance, the shortening of service life, and even the failure of titanium alloy components.
The results show that the cavitation resistance of titanium alloy can be improved by changing the microstructure of titanium alloy. Li Haibin heat treated Ti-6Al-4V alloy at different temperatures (1020 ℃, 950 ℃, and 850 ℃) to obtain widmanstatten structure, bimodal structure, and equiaxed structure respectively. After an 8 h cavitation test in deionized water, it was found that the cumulative weight loss of all samples obtained by heat treatment was less than that of the original Ti-6A-l4V.
Among them, the Widmanstatten sample obtained by 1020 ℃ + water quenching has the smallest cavitation weight loss (77.9% of the original sample), and the highest cavitation corrosion coefficient (1.83 times of the original sample).
The study shows that there are also certain differences in the cavitation corrosion resistance of Ti-6Al-4V alloys with different microstructures. Widmanstatten structure contains martensite α ′ phase or lamellar α phase, which enhances the fracture toughness and tensile strength of Ti-6Al-4V, and the material can absorb the energy enhancement of cavitation collapse; The primary α phase in the two-state structure has a strong work hardening ability, and the β transformation structure (secondary α phase) can increase the strength and hardness of the material, and it also enhances the energy that Ti-6Al-4V can absorb the collapse of the cavity; Although the equiaxed structure also contains secondary α phase, its content is less, so the improvement of anti-cavitation corrosion performance is not as obvious as that of the two-state structure. In this test, the Widmanstatten structure has the best cavitation corrosion resistance, followed by the two-state structure, and the equiaxed structure has the lowest cavitation corrosion resistance.
