Enhancing hot salt corrosion fatigue resistance of TC11 alloy through plasma zirconizing compound treatment

To enhance the fatigue resistance of TC11 titanium alloy under the thermal-salt-alternating load coupling conditions, the effect of plasma zirconizing compound treatment on the hot salt corrosion fatigue (HSCF) performance of TC11 titanium alloy was investigated. The results demonstrated that plasma zirconizing alone did not improve the HSCF resistance of TC11 alloy and even decreased its HSCF limit by 15.5%. Ultrasonic surface rolling processing (USRP) applied to TC11 alloy treated by plasma zirconizing increased the HSCF limit. This resulted from the nanocrystal structure generated by USRP facilitating protective oxide formation. Additionally, a compressive residual stress (CRS) field with high amplitude and deep distribution effectively inhibited the initiation and propagation of HSCF cracks. However, due to the high sensitivity to hot salt corrosion (HSC), the degree of improvement in HSCF resistance was not significant. When plasma electrolytic oxidation (PEO) was applied to TC11 alloy treated with combining plasma zirconizing and USRP, the HSCF resistance was substantially increased, with its limit rising 31.0% over the base material, due to the formation of a compound gradient modified layer. A dense amorphous PEO ceramic layer was formed on the surface, effectively reducing HSC sensitivity. Simultaneously, the initiation and propagation of fatigue cracks were effectively inhibited by the CRS field characterized by high amplitude and deep distribution. Furthermore, plasma zirconizing produced a solid solution strengthening effect, which markedly enhanced the thermal stability of the CRS field through dislocation pinning. This study can offer a new solution for enhancing HSCF resistance of titanium alloys.