The adsorption characteristics of corrosive anions (Cl⁻, HS⁻, S²⁻, HCO₃⁻ and CO₃²⁻) on TiO₂ of TC4 titanium alloy in a NaCl solution containing H₂S and CO₂ were studied by density functional theory (DFT). The stable adsorption configuration of each corrosive species on the TiO₂ (110) surface was obtained by geometric optimization, and the electronic structure and interface binding energy were calculated and analyzed. The results showed that the optimal adsorption positions of Cl⁻, HS⁻, S²⁻, HCO₃⁻ and CO₃²⁻ on TiO₂ (110) were all bridge positions. There was a strong charge interaction between the negatively charged Cl, S and O atoms in Cl⁻, HS⁻, S²⁻, HCO₃⁻ and CO₃²⁻ and the positively charged Ti atoms of TiO₂. The interface bonding was mainly caused by charge movement from around Ti atoms to around Cl, O, S atoms. The energy levels were mainly caused by the electron orbital hybridization of Cl-3p⁵, S-3p⁴, O-2p⁴ and Ti-3d². All adsorption configurations were chemical adsorption. The order of influence of the five ions on the stability of TiO₂ was S²⁻ > CO₃²⁻ > Cl⁻ > HS⁻ > HCO₃⁻. Finally, a novel corrosion mechanism was proposed to illustrate the dynamic evolution processes of pits.

Titanium alloy has become a promising candidate material for oil country tubular goods (OCTGs) in harsh service environments owing to its high specific strength, low density, low elastic modulus, excellent toughness, excellent anti-fatigue and corrosion resistance. However, because the high-quality natural gas resources in China are mainly concentrated deep underground, titanium alloy tubing and casing will bear great external pressure loads underground, so the collapse strength of titanium alloy tubing and casing is very important for the safety of the string in the well. In this paper, a new collapse strength calculation model, the strength collapse criterion model (SCM), was proposed for titanium alloy tubing and casing. 35 different specifications of titanium alloy tubing and casing were selected for the full-scale collapse tests to verify the reliability of the established SCM model. Furthermore, the effect of different key parameters (such as strength, ovality, eccentricity and residual stress) on collapse strength of titanium alloy pipes were investigated systematically and compared with the same specifications of steel pipes. The strength collapse criterion model and analysis results can provide a technical reference for the design and use of titanium alloy OCTGs in the petroleum and natural gas industries.

During the service process of the mechanized fishing boat, its low carbon steel hull and parts are extremely susceptible to Cl⁻ erosion and seawater scouring, which cause a decrease in strength and lead to failure. To increase its service life and reduce maintenance costs, coating protection technology is widely used. In order to solve the problem of poor adhesion between paint coating and substrate and low strength of metal coating, NiCrMo-WC coatings with different WC contents (0 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%) were prepared on the surface of Q235 substrate by plasma cladding technology. The coatings were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy spectrum analysis (EDS), etc. Its phase formation rule, microstructure and element distribution were studied. Microhardness test and electrochemical corrosion test were carried out. The study found that the 20 WC coating has the highest average hardness (563.1 HV). It is about 3.25 times of the Q235 substrate. It has the lowest friction, wear rate and lower friction coefficient, showing the best wear resistance. The 15 WC coating has the lowest self-corrosion current density (3.4934 × 10⁻⁷ A/cm²) and the lowest corrosion rate (0.0041 mm/a), which is only 3.7% of the corrosion rate of Q235 steel.

Systematically investigated the dynamic deformation behavior and microstructural evolution of a new Ti-4Al-2.5V-1.2Fe-0.5Ni alloy used for drill pipe, revealing strong positive strain rate sensitivity. Flow stress in the β phase regime exhibited gradual hardening followed by steady-state flow without a distinct peak, whereas the α+β region displayed pronounced peak and flow-softening characteristics. Peak flow stress was accurately predicted via hyperbolic-sine constitutive equations, yielding markedly different activation energies for the β (147.66 kJ/mol) and α+β (596.29 kJ/mol) phase fields. Based on the dynamic materials model (DMM) processing maps, an optimal hot-working window was identified at high temperatures (1070-1100℃) and low strain rates (0.01-0.1s-1), while two instability domains (800–930 ℃/0.01-0.1 s-1 and 800-900 ℃/5-10 s-1) must be strictly avoided. Microstructural evolution was strongly governed by thermomechanical processing (TMP) parameters: dynamic recovery (DRV) dominated in the β phase at low strain rates, transitioning to DRV-plus-static recrystallization at high rates, whereas dynamic globularization of α-lamellae prevailed in the α+β field. Increasing temperature promoted lamellae spheroidization and refinement, with high strain rates inducing fragmentation into granular morphologies and extensive nucleation of fine equiaxed α grains. Above the β transus, recrystallization governed, though excessive strain rates suppressed it, forming band-like distorted zones. Unstable regions exhibited shear bands, inhomogeneous plastic flow, and lamellar kinking, making premature ductile fracture highly probable. These findings provide critical scientific guidance for optimizing hot working parameters to ensure microstructural uniformity and avoid processing defects.