The preparation of Ti coatings on mild steel can both effectively improve the corrosion resistance of the substrate and reduce the application cost of Ti, which is an effective measure to improve the service performance of mild steel in the marine environment. Plasma cladding technology is an efficient method for preparing metal coatings, and the type of powder is a key process parameter for coating preparation. In this work, high-performance Ti coatings are prepared on the surface of mild steel by plasma cladding technology, and the effects of different particle sizes and shapes of Ti powders on the surface morphology, microstructure and properties of the coatings are studied. The results show that powder particle size and sphericity are the key factors affecting the morphology, structure and service performance of Ti coatings. After 1000 h of salt spray test, the spherical powder cladding coatings only suffer slight corrosion, while the irregular shape powder coating is more severely corroded. Powder cladding with moderate powder particle size and good sphericity have a smoother coating and fewer defects. Ti powders with different particle sizes and shapes all have the diffusion of Fe element during the cladding process. The surface of Ti coating prepared by spherical powder are dominated by α-Ti and Fe0.2Ti0.8 phases, while the surface of Ti coating prepared by irregular shape powder is dominated by FeTi and Ti2Fe. The interface between the coating and the substrate shows metallurgical bonding, and the increase in Ti-Fe brittle phase will deteriorate the mechanical properties and corrosion resistance of the coating. The shear strength of coatings prepared from spherical Ti powders of 75–150 μm can reach 105.18 MPa, the corrosion potential is the most positive (−0.2206 V), and the self-corrosion current density is the lowest (6.220 × 10−8 A/cm2).
In this paper, the tribocorrosion behavior and synergistic effect of 7075-T6 aluminum alloy under different applied loads (100, 150, and 200 N) and sliding velocities (100, 150, and 200 rpm) were studied in a 3.5 wt.% NaCl solution. Tribocorrosion experiments were conducted in a tribobocorrosion system with pin-on-disc testing. The results show that the interaction between applied load and sliding velocity significantly affects the mechanical and electrochemical properties of 7075-T6 aluminum alloy. Increases in sliding velocity and applied load will accelerate the corrosion. Due to the synergistic effect of corrosion and wear, the wear rate is almost unchanged as the sliding velocity increases. When the applied load increased from 100 to 200 N, the wear rate increased from 1.97 × 10−5 to 2.08 × 10−5 mm3/N·m, and the delamination wear phenomenon was aggravated.
8 November 2024 in Journal of Materials Research and Technology
In this paper, a portable residual stress tester and synchrotron radiation diffraction technique were used to measure the residual stress distribution of thick 2A14 aluminum alloy plates under different aging conditions after solution treatment. The stress changes after solution and aging were analyzed using metallographic structure observation, electron backscattered diffraction (EBSD), X-ray diffraction (XRD), and other characterization methods. The results show that after solution treatment at 500 °C and aging at 170 °C, the second phase precipitates, lattice distortion is released, and the stress level gradually decreases with aging time. The residual stress of the plate comprises compressive stress; there is stress concentration in the central area. The stress distribution obtained by the two residual stress calculation methods, cosα and sin2ψ, under different process conditions was consistent.
In this paper, based on in situ synchrotron radiation SAXS technology, the effects of stress field, temperature field and thermo-mechanical coupling conditions on the evolution of residual stress are discussed, respectively. The results show that the continuous increase of the external load led to the increase of the residual stress perpendicular to the tensile direction of the 2A14 aluminum alloy, and when the external load closed to the yield strength, the change of the residual stress was no longer significant. Under the action of temperature, the residual stress of 2A14 aluminum alloy reduced after the process of heating–holding–cooling. Under the action of thermo-mechanical coupling, the recovery effect of aluminum alloy was triggered, the energy storage of deformation was released, the lattice strain was reduced and the residual stress introduced by external load was reduced.
In this study, the surface nano treatment of TA2 titanium alloy was realized by means of surface mechanical wear treatment. The microstructure and electrochemical properties of the nanocrystalline layer were investigated by SEM, TEM, Electrochemical Impedance Spectroscopy, and Potentiodynamic Polarization, while the nucleation mechanism of the passivation film was discussed. The results indicate that the original coarse grains on the sample’s surface are transformed into randomly oriented nanocrystals by surface mechanical attrition treatment (SMAT). The corrosion current density of the surface nanocrystallized TA2 titanium alloy (9.2 nA·cm−2) experienced a reduction of two orders of magnitude compared to untreated TA2 titanium alloy (134.5 nA·cm−2) in 3.5 wt.% NaCl solution. The SMAT methods accelerates nucleation mechanism transitioning to continuous nucleation.