In order to enhance the contact fatigue performance of the Cr12Mo1V1 die steel component, the ultrasonic impact surface-modification process was introduced into the heat treatment process of 1060 °C quenching + cryogenic treatment (−150 °C × 2 h) + two times of tempering at 520 °C × 2 h in this paper. The influence of the ultrasonic impact number on the surface morphology, roughness, micro-hardness value, residual stress, microscopic morphology of spalling pits, contact fatigue life, and EBSD inverse pole figure of the Cr12Mo1V1 die steel component were investigated utilizing a laser confocal microscope, 3D laser confocal microscope, micro-hardness tester, X-ray stress meter, scanning electron microscope, rolling contact fatigue testing machine, and EDAX-TSL system equipped with a field-emission scanning electron microscope, respectively. In comparison to other ultrasonic impact numbers, the Cr12Mo1V1 die steel component owned the smallest roughness of 0.027 μm, the highest micro-hardness value of 867 Hv_0.1 and the largest residual compressive stress of −1318 MPa, respectively. Meanwhile, the contact fatigue life of the Cr12Mo1V1 die steel component was significantly improved by 223% to 5.231 × 10⁷ cycles. After ultrasonic impact treatment, the spalling pits revealed that the crack propagation angle increased from 28° to 34°, the depth increased from 153 μm to 175 μm, and the failure mode consisted of Hertz’s contact theory. This study provides an effective surface strengthening solution for enhancing the contact fatigue performance of Cr12Mo1V1 die steel components.

In this article, the Ni-TiN coatings deposited on the surface of Q235 steel substrate via a magnetic-assisted electrodeposition approach. The surface morphology, Ti content, phase structure, and corrosion resistance of Ni-TiN coatings were investigated using a scanning electron microscope (SEM), a transmission electron microscopy (TEM), an energy disperse spectroscopy (EDS), an X-ray diffraction (XRD) instrument, and electrochemical workstation facility, respectively. SEM images showed that the surface morphology and thickness value of Ni-TiN coatings prepared at 0.7 T were superior to those obtained at 0.3 T and 1.1 T. EDS and adhesion strength results presented that the Ti content and adhesion strength of Ni-TiN coatings was lower than those produced at 0.7 T and 1.1 T. Meanwhile, Ni-TiN coatings prepared at 0.7 T possessed the highest hardness of 817.3 Hv. XRD patterns exhibited the nickel diffraction peaks of the Ni-TiN coatings fabricated at 0.7 T were broad and low, demonstrating that the size of nickel grain was fine. In comparison to other two Ni-TiN coatings, the one manufactured at 0.7 T possessed a high corrosion potential and a low corrosion current density, illustrating its outstanding corrosion resistance. Corrosion surface morphology revealed that the obvious corrosion pits emerged on the surface of Ni-TiN coatings deposited at 0.3 T, while the obvious corrosion pits were not appeared on the surface of Ni-TiN coatings manufactured at 0.7 T. In addition, the average corrosive weight loss of Ni-TiN coatings prepared at 0.7 T possessed the lowest of 7.2 mg, indicating the excellent corrosion resistance.

In this article, electrodeposited Ni-Al₂O₃ coatings were fabricated on the surface of a cylinder liner to enhance its corrosion resistance. The effect of current density on the surface morphology, phase structure, and corrosion resistance of the Ni-Al₂O₃ coatings was investigated using a scanning electron microscope (SEM), X-ray diffraction (XRD) instrument, and electrochemical workstation, respectively. The observed results show that a dense, flat morphology emerged on the surface of the Ni-Al₂O₃ coatings prepared under a current density of 3.5 A/dm². Furthermore, among three Ni-Al₂O₃ coatings, the Al content of the one prepared under a current density of 3.5 A/dm² was the highest, with a value of 5.4 wt.%. XRD patterns demonstrated that the average nickel grain size of the Ni-Al₂O₃ coatings prepared at 3.5 A/dm² was only 251.6 nm, which was obviously smaller than those deposited under current densities of 2.5 A/dm² and 4.5 A/dm². Meanwhile, the adhesion strength of the Ni-Al₂O₃ coatings prepared under a current density of 3.5 A/dm² was the largest, with a value of 40.9 N. Polarization curves indicated the corrosion potential of the Ni-Al₂O₃ coatings prepared under a current density of 3.5 A/dm² was the highest, with a value of −0.42 V, while the corrosion current density of the coatings fabricated under a current density of 3.5 A/dm² was the lowest, with a value of 2.17 × 10⁻⁷ A/cm². In addition, the corrosive mass loss of Ni-Al₂O₃ coatings manufactured at 3.5 A/dm² was only 2.8 mg, illustrating excellent corrosion resistance. This study could enhance the service life and corrosion resistance of cylinder liners in internal combustion engines.

To enhance the anti-corrosion performance of storage tanks, Ni–SiC composites were successfully fabricated on the surface of Q345 steel substrate via the ultrasonic electrodeposition technique. The influence of ultrasonic power on the surface morphology, element content, phase structure, and anti-corrosion performance of Ni–SiC composites were explored utilizing a scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and an electrochemical workstation, respectively. SEM images showed that the Ni–SiC composites obtained at 120 W had a flat, dense surface morphology, with a uniform distribution of SiC nanoparticles (NPs) and a refined size of nickel grains. Meanwhile, the Si content (7.3 wt.%) of Ni–SiC composites prepared at 120 W was obviously higher than those obtained at 0 W (4.8 wt.%) and 60 W (6.1 wt.%). The thicknesses and adhesion force of Ni–SiC composites manufactured at 120 W were the largest of 103.5 μm and 51.2 N, respectively. XRD patterns presented that the diffraction peaks intensity and width of Ni–SiC composites manufactured at 120 W were lower and broader than that of Ni–SiC composites manufactured at 0 W and 60 W. A corrosion test illustrated that the Ni–SiC composites prepared at 120 W had the lowest corrosion current of 3.5 × 10⁻³ mA/cm², the lowest corrosive weight loss (4.2 mg) and corrosion rate (0.06 mg/h), while the corrosion potential was the highest of −0.41 V, which demonstrated the best anti-corrosion performance. In addition, the co-deposition mechanism of SiC NPs and Ni²⁺ ions was also analyzed.

Cuttings transport behavior plays a crucial role in downhole safety, drilling efficiency, and wellbore cleaning during underreaming operations. Because of the complex local flow passage and eccentric structural characteristics of a bidirectional eccentric micro-underreamer, cuttings migration and discharge are highly sensitive to downhole operating conditions. In this study, a three-dimensional solid–liquid two-phase flow model was established for a bidirectional eccentric micro-underreamer, and an Eulerian–Lagrangian approach was employed to describe the two-way coupling between the drilling fluid and cuttings particles. After the blade structural parameters were optimized, the effects of drill string rotational speed, weight on bit, drilling fluid density, and drilling fluid viscosity on cuttings transport behavior were systematically investigated. The results indicate that drill string rotational speed and weight on bit both exert non-monotonic effects on cuttings discharge efficiency, and relatively favorable cuttings-carrying performance was achieved at 50 r/min and 100 kN, respectively. By contrast, increasing drilling fluid density weakened cuttings transport performance, whereas increasing drilling fluid viscosity enhanced the drag and suspension capacities of the fluid for cuttings particles. Within the investigated range, a drilling fluid density of 1.6 g/cm³ and a viscosity of 50 mPa·s were associated with relatively favorable cuttings-carrying performance. These findings provide a theoretical basis for the optimization of operating parameters and the engineering application of bidirectional eccentric micro-underreamers.