Currently, the mechanical performances of polylactic acid (PLA) samples prepared using the fused filament fabrication (FFF) technique are relatively poor. Hence, the carbon fiber (CF) is used to improve the thermal stability and mechanical property of FFF-ed PLA samples in this paper. The crystalline structure, thermal stability, melt flow rate, tensile strength and fractured surface morphology of PLA and PLA/CF samples were investigated with an X-ray diffraction device, differential scanning calorimeter, thermogravimetric analyzer, melt flow rate equipment, universal tensile test machine and scanning electron microscope, respectively. Meanwhile, the reinforcement mechanism of CF on the mechanical property of PLA samples was also analyzed. XRD results revealed that the diffraction peaks intensities of PLA/CF sample were obviously lower than those of PLA sample. TGA and DSC curves illustrated that the initial thermal decomposition temperature, thermal stability and crystallinity of the PLA/CF sample improved significantly. The tensile strength of the PLA/CF sample was 91.58 MPa, which was 42.49% higher than that of the PLA sample. Moreover, SEM images showed that the fractured behavior of the PLA sample varied from brittle fracture to ductile fracture after the introduction of CF. The results concluded the CF is a feasible fiber for enhancing the performances of the PLA sample.

The corrosion resistance of nickel–titanium nitride (Ni/TiN) composites is significantly influenced by the operation parameters during the jet pulse electrodeposition (JPE) process. The effect of current density, jet rate, TiN concentration, and duty cycle impact on the anti-corrosion property of Ni/TiN composites were investigated and optimized using the response surface method (RSM). After the optimization of the operation parameters, the corrosion current of Ni/TiN composites decreased from 9.52 × 10⁻⁵ A/cm² to 4.63 × 10⁻⁵ A/cm². The corrosion current of Ni/TiN composites decreased initially and then increased with an increase in current density, jet rate, TiN concentration, and duty cycle. During the jet electrodeposition process, the influence of the duty cycle on the corrosion current of Ni/TiN composites was comparatively insignificant, whereas the concentration of TiN had a significant effect on the corrosion current. The error rate between the predicted value and the measured result from the corrosion current of Ni/TiN composites was only 0.64%, indicating the high accuracy of fitting the model. Furthermore, X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images revealed that the optimized Ni/TiN composites comprised significant Ti content, fine nickel gain, and a compact, smooth structure. In addition, the electrochemical measured results demonstrated that the optimized Ni/TiN composites possessed a low self-corrosion current and high self-corrosion potential. These findings show that the optimized composites have a substantially greater corrosion resistance compared to two other unoptimized Ni/TiN composites.

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.

Turbodrills are extensively utilized within the oilfield development industry. In order to enhance the performance output of turbodrills, a novel stator and rotor structure has been conceptualized. Fluent 19.0 numerical simulation software was employed to ascertain the output characteristics of the rotor within the flow field. The drilling engine output performance was the subject of a qualitative study, which was conducted using the drilling mud pump test equipment during drilling. Furthermore, a speed torque meter measurement system was designed to quantitatively analyze the output torque and speed performance of the prototype. The results show that: ① Through the numerical simulation method, it is verified that the new structural rotor has the output performance of a conventional rotor. ② Comparing the numerical solution and the test value, it can be seen that the relative error value is within 4.3%, indicating that the numerical simulation has a certain accuracy. ③ When the inlet displacement is 30 L/s and the speed is 1400 r/min, the maximum value of the numerical solution of the output torque of a single rotor group is 12.45 N/m. When the inlet displacement increases from 18 L/s to 30 L/s, the maximum torque numerical solution increases from 10.78 N/m to 27.44 N/m.

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.

Through hydraulic control principles, numerical simulation and indoor testing, the opening principle of a toe-end sliding sleeve with a time delay mechanism is explained. Conventional toe-end sliding sleeve in shale oil wells have problems with premature opening and a failure to open, which means they cannot ensure the whole-well pressure test process and can cause serious economic losses to the oil and gas industry. In order to solve the above problems, a new type of optimal design for toe-end sliding sleeve with a 30 min delayed opening is proposed. In this paper, based on the principle of hydraulic flow, ABAQUS 2022 numerical simulation software was used to study the influence of different states and the same hydraulic pressure on its internal stress–strain value. A qualitative study of the delayed-opening function was carried out using a pressurized pump unit. In addition, principle tests under different operating parameters were designed to quantitatively analyze the pin shear situation and the delayed opening time of the toe-end sliding sleeve when the tool was fitted with different numbers of pins and when the delay valve was fitted. In addition, the simulation results of the hydraulic fluid’s flow inside the time delay mechanism with different nozzle diameters were compared with the theoretical values, which showed that the hydraulic fluid’s flow rate inside the mechanism increased with the enlargement of the nozzle diameter, and the optimal nozzle diameter was 0.56 mm. The indoor test showed that when the tool was retrofitted with a time delay mechanism, installing six pins was the optimal combination. The field application of the slip-on was able to satisfy an opening time delay of 28.3 with a relative error of only 5.67%. These results complement the research on toe-end sliding sleeve and provide ideas for the optimization of toe-end slipcovers incorporating a time delay mechanism.