Cold spraying has a potential application prospect in the field of repairing and additive manufacturing. The critical velocity of the cold spray is a key factor that determines the adhesion of particles during the cold spraying process, and it only depends on the particle parameters under the same working conditions. In the present study, the relationship between particle parameters and critical velocity is investigated using a feature selection method to obtain the influence weight of different particle parameters. Based on the results of feature selection, linear and nonlinear artificial neural networks are established to predict the critical velocity, respectively. The results of the feature selection show that the mechanical parameters of the material have a higher influence weight on the critical velocity than thermal parameters. In the prediction model, the ANN (artificial neural network) method shows a good prediction, and the nonlinear ANN model achieves better generalization ability than the linear ANN model and empirical formula with 95.24% prediction accuracy on the original data set and 96.45% prediction accuracy on the new data set.

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Low-pressure cold spraying has gained much significance for its good economy in recent years. However, compared with high-pressure cold spraying, the unsatisfactory performance of coatings prepared by this method is a key problem restricting its further development. To improve the properties of the coating without incorporating severe conditions, the paper proposed an original shot-peening-assisted low-pressure cold-spraying method (i.e., SP-LPCS). By proceeding with cold spraying and shot peening alternately, SP-LPCS was proved to enhance the mechanical property of the coating effectively. Mixed particles of Zn, Al, and Al2O3 were adopted as the coating powder. Effects of shot-peening pressure, flow rate, and shot size on the micromorphology and the microhardness variance were studied. Results shows that the thickness of the plastic deformation layer stabilizes as the impact time increases to 6. The microscopic simulation of the deformation shows that according to the different metal characteristics of the powder, brittle grains fracture while plastic grains go through deformation and refinement. Meanwhile, the porosity decreases greatly after the impacts, resulting in a higher denseness of the coating. Several factors mutually contribute to the performance improvement of the coating. The microhardness of the material was increased after SP-LPCS, and obvious strengthening belts were observed, with the highest microhardness being 90.93Hv.

In this research, the four-ball tribometer was examined to evaluate the tribological behavior of environment-friendly nano-MoS2 water-based rolling liquid. This experimental method is used to measure the maximum non-seizure load (PB) and the coefficient of friction (μ). The newly introduced parameter ω can be combined with PB and μ to evaluate the tribological performances of the rolling liquid comprehensively. The rolling lubrication performance of nano-MoS2 water-base lubricant was investigated using a single stand 4-high reversing rolling mill. The surface morphologies and rolling textures of the samples were measured by laser scanning confocal microscope after cold rolling. The results show that when the concentration of nano-MoS2 is 0.4wt.%, the water-based rolling liquid has excellent tribological and lubricating properties. Meanwhile, compared with the surface quality of the rolled strip under other lubrication conditions, the surface quality of the cold-rolled strip using 0.4wt% nano-MoS2 rolling liquid as the lubrication condition is smooth without visible surface defects.

The abrasive particles in the working emulsion were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The wettability and lubricating properties of different emulsion samples were tested by MRS-10E four-ball friction and wear testing machine. The results show that the average particle size of the abrasive particles in the working emulsion is 2.72 μm, the smallest particle size of the abrasive particles is 0.36μm, and the largest size of the abrasive particles is 6.57μm. Furthermore, the abrasive particles can increase the internal friction of emulsions, which leads to the increasing wetting Angle. The abrasive particles cause the lubrication performance of working emulsion to decrease, which eventually leads to larger wear scar diameter and the worse morphology of wear scar on the tested ball.