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To systematically investigate the friction and wear behavior of TiC/Ni composites under microscopic, the molecular dynamics (MD) method was used to simulate nano-friction on the TiC/Ni composite. Mechanical properties, abrasion depth, wear rates, temperature change of the material during friction, the microscopic deformation behavior, and the evolution of nickel-based titanium carbide microstructure at high-speed friction have been systematically studied. It was found that the variation of tangential and normal forces is related to the relative position of the grinding ball and the TiC phase, when the grinding ball is located above the TiC phase, large fluctuations in the frictional force occur and extreme value of normal force appears, shallow abrasion depth and low wear rate. During the friction process, there is a high-stress area between the grinding ball and the TiC phase, generating a large number of dislocations. The presence of the TiC phase hinders the development and extension of defects, resulting in a significant increase in temperature. At the same time, dislocation entanglement occurs, which improves the wear resistance of the workpiece. In addition, it was also found that the internal atomic motion guided by the carbonized phase was related to the position of the grinding ball relative to the reinforced phase, with the reinforced phase presenting a tendency to rotate in different directions when the grinding ball was in different positions relative to the reinforced phase, which in turn affected the deformation of the whole workpiece. [ABSTRACT FROM AUTHOR]

In this work, molecular dynamics simulations are employed to study the nanotribological process of nickel-based polycrystalline superalloy coating. A series of simulations were carried out using the method of repeated friction to explore the influence of frictional force, friction coefficient, grinding groove morphology, wear scar depth, debris flow direction, subsurface damage degree and evolution of defects during the nano-friction process. In addition, the change mechanism of different grain sizes on wear scar depth, frictional force, friction coefficient, and internal damage in the repeated friction process is also explored. The results show that the frictional force is related to the direction of the dislocation slip, and that the friction coefficient change is related to the number of repeated frictions. Moreover, it is observed that the grinding ball has a shunting effect on the formed wear debris atoms, and the shunt point is located at the maximum horizontal radius. We reveal that the grain boundary structure has a strengthening effect. When the grinding ball rubs to the grain boundary, the nucleation of dislocation defects inside the workpiece is obviously hindered by it. Simultaneously, we also find that the closer the subsurface is to the bottom of the grinding ball, the greater the degree of damage to the workpiece by friction. Furthermore, with the grain size decreases that the material begins to soften, resulting in a decrease of frictional force, friction coefficient, and smaller defects are formed inside the workpiece. The research of this work can better clarify the microscopic mechanism of the polycrystalline friction process. [ABSTRACT FROM AUTHOR]

The Mo–Si–B alloys with good wear resistance are prominent for high-temperature applications. In this work, the effects of ZrB 2 content and test temperature on the tribological properties of the Mo–Si–B/ZrB 2 composites at 25–800 °C were investigated. It indicates that the composites show an enhanced wear resistance, which can be ascribed to the improved hardness and formation of Zr-rich borosilicate layer by introducing ZrB 2 particles. The main wear mechanism is abrasive wear accompanies with adhesive wear at 25–400 °C, where ZrB 2 addition can reduce the wear loss. And adhesive wear dominates at 600–800 °C, where the formed tribo-layer can provide a good self-lubricity and is beneficial for improving the wear resistance of the composites. • Tribological properties and wear mechanism at 25–800 °C were investigated. • The composites show lowest COF and wear rate at 600 °C for good self-lubricity. • The self-lubricity is mainly derived from MoO 3 containing oxides film. • The formation of Zr-rich borosilicate layer improves the wear resistance at 800 °C. • Abrasive wear dominates at 25–400 °C and adhesive wear dominates at 600–800 °C. [ABSTRACT FROM AUTHOR]

Abstract: The surface roughness and optical properties of diamond films untreated and treated by activated hydrogen have been investigated. After hydrogen ion treatment the surface of the film is modified effectively. Optical properties of the treated film are better than those of the untreated one. [Copyright &y& Elsevier]

The molecular dynamics method was used to simulate repeated nano-friction on a nickel-based single crystal (NBSC) superalloy. The friction force, atomic displacement, wear scar morphology, subsurface defects, potential energy, and other aspects were comprehensively studied to understand the friction mechanism of NBSC during working conditions. The frictional force fluctuated significantly and the coefficient of friction decreased during the repeated friction process. As the friction cycles increased, the wear scars of the γ' phase deepened, whereas those in the γ phase became shallower. Simultaneously, repeated friction reduced the volume and number of stacking faults. Additionally, the two phases softened to some extent at higher temperatures, but the phase boundary still had good wear resistance at high temperatures. • The grinding ball repeatedly rubs the workpiece in all directions, which can better study the friction behavior of the workpiece material in all directions. • In the model, the coherent interface of materials is reproduced and other elements are added to make the simulation more realistic. • The friction fluctuates greatly with the coherent interface as the turning point after repeated friction. • The coherent interface inhibits the movement of atoms and blocks the extension of stacking faults. • At the same time friction, the γ phase wear scar depth is always higher than γ' phase, and the γ' phase wear scars become deeper and deeper while the γ phase wear scars become shallower and shallower after repeated rubbing. [ABSTRACT FROM AUTHOR]