The tribological behavior of silicon nitride (Si₃N₄) ceramic with textured patterns under water lubrication was investigated in this paper. Different textured patterns were fabricated using laser surface texturing (LST). Surface wettability was characterized by contact angle. The original surface and textured Si₃N₄ ceramic with triangular patterns presented as hydrophobic. However, the textured Si₃N₄ ceramic with hexagonal patterns presented as hydrophilic. Surface wettability and textured patterns were important factors affecting the friction performance of the Si₃N₄ ceramic. Our results indicated that symmetrical textured patterns were more beneficial for decreasing the coefficient of friction (COF) at lower reciprocating frequencies. In contrast, better surface wettability played a more important role in reducing the COF at higher reciprocating frequencies. The most severe damage observed on the untextured Si₃N₄ ceramic led to a higher wear rate. The symmetrical structure of hexagonal patterns was more conducive to decreasing the wear rate than triangular patterns. However, the Si₃N₄ ceramic with triangular patterns was more suitable for use at high-speed frictions due to better lubrication. The textured patterns had the function of storing lubricants and capturing and cutting debris. Thus, friction performance was improved by introducing textured patterns onto the surface of the Si₃N₄ ceramic. The friction and wear mechanisms are also discussed in this study.

Silicon nitride (Si₃N₄) ceramic is widely used in the production of structural components. The surface wettability is closely related to the service life of materials. Laser surface texturing is considered an effective method for controlling surface wettability by processing specific patterns. This research focused on the laser surface texturing of a Si₃N₄ ceramic, employing rectangular patterns instead of the typical dimple designs, as these had promising applications in heat transfer and hydrodynamic lubrication. The effects of scanning speed and number of scans on the change of the morphologies and dimensions of the grooves were investigated. The results indicated that the higher scanning speed and fewer number of scans resulted in less damage to the textured surface. As the scanning speed increased, the width and depth of the grooves decreased significantly first, and then fluctuated. Conversely, increasing the number of scans led to an increase in the width and depth of the grooves, eventually stabilizing. The analysis of the elemental composition of different areas on the textured surface presented a notable increase in oxygen content at the grooves, while Si and N levels decreased. It was mainly caused by the chemical reaction between Si₃N₄ ceramic and oxygen during laser surface texturing in an air environment. This study also assessed the wettability of the textured surface, finding that the contact angle of the water droplet was significantly affected by the groove dimensions. After laser surface texturing, the contact angle increased from 35.51 ± 0.33° to 57.52 ± 1.83°. Improved wettability was associated with smaller groove volume, indicating better hydrophilicity at lower scanning speed and enhanced hydrophobicity with a fewer number of scans.

Laser surface texturing (LST) was used to process circular patterns on silicon nitride (Si₃N₄) ceramic. The surface wettability of un-textured and textured Si₃N₄ ceramic was studied. It was found that all samples were hydrophilic. The hydrophilicity of the textured Si₃N₄ ceramic with a smaller interval was weaker. Effect of the interval on the tribological performance of Si₃N₄ ceramic was investigated under different reciprocating frequencies. As the reciprocating frequency increased, the coefficient of friction (COF) of Si₃N₄ ceramic showed an overall upward trend. And the COFs of textured Si₃N₄ ceramic were higher. At the reciprocating frequency of 0.5 Hz, the COFs of textured samples with different intervals were relatively close. At higher reciprocating frequency, the difference in COF gradually increased. This can be attributed to the change in lubrication state that occurs during the frictional process. Debris and plough were found at surface of all samples, and the original surface was cleaner. The surface damage of textured samples was more severe than that of un-textured samples. EDS analysis on the wear area was performed. The wear rate of the frictional pair at the interval of 250 μm was higher. It was consistent with the more significant wear marks on the surface of the Si₃N₄ ceramic at this interval. There were significant differences in the frictional process between un-textured and textured samples. For the un-textured surface, the debris was mainly concentrated at the edges of the friction trajectory. In contrast, textured patterns had the function of storing lubricant, while also generating micro-shear effects on debris and improving the status of lubrication, resulting in more complex frictional process.

The finite element method has been able to simulate and solve practical machining problems, achieve the required accuracy and the highly reliability. In this paper, the simulation models based on the material properties of the self-prepared Si3N4 insert and HT250 were created. Using these models, the results of cutting force, cutting temperature and tool wear rate were obtained, and tool wear mode was predicted after cutting simulation. These approaches may develop as the new method for testing new cutting-tool materials, shortening development cycle and reducing the cost.