Tribological behaviours of Si3N4-hBN composites /2507 stainless steel sliding pair in electroplating wastewater

In the wastewater treatment device, the core moving parts (such as the check valve in the pump body) are prone to failure due to wear and corrosion. There is an urgent need to develop high-performance self-lubricating materials suitable for moving components in electroplating wastewater. Therein, the tribological properties of Si3N4 (silicon nitride) based composites with the addition of hBN (hexagonal boron nitride) against 2507 duplex stainless steel in electroplating wastewater were investigated using a Pin-On-Disc (POD) tribometer. The results show that the addition of hBN to the ceramic matrix could effectively improve the tribological properties of Si3N4 materials. The friction coefficient and wear rate of Si3N4 are lowered to 0.14 when the hBN content reaches 30 wt %, which is attributed to the formation of a lubricating films (containing hBN, Si(OH)4 and Cu and its oxides) on the worn surfaces. A segmental test results indicate that the lubricating film undergoes processes such as formation, spalling, and regeneration during the friction process. Meanwhile, hBN and Si(OH)4, due to their inherent structural characteristics, can lubricate and protect the worn surfaces. The molecular dynamics simulation results indicate that Cu and its oxides are prone to slip under normal and transverse forces, and have a positive effect on reducing friction.