Design, fabrication and properties of modified phosphate-based self-lubricating coatings for wide-temperature applications

To meet the lubrication requirements of advanced mechanical systems operating over a wide temperature range, a composite self-lubricating coating based on combined B 2 O 3 /SiO 2 -modified aluminum chromium phosphate (ACP) was developed. The effects of the combined incorporation of B 2 O 3 and SiO 2 on the high-temperature structural evolution of the ACP adhesive and the tribological performance of the coating were systematically investigated. The simultaneous incorporation of B 2 O 3 and SiO 2 promoted the formation of B-O and Si-O tetrahedral units, thereby improving the oxidation resistance and thermal stability of the adhesive. Meanwhile, the residual amorphous phase at elevated temperatures enhanced the toughness and interfacial bonding of the coating. The resulting coating exhibited an average pull-off bond strength of 4.60 MPa. After heat treatment at 300 and 800 °C, its room-temperature friction coefficients under loads of 2 and 5 N remained low, ranging from 0.120 to 0.196. During in situ high-temperature tribological tests, the average friction coefficients at 350, 500, 650, and 800 °C were 0.139, 0.311, 0.215, and 0.173, respectively. Furthermore, no obvious corrosion was observed after 3624 h of salt-spray exposure. These results demonstrate that the ACP-based coating prepared using the combined B 2 O 3 /SiO 2 -modified adhesive possesses excellent wide-temperature-range lubricity, thermal stability, and corrosion resistance, making it a promising candidate for complex service environments involving coupled thermal, mechanical, and corrosive conditions.