Long-Term Lubrication at 500 °C Using Continuously Replenishable Solid Lubricating Film Polymerized In Situ by Gasified Monomers PA and PPD

Re‐attainable lubrication films at 500°C converted through the positional polymerisation of DCDPS on the preset Na2S coating

“…The initially added Na 2 S and DCDPS would be almost entirely reacted after 10 min, and the DCPDS singly re-added at 10 min cannot form solid products at high temperature by itself. 18 Thus, residues with polymer structure after 30 min test could only be attributed to the re-polymerisation of secondary added DCDPS with the degradation products from the earlier stage.…”

“…With friction continues, these polymerised products would be degenerated, carbonised, and finally become residual carbon particles which have good slipping ability as a friction-reducing filler. 18 Meanwhile, some polymerised layer would be peeled off, forming transfer films on the steel balls. This could explain the further decrease of the COF (about 0.05) after 1 min.…”

“…PPSS provides bearing capacity and wear resistance, degradation products improve the cohesion of the transfer films, and the residual carbon could be treated as easily sheared materials which would reduce the COF of the composite lubricating films. 18,22,30 However, fresh DCDPS could contact and react with the broken main chains before further oxidising and degrading, as the re-polymerisation process in route 4. The re-polymerisation products would cause the secondary reduction of COF and the extended lubrication time in test B-30.…”

“…However, unlike the vapourdeposited lubrication, polymers cannot be gasified and introduced into friction system. Our group found that polymer products could be generated above 400 C through the gas-phase polymerisation of two monomers, 17 and developed a gas-phase polymerising lubrication method 18 : During the friction process, two gasified monomers, phthalic anhydride and p-phenylenediamine, were introduced into friction system at 500 C. They would be gasified, contacted and polymerised into polymer products with the structure of imides, thus forming lubricating films in real-time. In a 10 min friction test at 500 C with 50 N loading and 0.785 m/s sliding speed, the coefficient of friction (COF) and wear could be reduced by 56% and 97% through the gas-phase polymerising lubrication, and this frictionreducing effect could be re-attained by re-introducing monomers.…”

A review of advances in tribology in 2020–2021

“…Bi et al [802] used two gas-phase monomers phthalic anhydride (PA) and p-phenylenediamine (PPD) through their introduction into the contact region for synthesis of solid lubricant film and its replenishment during on friction couples for effective lubrication at high temperature of 500 °C. The authors illustrated the effectiveness of generating solid lubricating film by polymerization of PA and PPD in a 38-min medium-term test using a two E52100 steel balls on W6Mo5Cr4V2 high speed steel disc test configuration as can be seen from Fig.…”