Microstructure and high-temperature tribological properties of electro-jet mask printing (CFx)n/CaF2-ZrO2 interlaced coatings

The (CF_x)_n/CaF₂-ZrO₂ interlaced coating was prepared using electro-jet mask printing technology. The effects of CaF₂ content (0, 25, 50 wt%) on its microstructure, adhesion strength, and wear properties against 304 stainless steel balls at high temperatures (25, 200, 400 °C) were investigated. The results indicated that the interlaced structure of the coating helped prevent the loss of lubricant particles and reduced the actual contact area between the counterparts. The addition of CaF₂ reduced the surface roughness and porosity of the (CF_x)_n coating and suppressed thermal weight loss and fatigue peeling of the coating. At 25 °C, the (CF_x)_n-ZrO₂ interlaced coating showed the lowest friction coefficient of ∼ 0.13, although the brittle CaF₂ particles hindered lubrication. At 200 °C, the presence of CaF₂ reduced the wear rate of the friction pair. At 400 °C, the interlaced coating with 25 wt% CaF₂ showed the lowest friction coefficient of ∼ 0.29, and both the coating and counterpart had low wear rates. This improvement was primarily attributed to the brittle-to-ductile transition of CaF₂ at high temperatures and the formation of new lubricants. Adhesive wear, oxidative wear, and delamination were the predominant wear mechanisms.