Enhancing the Elevated Temperature Tribological Performance of Ni-Based Cermet Coatings for Industrial Applications Deposited by Atmospheric Plasma Spray

The present work reports the development of coatings for harsh environments by improving the understanding of interactions between solid lubricants under extreme conditions, thereby aiding the design of more effective lubrication systems for high-temperature applications. The study provides valuable insights into optimizing the content of solid lubricants in coating materials for the intended purpose. The tribological characteristics of plasma-sprayed coatings, namely Ni-Al-MoS₂-5 wt.% Ag (NM5), Ni-Al-MoS₂-10 wt.% Ag (NM10), Ni-Al-MoS₂-12.5 wt.% Ag (NM12.5), Ni-Al-MoS₂-15 wt.% Ag (NM15), and Ni-Al-MoS₂-12.5 wt.% Ag-7 wt.% Cr₂O₃ (NM12.5 + 7 wt.% Cr₂O₃), were evaluated using a ball-on-disk tribometer. The tests were conducted from room temperature (RT) 25-800 °C against Al₂O₃ balls. The NM12.5 + 7 wt.% Cr₂O₃ coating demonstrated the exceptional lubricity, especially at elevated temperature (800 °C), outperforming other coatings. The NM12.5 + 7 wt.% Cr₂O₃ initially exhibited a slightly higher coefficient of friction (COF) compared to NM12.5, particularly at temperatures up to 400 °C. Beyond 400 °C, NM12.5 + 7 wt.% Cr₂O₃ showed a decreasing trend in COF and wear and finally attained the lowest COF (0.21) and wear rate 4.3 × 10⁻⁵ mm³/Nm at 800 °C. It emphasizes the pivotal role of solid lubricants in order to form continuous compacted layers on the worn surface, and enhancing the lubrication and wear resistance at elevated temperatures. The ability of NM12.5 + 7 wt.% Cr₂O₃ coating to achieve the lowest COF and wear at elevated temperatures highlights its effectiveness in extreme conditions.