Microstructure, Physical Properties, and Tribological Characteristics of Composite Solid Lubricant Coatings with Gas Atomized BaF₂-CaF₂

Abstract

PS304 is a NASA-developed composite solid lubricant for friction and wear reduction at high temperatures. The microstructure, physical properties, and tribological performance of PS304 using standard comminuted BaF₂-CaF₂ and novel gas atomized BaF₂-CaF₂ were compared. Two atomized BaF₂-CaF₂ particle size distributions were used. Overall, feedstock powder with atomized BaF₂-CaF₂ flowed more freely than standard PS304 feedstock. The cohesion strength of coatings with atomized BaF₂-CaF₂ was lower than that of standard PS304, while the hardness of all of the studied coatings was essentially the same (approximately 58 HRA). Pin wear was lower against the new coatings and the coefficients of friction were essentially the same for all coatings. These results indicate that atomized BaF₂-CaF₂ can be substituted for comminuted BaF₂-CaF₂, providing a high-volume BaF₂-CaF₂ fabrication technique to reduce the cost of PS304 and improve its commercial availability.

KEY WORDS:

• Adverse Environments Tribology (High Temperatures; Solid Lubricated)
• Aerospace Tribology
• Solid Lubricants
• Surface Films/Coatings (Composite)

ACKNOWLEDGEMENTS

Thank you to Brian J. Edmonds, Jerome Singleton, and to the late Victor Lukaszewicz for technical assistance during this investigation. The helpful discussions with Dr. Christopher DellaCorte are also greatly appreciated.

Review led by Thierry Blanchet