In Situ Lubrication with Boric Acid: Powder Delivery of an Environmentally Benign Solid Lubricant

In situ deposition of boric acid in dry powder form is investigated as a potential environmentally benign solid lubricant for sliding metal contacts. Boric acid is widely used in industrial processes and agriculture, is not classified as a pollutant by EPA, and produces no serious illnesses or carcinogenic effects from exposure to solutions or aerosols. In this study, boric acid powder is aerosolized and entrained in a low-velocity jet of nitrogen gas, which is directed at a self-mated 302 SS sliding contact in a rotating pin-on-disc tribometer. The effects of powder flow rate, sliding speed, normal load, and track diameter on coefficient of friction and wear rate are investigated. Friction coefficients below μ = 0.1 can be consistently reached and maintained as long as the powder flow continues. Wear rates are reduced over 2 orders of magnitude.

Review led by Paul Bessette

KEYWORDS:

• Solid Lubrication
• Powder Delivery
• Environmentally Friendly
• Green Manufacturing

ACKNOWLEDGEMENTS

The authors gratefully thank Jeff Bardt, Jerry Bourne, Dan Dickrell, Ali Erdemir, Nicole McCook, and Jason Steffens for their assistance and helpful discussions during this project.

Notes

Review led by Paul Bessette

*Midpoint condition μ_avg = 0.044, standard deviation, σ = 0.009; K_avg = 1.54 σ = 1.15.