Superlubrious high temperature coatings
A low friction wear surface operable at high temperatures and high loads with a coefficient of friction in the superlubric regime including MoS 2 and graphene-oxide on the wear surface is provided, and methods of producing the low friction wear surface are also provided. The low friction wear surface remains with a coefficient of friction in the superlubric regime at temperatures in between about 200° C. and 400° C.
1. A method of forming a low friction wear surface comprising:
suspending graphene-oxide in a solvent to form a solution of at least 1 g/L;
adding at least 1 g/L of MoS 2 ultrafine nanocrystalline flakes to the solution;
sonicating the MoS 2 and the solution to form a homogenous solution; and
disposing the homogeneous solution by:
spraying the homogeneous solution on a substrate via a process of air-spray coating, wherein the substrate has a temperature at about 275° C.;
forming a wet film on the substrate; and
evaporating the solvent component to form a dry coating layer;
wherein the graphene oxide and the MoS 2 are in a range of ratios of 8:10 to 10:8 by weight.
2. The method of claim 1 , wherein the solvent component is water.
3. The method of claim 1 , wherein the solvent component is oil-free.
4. The method of claim 1 , further comprising evaporating the solvent component and encapsulating the MoS 2 flakes in large blankets of graphene-oxide in one step.
5. The method of claim 1 , further comprising achieving a coefficient of friction value in between about 0.001 and about 0.06 at a temperature in between about 200° C. and about 400° C.
6. The method of claim 5 , further comprising demonstrating a coefficient of friction value less than 0.06 for a duration of about 15 minutes to about 3.4 hours, inclusive at a temperature in between about 200° C. and about 400° C.
7. The method of claim 1 , wherein the substrate comprises a steel material.
8. The method of claim 1 , further comprising achieving a coefficient of friction value less than 0.1 at a temperature in between about 22° C. and about 100° C. in ambient conditions.
9. A low friction wear surface comprising:
a substrate;
graphene-oxide in an oil-free solvent disposed over the substrate; and
MoS 2 ultrafine nanocrystalline flakes disposed over the substrate;
wherein the graphene-oxide and the MoS 2 are in a range of ratios of (1±0.25):(1∓0.25) by weight, respectively.
10. The low friction wear surface of claim 9 , wherein the graphene-oxide and the MoS 2 are disposed on a substrate heated to about 275° C.
11. The low friction wear surface of claim 9 , wherein the solvent is water.
12. The low friction wear surface of claim 9 , further comprising a coefficient of friction value less than 0.06 for a duration of about 15 minutes to about 3.5 hours, inclusive, at a temperature in between about 200° C. and about 400° C.
13. The low friction wear surface of claim 9 , further comprising a maximum contact pressure in between about 0.1 GPa and 1.0 GPa at a temperature in between about 200° C. and about 400° C.
14. The low friction wear surface of claim 9 , further comprising a coefficient of friction value less than 0.1 at a temperature in between about 22° C. and about 100° C. in ambient conditions.
15. The low friction wear surface of claim 9 , wherein the substrate comprises at least a portion of a metal working die, a wind turbine, a polymer injection molding die, a piston, a piston ring, a piston sleeve, a ball and roller bearing element, an oil-free air compressor, a gas compressor, a gas seal, a sliding rail guide, or a heavy load bearing wheel guide.
16. A method of forming a sliding mechanical system with a low friction wear surface comprising:
forming a homogeneous solution comprising MoS 2 and graphene-oxide in a range of ratios in between 0.75:1.25 and 1.25:0.75;
disposing over a substrate, the homogeneous solution to form a first sliding component; and
sliding the first sliding component against a second sliding component in ambient air;
wherein scrolls of MoS 2 are formed and encapsulated in the graphene-oxide.
17. The method of claim 16 , wherein the second sliding component comprises a steel material.
18. The method of claim 16 , further comprising sliding the first sliding component and the second sliding component at a temperature in between about 200° C. and about 400° C.
19. The method of claim 16 , wherein disposing the solution over the substrate comprises a method of air-spray coating, wherein the substrate has a temperature at about 275° C.
20. The method of claim 16 , wherein the homogenous solution comprises an oil-free solvent.