Thermal barrier coatings for internal combustion engines
A thermal barrier coating for an internal combustion engine includes an insulating thermal spray coating, where a chosen material of the insulating thermal spray coating has a thermal conductivity lower than 2 W/mK in fully dense form and the chosen material includes a coefficient of thermal expansion within 5 ppm/K of a coefficient of thermal expansion of a material of a component of the internal combustion engine upon which the coating is placed.
1. A thermal barrier coating for an internal combustion engine, comprising:
an insulating thermal spray coating, wherein:
a chosen material of the insulating thermal spray coating has a thermal conductivity lower than 2 W/mK in fully dense form; and
the chosen material includes a coefficient of thermal expansion within 5 ppm/K of a coefficient of thermal expansion of a material of a component of the internal combustion engine upon which the coating is placed.
2. The thermal barrier coating of claim 1 , wherein the insulating thermal spray coating comprises a perovskite material.
3. The thermal barrier coating of claim 2 , wherein the perovskite material is of the A 2 B 2 O 9 category, where A and B are cations.
4. The thermal barrier coating of claim 1 , wherein the insulating thermal spray coating comprises lanthanum molybdate (La 2 Mo 2 O 9 ).
5. The thermal barrier coating of claim 1 , wherein the insulating thermal spray coating comprises lanthanum molybdate (La 2 Mo 2 O 9 ) with at least one dopant, wherein the dopant is one of Bi, Ni, Rb, Y, Gd, Nd, Ba, Sr, Ca.
6. The thermal barrier coating of claim 1 , wherein the insulating thermal spray coating comprises gadolinium zirconate (Gd 2 Zr 2 O 7 ).
7. The thermal barrier coating of claim 1 , wherein the insulating thermal spray coating comprises lanthanum strontium cobalt ferrites, of the type La y Sr 1-y Co 1-x Fe x O 3 oxides.
8. The thermal barrier coating of claim 7 , wherein the x=0.4.
9. The thermal barrier coating of claim 1 , wherein the insulating thermal spray coating comprises a material from the sodium zirconium phosphate (“NZP”) class of ceramics that have a single crystal coefficient of thermal expansion below 5 ppm/K.
10. The thermal barrier coating of claim 9 , wherein the material from the sodium zirconium phosphate (“NZP”) class of ceramics is one of Sr 0.5 Hf 2 (PO 4 ) 3 , Sr 0.5 Zr 2 (PO 4 ) 3 , Ca 0.25 Sr 0.25 Zr 2 (PO 4 ) 3 , CsHf 2 (PO 4 ) 3 , Ca 0.25 Sr 0.25 Zr 2 (PO 4 ) 3 , Cs 1.3 Gd 0.3 Zr 1.7 (PO 4 ) 3 .
11. The thermal barrier coating of claim 1 , wherein the insulating thermal spray coating comprises calcium hexa-aluminate.
12. The thermal barrier coating of claim 1 , wherein the component is steel and the insulating thermal spray coating comprises a material from the sodium zirconium phosphate (“NZP”) class of ceramics that have relatively low single crystal coefficient of expansion below 5 ppm/K.
13. The thermal barrier coating of claim 12 , wherein the material from the sodium zirconium phosphate (“NZP”) class of ceramics is one of Sr 0.5 Hf 2 (PO 4 ) 3 , Sr 0.5 Zr 2 (PO 4 ) 3 , Ca 0.25 Sr 0.25 Zr 2 (PO 4 ) 3 , CsHf 2 (PO 4 ) 3 , Ca 0.25 Sr 0.25 Zr 2 (PO 4 ) 3 , Cs 1.3 Gd 0.3 Zr 1.7 (PO 4 ) 3 .
14. The thermal barrier coating of claim 1 , further comprising surface treatments through application of a top layer to enhance smoothness or enhance erosion resistance or reduce surface porosity.
15. The thermal barrier coating of claim 1 , further comprising a material to absorb thermal radiation at or near a surface of the insulating thermal spray coating.
16. The thermal barrier coating of claim 15 , wherein the material to absorb thermal radiation is one of Phosphor bonded Al 2 O 3 , Phosphor bonded Cr or Fe doped Al 2 O 3 , Phosphor bonded SiO 2 , Phosphor bonded Cr or Fe doped SiO 2 , Phosphor bonded ZrO 2 , Phosphor bonded Cr or Fe doped ZrO 2 , or calcium magnesium aluminosilicate glass.
17. The thermal barrier coating of claim 15 , wherein the material further comprises silicon carbide or silicon nitride.
18. The thermal barrier coating of claim 1 , wherein the component is one of a piston crown, a combustion chamber, a valve face, an exhaust port, or an exhaust manifold section.
19. A method for forming a thermal barrier coating, the method comprising:
applying an insulating thermal spray coating, wherein:
a chosen material of the insulating thermal spray coating has a thermal conductivity lower than 2 W/mK in fully dense form; and
the chosen material includes a coefficient of thermal expansion within 5 ppm/K of a coefficient of thermal expansion of a material of a component of the internal combustion engine upon which the coating is placed.
20. The method of claim 19 , further comprising polishing the insulating thermal spray coating.