Adherent coating on carbide and ceramic substrates
View Patent ↗An adherent coating for carbide and ceramic substrates employs a thin layer of hafnium nitride (HfN) between the substrate and a subsequent layer or layers. The thin layer may be employed without thermal cracking due to heat during use, such as for the insert of a cutting tool, because the upper layer or layers provide a gradual transition of material properties to a harder, less thermally conductive material on the outermost layer. A particular arrangement of layers on the carbide or ceramic substrate and hafnium nitride layer may be, from innermost to outermost layer, titanium carbide, aluminum oxide, and titanium nitride.
1. A tool comprising:
a. a substrate; and
b. a first coating on and in contact with the substrate comprising hafnium nitride, wherein the first coating has a thickness of less than 2 microns.
2. The tool of claim 1 , wherein the substrate comprises at least one of a carbide, a nitride, and a ceramic.
3. The tool of claim 1 , wherein the substrate further comprises a flashed coating comprising at least one of a carbide, a nitride, and an oxide.
4. The tool of claim 1 , wherein the first coating further comprises zirconium nitride.
5. The tool of claim 2 , wherein the first coating comprises a first coating surface devoid of cracks.
6. The tool of claim 2 , wherein the substrate comprises a combination of tungsten carbide particles of varying size.
7. The tool of claim 2 , wherein the substrate comprises a ceramic material selected from the group consisting of silicon nitride, aluminum oxide, titanium carbide, zirconium oxide, zirconium carbide, tungsten carbide, and aluminum nitride.
8. The tool of claim 7 , wherein the substrate further comprises at least one of toughening and reinforcing agents.
9. The tool of claim 2 , wherein the substrate comprises a polycrystalline cubic boron nitride and a ceramic binder.
10. The tool of claim 1 , further comprising a second coating on and in contact with the first coating, wherein the second coating comprises a material selected from the group consisting of titanium carbide, titanium carbonitride, zirconium nitride, zirconium carbonitride, and aluminum oxide.
11. The tool of claim 10 , wherein the second coating comprises a thickness no greater than about 40 microns.
12. The tool of claim 10 , wherein the second coating comprises titanium carbide.
13. The tool of claim 12 , further comprising a third coating on and in contact with the second coating, wherein the third coating comprises a material selected from the group consisting of titanium carbide, titanium carbonitride, zirconia carbonitride, and aluminum oxide.
14. The tool of claim 13 , wherein the third coating comprises aluminum oxide.
15. The tool of claim 14 , further comprising a fourth coating on and in contact with the third coating, wherein the fourth coating comprises a material selected from the group consisting of titanium carbide, titanium nitride, titanium carbonitride, zirconia carbonitride, and aluminum oxide.
16. The tool of claim 15 , wherein the fourth coating comprises titanium nitride.
17. The tool of claim 1 , further comprising an additional coating over the first coating, wherein the additional coating has a hardness that is greater than a hardness of the first coating, and wherein the additional coating has a lower measure of thermal conductivity than a measure of thermal conductivity for the first coating.
18. The tool of claim 17 , further comprising a plurality of additional coatings over the first coating, wherein each additional coating has a hardness that is greater than a hardness of the coating that is immediately beneath such coating, and wherein each additional coating has a lower measure of thermal conductivity than a measure of thermal conductivity of the coating that is immediately beneath such coating.