Self-sharpening cutting tool with hard coating
There is disclosed a cutting tool having a blade coated on one side with a hard coating living a laminar or layered microstructure. The coating tends to wear evenly and smoothly, thereby keeping a cutting edge of the cutting tool smooth. Furthermore, by coating the cutting edge on one side only, the cutting edge becomes self-sharpening. The coating preferably includes at least one layer made of tungsten carbides substantially or entirely free of metallic tungsten.
1. A self-sharpening cutting tool comprising:
a cutting edge made of a first material, the cutting edge being coated only on one side thereof with a coating comprising tungsten carbide or mixtures of tungsten carbides, the coating substantially harder than the first material, wherein the coating has a layered or laminar microstructure aligned substantially parallel to the coated side of the cutting edge to enable wear or breaking off of micro-particles following the layered or laminar structure pattern.
2. A tool as claimed in claim 1 , wherein the coating is substantially or entirely free of metallic tungsten.
3. A tool as claimed in claim 1 , wherein the coating is a multilayered coating, with a topmost layer of the coating comprising tungsten carbide or mixtures thereof, substantially or entirely free of metallic tungsten.
4. A tool as claimed in claim 3 , wherein the layers are arranged in sequentially increasing hardness from the cutting edge to a topmost layer of the coating.
5. A tool as claimed in claim 1 , wherein the coating is a multilayered coating comprising layers of varying hardness.
6. A tool as claimed in claim 5 , wherein the hardest layer is a topmost layer of the coating.
7. A tool as claimed in claim 5 , wherein the hardest layer is an intermediate layer of the coating.
8. A tool as claimed in claim 5 , wherein the hardest layer is a base layer of the coating.
9. A tool as claimed in claim 5 , wherein the coating comprises layers of tungsten, tungsten carbides and/or mixtures of tungsten with tungsten carbides alloyed with fluorine in amounts ranging from about 0.0005 to about 0.5 wt %.
10. A tool as claimed in claim 5 , wherein the coating comprises layers of tungsten and tungsten carbides substantially or entirely free of metallic tungsten, being alloyed with fluorine in amounts ranging from about 0.0005 to about 0.5 wt %.
11. A tool as claimed in claim 5 , wherein the coating has a base layer of tungsten.
12. A tool as claimed in claim 1 , wherein the coating is a multilayered coating comprising layers of varying hardness, the hardest layer of which comprises tungsten carbide or mixtures thereof substantially or entirely free of metallic tungsten.
13. A tool as claimed in claim 1 , wherein the coating or a topmost layer thereof has a friction coefficient against WC/Co of no more than 0.3.
14. A tool as claimed in claim 1 , wherein the coating is produced by Vapour Deposition in a vacuum chamber at a pressure lower than atmospheric pressure and at a temperature above about 350° C.
15. A tool as claimed in claim 1 , wherein the coating has a total thickness from about 1 to about 25 micrometers.
16. A tool as claimed in claim 1 , wherein an exposed surface of the coating has a roughness of no more than about 0.8 Ra micrometers.
17. A tool as claimed in claim 1 , wherein the coating or a topmost layer thereof has a microhardness of at least about 2000 kG/mm 2 .
18. A tool as claimed in claim 1 , wherein an exposed surface of the coating is ground or polished in a direction substantially parallel to the coated surface of the cutting edge.
19. A tool as claimed in claim 1 , wherein the coating is produced by Chemical Vapour Deposition in a vacuum chamber at a pressure lower than atmospheric pressure and at a temperature from about 450 to about 550° C.
20. A tool as claimed in claim 1 , wherein the coating has a total thickness of about 3 to about 12 micrometers.
21. A tool as claimed in claim 1 , wherein an exposed surface of the coating has a roughness Ra of about 0.5 microns or less.
22. A tool as claimed in claim 1 , wherein the coating or a topmost layer thereof has a microhardness of at least 2500 kG/mm 2 .
23. A tool as claimed in claim 1 , wherein the coating or a topmost layer thereof has a microhardness of at least 2900 kG/mm 2 .
24. A method of manufacturing a self-sharpening cutting tool, the method comprising:
providing a cutting edge made of a first material or materials; and
coating only one side of the cutting edge with a coating comprising tungsten carbide or mixtures of tungsten carbides, the coating substantially harder than the first material or materials;
wherein the coating has a layered or laminar microstructure aligned substantially parallel to the coated side of the cutting edge to enable wear or breaking off of micro-particles following the layered or laminar structure pattern.
25. A method according to claim 24 , wherein the coating is substantially or entirely free of metallic tungsten.
26. A method according to claim 24 , wherein the coating is a multilayered coating, the topmost layer of the coating comprising tungsten carbide or mixtures thereof, substantially or entirely free of metallic tungsten.
27. A method according to claim 26 , wherein the layers are arranged in sequentially increasing order of hardness from the cutting edge to a topmost layer of the coating.
28. A method according to claim 24 , wherein the coating is a multilayered coating comprising layers of varying hardness.
29. A method according to claim 28 , wherein the hardest layer is a topmost layer of the coating.
30. A method according to claim 28 , wherein the hardest layer is an intermediate layer of the coating.
31. A method according to claim 28 , wherein the hardest layer is a base layer of the coating.
32. A method according to claim 28 , wherein the coating comprises layers of tungsten, tungsten carbides or mixtures thereof, alloyed with fluorine in amounts ranging from about 0.0005 to about 0.5 wt %.
33. A method according to claim 28 , wherein the coating comprises layers of tungsten and tungsten carbides substantially or entirely free of metallic tungsten, being alloyed with fluorine in amounts ranging from about 0.0005 to about 0.5 wt %.
34. A method according to claim 28 , wherein the coating has a base layer of tungsten.
35. A method according to claim 24 , wherein the coating is a multilayered coating comprising layers of varying hardness, the hardest layer of which comprises tungsten carbide or mixtures thereof, substantially or entirely free of metallic tungsten.
36. A method according to claim 24 , wherein the coating or a topmost layer thereof has a friction coefficient against WC/Co of no more than 0.3.
37. A method according to claim 24 , wherein the coating is applied by Chemical Vapour Deposition in a vacuum chamber at a pressure lower than atmospheric pressure and at a temperature of no less than about 350° C.
38. A method according to claim 24 , wherein the coating is applied to a total thickness from about 1 to about 25 micrometers.
39. A method according to claim 24 , wherein an exposed surface of the coating after application has a roughness Ra of no more than about 0.8 micrometer.
40. A method according to claim 24 , wherein the coating or a topmost layer thereof has a microhardness of at least about 2000 kG/mm 2 .
41. A method according to claim 24 , wherein an exposed surface of the coating, after application of the coating, is ground or polished in a direction substantially parallel to the coated surface of the cutting edge.
42. A method according to claim 24 , wherein the coating is applied by Chemical Vapour Deposition in a vacuum chamber at a pressure lower than atmospheric pressure and at a temperature from about 450 to about 550° C.
43. A method according to claim 24 , wherein the coating is applied to a total thickness from about 3 to about 12 micrometers.
44. A method according to claim 24 , wherein an exposed surface of the coating after application has a roughness Ra of no more than 0.5 micrometers.
45. A method according to claim 24 , wherein the coating or a topmost layer thereof has a microhardness of at least 2500 kG/mm 2 .
46. A method according to claim 24 , wherein the coating or a topmost layer thereof has a microhardness of at least 2900 kG/mm 2 .