Patent EA-003063-B1 (EA)
Title: Tungsten carbide coatings and method for producing the same
Inventor: LAKHOTKIN JURY VIKTOROVICH
IPC: C01B32/949
Filed: 1999-02-11
Abstract: 1. Material for wear, erosion and corrosion resistant coatings, consisting of tungsten carbide alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt%. 2. Material in accordance with Claim 1, wherein the said material is tungsten monocarbide WC alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt%. 3. Material in accordance with Claim 1, wherein the said material is tungsten semicarbideW2C alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt%. 4. Material in accordance with Claim 1, wherein the said material is tungsten subcarbideW3C alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt%. 5. Material in accordance with Claim 1, wherein the said material is tungsten subcarbideW12 C alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt%. 6. Material in accordance with Claims 1-5, wherein the said material additionally contains fluorocarbon compositions with carbon content up to 15 wt% and fluorine content up to 0.5 wt%. 7. Material for wear, erosion and corrosion resistant coatings comprising a mixture of at least two tungsten carbides alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt% and optionally with fluorocarbon compositions with carbon content up to 15 wt% and fluorine content up to 0.5 wt%. 8. Coating, characterised in that it contains: an internal layer consisting of tungsten deposited on a substrate; and an external layer deposited on the said internal layer and containing tungsten carbide in accordance with Claims 1-6. 9. Coating in accordance with Claim 6, characterised in that its outer layer additionally contains a mixture of tungsten carbides in accordance with Claim 7. 10. Coating in accordance with Claims 8 or 9, characterised in that its outer layer additionally contains tungsten. 11. Coating in accordance with Claims 8 or 9, characterised in that its outer layer additionally contains carbon. 12. Coating in accordance with any of Claims 8 to 11, characterised in that its internal layer has a thickness of 0.5-300 mu m and its outer layer has a thickness of 0.5-300 mu m, with the ratio of thicknesses of the internal and external layers ranging from 1:1 to 1:600. 13. Process for producing tungsten carbides by chemical vapour deposition on a heated substrate using a mixture of gases including tungsten hexafluoride, hydrogen, a carbon-containing gas and, optionally, an inert gas, characterised in that the carbon-containing gas is thermally activated beforehand by heating to temperature 500-850 degree C. 14. Process in accordance with Claim 13, characterised in that the said carbon-containing gas is propane. 15. Process in accordance with Claims 13 or 14, characterised in that it is performed at a pressure of 2-150 kPa, substrate temperature 400-900 degree C, ratio of carbon-containing gas to hydrogen 0.2-1.7 and ratio of tungsten hexafluoride to hydrogen 0.02-0.12. 16. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 1.0-1.5 and ratio of tungsten hexafluoride to hydrogen 0.08-0.10, and that the carbon-containing gas is heated beforehand to temperature 750-850 degree C; in this case, tungsten monocarbide WC is obtained. 17. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.75-0.90 and ratio of tungsten hexafluoride to hydrogen 0.06-0.08, and that the carbon-containing gas is heated beforehand to temperature 600-750 degree C; in this case, tungsten semicarbideW2C is obtained. 18. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.60-0.65 and ratio of tungsten hexafluoride to hydrogen 0.05-0.55, and that the carbon-containing gas is heated beforehand to temperature 560-720 degree C; in this case, tungsten subcarbideW3C is obtained. 19. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.35-0.45 and ratio of tungsten hexafluoride to hydrogen 0.040-0.045, and that the carbon-containing gas is heated beforehand to temperature 500-700 degree C; in this case, tungsten subcarbideW12 C is obtained. 20. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.90-1.00 and ratio of tungsten hexafluoride to hydrogen 0.07-0.09, and that the carbon-containing gas is heated beforehand to temperature 670-790 degree C; in this case, a mixture of the carbides WC and W2C is obtained. 21. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.70-0.75 and ratio of tungsten hexafluoride to hydrogen 0.055-0.060, and that the carbon-containing gas is heated beforehand to temperature 580-730 degree C; in this case, a mixture of the carbides W2C and W3C is obtained. 22. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.60-0.65 and ratio of tungsten hexafluoride to hydrogen 0.045-0.060, and that the carbon-containing gas is heated beforehand to temperature 570-700 degree C; in this case, a mixture of the carbidesW2C and W12C is obtained. 23. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.45-0.60 and ratio of tungsten hexafluoride to hydrogen 0.045-0.050, and that the carbon-containing gas is heated beforehand to temperature 550-680 degree C; in this case, a mixture of the carbidesW3C and W12C is obtained. 24. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.65-0.70 and ratio of tungsten hexafluoride to hydrogen 0.045-0.060, and that the carbon-containing gas is heated beforehand to temperature 570-710 degree C; in this case, a mixture of the carbides W2C, W3C and W12C is obtained. 25. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.70-0.90 and ratio of tungsten hexafluoride to hydrogen 0.08-0.09, and that the carbon-containing gas is heated beforehand to temperature 600-720 degree C; in this case, a mixture of the carbide WC and tungsten is obtained. 26. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.70-0.90 and ratio of tungsten hexafluoride to hydrogen 0.08-0.09, and that the carbon-containing gas is heated beforehand to temperature 600-720 degree C; in this case, a mixture of the carbidesW2C and tungsten is obtained. 27. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.60-0.65 and ratio of tungsten hexafluoride to hydrogen 0.055-0.070, and that the carbon-containing gas is heated beforehand to temperature 560-700 degree C; in this case, a mixture of the carbideW3C and tungsten is obtained. 28. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.20-0.35 and ratio of tungsten hexafluoride to hydrogen 0.045-0.070, and that the carbon-containing gas is heated beforehand to temperature 500-680 degree C; in this case, a mixture of the carbideW12C and tungsten is obtained. 29. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 0.35-0.60 and ratio of tungsten hexafluoride to hydrogen 0.05-0.07, and that the carbon-containing gas is heated beforehand to temperature 500-680 degree C; in this case, a mixture of the carbides W3C, W12C and tungsten is obtained. 30. Process in accordance with Claim 15, characterised in that it is performed at a ratio of carbon-containing gas to hydrogen 1.50-1.70 and ratio of tungsten hexafluoride to hydrogen 0.10-0.12, and that the carbon-containing gas is heated beforehand to temperature 750-850 degree C; in this case, a mixture of the carbide WC and carbon is obtained. 31. Process for the deposition of coatings consisting of an internal layer of tungsten and an external layer containing tungsten carbide on substrates, preferably on construction materials and on items made from them, characterised in that the said process includes the following stages: (a) placing the substrate in a chemical vapour deposition reactor; (b) evacuating the reactor; (c) heating the said substrate; (d) supplying tungsten hexafluoride and hydrogen to the reactor; (e) retaining the substrate in the said gaseous medium for the time interval necessary for the formation of the tungsten layer on the substrate; (f) in addition to the said tungsten hexafluoride and hydrogen, supplying a previously thermally activated carbon-containing gas to the reactor; (g) retaining the substrate in the gaseous medium formed at stage (f) for the time necessary for the formation of the outer layer containing tungsten carbides and mixtures of them with each other, with tungsten or with free carbon. 32. Process in accordance with Claim 31, characterised in that it is performed at a reactor pressure of 2-150 kPa, substrate temperature 400-900 degree C, ratio of carbon-containing gas to hydrogen 0.2-1.7 and ratio of tungsten hexafluoride to hydrogen 0.02-0.12. 33. Process in accordance with Claim 31, characterised in that, before the application of a coating to materials or items made from materials selected from a group including iron, carbon steels, stainless steels, cast irons, titanium alloys and hard alloys containing titanium, a coating is applied to them consisting of materials which are chemically resistant to hydrogen fluoride, namely nickel, cobalt, copper, silver, gold, platinum, iridium, tantalum, molybdenum and alloys, compounds and mixtures of these, by electrochemical or chemical deposition from aqueous solutions, electrolysis of melts or physical and chemical