| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | October 5, 2004 |
| PATENT TITLE |
Tungsten carbide coating and method for producing the same |
| PATENT ABSTRACT | New tungsten carbides alloyed with fluorine in amounts up to 0.5 wt % and possibly with fluorocarbon compositions are described. It is possible to produce them by means of a new process of chemical vapor deposition, in which tungsten hexafluoride, hydrogen and a carbon-containing gas are used. A specific feature of the new process is the preliminary thermal activation of the carbon-containing gas. The tungsten carbide coatings are deposited on construction materials and items made from them. They possess enhanced resistance to wear, corrosion and chemicals |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | December 3, 2001 |
| PATENT CT FILE DATE | February 11, 1999 |
| PATENT CT NUMBER | This data is not available for free |
| PATENT CT PUB NUMBER | This data is not available for free |
| PATENT CT PUB DATE | August 17, 2000 |
| PATENT CLAIMS |
What is claimed is: 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 semicarbide W.sub.2 C 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 subcarbide W.sub.3 C 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 subcarbide W.sub.12 C alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt %. 6. Material in accordance with claim 1, wherein the said material additionally contains fluorocarbon compositions with carbon content up to 15 wt % and fluorine content up to 0.5 wt %. 7. Coating in accordance with claim 6, characterized in that its outer layer additionally contains a mixture of at least two tungsten carbides alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt % and possible with fluorocarbon compositions with carbon content up to 15 wt % and fluorine content up to 0.5 wt %. 8. Coating, characterized 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 claim 1. 9. Coating in accordance with claim 8, characterized in that its outer layer additionally contains tungsten. 10. Coating in accordance with claim 8, characterized in that its outer layer additionally contains carbon. 11. Coating in accordance with any of claim 8, characterized 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. 12. Multilayer coating made from alternating layers of tungsten and layers containing tungsten carbide in accordance with claim 1. 13. Multilayer coating in accordance with claim 12, characterized in that the thickness of its individual layers ranges from 2 to 10 .mu.m and the ratio of the thicknesses of the alternating layers ranges from 1:1 to 1:5. 14. 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 possibly with fluorocarbon compositions with carbon content up to 15 wt % and fluorine content up to 0.5 wt %. 15. Multilaminar coating made from alternating layers of tungsten and layers containing tungsten carbide in accordance with claim 14. 16. 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, characterized in that the carbon-containing gas is thermally activated beforehand by heating to temperature 500-850.degree. C. 17. Process in accordance with claim 16, characterized in that the said carbon-containing gas is propane. 18. Process in accordance with claim 16, characterized 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. 19. Process in accordance with claim 18, characterized 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. 20. Process in accordance with claim 18, characterized 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 semicarbide W.sub.2 C is obtained. 21. Process in accordance with claim 18, characterized 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 subcarbide W.sub.3 C is obtained. 22. Process in accordance with claim 18, characterized 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 subcarbide W.sub.12 C is obtained. 23. Process in accordance with claim 18, characterized 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 W.sub.2 C is obtained. 24. Process in accordance with claim 18, characterized 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 W.sub.2 C and W.sub.3 C is obtained. 25. Process in accordance with claim 18, characterized 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 carbides W.sub.2 C and W.sub.12 C is obtained. 26. Process in accordance with claim 18, characterized 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 0.40-0.050, and that the carbon-containing gas is heated beforehand to temperature 550-680.degree. C.; in this case, a mixture of the carbides W.sub.3 C and W.sub.12 C is obtained. 27. Process in accordance with claim 18, characterized 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 W.sub.2 C, W.sub.3 C and W.sub.12 C is obtained. 28. Process in accordance with claim 18, characterized 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. 29. Process in accordance with claim 18, characterized 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 carbides W.sub.2 C and tungsten is obtained. 30. Process in accordance with claim 18, characterized 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 carbide W.sub.3 C and tungsten is obtained. 31. Process in accordance with claim 18, characterized 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 carbide W.sub.12 C and tungsten is obtained. 32. Process in accordance with claim 18, characterized 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 W.sub.3 C, W.sub.12 C and tungsten is obtained. 33. Process in accordance with claim 18, characterized 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. 34. Process for the deposition of coatings consisting of an internal layer of tungsten and an external layer containing tungsten subcarbide W.sub.12 C 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. 35. Process in accordance with claim 34, characterized 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. 36. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 1.00-1.50 and a 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, an external layer containing tungsten monocarbide WC is obtained. 37. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.75-0.90 and a 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, an external layer containing tungsten semicarbide W.sub.2 C is obtained. 38. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.60-0.65 and a ratio of tungsten hexafluoride to hydrogen 0.050-0.055, and that the carbon-containing gas is heated beforehand to temperature 560-720.degree. C.; in this case, an external layer containing tungsten subcarbide W.sub.3 C is obtained. 39. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.35-0.40 and a 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, an external layer containing tungsten monocarbide W.sub.12 C is obtained. 40. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.90-1.00 and a 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, an external layer containing a mixture of the carbides WC and W.sub.2 C is obtained. 41. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.70-0.75 and a 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, an external layer containing a mixture of the carbides W.sub.2 C and W.sub.3 C is obtained. 42. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.65-0.70 and a 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, an external layer containing a mixture of the carbides W.sub.2 C, W.sub.3 C and W.sub.12 C is obtained. 43. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.60-0.65 and a 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, an external layer containing a mixture of the carbides W.sub.2 C and W.sub.12 C is obtained. 44. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.40-0.60 and a 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, an external layer containing a mixture of the carbides W.sub.3 C and W.sub.12 C is obtained. 45. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.70-0.90 and a 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, an external layer containing a mixture of the carbide W.sub.2 C and tungsten is obtained. 46. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.60-0.65 and a 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, an external layer containing a mixture of the carbide W.sub.3 C and tungsten is obtained. 47. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.35-0.60 and a ratio of tungsten hexafluoride to hydrogen 0.050-0.070, and that the carbon-containing gas is heated beforehand to temperature 500-690.degree. C.; in this case, an external layer containing a mixture of the carbides W.sub.3 C and W.sub.12 C with tungsten is obtained. 48. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.20-0.35 and a 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, an external layer containing a mixture of the carbide W.sub.12 C and tungsten is obtained. 49. Process in accordance with claim 35, characterized in that it is performed at a ratio of the carbon-containing gas to hydrogen 0.70-0.90 and a 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, an external layer containing a mixture of the carbide WC and tungsten is obtained. 50. Process in accordance with claim 34, characterized 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 precipitation from aqueous solutions, electrolysis of melts or physical and chemical vapour precipitation. 51. Process in accordance with any of claim 34, characterized in that the coatings are deposited onto frictional assemblies. 52. Process in accordance with any of claim 34, characterized in that the coatings are deposited onto forming tools used for processing materials by means of pressing. 53. Process in accordance with any of claim 34, characterized in that the coatings are deposited onto components and units of machines and mechanisms operating with compressed gases and liquids or other pneumatic or hydraulic systems. 54. Material comprising: a substrate made from construction material; a coating deposited on the said substrate, consisting of an internal tungsten layer and an external layer containing tungsten carbide alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt % and possibly with fluorocarbon compositions with carbon content up to 15 wt % and fluorine content up to 0.5 wt %. 55. Material in accordance with claim 54, wherein the said tungsten carbide is monocarbide WC. 56. Material in accordance with claim 55, characterized in that the external layer of the said coating additionally contains tungsten. 57. Material in accordance with claim 55, characterized in that the external layer of the said coating additionally contains carbon. 58. Material in accordance with claim 55, characterized in that the internal layer of the said coating has thickness 0.5-300 .mu.m and the ratio of thicknesses of internal and external layers ranges from 1:1 to 1:600. 59. Material according to claim 55, characterized in that the said substrate layer adjacent to the coating contains alloys with nickel content exceeding 25 wt %, e.g. Invar, Nichrome, Monel. 60. Material in accordance with claim 54, wherein the said tungsten carbide is semicarbide W.sub.2 C. 61. Material in accordance with claim 54, wherein the said tungsten carbide is subcarbide W.sub.3 C. 62. Material in accordance with claim 54, wherein the said tungsten carbide is subcarbide W.sub.12 C. 63. Material comprising: a substrate made from construction material; and a coating deposited on the said substrate, consisting of an internal tungsten layer and an external layer containing a mixture of at least two tungsten carbides alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt % and possibly with fluorocarbon compositions with carbon content up to 15 wt % and fluorine content up to 0.5 wt %. 64. Material in accordance with claim 63, characterized in that the external layer of the said coating contains a mixture of the tungsten carbides WC and W.sub.12 C. 65. Material in accordance with claim 63, characterized in that the external layer of the said coating contains a mixture of the tungsten carbides W.sub.3 C and W.sub.2 C. 66. Material in accordance with claim 63, characterized in that the external layer of the said coating contains a mixture of the tungsten carbides W.sub.3 C and W.sub.12 C. 67. Material in accordance with claim 63, characterized in that the external layer of the said coating contains a mixture of tungsten carbides W.sub.2 C and W.sub.12 C. 68. Material in accordance with claim 63, characterized in that the external layer of the said coating contains a mixture of the tungsten carbides W.sub.2 C, W.sub.3 C and W.sub.12 C. 69. Process for the deposition of multilaminar coatings on substrates, preferably on construction materials and items made from them, consisting of alternating layers of tungsten and layers containing tungsten carbide or mixtures of tungsten carbides with each other, with tungsten or with free carbon, said process to include 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 carbide or mixtures of tungsten carbides with each other, with tungsten and with free carbon; stages (d) and (g) are repeated several times in order to form alternating layers of tungsten and layers containing tungsten carbides. 70. Process in accordance with claim 69, characterized in that it is conducted at reactor pressure 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. 71. Process in accordance with claim 69, characterized 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 precipitation from aqueous solutions, electrolysis of melts or physical and chemical vapour precipitation. 72. Process in accordance with any of claim 69, characterized in that the coating is deposited onto friction assemblies. 73. Process in accordance with any of claim 69, characterized in that the coating is deposited onto a forming tool used for processing materials by means of pressing. 74. Process in accordance with any of claim 69, characterized in that the coating is deposited onto units of machines and mechanisms operating with compressed gases and liquids or of other pneumatic or hydraulic systems. 75. Construction material comprising a substrate and a multilaminar coating consisting of alternating layers of tungsten and layers containing tungsten carbide alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt % and possibly with fluorocarbon compositions with carbon content up to 15 wt % and fluorine content up to 0.5 wt %. 76. Material in accordance with claim 75, wherein the said tungsten carbide is tungsten monocarbide WC. 77. Material in accordance with claim 75, wherein the said tungsten carbide is tungsten semicarbide W.sub.2 C. 78. Material in accordance with claim 75, wherein the said tungsten carbide is tungsten subcarbide W.sub.3 C. 79. Material in accordance with claim 75, wherein the said tungsten carbide is tungsten subcarbide W.sub.12 C. 80. Material in accordance with any of claim 75, characterized in that the said carbide layers additionally contain tungsten. 81. Material in accordance with any of claim 75, characterized in that the said carbide layers additionally contain carbon. 82. Materials according to any of claim 75, characterized in that the thickness of its layers ranges from 2 to 10 .mu.m and the ratio of the thicknesses of the alternating layers ranges from 1:1 to 1:5. 83. Construction material comprising a substrate and a multilaminar coating consisting of alternating layers of tungsten and layers containing a mixture of at least two tungsten carbides alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt % and possibly with fluorocarbon compositions with carbon content up to 15 wt % and fluoride content up to 0.5 wt %. 84. Material in accordance with claim 83, wherein the said carbide layers contain a mixture of tungsten carbides WC and W.sub.2 C. 85. Material in accordance with claim 83, wherein the said carbide layers contain a mixture of tungsten carbides W.sub.2 C and W.sub.3 C. 86. Material in accordance with claim 83, wherein the said carbide layers contain a mixture of tungsten carbides W.sub.3 C and W.sub.12 C. 87. Material in accordance with claim 83, wherein the said carbide layers contain a mixture of tungsten carbides W.sub.2 C and W.sub.12 C. 88. Material in accordance with claim 83, wherein the said carbide layers contain a mixture of tungsten carbides W.sub.2 C, W.sub.3 C and W.sub.12 C. 89. 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 %, wherein the material is deposited on a heated substrate by way of chemical vapour deposition in a chemical vapour deposition reactor using a mixture of gases including tungsten hexafluoride, hydrogen, a carbon-containing gas and, optionally, an inert gas, and wherein the carbon-containing gas is heated to a temperature of 500 to 850.degree. C. prior to being supplied to the reactor. 90. Material in accordance with claim 89, wherein the said material is tungsten monocarbide WC alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt %. 91. Material in accordance with claim 89, wherein the said material is tungsten semicarbide W.sub.2 C alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt %. 92. Material in accordance with claim 89, wherein the said material is tungsten subcarbide W.sub.3 C alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt %. 93. Material in accordance with claim 89, wherein the said material is tungsten subcarbide W.sub.12 C alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt %. 94. Material in accordance with claim 89, wherein the said material additionally contains fluorocarbon compositions with carbon content up to 15 wt % and fluorine content up to 0.5 wt %. 95. 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 %, wherein the material is deposited on a heated substrate by way of chemical vapour deposition in a chemical vapour deposition reactor using a mixture of gases including tungsten hexafluoride, hydrogen, a carbon-containing gas and, optionally, an inert gas, and wherein the carbon-containing gas is heated to a temperature of 500 to 850.degree. C. prior to being supplied to the reactor. 96. 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 material in accordance with claim 1. 97. Coating in accordance with claim 96, wherein the external layer additionally contains 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 %. 98. Coating in accordance with claim 96, wherein the external layer additionally contains tungsten. 99. Coating in accordance with claim 96, wherein the external layer additionally contains carbon. 100. Coating in accordance with claim 96, wherein the internal layer has a thickness of 0.5-300 .mu.m and the external 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. 101. Process for producing tungsten carbides in a chemical vapour deposition reactor 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, wherein the carbon-containing gas is thermally activated before being supplied to the reactor by heating to a temperature of 500-850.degree. C., and wherein fluorine is alloyed with the tungsten carbides in amounts ranging from 0.0005 to 0.5 wt %. 102. Process in accordance with claim 101, wherein the said carbon-containing gas is propane. 103. Process in accordance with claim 101, wherein the process is performed at a pressure of 2-150 kPa, a substrate temperature of 400-900.degree. C., a ratio of carbon-containing gas to hydrogen of 0.2-1.7 and a ratio of tungsten hexafluoride to hydrogen of 0.02-0.12. 104. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 1.0-1.5 and a ratio of tungsten hexafluoride to hydrogen of 0.08-0.10, and wherein the carbon-containing gas is heated to a temperature of 750-850.degree. C. before being supplied to the reactor, and wherein tungsten monocarbide WC is obtained. 105. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.75-0.90 and a ratio of tungsten hexafluoride to hydrogen of 0.06-0.08, and wherein the carbon-containing gas is heated to a temperature of 600-750.degree. C. before being supplied to the reactor, and wherein tungsten semicarbide W.sub.2 C is obtained. 106. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.60-0.65 and a ratio of tungsten hexafluoride to hydrogen of 0.05-0.55, and wherein the carbon-containing gas is heated to a temperature of 560-720.degree. C. before being supplied to the reactor, and wherein tungsten subcarbide W.sub.3 C is obtained. 107. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.35-0.45 and a ratio of tungsten hexafluoride to hydrogen of 0.040-0.045, and wherein the carbon-containing gas is heated to a temperature of 500-700.degree. C. before being supplied to the reactor, and wherein tungsten subcarbide W.sub.12 C is obtained. 108. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.90-1.00 and a ratio of tungsten hexafluoride to hydrogen of 0.07-0.09, and wherein the carbon-containing gas is heated to a temperature of 670-790.degree. C. before being supplied to the reactor, and wherein a mixture of the carbides WC and W.sub.2 C is obtained. 109. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.70-0.75 and a ratio of tungsten hexafluoride to hydrogen of 0.055-0.060, and wherein the carbon-containing gas is heated to a temperature of 580-730.degree. C. before being supplied to the reactor, and wherein a mixture of the carbides W.sub.2 C and W.sub.3 C is obtained. 110. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.60-0.65 and a ratio of tungsten hexafluoride to hydrogen of 0.045-0.060, and wherein the carbon-containing gas is heated to a temperature of 570-700.degree. C. before being supplied to the reactor, and wherein a mixture of the carbides W.sub.2 C and W.sub.12 C is obtained. 111. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.45-0.60 and a ratio of tungsten hexafluoride to hydrogen of 0.045-0.050, and wherein the carbon-containing gas is heated to a temperature of 550-680.degree. C. before being supplied to the reactor, and wherein a mixture of the carbides W.sub.3 C and W.sub.12 C is obtained. 112. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.65-0.70 and a ratio of tungsten hexafluoride to hydrogen of 0.045-0.060, and wherein the carbon-containing gas is heated to a temperature of 570-710.degree. C. before being supplied to the reactor, and wherein a mixture of the carbides W.sub.2 C, W.sub.3 C and W.sub.12 C is obtained. 113. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.70-0.90 and a ratio of tungsten hexafluoride to hydrogen of 0.08-0.09, and wherein the carbon-containing gas is heated to a temperature of 600-720.degree. C. before being supplied to the reactor, and wherein a mixture of the carbide WC and tungsten is obtained. 114. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.70-0.90 and a ratio of tungsten hexafluoride to hydrogen of 0.08-0.09, and wherein the carbon-containing gas is heated to a temperature 600-720.degree. C. before being supplied to the reactor, and wherein a mixture of the carbides W.sub.2 C and tungsten is obtained. 115. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.60-0.65 and a ratio of tungsten hexafluoride to hydrogen of 0.055-0.070, and wherein the carbon-containing gas is heated to a temperature of 560-700.degree. C. before being supplied to the reactor, and wherein a mixture of the carbide W.sub.3 C and tungsten is obtained. 116. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.20-0.35 and a ratio of tungsten hexafluoride to hydrogen of 0.045-0.070, and wherein the carbon-containing gas is heated to a temperature of 500-680.degree. C. before being supplied to the reactor, and wherein a mixture of the carbide W.sub.12 C and tungsten is obtained. 117. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 0.35-0.60 and a ratio of tungsten hexafluoride to hydrogen of 0.05-0.07, and wherein the carbon-containing gas is heated to a temperature of 500-680.degree. C. before being supplied to the reactor, and wherein a mixture of the carbides W.sub.3 C, W.sub.12 C and tungsten is obtained. 118. Process in accordance with claim 103, wherein the process is performed at a ratio of carbon-containing gas to hydrogen of 1.50-1.70 and a ratio of tungsten hexafluoride to hydrogen of 0.10-0.12, and wherein the carbon-containing gas is heated to a temperature of 750-850.degree. C. before being supplied to the reactor, and wherein a mixture of the carbide WC and carbon is obtained. 119. Material for wear, erosion and corrosion resistant coatings, the material including tungsten carbide alloyed with fluorine in amounts ranging from 0.0005 to 0.5 wt %, and having a microhardness of at least 3100 kg/mm.sup.2. 120. Material as claimed in claim 119, having a microhardness of at least 3400 kg/mm.sup.2. 121. Material as claimed in claim 119, having a microhardness of at least 3500 kg/mm.sup.2. |
| PATENT DESCRIPTION |
TECHNOLOGY FIELD The invention is related to the technology of the deposition of composite surface systems possessing high resistance to wear, erosion and chemicals. More specifically, the invention is related to the technology of the deposition of coatings containing tungsten carbides and mixtures of them with each other and with tungsten or free carbon. Superhard erosion and corrosion resistant coatings, including those containing tungsten carbides, are widely used in manufacturing various articles of tools in present-day mechanical engineering. Such coatings possess high resistance to erosion, chemicals and wear, and thus substantially increase the life of mechanical engineering products and of tools operated under demanding conditions. PRIOR ART Patent GB 2 179 678 describes a surface composite system with high resistance to wear and erosion consisting of a mixture of tungsten (for plasticity) and tungsten carbide W.sub.2 C (for hardness). These hard coatings made from a fine-grain mixture of tungsten carbide with metallic tungsten were obtained by means of physical vapour deposition (PVD) by spraying tungsten and carbon from separate sources. The tungsten and carbon are condensed on different-type substrates to form the said alloys of tungsten with tungsten carbide. However, the rate of synthesis of tungsten carbides is very low, and internal stresses in the coatings increase sharply as the tungsten-carbon layer grows, resulting in delamination of the coatings. For this reason, it is impossible to produce sufficiently thick coatings by the PVD method. Furthermore, the physical vapour deposition method is intrinsically inapplicable for deposition of coatings on items of complex shape due to the impossibility of depositing the coatings on the parts of the item shadowed relative to the incident beam. The chemical vapour deposition process (CVD) eliminates these disadvantages. The CVD process can be used to deposit wear and erosion resistant coatings on substrates and on items of complex shape. In a typical CVD process for the deposition of composite coatings, the substrate is heated in the reaction chamber, and the previously mixed gas reagents are then introduced into this chamber. By varying the composition of the reaction mixture and of the parameters of the process (temperature of the substrate, composition of the reaction mixture, flow rate, total pressure in the reaction mixture, temperature of the gases supplied, etc.), it is possible to obtain a variety of coatings. Among the CVD methods of tungsten carbide coating deposition, only the fluoride method makes it possible to form tungsten carbides of high quality at a low temperature. For this purpose, one may use thermal decomposition of a mixture of tungsten hexafluoride, hydrogen and carbon-containing gas in the CVD process. Various reagents were used as carbon-containing gases, e.g. dimethylether, amines, propylene, etc., with the aid of which one may synthesise tungsten carbide of one or two compositions. For example, the thermal decomposition of dimethylether (DME) (EP 0 328 084 B1) results in the formation of the mixture W+W.sub.3 C; W+W.sub.2 C+W.sub.3 C; W+W.sub.2 C in the form of bilaminar coatings. The internal tungsten layer of the coating is obtained from the as mixture WF.sub.6 (0.3 l/min), H.sub.2 (3 l/min), Ar (4.0 l/min) at 460.degree. C. The external layer containing a mixture of tungsten with W.sub.3 C is obtained from a mixture of WF.sub.6 (0.3 l/min), H.sub.2 (3 l/min) and DME (0.4 l/min) at 460.degree. C. at a total pressure of 40 torr. The external coating W+W.sub.2 C is obtained from a mixture of WF.sub.6 (0.3 l/min) and DME (0.55 l/min) at 460.degree. C. at a total pressure of 40 torr. The external coating W+W.sub.2 C is obtained from a mixture of WF.sub.6 (0.3 l/min), Ar (4.5 l/min) and DME (0.85 l/min) at 460.degree. C. and a total pressure of 40 torr. Patent JP 9113527 A 19910204 describes how tungsten carbide WC is obtained from a gaseous mixture of WF.sub.6, H.sub.2 and amines with an atomic ratio of C to N equal to 1:20 and H to W equal to 1:15 at 400-900.degree. C. The patent cites the production of WC from the mixture WF.sub.6 :trimethylamine:H.sub.2 =1:2:3 (the atomic ratios are C/W=6.0, H/W=6.0). The flow rate is 120 cm.sup.3 /min at 800.degree. C. and the total pressure is equal to atmospheric. A 70 .mu.m layer forms in 30 minutes. Patent JP 8857301 A 19880310 describes how a W.sub.3 C coating on an aluminium substrate is obtained from a gaseous mixture of WF.sub.6, H.sub.2 and aromatic hydrocarbon with atomic ratios C/W equal to 2-10 and H/C exceeding 3 at temperature 250-500.degree. C. Patent JP 84280063 A 19841228 describes how a W.sub.2 C coating on a graphite substrate is obtained from a gaseous mixture of WF.sub.6, C.sub.3 H.sub.6 and H.sub.2 with inert gas. The preferred regime:mixture WF.sub.6 :H.sub.2 =1:3-1:15 with an admixture of C.sub.3 H.sub.6 in the reaction mixture with molar ratio 0.01-0.3; the temperature of the substrate is 350-600.degree. C. Patent JP 84204563 A 19840929 describes how a W.sub.2 C coating is obtained from a gaseous mixture of WF.sub.6, H.sub.2 (molar ratio WF.sub.6 :H.sub.2 =1:3-1.15) and cyclopropane with molar ratio in the mixture 0.01-0.3 at a substrate temperature of 350-600.degree. C. The example cited is the manufacturing of a W.sub.2 C coating on a copper substrate from the mixture WF.sub.6 : 40, H.sub.2 : 320, Ar: 40, C.sub.3 H.sub.8 : 10 cm.sup.3 /min at 500.degree. C. with a growth rate of 3.3 .mu.m/min. EP A 0 305 917 describes how super-hard fine-grain non-columnar laminar tungsten-carbon alloys are obtained by chemical vapour deposition. The described alloys contain carbide phases consisting of W.sub.2 C or W.sub.3 C or mixtures of them with each other. It is demonstrated that these tungsten carbon alloys, when deposited on certain types of substrate, have a net of very fine micro-cracks all over the deposit. Coatings made from these alloys have inadequate resistance to wear and erosion. EP 0 411 646 A1 describes a multilayer coating containing alternating layers of tungsten and a mixture of tungsten with tungsten carbides in the form of W.sub.2 C, W.sub.3 C or a mixture of them. It is demonstrated that such a coating increases the resistance of the material to wear and erosion. It is known, however, that the maximum composition effect is observed for layers with a distinct boundary between them. This is obviously not the case for the conjunction of layers of tungsten and the mixture of tungsten with tungsten carbide which is characteristic of this patent. SUBSTANCE OF THE INVENTION It follows from the patents cited above that different reagents and different technologies are used for the production of different types of tungsten carbides. In this connection, the main aim of this invention is to develop a universal technology making it possible to obtain all the known carbides, mixtures of them and also new carbides. Furthermore, the problem of increasing the hardness of tungsten carbide coatings remains very important, because such key parameters as strength and wear resistance are related specifically to hardness. A solution to these and other problems is provided by this invention, due to the development of a new method for the production of tungsten carbides and mixtures of them. The main distinguishing feature of the method is the preliminary thermal activation of the hydrocarbons used in the CVD process. The synthesis of a tungsten carbide layer of a certain composition depends on an activation temperature that varies from 500 to 850.degree. C., on a total pressure in the reactor that varies from 2 to 150 kPa, and on the partial pressure of the hydrocarbon reagent. Preliminary activation of the hydrocarbons results in the formation of the necessary concentration of hydrocarbon radicals and their associates with fluorine in the gaseous phase over a wide range. The proposed method makes it possible to alloy the carbides and/or mixtures of them with fluorine and fluoride-carbon compositions. Fluorine, as the most active chemical element, strengthens the interatomic bonds when it penetrates into the carbide lattice. It is the strengthening of the interatomic bonds in the carbide which produces the increase in hardness. This process is similar to the formation of oxycarbide phases instead of purely carbide structures. On the other hand, fluorine stabilises the structure of the low-temperature phases (tungsten subcarbides) due to the high energy of the fluorine-carbon bond. Along with fluorine as an element, fluorine-carbon compounds with carbon content up to 15 wt % and fluorine content up to 0.5 wt % can be introduced into the composition of the tungsten carbide. These admixtures have two roles: firstly, they increase the hardness of the tungsten carbides; and secondly, they stabilise the structure of the tungsten subcarbides. Thus, the introduction of fluorine and fluorine-carbon admixtures makes it possible to obtain such tungsten carbides as monocarbide WC, semicarbide W.sub.2 C and subcarbides W.sub.3 C and W.sub.12 C. The application of the new tungsten carbides makes it possible to manufacture a bilaminar coating, the internal layer of which (deposited on the substrate--a construction material or items made of it) is composed of tungsten. The external layer contains tungsten carbide alloyed with fluorine and possibly with fluorine-carbon compositions, or mixtures of such carbides with each other and also with tungsten and free carbon. The construction material with the deposited composition coating has an internal tungsten layer of thickness 0.5-300 .mu.m. The thickness of the external layer is 0.5-300 .mu.m. The ratio of thicknesses of the internal and external layers ranges from 1:1 to 1:600. In accordance with this invention, tungsten carbides are deposited in the chemical reactor on the substrate from a gaseous phase consisting of tungsten hexafluoride, hydrogen, a carbon-containing gas (e.g. propane), and, optionally, an inert gas (e.g. argon). The carbon-containing gas is thermally activated before being introduced into the reactor by heating it to 500-850.degree. C. The pressure in the reactor ranges from 2 to 150 kPa. The substrate is heated to temperature 400-900.degree. C. The ratio of carbon-containing gas to hydrogen ranges from 0.2 to 1.7, and the ratio of tungsten hexafluoride to hydrogen ranges from 0.02 to 0.12. Within the stated limits, the parameters of the process are determined depending on which carbide or mixture of carbide with each other or with tungsten or with carbon is required to be produced. Thus, to produce tungsten monocarbide WC, the preliminary thermal activation of the carbon-containing gas is conducted at a temperature of 750-850.degree. C. The ratio of propane to hydrogen is set in the interval 1.00-1.50, and the ratio of tungsten to hydrogen in the interval 0.08-0.10. The corresponding parameters for the production of single-phase tungsten semicarbide W.sub.2 C are as follows: 600-750.degree. C., 0.75-0.90 and 0.06-0.08. The parameters for the production of tungsten subcarbide W.sub.3 C are: 560-720.degree. C., 0.60-0.65 and 0.050-0.055. A previously unknown tungsten subcarbide, W.sub.12 C, with hardness 3500 kG/mm.sup.2, greater than that of any of the known carbides, was obtained by the method proposed in this invention. For the production of this subcarbide, propane was thermally activated at temperature 500-700.degree. C. The ratio of propane to hydrogen was within the interval 0.35-0.40 and that of tungsten hexafluoride to hydrogen was 0.040-0.045. This process makes it possible to obtain mixtures of tungsten carbides and mixtures of the carbides with free tungsten and carbon. The values of the parameters for these cases are shown in Table 1. TABLE 1 Propane Tungsten activation Propane to hexafluoride to No. Composition temperature .degree. C. hydrogen ratio hydrogen ratio 1. WC + W.sub.2 C 670-790 0.90-1.00 0.07-0.09 2. W.sub.2 C + W.sub.3 C 580-730 0.70-0.75 0.055-0.060 3. W.sub.2 C + W.sub.12 C 570-700 0.60-0.65 0.045-0.060 4. W.sub.3 C + W.sub.12 C 550-680 0.40-0.60 0.045-0.050 5. W.sub.2 C + W.sub.3 C + W.sub.12 C 570-710 0.65-0.70 0.045-0.060 6. WC + W 600-720 0.70-0.90 0.08-0.09 7. W.sub.2 C + W 600-720 0.70-0.90 0.08-0.09 8. W.sub.3 C + W 560-700 0.60-0.65 0.055-0.070 9. W.sub.12 C + W 500-680 0.20-0.35 0.045-0.070 10. W.sub.3 C + W.sub.12 C + W 500-680 0.35-0.60 0.05-0.07 11. WC + C 750-850 1.50-1.70 0.10-0.12 As mentioned above, control of the content of active hydrocarbon radicals within wide limits is provided by means of the preliminary thermal activation of the initial carbon-containing reagent. This makes it possible to form carbide phases and mixtures of them with free carbon content of up to 15 wt %. The thermal activation of the carbon-containing reagent takes place in a hydrofluoric atmosphere, which provides additional formation of fluorine-carbon radicals. Radicals of both types take part in alloying the carbide phases and mixtures of them with fluorine and carbon, producing an increase in their hardness and enhanced tribotechnical properties. Internal stresses increase slowly as the coatings of single-phase tungsten carbides grow; thus, high wear resistance is observed even with quite thick coatings (up to 300 .mu.m). Their chemical resistance and high hardness are due to the strong interatomic bonds in the carbide lattice and the absence of free tungsten. In order to bring about a microplastic effect in the coatings, one can use mixtures of carbides with each other and mixtures of them with tungsten and free carbon, in this case losing some chemical and electrochemical stability. Note that coatings of tungsten carbide with free carbon have a reduced friction coefficient in addition to the said microplastic effect. This is very important where mixtures of carbides with free carbon are used as wear-resistant tribotechnical coatings in friction assemblies. By using the proposed invention and also the described new method of coating deposition, one can also obtain multilayer coatings with alternating layers of tungsten and layers containing tungsten carbides alloyed with fluorine and possibly with fluorocarbon compositions, including mixtures of these carbides with each other and with tungsten or carbon. The ratio of thicknesses of the alternating layers ranges from 1:1 to 1:5. The construction material itself, with a bilaminar or multilayer coating deposited in accordance with the proposed method, is also an object of this invention. |
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