Process for the formation of hardened layers on metals and their alloys
French republic patent/ Gr. 8.-Cl. 2/A [...] i 1.056.564. ', -\ d; -, ^ On OFFICE NATIONAL AND RESEARCH [...] STUDIES DE residing in France (Seine). SERVICE iNTELLECTUAL INDUSTRIELLE of the Demanded 15 May 1952, to 14] i 30 ", to Paris. Issued 21 October 1953 Published the.-er 1 March 1954. The invention, due to Helmut m. Buckle, to a method for film formation extra-hard on metals or alloys thereof. It is particularly applicable to the formation of layers extra-hard on molybdenum, tungsten, -mixtures thereof. rate the like and alloys in the composition which between a and/or the other of these metals. Are known methods for forming layers relatively hard on metals such as iron, by introducing carbon or nitrogen. The methods most often lead to the formation, on the base metal, a layer of a eutectoid or precipitate, i.e. a two-phase mixture distinct crystal, although the small size crystals sometimes concealed has the advantage- [...] to the examination. In the best conditions, is obtained to the steel layers with micro-hardness is, at best, about 1.000 kg/mm2, without ever reach values of 1.300 to 1.400 kg/mm2. It has already been found the exceptional hardness of the molybdenum carbide or tungsten carbide and it is endeavoured to take advantage of the hardness in the manufacture of cutting tools. However, when a such carbide is obtained by sintering a powder of the metal with carbon black, a product is obtained too brittle to be used. Is also known sintered product obtained from tungsten, carbon black and cobalt. In said product, the tungsten carbide particles are embedded in a mass of cobalt. The hardness of the assembly is much lower than the hardness pi point tungsten carbide. It is an object of the invention to provide a method which is capable of forming a layer on a metal the microhardness which is of the order of 1.400 to 3.600 kg/mm2. It is another aim of the invention to provide a such method for providing extra layer- hard that adheres well on the base metal. It is also a further aim of the invention to provide a method that is carried out in a extremely easy. According to the invention, the molybdenum, or tungsten, or the like, or their alloys, to the action of the carbon or nitrogen. This forms, by simple diffusion, a layer of carbide and/or nitride, which has a hardness which extraordinary and good adhesion to the base metal. While the layers formed on the iron or were the eutectics acid or [...] as recalled above, the layer formed according to the invention, on the molybdenum, tungsten, or the like, is a layer, constituted by a single phase carbide, or nitride, or a mixture of carbide and nitride. The formation of the superhard layer can take place by diffusion solid, liquid or gas. I. Forming a carbide layer: For example, indicating that by heating a piece of molybdenum in contact with carbon black to 1.200 °C for thirty minutes, is formed an adhesive layer of Mo2 C p thickness of 10. This layer has a micro-hardness of 2.000 kg/mm2. Is formed, in a similar manner, on tungsten, a W layer2 C and-or a WC layer. In practice, no attempt is made to form a W layer2 C that a layer of WC, or vice versa, because these layers have micro-hardnesses comparable: the W layer2 has a micro-C hardness of 2.200 kg/mm2, and the WC layer has a layer of a micro-hardness of 2.400 kg/mm2. II. Forming a nitride layer: The invention also relates to an alternative for the formation of layers on the extra-hard tantalum, niobium, zirconium, titanium. The invention is then characterized in in that on such a base metal, or an alloy, a nitride layer by diffusing nitrogen. The layer formed is also a single phase consisting of nitride crystals. In reality, to less than the use of high purity nitrogen is simultaneously forms a carbide and a nitride, but which constitute a single phase, the atoms of "C" and "N" replaceable indifferently, and without that the hardness is substantially modified. The presence of small amounts of oxygen, or even hydrogen, without repercussions is also undesirable, because the atoms of "H" and "O" can largely replace the atoms of "C" and "N" without impairing the hardness. In the case of the treatment of a metal, with carbon as indicated above, to be produced as very often a phase carbide and nitride. If pure carbide, carbon black is used carefully purified by a prolonged annealing under high vacuum. With niobium or tantalum treated as described, have been effected layers, the micro-hardness varies of 1.400 to 1.800 kg/mm2. With zirconium, and titanium, is obtained of the layers on the micro-hardness reaches 3.600 to 3.800 kg/mm2. The invention is also applicable to the formation of extra-hard layers on different sizes of those mentioned above. For this purpose, is applied in advance on said body, by any suitable means, a layer consisting of one of these metals. The body thus coated is treated in the manner that has been described. Can be, further, interposed between the base body and the--layer of the metal or alloy, one or more additional layers having good adhesion both to the base only on the layer of the metal or alloy. The invention applies particularly interest for the constitution of parts which, free of abrupt mechanical shock, must have a surface hardness is as large as possible. Size can thus be manufactured, micron stops, [...] keys. The very low coefficient of expansion of the molybdenum and tungsten fitting these metals for the construction of such parts. . The method according to the invention is also applicable to the constitution of timepieces, hard points of strain gauges, andc. SUMMARY The invention relates to a method for film formation on extra-hard metals such as molybdenum, tungsten, and similar metals, and alloys thereof. The method is characterized by the fact that said metal is subjected to the action of the carbon or nitrogen under conditions sufficient to form by diffusion to the surface of the metal with a layer of a compound defined thereof and carbon and/or nitrogen. The invention also relates to: A. A execution mode of the method, film forming extra-hard, on a piece of molybdenum, tungsten, tantalum, niobium, titanium, zirconium or an alloy containing one of these metals characterized by the following features, considered in isolation or in combination: 1° The part is brought into contact with pure carbon, as carbon black, or graphite, and it is heated in a non-oxidizing atmosphere; 2° Molybdenum carbon coated is heated to form a layer of Mo C 2; 3° The tungsten is heated to form a W layer2 C; 4° Ke tungsten is heated to form a layer of WC; 5° Alternatively, carbon is supplied in gaseous form, the partial pressure of the carbon at the processing temperature exceeds the pressure of equilibrium of the carbide to form; 6° Optionally, the carbonated gas catalytically decomposes to the metal surface by coating the substrate with carbon; B. A process for forming a superhard layer on the tantalum, niobium, zirconium, titanium, characterized by the following features, considered in isolation or in combination: 7° The metal is heated in a nitrogen-containing atmosphere, thereby to form a diffusion layer of a nitride; 8° The partial pressure of the nitrogen is greater than that of the equilibrium pressure of the nitride to form. C. A process for forming a superhard layer on a metal other than those mentioned above, characterized in that is initially formed from said metal a layer of one of the metals mentioned, and the latter is subjected to a treatment for forming a superhard layer by applying the method or according to A B above. The invention provides for, as industrial products, the parts or articles into a metal or alloy having a superhard layer obtained by application of this method. National as studies Aeronautical and research. For proxy: André [...]. For the sale of the fascicles, be directed to[...] Nationale, 27, the street Convention, Paris ( 15e). A process for the formation of layers on the extra-hard [...] and alloys thereof.
Ministry
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