Method of using a thermal plasma to produce a functionally graded composite surface layer on metals
First Claim
1. A method of providing a surface layer on an electrically conductive work piece substrate, the method comprising:
- using a scanning plasma torch to impinge a high temperature arc plasma stream on the surface of the work piece, said plasma stream comprising an initial plasma stream and a stream of nitrogen gas or a carbon containing gas that is blended into the initial plasma stream, said work piece forming an electrode and completing an electrical circuit with said plasma arc and the torch power supply, said plasma having sufficient energy to ionize the nitrogen gas or the carbon containing gas, so as to heat the surface of the substrate to a temperature below the melting point of the metal;
causing the metal substrate to react with the nitrogen ions or carbon ions forming a composite surface layer of the metal and the corresponding metal nitride or the corresponding metal carbide; and
directing a cooling jet stream of an inert gas onto the plasma heated area of the substrate.
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Accused Products
Abstract
A method of material treatment in which the surface of a metal substrate is converted to a composite structure of the metal and its nitride or carbide utilizing a high temperature chemically active thermal plasma stream, and the product obtained from that method. The complex thermal plasma contains controllable additions of active gas, liquid or solid substances. The surface layer obtained is functionally graded to the substrate resulting in an excellent bond that resists delamination and spalling, and provides a significant increase in hardness, wear and erosion resistance, and corrosion resistance, and a decrease in coefficient of friction.
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Citations
18 Claims
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1. A method of providing a surface layer on an electrically conductive work piece substrate, the method comprising:
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using a scanning plasma torch to impinge a high temperature arc plasma stream on the surface of the work piece, said plasma stream comprising an initial plasma stream and a stream of nitrogen gas or a carbon containing gas that is blended into the initial plasma stream, said work piece forming an electrode and completing an electrical circuit with said plasma arc and the torch power supply, said plasma having sufficient energy to ionize the nitrogen gas or the carbon containing gas, so as to heat the surface of the substrate to a temperature below the melting point of the metal; causing the metal substrate to react with the nitrogen ions or carbon ions forming a composite surface layer of the metal and the corresponding metal nitride or the corresponding metal carbide; and directing a cooling jet stream of an inert gas onto the plasma heated area of the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of thermo-chemical treatment including nitriding, carbonizing, carbonitriding, and boronating of a metal work piece substrate using a direct arc plasma stream, comprising the steps of:
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providing said metal work piece; using the work piece as an electrode to create an initial high temperature arc plasma stream; blending nitrogen and/or carbon containing gases and/or BCl3 inside of said plasma stream causing decomposition of said gases to atoms and ionization of the atoms to obtain an active plasma mix; scanning said active plasma mix in a stream along a surface of said substrate in a duration sufficient to locally heat said substrate to a temperature about 5-200°
C. lower than the melt temperature of the substrate to permit nitrogen and/or carbon ions and/or boron ions to be absorbed by the heated area; anddirecting a cooling jet stream of an inert gas onto the plasma heated area of the substrate to obtain a desired structure or property in at least part of said substrate. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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Specification