Abstract: A furnace of heat treatment capable of keeping a stable nitriding quality for a long period of time is provided. The furnace of heat treatment performs a halogenation treatment and a nitriding treatment by heating a steel material under a predetermined atmosphere. An alloy containing Ni ranging between 50 mass % or more and 80 mass % or less and Fe ranging between 0 mass % or more and 20 mass % or less is used as a material of surfaces of core internals exposed to a treatment space where the nitriding treatment is performed. Accordingly, a nitriding reaction is hardly caused on the surfaces of the core internals, and the halogenation treatment and the nitriding treatment to an article to be treated can be stably executed for a long period of time. Further, a nitrided layer can be stably formed according to purposes on any types of steel materials including a steel type hard to be nitride.

Abstract: A method of fluoridation that can maintain a stable treatment quality is provided. The method of the fluoridation treatment performs the fluoridation treatment by heating and keeping a workpiece in a fluoridation treatment space filled with a predetermined fluoride atmosphere. By exposing an interior space structure that is reactive against fluorine within the fluoridation treatment space, forming a fluoride layer in advance on a surface of the interior space structure exposed within the fluoridation treatment space, and performing the fluoridation treatment, a fluoridation source gas supplied for the fluoridation treatment of the workpiece is not significantly consumed for fluoridating the surface of the interior space structure during the fluoridation treatment. Further, even when a fluoridation potential of the supplied fluoridation source gas is insufficient, the fluoride layer on the surface of the interior space structure discharges the fluoridation gas.

Abstract: A furnace of heat treatment capable of keeping a stable nitriding quality for a long period of time is provided. The furnace of heat treatment performs a halogenation treatment and a nitriding treatment by heating a steel material under a predetermined atmosphere. An alloy containing Ni ranging between 50 mass % or more and 80 mass % or less and Fe ranging between 0 mass % or more and 20 mass % or less is used as a material of surfaces of core internals exposed to a treatment space where the nitriding treatment is performed. Accordingly, a nitriding reaction is hardly caused on the surfaces of the core internals, and the halogenation treatment and the nitriding treatment to an article to be treated can be stably executed for a long period of time. Further, a nitrided layer can be stably formed according to purposes on any types of steel materials including a steel type hard to be nitride.

Abstract: To provide a steel product excelling in both corrosion resistance and adhesion. A steel product having a nitride layer and a nitrogen diffused layer formed on the surface of a steel base material is provided. The nitride layer includes a first compound layer formed on a nitrogen diffused layer side and a second compound layer formed on a surface side of the first compound layer. The first compound layer has an ?-structure mainly made of Fe3N, and the second compound layer has a higher nitrogen concentration than the first compound layer and has a concavoconvex formed on the surface thereof. Thus, the nitride layer having excellent adhesion, an extremely small carbon containing amount, and high corrosion resistance can be formed.

Abstract: A furnace of heat treatment capable of keeping a stable nitriding quality for a long period of time is provided. The furnace of heat treatment performs a halogenation treatment and a nitriding treatment by heating a steel material under a predetermined atmosphere. An alloy containing Ni ranging between 50 mass % or more and 80 mass % or less and Fe ranging between 0 mass % or more and 20 mass % or less is used as a material of surfaces of core internals exposed to a treatment space where the nitriding treatment is performed. Accordingly, a nitriding reaction is hardly caused on the surfaces of the core internals, and the halogenation treatment and the nitriding treatment to an article to be treated can be stably executed for a long period of time. Further, a nitrided layer can be stably formed according to purposes on any types of steel materials including a steel type hard to be nitride.

Abstract: A method of fluoridation that can maintain a stable treatment quality is provided. The method of the fluoridation treatment performs the fluoridation treatment by heating and keeping a workpiece in a fluoridation treatment space filled with a predetermined fluoride atmosphere. By exposing an interior space structure that is reactive against fluorine within the fluoridation treatment space, forming a fluoride layer in advance on a surface of the interior space structure exposed within the fluoridation treatment space, and performing the fluoridation treatment, a fluoridation source gas supplied for the fluoridation treatment of the workpiece is not significantly consumed for fluoridating the surface of the interior space structure during the fluoridation treatment. Further, even when a fluoridation potential of the supplied fluoridation source gas is insufficient, the fluoride layer on the surface of the interior space structure discharges the fluoridation gas.

Abstract: There is provided a surface treatment method for improving high temperature resistance oxidizability of a Ti—Al alloy in a manner suitable for mass production and the Ti—Al alloy. A Ti—Al alloy base material containing 15 at % or more to 55 at % or less of Al is heated and held in a gas atmosphere containing a fluorine source gas to form a fluorine inspissation layer with a thickness of 0.1 ?m or more to 10 ?m or less on the surface of the Ti—Al alloy base material, and a maximum concentration of F in the fluorine inspissation layer is made to be 2 at % or more to 35 at % or less. Thereby, when exposed to a high temperature oxidizing atmosphere, the surface of the Ti—Al alloy base is coated with an Al2O3 coating film having extremely low oxygen permeability. The alloy hence has excellent insusceptibility to high temperature oxidation.