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OwnerTakanori Watanabe, Hideaki Iwamura +1inventors
InventorsTakanori Watanabe, Hideaki Iwamura, Koji Nishikawa
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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 μm or more to 10 μm 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. Thus, the poor insusceptibility to high temperature oxidation, which is a most serious disadvantage of the Ti—Al alloy which is lightweight and has high temperature strength, can be improved in a manner suitable for mass production. Therefore, the alloy can be used suitably for a supercharger turbine wheel, an engine valve, turbine blades for a gas turbine or the like, for example.
A method for surface treatment of a Ti—Al alloy comprising heating and holding a Ti—Al alloy base material containing 15 at % or more to 55 at % or less of Al, in an atmosphere containing a fluorine source gas at 100° C. to 500° C. to form a fluorine inspissation layer with a thickness of 0.1 μm or more to 10 μm or less on a surface of the Ti—Al alloy base material.
A Ti—Al alloy comprising a Ti—Al alloy base material containing 15 at % or more to 55 at % or less of Al, wherein the Ti—Al alloy base material has a fluorine inspissation layer having a thickness of 1 μm or more to 10 μm or less on a surface part thereof, and a maximum concentration of F in the fluorine inspissation layer is 2 at % or more to 35 at % or less.
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